A&P Final Exam

1.1 Origins of Medical Science

1. Early interest in the human body probably developed as people became concerned about injuries and illnesses.

2. Early doctors began to learn how certain herbs and potions affected body functions.

3. The idea that humans could understand forces that caused natural events led to the development of modern science.

4. A set of terms originating from Greek and Latin formed the basis for the language of anatomy and physiology.

5. Much of what we know about the human body was discovered using the scientific method.

1.2 Anatomy and Physiology

1. Anatomy deals with the form and organization of body parts.

2. Physiology deals with the functions of these parts.

3. The function of a part depends upon the way it is constructed.

1.3 Levels of Organization

The body is composed of parts that can be considered at different levels of organization. 

1. Matter is composed of atoms, which are composed of subatomic particles.

2. Organelles consist of aggregates of interacting large molecules (macromolecules).

3. Cells, composed of organelles, are the basic units of structure and functions of the body.

4. Cells are organized into layers or masses called tissues.

5. Tissues are organized into organs.

6. Organs form organ systems.

7. Organ systems constitute the organism.

8. These parts vary in complexity progressively from one level to the next.

1.4 Core Themes in Anatomy and Physiology

1. Certain key concepts provide a foundation for understanding anatomy and physiology.

   1. The cell is the basic unit of life.

   2. Cells live in the internal environment.

   3. Homeostasis is the maintenance of the internal environment.

   4. Cells are interdependent.

   5. Structure and function are closely related.

2. Maintenance of homeostasis involves specific mechanisms.

   1. A number of mechanisms involve structures in the cell membrane.

   2. Some cell membrane structures enable cells to communicate.

   3. Substances move down concentration gradients and down pressure gradients.

   4. Cells access information in the specific genes in order to make the proteins that determine their function.

   5. Balance must be maintained in the internal environment, such that output of substances equals intake and production of those substances.

   6. Homeostatic mechanisms work primarily through negative feedback loops, although there are some positive feedback loops.

   7. Cellular function requires a source of energy.

1.5 The Characteristics and Maintenance of Life

Characteristics of life are traits all organisms share. The structures and functions of body parts maintain the life of the organism.

1. These characteristics include

   1. Growth-increasing in size without changing in shape.

   2. Reproduction-producing offspring.

   3. Responsiveness-sensing and reacting to internal or external changes. 

   4. Movement-changing body position or moving internal parts.

   5. Metabolism-energy and nutrient cycling.

      1. Respiration-obtaining oxygen, using oxygen to release energy from foods, and removing gaseous wastes.

      2. Digestion-breaking down food substances into forms that can be absorbed.

      3. Circulation-moving substances through the body in body fluids.

      4. Excretion-removing body wastes.

2. Requirements of organisms

   1. Chemicals: Water is the most abundant chemical in the human body. Oxygen and carbon dioxide are exchanged with the environment, Food, also called nutrients, is taken in and waste is eliminated.

   2. Heat is part of our environment and is a product of metabolic reactions; heat helps control rates of these reactions.

   3. Pressure is an application of force; in humans, atmospheric and hydrostatic pressures help breathing and blood movements, respectively.

3. Homeostasis

   1. If an organism is to survive, the conditions within its body fluids must remain relatively stable.

   2. The tendency to maintain a stable internal environment is called homeostasis.

   3. Homeostatic mechanisms involve sensory receptors, a control center with a set point, and effectors.

   4. Homeostatic mechanisms include those that regulate body temperature, blood pressure, and blood glucose concentration.

   5. Homeostatic mechanisms employ negative feedback.

1.6 Organization of the Human Body

1. Body cavities

   1. The axial portions of the body contain the cranial cavity and vertebral canal, as well as the thoracic and abdominopelvic cavities, which are separated by the diaphragm.

   2. The organs within thoracic and abdominopelvic cavities are called viscera.

   3. Other body cavities include the oral, nasal, orbital, and middle ear cavities.

2. Thoracic and abdominopelvic membranes

Parietal serous membranes line the walls of these cavities; visceral serous membranes cover organs within them, They secrete serous fluid/

1. Thoracic membranes

   1. Pleural membranes line the thoracic cavity and cover the lungs.

   2. Pericardial membranes surround the heart and cover its surface.

   3. The pleural and pericardial cavities are potential spaces between these membranes.

2. Abdominopelvic membranes

   1. Peritoneal membranes line the abdominopelvic cavity and cover the organs inside.

   2. The peritoneal cavity is a potential space between these membranes.

3. Organ systems

   1. Integumentary system

      1. The integumentary system covers the body. 

      2. It includes the skin, hair, nails, sweat glands, and sebaceous glands.

      3. It protects underlying tissues, regulates body temperature, houses sensory receptors, and synthesizes substances.

   2. Skeletal system

      1. The skeletal system is composed of bones and the ligaments and cartilages that bind bones together.

      2. It provides framework, protective shields, and attachments for muscles; it also produces blood cells and stores inorganic salts.

   3. Muscular system

      1. The muscular system includes the muscles of the body.

      2. It moves body parts, maintains posture, and produces body heat.

   4. Nervous system

      1. The nervous system consists of the brain, spinal cord, nerves, and sense organs.

      2. It receives signals from the sensory receptors, interprets the information, and acts by causing muscles or glands to respond.

   5. Endocrine system

      1. The endocrine system consists of glands that secrete hormones.

      2. Hormones help regulate metabolism by stimulating target tissues.

      3. It includes the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, testes, pineal gland, and thymus.

   6. Cardiovascular system

      1. The cardiovascular system includes the heart, which pumps blood, and the blood vessels, which carry blood to and from body parts.

      2. Blood carries oxygen. Nutrients, hormones, and wastes.

   7. Lymphatic system

      1. The lymphatic system is composed of lymphatic vessels, lymph nodes, the thymus, and the spleen.

      2. It transports lymph from tissue spaces to the bloodstream and carries certain fatty substances away from the digestive organs. Lymphocytes defend the body against disease-causing agents.

   8. Digestive system

      1. The digestive system receives food, breaks down nutrients into forms that can pass through cell membranes, and eliminates unabsorbed materials.

      2. Some digestive organs produce hormones.

      3. The digestive systems include the mouth, tongue, teeth, salivary glands, pharynx, esophagus, stomach, liver, gallbladder, pancreas, small intestine, and large intestine.

   9. Respiratory system

      1. The respiratory system takes in and releases air and exchanges gases between the blood and the air. 

      2. It includes the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs.

   10. Urinary system

       1. The urinary system includes the kidneys, ureters, urinary bladder, and urethra.

       2. It filters wastes from the blood and helps maintain fluid and electrolyte balance.

   11. Reproductive systems

       1. The reproductive system enables an organism to produce progeny.

       2. The male reproductive system produces, maintains, and transports male sex cells. It includes the scrotum, testes, epididymides, ductus, deferentia, seminal vesicles, prostate gland, bulbourethral glands, urethra, and penis.

1.7 Life-Span Changes

Aging occurs from conception on and has effects at the cell, tissue, organ, and organ system levels.

1. The first signs of aging are noticeable in one’s thirties, Female fertility begins to decline during his time. 

2. In the forties and fifties, adult-onset disorders may begin.

3. Skin changes reflect less elastin, collagen and subcutaneous fat.

4. Older people may metabolize certain drugs at different rates than younger people. 

5. Cells divide a limited number of times. As DNA repair falters, mutations may accumulate.

6. Oxygen free radical damage produces certain pigments. Metabolism slows, and beta amyloid protein may build up in the brain.

1.8 Anatomical Terminology

Investigators use terms with precise meaning to effectively communicate with one another.

1. Relative position

   1. These terms describe the location of one part with respect to another part.

2. Body sections

   1. Body sections are planes along which the body may be cut to observe the relative location and arrangements of internal parts.

3. Body regions

   1. Special terms designate various body regions.

2.1 The Importance of Chemistry in Anatomy and Physiology

Chemicals are all around us. Household products such as soap and shampoo as well as food and medicine are composed of chemicals. The human body is also made of chemicals. We begin our examination of anatomy and physiology with a study of basic chemistry.

2.2 Fundamentals of Chemistry

Matter is anything that has mass and takes up space. 

1. Elements and atoms

   1. Naturally occurring matter on Earth is composed of ninety-two elements.

   2. Elements usually combine to form compounds.

   3. Elements are composed of atoms. 

   4. Atoms of different elements vary in size, weight, and ways of interacting.

2. Atomic structure

   1. An atom consists of electrons surrounding a nucleus, which has protons and neutrons. The exception is hydrogen, which has only a proton in its nucleus.

   2. Electrons are negatively charged, protons positively charged, and neutrons uncharged.

   3. A complete atom is electrically neutral.

   4. The atomic number of an element is equal to the number of protons in each atom. 

3. Isotopes

   1. Isotopes are atoms with the same atomic number but different mass numbers (due to differing numbers of neutrons). The atomic weight of an element is the average of the mass numbers of its various isotopes.

   2. All the isotopes of an element react chemically in the same manner.

   3. Some isotopes are radioactive and release atomic radiation. 

4. Molecules and compounds

   1. Two or more atoms may combine to form a molecule.

   2. A molecular formula represents the numbers and types of atoms in a molecule.

   3. If atoms of the same element combine, they produce molecules of that element.

   4. If atoms of different elements combine, they form molecules called compounds.

2.3 Bonding of Atoms

When atoms form links called bonds, they gain, lose, or share electrons. Electrons occupy space in areas called electron shells that encircle an atomic nucleus. Atoms with completely filled outer shells are inert, whereas atoms with incompletely filled outer shells gain, lose, or share electrons and thus become stable.

1. Ionic bonds

   1. Atoms that lose electrons become positively charged (cations); atoms that gain electrons become negatively charged (anions).

   2. Ions with opposite charges attract and join by ionic bonds.

2. Atoms that share electrons joined by covalent bonds.

   1. Nonpolar molecules result from an equal sharing of electrons.

   2. Polar molecules result from an unequal sharing of electrons.

   3. Hydrogen bonds may form within and between polar molecules. 

3. Chemical reactions

   1. In a chemical reaction, bonds between atoms, ions, or molecules break or form. Starting materials are called reactants; the resulting atoms or molecules are called products.

   2. Three types of chemical reactions are synthesis, in which large molecules build up from smaller ones; decomposition, in which molecules break down; and exchange reactions, in which parrots of two different molecules trade positions. 

   3. Many reactions are reversible. The directions of a reaction depend upon the proportion of reactants and products and the energy available.

   4. Catalysts (enzymes) influence the rate (not the directions) of the reaction.

2.4 Electrolytes, Acids and Bases, and Salts

Compounds that ionize in water are electrolytes.

1. Electrolytes that release hydrogen ions are acids, and those that release hydroxide or other ions that react with hydrogen ions are bases.

   1. Acids and bases react to form water and electrolytes called salts.

2. Acid and base concentrations

   1. pH represents the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution.

   2. A solution with equal numbers of H+ and OH- is neutral and has a pH of 7.0; a solution with more H+ than OH- is acidic (pH less than 7.0); a solution with fewer H+ than OH- is basic (pH greater than 7.0).

   3. A tenfold difference in hydrogen ion concentration separates each whole number in the pH scale.

   4. Buffers are chemicals that resist pH change.

2.5 Chemical Constituents of Cells

Molecules containing carbon and hydrogen atoms are organic and are usually nonelectrolytes; other molecules are inorganic and are usually electrolytes. 

1. Inorganic substances

   1. Water is the most abundant compound in the body. Many chemical reactions take place in water, Water transports chemicals and heat and helps release excess body heat. 

   2. Oxygen releases energy for metabolic activities from glucose and other molecules.

   3. Carbon dioxide is produced when certain metabolic processes release energy.

   4. Inorganic salts provide ions needed in a variety of metabolic processes.

   5. Electrolytes must be present in certain concentrations inside and outside of cells. 

2. Organic substances

   1. Carbohydrates provide much of the energy cells require and are built of simple sugar molecules.

   2. Lipids, such as triglycerides (fats), phospholipids, and steroids, supply energy and are used to build cell parts.

      1. The building blocks of triglycerides are glycerol and three fatty acids.

      2. The building blocks of phospholipids are glycerol, two fatty acids, and a phosphate group. 

      3. Steroids include rings of carbon atoms and are synthesized in the body from cholesterol. 

   3. Proteins serve as structural materials, energy sources, hormones, cell surface receptors, antibodies, and enzymes that speed chemical reactions without being consumed.

      1. The building blocks of proteins are amino acids.

      2. Proteins vary in the numbers and types of their constituent amino acids; the sequences of these amino acids; and their three-dimensional structures, or conformations.

      3. Primary structure is the amino acid sequence. Secondary structure comes from attractions between amino acids that are close together in the primary structure. Tertiary structure reflects attractions of far-apart amino acids and folds the molecule.

      4. The amino acid sequence determines the protein's conformation.

      5. The protein's conformation determines its function.

      6. Exposure to excessive heat, radiation, electricity, or certain chemicals can denature proteins. 

   4. Nucleic acids constitute genes, the instructions that control cell activities, and direct protein synthesis.

      1. The two types are RNA and DNA.

      2. Nucleic acid building blocks are nucleotides.

      3. DNA molecules store information that cell parts use to construct specific proteins.

      4. RNA molecules help synthesize proteins.

      5. DNA molecules are replicated, and an exact copy of the original cell’s DNA is passed to each of the newly formed cells resulting from cell division.

3.1 Cells Are the Basic Units of the Body

1. Differentiated cells vary considerably in size, shape, and function.

2. The shapes of cells are important in determining their functions.

3. Specialized cells descend from less specialized cells. 

3.2 Composite Cell

1. The three major parts of a cell are the nucleus, the cytoplasm, and the cell membrane.

2. Cytoplasmic organelles suspended in the cytosol perform specific vital functions. The nucleus, also an organelle, contains DNA and controls activities of the cell.

3. Cell membrane

   1. The cell membrane forms the outermost limit of the living material. 

   2. It acts as a selectively permeable passageway that controls the movements of substances between the cell and its surroundings.

   3. It includes lipid, protein, and carbohydrate molecules.

   4. The cell membrane framework is mainly a double layer (bilayer) of phospholipid molecules.

   5. Molecules that are soluble in lipids pass through the membrane easily, but water-soluble molecules do not.

   6. Cholesterol molecules help stabilize the cell membrane.

   7. Proteins provide the special function of the membrane, as transporters, receptors, enzymes, cell surface markers or self, and cellular adhesion molecules.

   8. Cellular adhesion molecules oversee some cell interactions and movements.

4. Cytoplasmic organelles

   1. Cytoplasm contains membranous and nonmembranous organelles and other cytoplasmic structures scattered within the more-liquid cytosol.

   2. Cytoplasmic organelles have specific functions.

      1. Ribosomes are structures of protein and RNA that function in protein synthesis. 

      2. Endoplasmic reticulum is composed of connected membranous sacs, canals, and vesicles that provide a tubular communication system and an attachment for ribosomes; it also is the site of synthesis of lipids. 

      3. Vesicles are membranous sacs containing substances that recently entered or were produced in the cell. 

      4. The Golgi apparatus is a stack of flattened, membranous sacs that package glycoproteins for secretion.

      5. Mitochondria are membranous sacs containing enzymes embedded in an inner membrane that catalyze the reactions that release energy from nutrient molecules and change it into a usable form. 

      6. Lysosomes are membranous sacs containing digestive enzymes that destroy debris and worn-out organelles.

      7. Peroxisomes are membranous vesicles where enzymes catalyze a variety of metabolic reactions. 

5. Other cytoplasmic organelles

   1. Some structures are not considered organelles, such as the cytoskeleton and structures composed of similar components, and chemicals or molecules stored in cells. 

   2. Other cytoplasmic structures carry out varied functions.

      1. Microfilaments and microtubules are threadlike structures built of actin and tubulin proteins, respectively, that aid cellular movements and support and stabilize the cytoplasm. Intermediate filaments serve a variety of functions and are composed of different proteins in different body parts. 

      2. The centrosome is a non membranous structure consisting of two centrioles, which produce the spindle fibers that distribute replicated chromosomes during cell division.

      3. Cilia and flagella are extensions on some cell surfaces.

         1. Motile cilia are tiny, hairlike structures that wave, moving fluids across cell surfaces. Cells have many motile cilia.

         2. Primary cilia are one per cell and transmit signals.

         3. Flagella are extensions that are longer than cilia.

      4. Microvilli are tiny extensions of the plasma membrane that increase the surface area.

      5. Inclusions are chemical substances that may or may not be present in a cell and are not necessary for the cell’s survival.

6. Cell nucleus

   1. The nucleus is enclosed in a double-layered nuclear envelope that has nuclear pores that control movement of substances between the nucleus and cytoplasm.

   2. A nucleolus is a dense body of protein and RNA where ribosome synthesis occurs.

   3. Chromatin is composed of loosely coiled fibers of protein and DNA that coil tightly into chromosomes during cell division.

3.3 Movements Into and Out of the Cell

Several passive (not requiring energy) and active (requiring energy) processes move substances into and out of cells.

1. Passive mechanisms

   1. Diffusion

      1. Diffusion is due to the random movement of atoms, molecules, or ions in air or solution.

      2. Diffusion is movement of atoms, molecules, or ions from regions of higher concentration towards regions of lower concentration (down a concentration gradient). 

      3. Oxygen and carbon dioxide are exchanged by diffusion in the body.

      4. Important factors determining the rate of diffusion in the body include distance, the concentration gradient, and temperature. 

   2. Facilitated diffusion

      1. Facilitated diffusion uses protein channels or carrier molecules in the cell membrane.

      2. This process moves substances such as ions, sugars, and amino acids from regions of higher concentration to regions of lower concentration.

   3. Osmosis

      1. Osmosis is a process in which water molecules move through a selectively permeable membrane toward the solution with greater osmotic pressure, lifting a volume of water.

      2. Osmotic pressure increases as the number of impermeant solute particles dissolved in a solution increases.

      3. A solution is isotonic when it contains the same concentration of dissolved particles as the cell contents.

      4. Cells lose water when placed in hypertonic solutions and gain water when placed in hypotonic solutions.

   4. Filtration

      1. In filtration, molecules move through a membrane from regions of higher hydrostatic pressure toward regions of lower hydrostatic pressure.

      2. Blood pressure filters water and dissolved substances through porous capillary walls.

2. Active mechanisms

   1. Active transport

      1. Active transport moves molecules or ions from regions of lower concentration to regions of higher concentration.

      2. It requires ATP and carrier molecules in the cell membrane.

      3. Secondary active transport does not use ATP but depends on the sodium gradient set by sodium/ potassium pumps to cotransport or countertransport molecules or ions.

   2. Endocytosis

      1. In pinocytosis, a cell membrane engulfs tiny droplets of liquid.

      2. In phagocytosis, a cell membrane engulfs solid particles.

      3. In receptor-mediated endocytosis, receptor proteins combine with specific molecules in the cell surroundings. The membrane engulfs the combinations. 

   3. Exocytosis

      1. Exocytosis has the reverse effect of endocytosis but the steps differ.

      2. In exocytosis, vesicles containing secretions fuse with the cell membrane, releasing the substances to the outside.

   4. Transcytosis

      1. Transcytosis combines endocytosis and exocytosis.

      2. In transcytosis, a substance or particle crosses a cell.

      3. Transcytosis is specific. 

      4. Exosomes are extracellular vesicles involved in intracellular communication.

3.4 The Cell Cycle

1. The cell cycle includes interphase, mitosis and cytokinesis.

2. Interphase

   1. Interphase is the stage when a cell grows, DNA replicates, and new organelles form. 

   2. It terminates when the cell begins mitosis.

3. Mitosis

   1. Mitosis is the division and distribution of DNA to daughter cells.

   2. The stages of mitosis are prophase, metaphase, anaphase, and telophase.

4. In cytokinesis the cytoplasm divides, distributing organelles to the two daughter cells.

3.5 Control of Cell Division

1. Cell division capacities vary greatly among cell types.

2. Chromosomes tips that shorten with each mitosis provide a mitotic clock, limiting the number of divisions to about fifty.

3. Internal and external factors control cell division.

4. As a cell grows, its surface area increases to a lesser degree than its volume, and eventually the surface area limits the cell’s ability to take in nutrients. Cell division restores the more favorable surface area-volume relationship.

5. Growth factors and hormones stimulate cell division. 

6. Cancer is the consequence of a loss of cell cycle control. 

3.6 Stem and Progenitor Cells

1. A stem cell divides to yield another stem cell and a partially differentiated progenitor cell.

2. Cells that may give rise to any differentiated cell type are totipotent. Cells with more restricted fates are pluripotent.

3. Stem cells are present in adult organs and migrate from the bone marrow to replace damaged cells.

4. As cells specialize, they express different sets of genes that provide their distinct characteristics. 

3.7 Cell Death

1. Apoptosis is a form of cell death that is part of normal development and growth. 

2. It is a fast, orderly multistep process that begins when a cell surface receptor receives a signal to die. Caspases start a chain reaction that cuts up the cell into membrane-bounded pieces. A phagocyte destroys the remains.

3. Apoptosis and mitosis are synchronized throughout development, maturation, and aging.

24.1 Overview of Genetics

1. Genetics is the study of inheritance of characteristics and human variation.

2. Genes are DNA sequences that encode proteins.

3. Genetic information is passed from generation to generation through meiosis and fertilization, when the haploid genomes of the parents join. 

4. The protein-encoding portion of the genome is small and called the exome.

5. The human genome assembles many more proteins than there are genes by combining gene parts.

6. Genetic information functions at the biochemical, cell, tissue, individual, family, and population levels.

7. Genes influence each other, and their expression responds to environmental influences.

24.2 Modes of Inheritance

1. Chromosomes and genes are paired.

   1. Chromosome charts are called karyotypes.

   2. Chromosomes 1 through 22, numbered in decreasing size order, are autosomes. They do not have genes that determine sex.

   3. The X and Y chromosomes are sex chromosomes, They have genes that determine sex.

   4. An allele is an alternate form (variant) of a gene. A person can have a maximum of two different alleles for a gene, but the gene can have many alleles, because a gene consists of many building blocks, any of which may be altered. 

   5. A person with a pair of identical alleles for a particular gene is homozygous; if the alleles are different, the individual is heterozygous.

   6. The combination of gene variants in an individual’s cells constitutes the genotype; the appearance of traits of the individual is the phenotype.

2. Mendelian inheritance 

   1. In a heterozygote, an allele expressed when the other is not expressed is dominant. The masked allele is recessive. 

   2. Punnett squares and pedigrees depict modes of inheritance.

3. Extensions of Mendelian inheritance

   1. In codominance, each allele in the heterozygote is expressed. Some genes have more than two versions of an allele. This is called a multiple allele system such as the A, B, O blood type.

   2. In incomplete dominance, a heterozygote has a phenotype intermediate between those of both homozygotes

   3. Polygenic inheritance and pleiotropy

      1. Traits coded for by two or more genes are called polygenic traits. A frequency distribution for a polygenic trait forms a bell curve. 

      2. Pleiotropy results from a gene product that is part of more than one biochemical reaction or is in several organs or structures.

      3. In pleiotropy, a disorder has several symptoms, different subsets of which may affect individuals.

   4. Chromosomal and sex-linked inheritance

      1. A female has two X chromosomes; a male has one X and one Y chromosome. The X chromosome has many more genes than the Y. 

      2. Sex determination

         1. A male zygote forms when a Y-bearing sperm fertilizes an oocyte. A female zygote forms when an X-bearing sperm fertilizes an oocyte. 

         2.  A gene on the Y chromosome, SRY, switches on genes in the embryo that promote development of male characteristics. 

         3. Lack of SRY and activation of Wnt4 direct development as a female.

      3. Genes on the sex chromosomes 

         1. Genes on the sex chromosomes follow different inheritance patterns than those on autosomes.

         2. Y-linked genes are in three functional groups; those with counterparts on the X; those similar to genes on the X; and genes unique to the Y, many of which affect male fertility, Y-linked genes pass from fathers to sons. 

24.3 Other Factors That Affect Expression of Genes

1. Penetrance and expressivity

   1. A genotype is incompletely penetrant if not all individuals inheriting it express the phenotype.

   2. A genotype is variably expressive if it's expressed at different degrees in different individuals.

2. Genetic heterogeneity

   1. Genetic heterogeneity refers to a phenotype resulting from mutation in more than one gene. 

   2. The same symptoms may result from mutations in genes whose products are enzymes in the same biochemical pathway.

3. Gender effects on phenotype

   1. Sex-limited traits affect structures or functions seen in only one sex and may be autosomal.

   2. Sex-influecned traits are dominant in one sex and recessive in the other. 

4. A trait caused by the action of one or more genes and the environment is multifactorial. 

   1. Height skin color, eye color, and many common illnesses are multifactorial traits.

24.4 Chromosome Disorders

Extra, missing, or rearranged chromosomes or parts of them can cause syndromes, because they alter the balance of genetic material or disrupt a vital gene.

1. Polyploidy

   1. Polyploidy is an extra chromosome set.

   2. Polyploidy results from fertilization with or by a diploid gamete.

   3. Polyploids do not survive long.

2. Aneuploidy

   1. Cells with the normal chromosome number are euploid. Cells with an extra or missing chromosome are aneuploid.

   2. Aneuploidy results from nondisjunction, in which a chromosome pair does not separate, in meiosis 1 or meiosis 2, producing a gamete with a missing or extra chromosome. At fertilization, a monosomy or trisomy results. 

   3. A cell with an extra chromosome is trisomic. A cell with a missing chromosome is monosomic. Individuals with trisomies are more likely to survive to be born than those with monosomies. 

   4. Autosomal aneuploids are more severe than sex chromosome aneuploids.

3. Prenatal tests detect chromosome abnormalities

   1. Ultrasound can detect large-scale structural abnormalities and assess growth. 

   2. Maternal serum marker tests indirectly detect a small fetal liver, which can indicate a trisomy.

   3. Chorionic villus sampling obtains and examines chorionic villus cells, which descend from the fertilized egg and therefore are presumed to be genetically identical to fetal cells. 

   4. Amniocentesis samples and examines fetal chromosomes from fetal cells of amniotic fluid.

   5. Cell-free fetal DNA testing detects aneuploid from fetal DNA in the maternal circulation. 

24.5 Genomics and Health Care

1. Genetic tests are used to diagnose single-gene diseases, to identify gene variants associated with elevated risk of developing certain conditions, and to select treatments most likely to benefit a particular patient with minimal risk of adverse effects. 

2. The scope of genetic tests ranges from detecting single DNA base changes to sequencing exomes and genomes.

3. Genomics is the study of all the genetic information of an individual organism. 

4. An inherited mutation is transmitted from parent to offspring, but a de novo mutation occurs in a gamete or early in fetal development. The inherited mutation affects siblings of an affected individual with a predictable frequency, but the siblings or a person with a de novo mutation are not at elevated risk.

5. Exome sequencing and genome sequencing reveal actionable and secondary findings. 

6. Treatments for genetic disease target proteins (enzyme replacement therapy, substrate reduction therapy, pharmacological; chaperone therapy) and genes (gene therapy).

4.1 Metabolic Reactions

Metabolism refers to the reactions and pathways that build up and break down molecules.

1. Anabolism

   1. Anabolism builds molecules.

   2. In dehydration synthesis, hydrogen atoms and hydroxy; groups are removed, water forms, and smaller molecules bind by sharing atoms.

   3. Anabolic reactions include complex carbohydrates synthesized from monosaccharides, triglycerides synthesized from glycerol and fatty acids, and proteins synthesized from amino acids.

2. Catabolism

   1. Catabolism breaks down molecules.

   2. In hydrolysis, a water molecule adds a hydrogen atom to one portion of a molecule and a hydroxyl group to a second portion, breaking the bond between these parts.

   3. Catabolic reactions include complex carbohydrates decomposed into monosaccharides, triglycerides decomposed into glycerol and fatty acids, and proteins broken down into amino acids. 

4.2 Control of Metabolic Reactions

Metabolic processes have many steps that occur in a specific sequence and are interconnected.

1. Enzyme action

   1. Metabolic reactions require energy to start.

   2. Most enzymes are proteins that increase the rate of (catalyze) specific metabolic reactions.

   3. Many enzymes are named after their substrates, with -ase at the end.

   4. An enzyme acts when its active site temporarily combines with the substrate, altering its chemical structure. This enables the substrate to react, forming a product. The enzyme is released in its original form. 

   5. The rate of enzyme-controlled reactions depends upon the numbers of enzyme and substrate molecules and the efficiency of the enzyme. 

2. Enzymes and metabolic pathways

   1. Sequences of enzyme-controlled reactions are metabolic pathways.

   2. Enzyme-catalyzed reactions from pathways when a reaction’s product is another’s substrate.

   3. A rate-limiting enzyme may regulate a metabolic pathway.

   4. A negative feedback mechanism in which the product of a pathway inhibits the regulatory enzyme may control the regulatory enzyme.

   5. The rate of product formation usually remains stable on a pathway because of feedback mechanisms.

3. Factors that alter enzymes

   1. Cofactors are chemical groups added to some enzymes that are necessary for their function. 

   2. A cofactor may be an ion or a small organic molecule called a coenzyme.

   3. Many coenzymes are vitamins or derives from vitamins, which are nutrients that the body cannot produce or produces in insufficient amounts. 

   4. Excessive heat, radiation, electricity, and phH can disrupt the conformation of an enzyme, causing it to denature.

4.3 Energy for Metabolic Reactions

Energy is a capacity to produce change or to do work. Form of energy include heat, light, sound, and electrical, mechanical, and chemical energies.

1. Release of chemical energy

   1. The energy liberated from breaking bonds of glucose, in the process of oxidation, is used for metabolism. 

   2. The reactions of cellular respiration use and release chemical energy.

   3. Enzymes in the cytoplasm and mitochondria control cellular respiration.

   4. Energy from breaking chemical bonds is released as heat and used to synthesize adenosine triphosphate(ATP).

2. ATP molecules 

   1. ATP is the primary energy-carrying molecule in a cell.

   2. Energy is captured in the bond of the terminal phosphate of ATP. 

   3. Captured energy is released when the terminal phosphate bond of an ATP molecule breaks.

   4. ATP that loses its terminal phosphate becomes ADP.

   5. ADP can become ATP by capturing energy and a phosphate, a process called phosphorylation.

4.4 Cellular Respiration

Cellular respiration transfers energy from molecules such as glucose and makes it available for cellular use. Phosphorylation of glucose encourages movement into cells by facilitated diffusion. Cellular respiration occurs in three distinct, interconnected series of reactions: glycolysis, the citric acid cycle, and the electron transport chain. Some of the steps require oxygen (aerobic) and some do not (anaerobic).

1. Glycolysis

   1. Glycolysis, the first step of glucose catabolism, occurs in the cytosol and does not require oxygen. 

   2. The three stages of glycolysis release and transfer some energy to ATP, while splitting a molecule of glucose into 2 molecules of pyruvic acid. 

   3. Some of the released energy is in the form of hydrogen atoms attached to hydrogen carriers. 

2. Anaerobic reactions (absence of oxygen)

   1. In the anaerobic reactions, NADH and H+ donate electrons and protons of hydrogen atoms to pyruvic acid, generating lactic acid.

   2. Lactic acid builds up, eventually inhibiting glycolysis and ATP formation.

   3. When oxygen returns, in lover cells lactic acid reacts to form pyruvic acid.

3. Aerobic reactions (presence of oxygen)

   1. The second phase of glucose catabolism occurs in the mitochondria and requires oxygen.

   2. These reactions include the citric acid cycle and the electron transport chain.

   3. Considerably more energy  is transferred to ATP during the aerobic reactions than during glycolysis.

   4. The products of the aerobic reactions of cellular respiration are heat, carbon dioxide, water, and energy.

   5. The citric acid cycle decomposes molecules, releases carbon dioxide, releases hydrogen atoms that have high-energy electrons, and forms ATP.

   6. High-energy electrons from hydrogen atoms enter an electron transport chain, releasing energy used to form ATP.

   7. Complete oxidation of glucose yields an estimated theoretical maximum of 32 ATP molecules, with most produced by oxidative phosphorylation in the electron transport chain.

   8. Excess carbohydrates may enter anabolic pathways and be linked into and stored as glycogen or react to produce lipids. 

4.5 DNA (Deoxyribonucleic Acid)

DNA molecules contain and maintain information that tells a cell how to synthesize polypeptides, which comprise or associate to form proteins. 

1. Genetic information

   1. DNA information specifies inherited traits 

   2. A gene is a sequence of nucleotide bases along one DNA strand that contains the genetic information for a particular protein’s amino acid sequence. 

   3. The DNA nucleotides from both strands form complementary base pairs, joining the two strands.

   4. The nucleotide bases are adenine (A), which pairs with thymine (T), and guanine (G), which pairs with cytosine (.C). A and G are 2-ringed structures called purines, and T and C are single-ringed structures called pyrimidines.

   5. All of the DNA in a cell is called the genome, The protein-encoding part is called the exome. 

2. DNA replication

   1. Each new cell requires a copy of the original cell’s genetic information. 

   2. DNA molecules are replicated during interphase of the cell cycle. 

   3. Each new DNA molecule consists of one old strand and one new strand. 

4.6 Protein Synthesis

1. Genetic code

   1. Three nucleotides in a DNA sequence code for a three nucleotide sequence of mRNA that code for one type of amino acid. 

   2. RNA (ribonucleic acid) molecules transfer genetic information from the nucleus to the cytoplasm. 

2. Transcription

   1. RNA molecules are usually single-stranded, have ribose instead of deoxyribose, and uracil in place of thymine.

   2. The process of RNA synthesis transcription. \

   3. Messenger RNA (mRNA) molecules, synthesized in the nucleus, have a nucleotide sequence complementary to that of an exposed strand of DNA.

3. Translation

   1. Messenger RNA molecules move into the cytoplasm, associate with ribosomes, which consist of proteins and ribosomal RNA (rRNA) subunits, and are templates for the synthesis of polypeptide molecules in the process of translation.

   2. Molecules of transfer RNA (tRNA) position amino acids along a strand of mRNA.

   3. A ribosome binds to an mRNA and allows a tRNA anticodon to recognize its correct position based on the mRNA codon.

   4. The ribosome has enzymatic activity required to synthesize the polypeptide and holds it until it is completed.

   5. As the polypeptide forms, it folds into a characteristic conformation. 

   6. ATP provides the energy for protein synthesis.

   7. Protein synthesis is efficient, recycling components and translating many copies of a protein at a time. 

4. Gene expression regulation

   1. The rate at which mRNA is transcribed is proportional to the rate at which it is destroyed by enzymes in a cell.

   2. Extracellular signals activate transcription factors that activate genes and, therefore, control which proteins are produced by cells.

   3. Epigenetics is a field of biology that researches gene expression modification that do not involve changes in the genome. 

4.7 Changes in Genetic Information

Mutation is a change in a DNA sequence.

1. Nature of mutations

   1. Mutations are rare and alter health or appearance. 

   2. Mutations may be spontaneous or induced by mutagens.

   3. A protein synthesized from an altered DNA sequence may or may not function normally. 

   4. DNA changes are transmitted when the cell divides.

2. Protection against mutation

   1. DNA repair enzymes can correct some form of DNA damage.

   2. The genetic code protects against effects of some mutations.

   3. A mutation in a sex cell, fertilized egg, or embryo may have more effects than a later mutation because a greater proportion of cells bear the mutation.

5.1 Cells are Organized into Tissues

Cells are organized in layers or groups to form tissues. The four major types of human tissue are epithelial, connective, muscle, and nervous.

1. Intercellular junctions

   1. Specialized intercellular junctions (tight junctions, desmosomes, and gap junctions) connect cells.

2. Histology

   1. Histology is the microscopic study of tissues.

5.2 Epithelial Tissues

Epithelial tissues cover all free body surfaces, form the inner lining of body cavities, line hollow organs, and are the major tissue of glands. A basement membrane anchors epithelium to connective tissue. Epithelial tissue lacks blood vessels, has cells that are tightly packed, and is continuously replaced. It protects, secretes, absorbs, and excretes. Epithelial tissue is classified according to cell shape and the number of cell layers. 

1. Simple squamous epithelium

   1. This tissue consists of a single layer of thin, flattened cells through which substances pass easily.

   2. It functions in the gas exchange in the lungs and line blood vessels, lymph vessels, and is part of the membranes lining body cavities and covering viscera. 

2. Simple cuboidal epithelium

   1. This tissue consists of a single layer of cube-shaped cells.

   2. It carries on secretion and absorption in the kidneys and various glands.

3. Simple columnar epithelium

   1. This tissue is composed of elongated cells whose nuclei are near the basement membrane.

   2. It lines the uterus and digestive tract, where it functions in protection, secretion, and absorption.

   3. Absorbing cells often possess microvilli.

   4. This tissue has goblet cells that secrete mucus. 

4. Pseudostratified columnar epithelium

   1. This tissue appears stratified because the nuclei are at two or more levels.

   2. Its cells commonly have cilia that move mucus over the surface of the tissue.

   3. It lines the respiratory passages.

5. Stratified squamous epithelium

   1. This tissue is composed of many layers of cells; the top layers are flattened.

   2. It protects underlying cells from harmful environmental effects.

   3. It is the outer layer of the skin and lines the oral cavity, esophagus, vagina, and anal canal.

6. Stratified cuboidal epithelium

   1. This tissue is composed of two or three layers of cube-shaped cells. 

   2. It lines the ducts of the mammary glands, sweat glands, salivary glands, and pancreas.

   3. It functions in protection.

7. Stratified columnar epithelium

   1. The cells in the top layer of this tissue are elongated. Cube-shaped cells make up the bottom layers.

   2. It is in the part of the male urethra and lining of the larger ducts of exocrine glands.

   3. This tissue functions in protection and secretion. 

8. Transitional epithelium

   1. This tissue is specialized to stretch.

   2. It lines the urinary bladder, uterus, and superior urethra.

   3. It helps prevent the contents of the urinary passageways from diffusing out.

9. Glandular epithelium

   1. Glandular epithelium is composed of cells specialized to secrete substances.

   2. A gland consists of one or more cells.

      1. Exocrine glands secrete into ducts.

      2. Endocrine glands secrete into tissue fluid or blood. 

   3. Exocrine glands are classified according to the organization of their cells. 

      1. Simple glands have ducts that do not branch before reaching the secretory portion.

      2. Compound glands have ducts that branch repeatedly before the secretory portion.

      3. Tubular glands consist of epithelial-lined tubes.

      4. Alveolar glands consist of saclike dilations connected to the surface by narrowed ducts. 

   4. Exocrine glands are classified according to the composition of their secretions.

      1. Merocrine glands secrete fluids without loss of cytoplasm. Most secretory cells are merocrine.

         1. Serous cells secrete watery fluid.

         2. Mucous cells secrete mucus.

      2. Apocrine glands lose portions of their cells during secretion.

      3. Holocrine glands release cells filled with secretions. 

5.3 Connective Tissue

Connective tissue connects, supports, protects, provides frameworks, fills spaces, stores fat, produces blood cells, protects against infection, and helps repair damaged tissues. Two categories are recognized: connective tissue proper and specialized connective tissues, Connective tissue cells usually have considerable extracellular matrix between them. This extracellular matrix consists of fibers and a ground substance. 

1. Major cell types

   1. Fibroblasts produce collagen and elastic fibers.

   2. Macrophages are phagocytes.

   3. Mast cells may release heparin and histamine.

2. Connective tissue fibers

   1. Collagen fibers have great tensile strength.

   2. Elastic fibers are composed of elastin and are stretchy.

   3. Reticular fibers are fine collagen fibers. 

3. Connective tissue proper

Connective tissue proper includes loose connective tissue (areolar, adipose, reticular) and dense connective tissue (dense regular, dense irregular, elastic).

1. Areolar connective tissue

   1. Areolar connective tissue forms thin membranes between organs and binds them.

   2. It is beneath the skin and surrounds organs.

2. Adipose tissue

   1. Adipose tissue is a specialized form of loose connective tissue that stores fat, cushions and insulates.

   2. It is found beneath the skin; in certain abdominal membranes; and around the kidneys, heart, and various joints.

3. Reticular connective tissue

   1. Reticular connective tissue largely consists of thin, branched reticular fibers.

   2. It supports the walls of the liver and spleen.

4. Dense regular connective tissue

   1. Dense regular connective tissue is largely composed os strong, collagen fibers that bind structures as parts of tendons and ligaments.

5. Dense irregular connective tissue

   1. Dense irregular connective tissue has thicker, randomly distributed collagen fibers and is found in the periosteum, perichondrium, capsules of some organs, and dermis. 

6. Elastic connective tissue

   1. Elastic connective tissue is mainly composed of elastic fibers and imparts an elastic quality to the walls of certain hollow internal organs such as the lungs and blood vessels. 

4. Specialized connective tissue 

Specialized connective tissues include cartilage, bone, and blood.

1. Cartilage

   1. Cartilage provides a supportive framework for various structures.

   2. Its extracellular matrix is composed of fibers and a solid gel-like ground substance.

   3. It lacks a direct blood supply and is slow to heal.

   4. Most cartilaginous structures are enclosed in a perichondrium, which contains blood vessels. 

   5. Major types are hyaline cartilage, elastic cartilage, and fibrocartilage. 

   6. Cartilage is at the ends of various bones; in the ear; in the larynx; and in the pads between the bones of the spinal column, pelvic girdle, and knees.

2. Bone

   1. The extracellular matrix of bone contains mineral salts and collagen.

   2. The cells of compact bone are arranged in a bony matrix of concentric circles around central canals, whereas the cells of spongy bone are embedded in bony plates with spaces between the plates. Canaliculi connect cells.

   3. It is an active tissue that heals rapidly.

3. Blood 

   1. Blood is composed of formed elements suspended in fluid.

   2. The formed elements include red blood cells, white blood cells, and platelets, which are all produced by special tissue in the hollow parts of certain bones. 

5.4 Membranes

1. Epithelial membranes

   1. Serous membranes

      1. Serous membranes line body cavities that do not open to the outside and cover organs in these cavities.

      2. They are composed of epithelium and areolar connective tissue.

      3. Cells of serous membranes secrete watery serous fluid that lubricants membrane surfaces. 

   2. Mucous membranes

      1. Mucous membranes line cavities and tubes opening to the outside of the body.

      2. They are composed of epithelium and areolar connective tissue.

      3. Cells of mucous membranes secrete mucus. 

   3. The cutaneous membrane is the external body covering commonly called skin. 

2. Synovial membranes are composed of connective tissue only, and line joints. 

5.5 Muscle Tissues

Muscle tissue contracts, generates forces, and moves structures attached to it, Three types are skeletal, smooth, and cardiac muscle tissues. 

1. Skeletal muscle tissue

   1. Muscles containing this tissue usually attach to bones and can be controlled by conscious effort. 

   2. Skeletal muscle cells, also called muscle fibers, are long and threadlike, containing several nuclei, with alternating light and dark cross-markings (striations). 

   3. A muscle cell contracts when stimulated by a nerve cell, then relaxes when no longer stimulated.

2. Smooth muscle tissue

   1. This tissue of spindle-shaped cells, each with one nucleus, is in the walls of hollow internal organs.

   2. It is voluntarily controlled.

3. Cardiac muscle tissue

   1. This tissue is found only in the heart.

   2. Striated cells, each with a single nucleus, are joined by intercalated discs and from branched networks.

   3. Cardiac muscle tissue is involuntarily controlled.

5.6 Nervous Tissue

1. Nervous tissue is in the brain, spinal cord, and peripheral nerves.

2. Neurons

   1. Neurons sense changes and respond by conducting electrical impulses to other neurons or to muscles or glands.

   2. They coordinate, regulate, and integrate body activities.

3. Neuroglia

   1. Some of these cells bind and support nervous tissue.

   2. Others carry on phagocytosis.

   3. Still others connect neurons to blood vessels.

   4. Some are involved in cell-to-cell communication.

6.1 Layers of the Skin

Skin is composed of an epidermis and a dermis separated by a basement membrane. A subcutaneous layer, not part of the skin, lies beneath the dermis. THe subcutaneous layer is composed of areolar connective tissue and adipose tissue that helps conserve body heat. The subcutaneous layer contains blood vessels that supply the skin. 

1. Epidermis

   1. The epidermis is stratified squamous epithelium that lacks blood vessels

   2. The deepest layer (stratum basale) contains cells called keratinocytes that divide and grow

   3. Epidermal cells undergo keratinization as they are pushed toward the surface

   4. The outermost layer (stratum corneum) is composed of dead epidermal cells

   5. Production of epidermal cells in the stratum basale balances the rate at which they are lost at the surface

   6. Phagocytes called dendritic cells protect the skin from pathogens

   7. Tactile cells in the stratum basale detect light touch, stimulating the sensory ending of the tactile disc

   8. Melanocytes produce the pigment melanin and transfer it to nearby epidermal cells

   9. Melanin is produced from the amino acid tyrosine, provides skin color, and protects underlying cells from the effects of uv light

   10. Although all humans have about the same number of melanocytes, skin color is largely due to the amount of melanin (specifically eumelanin) in the epidermis

1. Each person inherits genes for melanin production

-dark skin is due to genes that cause large amounts of melanin to be produced; lighter skin is due to genes that cause lesser amounts of melanin to form

-mutant genes may cause lack of melanin in the skin

2. Environmental factors that influence skin color include sunlight, uv light, and xrays. These factors darken existing melanin and stimulate additional melanin production.

3.physiological factors influence skin color

-the oxygen content of the blood in dermal vessels may cause the skin of light complexioned persons to appear pinkish or bluish

-carotene in the subcutaneous layer may cause the skin to appear yellowish

-disease may affect skin color

2. Dermis

   1. Cone-shaped dermal papillae contain blood capillaries that provide epidermal cells with oxygen and nutrients

   2. Dermal papillae create ridges that leave a fingerprint when a finger presses against a surface

   3. The dermis has two layers

1. The upper papillary layer is areolar connective tissue

2.the lower reticular layer is dense irregular connective tissue that binds the epidermis to underlying tissues

4. Ink used in tattooing is injected into the region between the epidermis and the dermis and remains in the superior part of the dermis

5. The dermis contains smooth and skeletal muscle tissues

6. Dermal blood vessels supply nutrients to skin cells and help regulate body temperature

7. Nervous tissue is scattered throughout the dermis

   1. Some dermal nerve cell processes conduct impulses out of the brain or spindle cord to muscles and glands of the skin

   2. Other dermal nerve cell processes conduct impulses away from sensory receptors in the skin and into the brain or spinal cord

6.2 Accessory Structures of the Skin: Epidermal Derivatives

1. Nails

   1. Nails are protective covers on the ends of fingers and toes

   2. They consist of keratinized epidermal cells

2. Hair follicles

   1. Hair covers nearly all regions of the skin

   2. Each hair develops from epidermal cells at the base of a tubelike hair follicle

   3. As newly formed cells develop and grow, older cells are pushed toward the surface and undergo keratinization

   4. A hair usually grows for a while, rests, and then is replaced by new hair

   5. Hair color is determined by genes that direct the type and amount of pigment in the hair cells

   6. A bundle of smooth muscle cells and one or more sebaceous glands are attached to each hair follicle

3. Skin glands

   1. Sebaceous glands secrete sebum, which softens and waterproofs both the skin and hair

   2. Sebaceous glands are usually associated with hair follicles

   3. Sweat glands are located in nearly all regions of the skin

   4. Each sweat gland consists of a coiled tube

   5. Merocrine sweat glands: located on the forehead, neck, back, palms, and soles, respond to elevated body temperature and produce sweat that is primarily water, but also contains salts and waste products

   6. Apocrine sweat glands: located in the axillary regions and groin, moisten the skin when a person is emotionally upset, scared, in pain, or sexually aroused and produce sweat containing proteins and lipids

   7. Ceruminous glands are modified apocrine glands of the ear canal and secrete ear wax

   8. Mammary glands are modified apocrine glands in the female breast that secrete milk

6.3 Skin Functions

The skin is vital to maintaining homeostasis by providing a protective covering, sensation, vitamin D synthesis, and regulation of body temperature

1. The skin is a protective covering and retards water loss

2. Within the skin are sensory receptors that detect pressure, touch, temperature and pain

3. Some skin cells produce vitamin D precursor

4. The skin helps regulate body temperature

   1. Heat production and loss

      1. Heat is a by-product of cellular respiration

      2. When body temperature rises above normal, more blood enters dermal blood vessels and the skin reddens

      3. Heat is lost to the outside by radiation, conduction, convection, and evaporation

      4. Sweat gland activity increases heat loss by evaporation

      5. When body temperature drops below normal, dermal blood vessels constrict, causing the skin to lose color, and merocrine sweat glands to become inactive

      6. If body temperature continues to drop, skeletal muscles contract; this increases cellular respiration, which produces additional heat

   2. Problems in temperature regulation

      1. Air can hold a limited volume of water vapor

      2. When the air is saturated with water, swear may fail to evaporate and body temperature may remain elevated

      3. Hypothermia is a body temperature above 38.5 C (101 F) It causes weakness, dizziness, nausea, headache, and a rapid, irregular pulse

      4. Hypothermia is lowered body temperature. It causes shivering, mental confusion, lethargy, loss of reflexes and consciousness, and eventually major organ failure.

6.4 Healing of Wounds and Burns

Skin injuries trigger inflammation. The affected area becomes red, warm, swollen, and tender

1. A cut in the epidermis is filled in by dividing epithelial cells

   1. Clots close deeper cuts, sometimes leaving a scar where connective tissue produces collagen fibers, forming an elevation above the normal epidermal surface

   2. Granulations form as part of the healing process in large, open wounds

2. Burns are classified by extent of tissue damage

   1. A superficial partial-thickness burn heals quickly with no scarring, although the area is warm and red

   2. A burn penetrating to the dermis is a deep partial-thickness burn, and results in blistering

   3. A full-thickness burn is the most severe, destroying the entire thickness of the skin and its accessory structures, and may require a skin graft

3. The “rule of nines” is used to estimate the extent  of the body’s affected surface in determining burn treatment

6.5 Life-Span Changes

1. Aging skin affects appearance as “age spots” or “liver spots” appear and grow, along with wrinkling and 

2. Thinning skin and fewer fibroblasts increase risk of bruising and slower wound healing

3. Older skin has a diminished ability to produce vitamin D, which is necessary for skeletal health

4. Due to changes in the number of sweat glands and shrinking capillary beds in the skin, older people are less able to tolerate the cold and cannot regulate heat well.

7.1 Overview of the Skeletal System

Skeleton means “dried framework.” Bones have many functions including support, movement, mineral storage, and blood cell production.

7.2 Bone Shape and Structure

Bones are grouped according to their shapes– long, short, flat, or irregular

1. Parts of the long bone

   1. Epiphyses at each end are covered with articular cartilage and articulate with other bones

   2. The shaft of the bone is called the diaphysis

   3. The region between the epiphysis and diaphysis is the metaphysis

   4. Except for the articular cartilage, a bone is covered by a periosteum

   5. Compact bone, has a continuous extracellular matrix with no gaps

   6. Spongy bone has irregular interconnecting spaces between bony plates called trabeculae

   7. Both compact and spongy bone are strong and resist bending

   8. The diaphysis contains a medullary cavity filled with marrow

2. Microscopic structure

   1. Osteocytes are in bony chambers called lacunae 

   2. Compact bone contains osteons held together by bone matrix

   3. Central canals in compact bone contain blood vessels that nourish the cells of osteons

   4. Perforating canals in compact bone connect central canals transversely and communicate with the bone’s surface and the medullary cavity

   5. Diffusion from the surface of thin bony plates nourishes cells of spongy bones

7.3 Bone Function

1. Support, protection, and movement

   1. Bone shape and form body structures

   2. Bones support and protect softer, underlying tissues

   3. Bones and muscles interact, producing movement

2. Blood cell formation

   1. At different stages in life, hematopoiesis occurs in the yolk sac, the liver, the spleen, and red bone marrow

   2. Red bone marrow houses developing red blood cells, white blood cells, and blood platelets

3. Inorganic salt storage

   1. The extracellular matrix of bone tissue contains abundant calcium phosphate in the form of hydroxyapatite

   2. When blood calcium ion concentration is low, osteoclasts resorb bone, releasing calcium salts

   3. When blood calcium ion concentration is high, osteoblasts are stimulated to form bone tissue and store calcium salts

   4. Bone stores small amounts of sodium, magnesium, potassium, and carbonate ions

   5. Bone tissues may accumulate lead, radium, or strontium

7.4 Bone Development, Growth, and Repair

1. Intramembranous Bones

   1. Flat bones of the skull, the clavicles, the sternum, and some facial bones are intramembranous bones.

   2. They develop from sheetlike layers of embryonic connective tissues (mesenchyme)

   3. Osteoblasts within the membranous layers form bone tissue

   4. Osteoblasts surrounded by extracellular matrix are called osteocytes

   5. Mesenchyme outside the developing bone gives rise to the periosteum

2. Endochondral Bones

   1. Most of the bones of the skeleton are endochondral 

   2. They develop as hyaline cartilage that bone tissue later replaces

   3. The primary ossification center appears in the diaphysis, whereas secondary ossification centers appear in the epiphyses

   4. An epiphyseal plate remains between the primary and secondary ossification centers

3. Growth at the epiphyseal plate

   1. An epiphyseal plate consists of layrs of cells, zone of resting cartilage, zone of proliferating cartilage, zone of hypertrophic cartilage, and zone of calcified cartilage

   2. The epiphyseal plates are responsible for bone lengthening

   3. Long bones continue to lengthen until the epiphyseal plates are ossified

   4. Growth in bone thickness is due to ossification beneath the periosteum

   5. The action of osteoclasts forms the medullary cavity

4. Homeostasis of bone tissue

   1. Osteoclasts and osteoblasts continually remodel bone

   2. The total mass of bone remains nearly constant

5. Factors affecting bone development, growth, and repair

   1. Deficiencies of vitamin A, C, or D result in abnormal bone development

   2. Insufficient secretion of pituitary growth hormone may result in dwarfism; excessive secretion may result in gigantism

   3. Thyroxine stimulates replacement of cartilage in the epiphyseal plates with bone

   4. Male and female sex hormones promote bone formation and stimulate ossification of the epiphyseal plates

   5. Physical stress stimulates bone growth

7.5 Skeletal Organization

1. Number of bones

   1. Usually 206, but number may vary

   2. Extra bones include sutural bones and sesamoid bones

2. Divisions of the skeleton

   1. The skeleton can be divided into axial and appendicular portions

   2. The axial skeleton consists of the skull, hyoid bone, vertebral column, and thoracic cage

   3. The appendicular skeleton consists of the pectoral girdle, upper limbs, pelvic girdle, and lower limbs

7.6 Skull

The skull consists of 22 bones, which include 8 cranial bones and 14 facial bones

1. Cranium

   1. The cranium encloses and protects the brain and provides attachments for muscles

   2. Some cranial bones contain air-filled paranasal sinuses that help reduce the weight of the skull

   3. Cranial bones include the frontal bone, parietal bones, occipital bone, temporal bones, sphenoid bone, and ethmoid bone

2. Facial skeleton

   1. Facial bones form the basic shape of the face and provide attachments for muscles 

   2. Facial bones include the maxillae palatine bones zygomatic bones, lacrimal bones, nasal bones, vomer, inferior nasal conchae, and mandible

3. Infantile skull

   1. Incompletely developed bones, connected by fontanels, enable the infantile skull to change shape slightly during childbirth

   2. Infantile skull bones are thin, somewhat flexible and less easily fractured

7.7 Vertebral Column

The vertebral column extends from the skull to the pelvis and protects the spinal cord. It is composed of vertebrae separated by intervertebral discs. An infant has 33 vertebral bones and an adult has 26. The vertebral column has four curvatures– cervical, thoracic, lumbar, and sacral

1. A typical vertebrae

   1. A typical vertebra consists of a body, pedicles, laminae, spinous process, transverse, processes, and superior and inferior articular processes

   2. Notches on the upper and lower surfaces of the pedicles on adjacent vertebrae form intervertebral foramina through which spinal nerves pass

2. Cervical vertebrae

   1. Cervical vertebrae comprise the bones of the neck

   2. Transverse processes have transverse foramina

   3. The atlas (c1) supports the head

   4. The dens of the axis (c2) provides a pivot for the atlas that allows the head to turn from side to side

3. Thoracic vertebrae

   1. Thoracic vertebrae are larger than cervical vertebrae

   2. Their transverse processes project posteriorly at sharp angles

   3. Their spinous processes slope downward, and facets on the sides of the vertebral bodies articular with the heads of ribs

4. Lumbar vertebrae

   1. Vertebral bodies of lumbar vertebrae are large and strong

   2. Their transverse processes project laterally, and trier spinous processes project posteriorly nearly horizontally

5. Sacrum

   1. The sacrum, formed of five fused vertebrae, is a triangular structure that has rows of dorsal sacral foramina

   2. It is united with the hip bones at the sacroiliac joints

   3. The sacral promontory provides a guide for determining the size of the pelvis

6. Coccyx

   1. The coccyx, composed of four fused vertebrae, forms the lowest part of the vertebral column

   2. It acts as a shock absorber when a person sits and is an attachment for muscles of the pelvic floor

7.8 Thoracic Cage

The thoracic cage includes the ribs, thoracic vertebrae, sternum, and costal cartilages that attach the ribs to the sternum. It supports the pectoral girdle and upper limbs, protects viscera, and functions in breathing

1. Ribs

   1. Twelve pairs of ribs are attached to the twelve thoracic vertebrae

   2. Costal cartilages of the true ribs join the sternum directly; those of the false ribs join indirectly or not at all

   3. A typical rib has a shaft, head, and tubercles that articulate with the thoracic vertebrae

2. Sternum

   1. The sternum consists of a manubrium, body, and xiphoid process

   2. It articulates with costal cartilages of the ribs and the clavicles

7.9 Pectoral Girdle

The pectoral girdle is composed of 2 clavicles and 2 scapulae. It forms an incomplete ring that supports the upper limbs and provides attachments for muscles that move the upper limbs

1. Clavicle

   1. Each clavicle is a rodlike bone that runs horizontally between the sternum and shoulder

   2. They help hold the shoulders in place and provide attachments for muscles

2. Scapula

   1. Each scapula is a broad, triangular bone with a body, spine, acromion process, coracoid process, glenoid cavity, supraspinous and infraspinous fossae, superior border, axillary border, and vertebral border

   2. Each articulates with the humerus of each upper limb and provides attachments for muscles of the upper limbs and chest

7.10 Upper Limb

Bones of the upper limb provide the framework for the limb and provide the attachments for muscles that move the limb

1. Humerus

   1. The humerus extends from the scapula to the elbow

   2. It has a head, greater tubercle, lesser tubercle, intertubercular sulcus, anatomical neck, surgical neck, deltoid tuberosity, capitulum, trochlea, epicondyles, coronoid fossa, and olecranon fossa

2. Radius

   1. The radius is on the thumb side of the forearm between the elbow and wrist

   2. It has a head, radial tuberosity, styloid process, and ulnar notch

3. Ulna

   1. The ulna, on the medial side of the forearm, is longer than the radius and overlaps the humerus posteriorly

   2. It has a trochlear notch, olecranon process, coronoid process, head, styloid process, and radial notch

4. Hand

   1. The wrist has 8 carpals

   2. The palm has 5 metacarpals

   3. The 5 fingers have 14 phalanges

7.11 Pelvic Girdle

The pelvic girdle consists of two hip bones that articulate with each other anteriorly and with the sacrum posteriorly. THe sacrum, coccyx, and pelvic girdle form the pelvis. THe girdle provides support for body weight and attachments for muscles and protects visceral organs

1. Hip Bones: each hip bone consists of an illium, ischium, and pubis, fused in the region of the acetabulum

   1. Ilium

      1. The ilium, the largest portion of the hip bone, joins the sacrum at the sacroiliac joint

      2. It has an iliac crest with anterior and posterior iliac spines and iliac fossae

   2. Ischium

      1. The ischium is the lowest portion of the hip bone

      2. It has an ischial tuberosity and ischial spine

   3. Pubis

      1. The pubis is the anterior portion of the hip bone

      2. Pubic bones are joined anteriorly at the pubic symphysis

2. True pelvis versus false pelvis

   1. The false pelvis is superior to the pelvic brim; the true pelvis is inferior to the pelvic brim

   2. The false pelvis helps support abdominal organs; the true pelvis functions as a birth canal.

3. Differences between a male and female pelvis

   1. Differences between the male and female pelves reflect the function of the female pelvis as a birth canal

   2. Usually the female pelvis is more flared; pubic arch is broader; distance between the ischial spines and the ischial tuberosities is greater; and sacral curvature is shorter.

7.12 Lower Limb

Bones of the lower limb provide the framework for the limb and provide the attachments for muscles that move the limb

1. Femur

   1. The femur extends from the hip to the knee

   2. It has a head, fovea capitis, neck, greater trochanter, lesser trochanter, linea aspera, lateral condyle, and medial condyle

2. Patella

   1. The patella is a sesamoid bone in the tendon that passes anteriorly over the knee.

   2. It controls the angle of this tendon and functions in lever actions associated with lower limb movements.

3. Tibia

   1. The tibia is located on the medial side of the leg

   2. It has medial and lateral condyles, tibial tuberosity, anterior crest, and medial malleolus.

   3. It articulates with the talus of the ankle

4. Fibula

   1. The fibula is located on the lateral side of the tibia

   2. It has a head that proximally articulates with the tibia and distally the lateral malleolus articulates with the ankle, but the fibula does not bear body weight.

5. Foot

   1. The ankle includes the talus, the calcaneus, and five other tarsals

   2. The instep has 5 metatarsals

   3. The five toes have 14 phalanges

7.13 Life Span Changes

Aging-associated changes in the skeleton are apparent at the cellular and whole-body levels

1. Incremental decrease in height begins at about age thirty

2. gradually , bone loss exceeds bone replacement

   1. In the first decade following menopause, bone loss occurs more rapidly in women or premenopausal women. By age seventy, both sexes are losing bone at about the same rate. 

   2. Aging increases risk of bone fractures.

8.1 Types of Joints 

Joints are classified according to structure (the type of tissue that binds the bones) and function (the degree of movement possible)

1. Fibrous Joints

   1. There are fibrous joints are tightly fastened to each other by a layer of dense connective tissue with many collagen fibers.

   2. There are 3 types of fibrous joints

      1. A syndesmosis has bones bound by long connective tissue fibers

      2. A suture is where flat bones are united by a thin layer of connective tissue and are interlocked by a set of bony processes

      3. A gomphosis is formed by the union of a cone shaped bony process with a bony socket

2. Cartilaginous joints

   1. A layer of cartilage holds together bones of cartilaginous joints

   2. There are 2 types of cartilaginous joints

      1. A synchondrosis occurs where bones are united by hyaline cartilage that may disappear as a result of bone growth

      2. A symphysis is found where articular surfaces of the bone are covered by hyaline cartilage and the bones are connected by a pad of fibrocartilage

3. Synovial joints 

   1. Synovial joints have more complex structure than other types of joints

      1. Articular cartilage covers articular ends of bones in a synovial joint

      2. A joint capsule strengthened by ligaments hold bones together

      3. A synovial membrane that secretes synovial fluid lines the inner layer of a joint capsule

      4. Synovial fluid moistens, provides nutrients, and lubricates the articular surfaces

      5. Menisci divide some synovial joints into compartments

      6. Some synovial joints have fluid filled bursae

         1. Most bursae are located between the skin and underlying bony prominences

         2. Bursae cushion and aid movements of tendones over bony parts

         3. Bursae are named according to their locations

   2. There are 6 major types of synovial joints

      1. In  ball-and-socket joint, the globular head of a bone fits into the cup-shaped cavity of another bone.

         1. These joints permit a wide variety of movements

         2. The hip and shoulder are ball-and-socket joints

      2. A condylar join consists of an ovoid condyle of one bone fitting into an elliptical cavity of another bone

         1. This joint permits movement in two planes

         2. The joints between the metacarpals and phalanges are condylar

      3. Articular surfaces of plane joints are nearly flat

         1. These joints permit the articular surfaces to slide back and forth

         2. Most of the joints of the wrist and ankle are plane joints.

      4. In a hinge joint, the convex surface of one bone fits into the concave surface of another bone.

         1. This joint permits movement in one plane only.

         2. The elbow and the joints of the phalanges are the hinge type

      5. In a pivot joint, a cylindrical surface of one bone rotates within a ring of bone and ligament

         1. This joint permits rotational movement

         2. The articulation between the proximal ends of the radius and the ulna is a pivot joint

      6. A saddle joint forms between bones that have complementary surfaces with both concave and convex regions. 

         1. This joint permits a variety of movements

         2. The articulation between the carpal and metacarpal of the thumb is a saddle joint.

8.2 Types of Joint Movements

1. Muscles acting at synovial joints produce movements in different directions and in different planes

2. Joint movements include flexion, extension, dorsiflexion, plantar flexion, abduction, adduction, rotation, circumduction, supination, pronation, eversion, inversion, protraction, retraction, elevation, and depression.

   1. Flexion: movement decreasing the angle between bones at a joint

   2. Extension: movement increasing the angle between parts at a joint

   3. Dorsiflexion: ankle movement that moves the anterior portion of the foot closer to the shin

   4. Plantar flexion: ankle movement that moves the anterior portion of the foot farther from the shin

   5. Abduction: movement of a body part away from the midline

   6. Adduction: movement of a body part toward the midline

   7. Rotation: movement turning a body part on its longitudinal axis

   8. Circumduction: movement of a body part, such as a limb, so that the end follows a circular path

   9. Supination: upward or forward rotation of the palm

   10. Pronation: downward or backward rotation of the palm

   11. Eversion: turning the plantar surface of the foot outward, away from the midline

   12. Inversion: turning the plantar surface of the foot inward, toward midline

   13. Protraction: forward movement of a body part

   14. Retraction: movement of a part toward the back

   15. Elevation: upward movement of a body part

   16. Depression: downward displacement

8.3 Examples of Synovial Joints

1. Shoulder Joint

   1. The shoulder joint is a ball-and-socket joint that consists of the head of the humerus and the glenoid cavity of the scapula.

   2. A cylindrical joint capsule envelops the joint

      1. The capsule is loose and by itself cannot keep the articular surfaces together

      2. It is reinforced by surrounding muscles and tendons

   3. Several ligaments help prevent displacement of the bones

   4. Several bursae are associated with the shoulder joint

   5. Its parts are loosely attached, so the shoulder joint permits a wide range of movement.

2. Elbow Joint

   1. The elbow has a hinge joint between the humerus and the ulna and a plane joint between the humerus and the radius

   2. Collateral ligaments reinforce the joint capsule

   3. A synovial membrane partially divides the joint cavity into 2 portions

   4. The joint between the humerus and the ulna permits flexion and extension only.

3. Hip joint

   1. The hip joint is a ball-and-socket joint between the femur and the hip bone

   2. A ring of fibrocartilage deepens the cavity of the acetabulum

   3. The articular surfaces are held together by a heavy joint capsule reinforced by ligaments

   4. The hip joint permits a wide variety of movements

4. Knee joint 

   1. The knee joint includes a modified hinge joint between the femur and the tibia and a plane join between the femur and the patella

   2. Ligaments and tendons strengthen the thin joint capsule

   3. Several ligaments, some in the joint capsule, bind the articular surfaces of the joint bones

   4. Two menisci separate the articulating surfaces of the femur and the tibia

   5. Several bursae are associated with the knee joint

   6. The knee joint permits flexion and extension; when the knee is flexed, some lower limb rotation is possible.

8.4 Life-Span Changes

1. Joint stiffness is often the earliest sign of aging

   1. Collagen changes causes the feeling of stiffness

   2. Regular exercise can lessen the effects

2. Fibrous joints are the first to begin to change and strengthen over a lifetime

3. Synchondroses of the long bones disappear with growth and development

4. Changes in the symphysis joints of the vertebral column diminish flexibility and decrease height

5. Over time, synovial joints lose elasticity.

9.1 Muscles

Muscles are organs made of cells that are specialized to generate forces. There are three types of muscle tissue: skeletal, smooth, and cardiac

9.2 Structure of a Skeletal Muscle

Skeletal muscles are composed of nervous, vascular, and various other connective tissues, as well as skeletal muscle tissue.

1. Connective tissue coverings

   1. Fascia covers each skeletal muscle

   2. Other connective tissues surround cells and groups of cells within the muscle’s structure (epimysium, perimysium, endomysium).

   3. Fascia is part of a complex network of connective tissue that extends throughout the body.

2. Skeletal muscle fibers

   1. Each skeletal muscle fiber is a single muscle cell, the unit of contraction

   2. Muscle fibers are cylindrical cells with many nuclei

   3. The cytoplasm contains mitochondria, sarcoplasmic reticulum, and myofibrils of actin and myosin.

   4. The arrangement of the actin and myosin filaments causes striations forming repeating patterns of sarcomeres (I bands, Z lines, A bands, Hzone, and M line)

   5. Troponin and tropomyosin molecules associate with actin filaments

   6. Transverse tubules extend from the cell membrane into the cytoplasm and are associated with the cisternae of the sarcoplasmic reticulum

9.3 Skeletal Muscle Contraction

Muscle fiber contraction results from a sliding movement of actin and myosin filaments overlapping that shortens the muscle fiber.

1. Neuromuscular junction

   1. The functional connection between a neuron and another cell is a synapse. The neuromuscular junction is a synapse.

   2. Motor neurons stimulate muscle fibers to contract

   3. The motor end plate of a muscle fiber lies on one side of a neuromuscular junction

   4. In response to an action potential, the end of a motor neuron axon releases a neurotransmitter, which diffuses across the junction and stimulates the muscle fiber

2. Stimulus for contraction

   1. Acetylcholine released from the end of a motor neuron axon stimulates a muscle fiber

   2. Stimulation causes a muscle fiber to conduct an impulse that travels over the surface of the sarcolemma and reaches the deep parts of the fiber by means of the transverse tubules

3. Excitation-contraction coupling

   1. In response to stimulation the sarcoplasmic reticulum releases calcium ions

   2. Calcium ions combine with troponin, causing the tropomyosin to shift and expose active sites on the actin for myosin binding

   3. Cross-bridges form between myosin and actin, and the actin filaments move inward, shortening the sarcomere

4. The sliding filament model of muscle contraction

   1. The sarcomere is a functional unit of the skeletal muscle

   2. When the overlapping thick and thin myofilaments slide past one another, the sarcomeres shorten. The muscles contract.

5. Cross-bridge cycling

   1. A myosin head can attach to an actin binding site to form a cross-bridge which pulls on the actin filament, the myosin head can then release the actin and attach to another active binding site farther down the actin filament and pull again

   2. The breakdown of ATP releases energy that provides the repetition of the cross-bridge cycle

6. Relaxation

   1. Acetylcholinesterase rapidly decomposes acetylcholine remaining in the synaptic cleft, preventing continuous stimulation of a muscle fiber

   2. The muscle fiber relaxes when calcium ions are transported back into the sarcoplasmic reticulum

   3. Cross-bridge linkages break and do not reform– the muscle fiber relaxes

7. Energy sources for contraction

   1. ATP supplies the energy for muscle fiber contraction

   2. Creatine phosphate stores energy that can  be used to synthesize ATP as it is decomposed

   3. Active muscles require cellular respiration for energy

8. Oxygen supply and cellular respiration

   1. Anaerobic reactions of cellular respiration yield few ATP molecules whereas aerobic reactions of cellular respiration provide many ATP molecules

   2. Hemoglobin in red blood cells carries oxygen from the lungs to body cells

   3. Myoglobin in muscle cells temporarily stores some oxygen

9. Oxygen debt

   1. During rest or moderate exercise, oxygen is sufficient to support the aerobic reactions of cellular respiration

   2. During strenuous exercise, oxygen deficiency may develop, and lactic acid may accumulate as a result of the anaerobic reactions of cellular respiration

   3. The oxygen debt includes the amount of oxygen required to react accumulated lactic acid to form glucose and to restore supplies of ATP and creatine phosphate

10. Muscle fatigue

    1. A fatigued muscle loses its ability to contract

    2. The causes of muscle fatigue are not fully understood

    3. Athletes usually have an increased ability to supply oxygen and nutrients to muscles

11. Heat production

    1. Muscular contraction generates body heat

    2. Most of the energy released by cellular respiration is lost as heat.

9.4 Muscular Responses 

1. Threshold stimulus is the minimal stimulus needed to elicit a muscular contraction

2. Recording of a muscle contraction

   1. A twitch is a single, short contraction of a muscle fiber

   2. A myogram is a recording of the contraction of an electrically stimulated isolated muscle or muscle fiber.

   3. The latent period is the time between stimulus and responding contraction

   4. The length to which a muscle is stretched before stimulation affects the force it will develop

      1. Normal activities occur at optimal length

      2. Too long or too short decreases force

   5. Sustained contractions are more important than twitch contractions in everyday activities

3. Summation

   1. A rapid series of stimuli may produce summation of twitches and sustained contraction

   2. At higher frequencies of stimulation, contraction with little time for relaxation is called partial tetany

   3. Forceful, sustained contraction without any relaxation is called complete (fused) tetany

4. Recruitment of motor units

   1. One motor neuron and the muscle fibers associated with it constitute a motor unit

   2. Muscles whose motor units have few muscle fibers produce finer movements

   3. Motor units respond in an all-or-none manner

   4. At low intensity of stimulation, other motor units are recruited until the muscle contracts with maximal tension

5. Sustained contractions

   1. Tetanic contractions are common in everyday activities

   2. Even when a whole muscle appears at rest, some of its fibers undergo sustained contraction. This is called muscle tone.

6. Types of contractions

   1. One type of contraction called isotonic occurs when a muscle contracts and it ends are pulled closer together. Because the muscle shortens, it is called a concentric contraction. 

   2. In another type of isotonic contraction the force a muscle generates is less than that required to move or lift an object. This lengthening contraction is an eccentric contraction

   3. When a muscle contracts but its attachments do not move, the contraction is isometric.

   4. Most body movements involve both isometric and isotonic contractions

7. Fast- and slow-twitch muscle fibers

   1. The speed of contraction is related to a muscle’s specific function

   2. Slow-contraction, or red muscles can generate ATP fast enough to keep up with ATP breakdown and can contract for long periods

   3. Fast-contracting, or white muscles have reduced ability to carry on the aerobic reactions of cellular respiration and tend to fatigue rapidly.

9.5 Smooth Muscle

The contractile mechanisms of smooth and cardiac muscle are similar to those of skeletal muscle

1. Smooth muscle cells

   1. Smooth muscle cells contain filaments of myosin and actin, but these filaments are not organized into myofibrils

   2. They lack transverse tubules, and the sarcoplasmic reticula are not well developed

   3. Types include multiunit smooth muscle and visceral smooth muscle

   4. Visceral smooth muscle displays rhythmicity

   5. Peristalsis aids movement of material through hollow organs

2. Smooth muscle contractions

   1. In smooth muscle, calmodulin binds to calcium ions and activates the contraction mechanism

   2. Both acetylcholine and norepinephrine are neurotransmitters for smooth muscles

   3. Hormones and stretching affect smooth muscle contractions

   4. With a given amount of energy, smooth muscle can maintain a contraction longer than skeletal muscle

   5. Smooth muscle can change length without changing tautness

9.6 Cardiac Muscle

1. Cardiac muscle contracts for a longer time than skeletal muscle because transverse tubules supply extra calcium ions

2. Intercalated discs connect the ends of cardiac muscle cells and hold the cells together

3. A network of cells contracts as a unit and responds to stimulation in an all-or-none manner

4. Cardiac muscle is self-exciting, rhythmic, and remains refractory to further stimulation until a contraction is completed

9.7 Skeletal Muscle Actions

1. Body movement

   1. Bones and muscles function together as levers

   2. A lever consists of a rod, a fulcrum (pivot), a resistance, and a force that supplies energy

   3. Parts of a first-class lever are arranged resistance-fulcrum-force; of a second-class lever, fulcrum-resistance-force; and of a third-class lever, resistance-force-fulcrum

2. Origin and insertion

   1. The less moveable end of an attachment of a skeletal muscle to a bone is its origin, and the more movable end is its insertion

   2. The origin may also be described as more superior or medial, with the insertion more distal or inferior

   3. Some muscles have more than one origin or insertion

3. Interaction of skeletal muscles

   1. Skeletal muscles function in groups 

   2. A muscle that causes a specific movement is an agonist for that movement; antagonists can resist a movement; synergists work together to perform a specific movement

   3. Smooth movements depend upon antagonists giving way to the actions of agonists

9.8 Major Skeletal Muscles

Muscle names often describe sizes, shapes, locations, actions, number of attachments, or direction of fibers

1. Muscles of facial expression

   1. These muscles lie beneath the skin of the face and scalp and are used to communicate feelings through facial expression

   2. They include the epicranius, orbicularis oculi, orbicularis oris, buccinator, zygomaticus major, zygomaticus minor, and platysma

2. Muscles of mastication

   1. These muscles are attached to the mandible and are used in chewing

   2. They include the masseter, temporalis, medial pterygoid, and lateral pterygoid

3. Muscles that move the head and vertebral column

   1. Muscles in the neck and back move the head

   2. They include the sternocleidomastoid, splenius capitis, semispinalis capitis, scalenes, quadratus lumborum, and erector spinae.

4. Muscles that move the pectoral girdle

   1. Most of these muscles connect the scapula to nearby bones and are closely associated with muscles that move the arm

   2. They include the trapezius, rhomboid major, rhomboid minor, levator scapulae, serratus anterior, and pectoralis minor.

5. Muscles that move the arm

   1. These muscles connect the humerus to various regions of the pectoral girdle, ribs, and vertebral column

   2. They include the coracobrachialis, pectoralis major, teres major latissimus dorsi, supraspinatus, deltoid, subscapularis, infraspinatus, and teres minor.

6. Muscles that move the forearm

   1. These muscles connect the radius and ulna to the humerus and pectoral girdle

   2. They include the biceps brachii, brachialis, brachioradialis, triceps brachii, supinator, pronator teres, and pronator quadrus.

7. Muscles that move the hand

   1. These muscles arise from the distal end of the humerus and form the radius and ulna.

   2. They include the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor digitorum profundus, flexor digitorum superficialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digitorum

   3. An extensor retinaculum forms sheaths for tendons of the extensor muscles

8. Muscles of the abdominal wall

   1. These muscles connect the rib cage and vertebral column to the pelvic girdle

   2. They include the external oblique, internal oblique, transversus abdominis, and rectus abdominis.

9. Muscles of the pelvic floor and perineum

   1. These muscles form the floor of the pelvic cavity and fill the space of the pubic arch

   2. They include the levator ani, coccygeus, deep transversus perinei, superficial transversus perinei, bulbospongiosus, ischiocavernosus, external urethral sphincter, and external anal sphincter.

10. Muscles that move the thigh 

    1. These muscles are attached to the femur and to some part of the pelvic girdle

    2. They include the psoas major, iliacus, gluteus maximus, gluteus medius, gluteus minimus, piriformis, tensor fasciae latae, pectineus, adductor brevis, adductor longus, adductor magnus, and gracilis

11. Muscles that move the leg

    1. These muscles connect the tibia or fibula to the femur or pelvic girdle

    2. They include the biceps femoris, semitendinosus, semimembranosus, sartorius rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius

12. Muscles that move the foot

    1. These muscles attach the femur, tibia, and fibula to various bones of the foot

    2. They include the tibialis anterior, fibularis tertius, extensor digitorum longus, extensor hallucis longus, gastrocnemius, soleus, plataris, flexor digitorum longus, tibialis posterior, and fibularis longus

    3. Retinacula form sheaths for tendons passing to the foot

9.9 Life-Span Changes

1. Beginning in one’s forties, supplies of ATP, myoglobin, and creatine phosphate begin to decline.

2. By age eighty, muscle mass may be halved. Reflexes slow. Adipose cells and connective tissue replace some muscle tissue

3. Exercise is beneficial in maintaining muscle function.

17.1 General Characteristics of the Digestive System 

Digestion is the process of mechanically and chemically breaking down foods so that they can be absorbed. The digestive system consists of an alimentary canal and several accessory organs that carry out the processes of ingestion, propulsion, digestion, absorption, and defecation. 

1. Structure of the alimentary canal wall

   1. The wall consists of four layers

   2. These layers include the mucosa, submucosa, muscularis, and serosa

2. Movements of the alimentary canal wall

   1. Motor functions include mixing and propelling movements

   2. Peristalsis is responsible for propelling movements

   3. The wall of the tube undergoes receptive relaxation just ahead of a peristaltic wave

3. Innervation of the alimentary canal wall

   1. The tube is innervated by branches of the sympathetic and parasympathetic divisions of the autonomic nervous system

   2. Parasympathetic impulses generally increase digestive activities; sympathetic impulses generally inhibit digestive activities.

   3. Sympathetic impulses contract certain sphincter muscles, controlling movement of digesting food through the alimentary canal.

17.2 Mouth

The mouth is adapted to receive food and begin digestion by mechanically breaking up solid particles (mastication). It also serves as an organ of speech and sensory perception. 

1. Cheeks and lips

   1. Cheeks form the lateral walls of the mouth

   2. Lips are highly mobile and have a variety of sensory receptors useful in judging the characteristics of food.

2. Tongue

   1. The tongue is a thick, muscular organ that mixes food with saliva and moves it toward the pharynx

   2. The rough surface of the tongue handles food and has taste buds

   3. Lingual tonsils are located on the root of the tongue

3. Palate

   1. The palate comprises the roof of the mouth and includes hard and soft portions

   2. The soft palate, including the uvula, closes the opening to the nasal cavity during swallowing

   3. Palatine tonsils are located on either side of the tongue in the back of the mouth

   4. Tonsils consist of lymphatic tissues.

4. Teeth 

   1. Two sets of teeth develop in sockets of the mandibular and maxillary bones

   2. There are 20 primary and 32 secondary teeth

   3. Teeth mechanically break food into smaller pieces, increasing the surface area exposed to digestive actions

   4. Different types of teeth are adapted to handle foods in different ways, such as biting, grasping, or grinding. 

   5. Each tooth consists of a crown and root and is composed of enamel, dentin, pulp, nerves, and blood vessels. 

   6. A tooth is attached to the alveolar process by the periodontal ligament

17.3 Salivary Glands

Salivary glands secrete saliva, which moistens food, helps bind food particles, begins chemical digestion of carbohydrates, makes taste possible, helps cleanse the mouth, and regulates pH in the mouth

1. Salivary secretions

   1. Salivary glands include serous cells that secrete salivary amylase and mucous cells that secrete mucus

   2. Parasympathetic impulses stimulate the secretion of a large volume of watery saliva

2. Major salivary glands

   1. The parotid glands are the largest, and they secrete saliva rich in amylase

   2. The submandibular glands in the floor of the mouth produce viscous saliva containing amylase

   3. The sublingual glands in the floor of the mouth primarily secrete mucus

17.4 Pharynx and Esophagus 

The pharynx and esophagus serve as passageways

1. Structure of the pharynx

   1. The pharynx is divided into a nasopharynx, oropharynx, and laryngopharynx

   2. The muscular walls of the pharynx contain fibers in circular and longitudinal groups

2. Swallowing mechanism 

   1. Swallowing (deglutition) occurs in three stages

      1. Food is mixed with saliva and forced into the pharynx

      2. Involuntary reflex actions move the food into the esophagus

      3. Peristalsis transports food in the esophagus to the stomach

   2. Swallowing reflexes momentarily inhibit breathing

3. Esophagus

   1. The esophagus passes through the mediastinum and penetrates the diaphragm

   2. The lower esophageal sphincter, at the distal end of the esophagus, helps prevent regurgitation of food from the stomach.

17.5 Stomach

The stomach receives food, mixes it with gastric juice, carries on a limited amount of absorption, and moves food into the small intestine

1. Parts of the stomach

   1. The stomach is divided into the cardia, fundus, body, and pylorus

   2. The pyloric sphincter serves as a valve between the stomach and the small intestine

2. Gastric secretions

   1. Gastric glands secrete gastric juice

   2. Alkaline mucus protects the inner stomach wall

   3. Gastric juice contains mucus, chemical messengers, pepsin (begins digestion of proteins), hydrochloric acid lipase, and intrinsic factor

3. Regulation of gastric secretion

   1. Parasympathetic impulses and the hormone gastrin enhance gastric secretion

   2. There are 3 stages of gastric secretion

      1. The cephalic phase is the though and sense of foods before they reach the stomach

      2. The gastric phase occurs when food enters the stomach

      3. The intestinal phase occurs when food begins to leave the stomach and enter the small intestine; the small intestine reflexively inhibits gastric secretion;  the hormone cholecystokinin acts on the stomach to decrease gastric activity.  ` 

4. Gastric Absorption

   1. The stomach is not well adapted for absorption

   2. A few substances such as water and other small molecules are absorbed through the stomach wall

5. Mixing and emptying actions

   1. As the stomach fulls, its wall stretches but its internal pressure remains unchanged

   2. Mixing movements aid in producing chyme; peristaltic waves move chyme into the pylorus

   3. The muscular wall of the pylorus regulates chyme movement into the small intestine

   4. The rate of emptying depends on the fluidity of the chyme and the type of food present

   5. The upper part of the small intestine fills, and the enterogastric reflex inhibits peristalsis in the stomach.

6. Vomiting

   1. Vomiting results from a complex reflex that has many stimuli

   2. Motor responses ultimately increase abdominal pressure to force contents upward and out. 

17.6 Pancreas

The pancreas is closely associated with the duodenum

1. Structure of the pancreas

   1. It produces pancreatic juice secreted into a pancreatic duct

   2. The pancreatic duct leads to the duodenum

2. Pancreatic juice

   1. Pancreatic juice contains enzymes that can break down carbohydrates, proteins, fats, and nucleic acids

   2. Pancreatic juice has a high bicarbonate ion concentration that helps neutralize chyme ansd causes the intestinal contents to be alkaline

3. Regulation of pancreatic secretion

   1. Secretin from the duodenum stimulates the release of pancreatic juice that contains few digestive enzymes but has a high bicarbonate ion concentration

   2. Cholecystokinin from the intestinal wall stimulates the release of pancreatic juice that has a high concentration of digestive enzymes

17.7 Liver and Gallbladder

The liver is located in the upper-right quadrant of the abdominal cavity

1. Liver structure

   1. The liver is a highly vascular organ, enclosed in a fibrous capsule, and divided into lobes.

   2. Each lobe consists of hepatic lobules, the functional units of the liver

   3. Bile from the lobules is carried by bile ductules to hepatic ducts that unite to form the common hepatic duct

2. Liver functions

   1. The liver has many functions It removes toxic substances from the blood (detoxifies); metabolizes carbohydrates, lipids, and proteins; stores some substances; and secretes bile

   2. Bile is the only liver secretion that directly affects digestion

3. Composition of bile

   1. Bile contains bile salts, bile pigments, cholesterol, and electrolytes

   2. Only the bile salts have digestive functions

   3. Bile pigments are products of red blood cell breakdown

4. Gallbladder

   1. The gallbladder stores bile between meals

   2. A sphincter muscle controls release of bile from the bile duct

   3. Gallstones may form within the gallbladder

5. Regulation of bile release

   1. Cholecystokinin from the small intestine stimulates bile release

   2. The sphincter muscle at the base of the bile duct relaxes as a peristaltic wave as the duodenal wall approaches

6. Functions of bile salts

   1. Bile salts emulsify fats and aid in the absorption of fatty acids, cholesterol, and certain vitamins

   2. Bile salts are reabsorbed in the small intestine

17.8 Small Intestine

The small intestine extends from the pyloric sphincter to the large intestine. It receives secretions from the pancreas and liver, completes digestion of nutrients, absorbs the products of digestion, and transports the residues to the large intestine

1. Parts of the small intestine

   1. The small intestine consists of the duodenum, jejunum, and ileum

   2. The small intestine is suspended from the posterior abdominal wall by mesentery

2. Structure of the small intestinal wall

   1. The wall is lined with villi that greatly increase the surface area of the intestinal lining, aiding absorption of digestive products

   2. Microvilli on the free ends of epithelial cells increase the surface area even more

   3. Intestinal glands are located between the villi

   4. Circular folds in the lining of the intestinal wall also increase its surface area

3. Secretions of the small intestine

   1. Intestinal glands secrete a watery fluid that does not have digestive enzymes but provides a vehicle for moving chyme to the villi

   2. Digestive enzymes embedded in the surfaces of microvilli break down molecules of sugars, proteins, and fats

4. Regulation of small intestinal secretion

   1. Secretion is stimulated by chyme and parasympathetic reflexes stimulated by sitension of the small intestinal wall

5. Absorption in the small intestine

   1. Blood capillaries in the villi absorb monosaccharides and amino acids

   2. Fatty acids diffuse into small intestinal epithelial cells where they are processed to form chylomicrons, which enter the lacteals of the villi

   3. Blood capillaries in the ville also absorb electrolytes and water

6. Movements of the small intestine

   1. Movements include mixing by segmentation and peristalsis

   2. Overdistension or irritation may stimulate a peristaltic rush and result in diarrhea

   3. The ileocecal sphincter controls movement of the intestinal contents from the small intestines into the large intestine.

17.9 Large Intestine

The large intestine absorbs water and electrolytes and forms and stores feces

1. Parts of the large intestine

   1. The large intestine consists of the cecum, colon, rectum, and anal canal

   2. The colon is divided into ascending, transverse, descending, and sigmoid portions

2. Structure of the large intestinal wall

   1. The large intestinal wall resembles the wall in other parts of the alimentary canal

   2. The large intestinal wall has a unique layer of longitudinal muscle fibers, arranged in district bands, that extend the entire length of the colon

3. Functions of the large intestine

   1. The large intestine has little digestive function, although it secretes mucus

   2. Mechanical stimulation and parasympathetic impulses control the rate of mucus secretion

   3. The large intestine absorbs water and electrolytes

   4. Many bacteria inhabit the large intestine, where they break down some indigestible substances, such as cellulose, and synthesize vitamin K, B12, thiamine, and riboflavin

4. Movements of the large intestine

   1. Movements are similar to those in the small intestine

   2. Mass movements occur two to three times each day

   3. A reflex stimulates defecation

5. Feces

   1. The large intestine forms and stores feces

   2. Feces consists of water, undigested material, mucus, and bacteria

   3. The color of feces is due to bile pigments that have been altered by bacterial action

17.10 Life Span Changes

1. Older people sometimes do not chew food thoroughly because thinning enamel makes teeth more sensitive to hot and cold foods, gums recede, and teeth may loosen

2. Slowing peristalsis in the digestive tract may cause heartburn and constipation

3. Aging affects nutrient absorption in the small intestine

4. Accessory organs to digestion also age, but not necessarily in ways that affect health.

18.1 Overview of Nutrition and Metabolism

Food is broken down into the usable nutrients, amino acids, monosaccharides, and fatty acids. From the extraction of energy, they are used to fuel all cellular processes.

18.2 Carbohydrates

Carbohydrates are organic compounds primarily used to supply cellular energy

1. Carbohydrate Sources

   1. Carbohydrates are ingested in a variety of forms

   2. Polysaccharides, disaccharides, and monosaccharides are carbohydrates.

   3. Cellulose is a polysaccharide that human enzymes cannot digest, but it provides bulk that facilitates movement of intestinal content

2. Carbohydrate Use

   1. Carbohydrates are absorbed as monosaccharides

   2. Enzymes in the liver catalyze reactions that convert fructose and galactose into glucose

   3. Oxidation releases energy from glucose

   4. Excess glucose is stored as glycogen or combined to produce fat

   5. Some cells, such as neurons, require a continuous supply of glucose to survive

   6. If glucose is scarce, amino acids may react to produce glucose

   7. Most carbohydrates supply energy; some are used to produce sugars (ribose, deoxyribose, lactose)

3. Carbohydrate Requirements

   1. Humans survive with a wide range of carbohydrate intakes

   2. Poor nutritional status is usually related to low intake of nutrients other than carbohydrates.

18.3 Lipids

Lipids are organic compounds that supply energy and are used to build cell structures. They include fats, phospholipids, and cholesterol

1. Lipid sources 

   1. Triglycerides are obtained from foods of plant and animal origins

   2. Cholesterol is mostly obtained in foods of animal origin

2. Lipid use

   1. Before fats can be used as an energy source, they must be broken down into glycerol and fatty acids

   2. Beta oxidation decomposes fatty acids

      1. Beta oxidation activates fatty acids and breaks them down into segments of two carbon atoms each

      2. Fatty acid segments are converted into acetyl coenzyme A, which can then be oxidized in the citric acid cycle

   3. The liver and adipose tissue control triglyceride metabolism

   4. Liver enzymes can alter the molecular structures of fatty acids

   5. Linoleic acid and linolenic acid are essential fatty acids which must be obtained through the diet

   6. The liver regulates cholesterol level by synthesizing or excreting it

3. Lipid requirements

   1. Humans survive with a wide range of lipid intakes

   2. The amounts and types of lipids needed for health are unknown

   3. Fat intake must be sufficient to support absorption and transport of fat-soluble vitamins

18.4 Proteins

Proteins are broken down in digestion, the resulting amino acids can be used to form new protein molecules such as enzymes, clotting factors, keratin, elastin, collagen, actin, myosin, hormones, and antibodies, or can be used as energy sources. Before amino acids can be used as energy sources, they must be deaminated, forming the waste urea. During starvation, tissue proteins may be used as energy sources, causing the tissues to waste away. 

1. Protein sources

   1. Proteins are mainly obtained from eating meats, dairy products, cereals, and legumes

   2. 8 amino acids are essential for adults, whereas 10 are essential for growing children

   3. All essential amino acids must be present at the same time for growth and repair of tissues to take place

   4. Complete proteins contain adequate amounts of all the essential amino acids needed to maintain the tissues and promote growth

   5. Incomplete proteins do not contain adequate amounts of one or more essential amino acids

2. Nitrogen balance 

   1. In healthy adults, the gain of protein equals the loss of protein, and a nitrogen balance exists

   2. A starving person has a negative nitrogen balance; a growing child, a pregnant woman, or an athlete in training usually has a positive nitrogen balance

3. Protein Requirements

   1. Proteins and amino acids are needed to supply essential amino acids and nitrogen for the synthesis of nitrogen-containing molecules

   2. The consequences of protein deficiencies are particularly severe among growing children

18.5 Energy Expenditures

Energy is of prime importance to survival and may be obtained from carbohydrates, fats, or proteins.

1. Energy values of food

   1. The potential energy values of foods are expressed in calories

   2. When energy losses due to incomplete absorption and incomplete oxidation are taken into account, 1 gram of carbohydrates or 1 gram of proteins yields about 4 calories, whereas 1 gram of fat yields about 9 calories

2. Energy requirements 

   1. The amount of energy required varies from person to person

   2. Factors that influence energy requirements include basal metabolic rate, muscular activity, body temperature, and nitrogen balance. 

3. Energy balance

   1. Energy balance exists when caloric intake equals caloric output

   2. If energy balance is positive, body weight increases; if energy balance is negative, body weight decreases.

4. Desirable Weight

   1. The most common nutritional disorders involve caloric imbalances

   2. Average weights of persons 25-35 years old are desirable for older persons as well

   3. Body mass index (BMI) assesses weight taking height into account

   4. A BMI between 25 and 30 indicated overweight, and above 30, obesity. 

18.6 Appetite Control

1. Appetite is the drive that compels us to eat. Food powers the activities of life

2. Hormones control appetite by affecting the arcuate nucleus, a part of the hypothalamus

3. Leptin and ghrelin are hormones that affect appetite

18.7 Vitamins

Vitamins are organic compounds that cannot be synthesized by body cells in adequate amounts and are essential for normal metabolic processes.

1. Fat-soluble vitamins

   1. General characteristic 

      1. Fat soluble vitamins are carried in lipids and are influenced by the same factors that affect lipid absorption

      2. They resist the effects of heat; thus, they are not destroyed by cooking or food processing

   2. Vitamin A

      1. Vitamin A exists in several forms, is synthesized from carotenes, and is stored in the liver

      2. It is an antioxidant required for production of visual pigments

   3. Vitamin D

      1. Vitamin D is a group of related steroids.

      2. It is found in certain foods and is produced commercially; it can also be synthesized in the skin

      3. When needed, vitamin D is converted by the kidneys to an active form that functions as a hormone and promotes the intestine’s absorption of calcium and phosphorus

   4. Vitamin E

      1. Vitamin E is an antioxidant

      2. It is stored in muscles and adipose tissue

      3. It prevents breakdown of polyunsaturated fatty acids and stabilizes cell membranes.

   5. Vitamin K

      1. Vitamin K is in foods and is produced by intestinal bacteria

      2. Some vitamin K is stored in the liver

      3. It is used to produce prothrombin, required for blood clotting

2. Water-soluble vitamins

   1. General characteristics

      1. Water-soluble vitamin s include the B vitamins and vitamin C

      2. Cooking or processing food destroys some water-soluble vitamins.

      3. B vitamins make up a group called the vitamin B complex and oxidize carbohydrates, lipids, and proteins

   2. Vitamin B Complex

      1. Thiamine (vitamin B1)

         1. Thiamine functions as part of coenzymes that oxidize carbohydrates and synthesize ribose

         2. Small amounts are stored in the tissues; excess is excreted in the urine

         3. Quantities needed vary with caloric intake

      2. RIboflavin (vitamin B2)

         1. Riboflavin functions as part of several enzymes and coenzymes essential to the oxidation of glucose and fatty acids

         2. Its absorption is regulated by an active transport system; excess is excreted in the urine

         3. Quantities required vary with caloric intake

      3. Niacin (vitamin B3/nicotinic acid)

         1. Niacin functions as part of coenzymes required for the oxidation of glucose and for the synthesis of proteins and fats

         2. It can be synthesized from tryptophan; daily requirement varies within the tryptophan intake

      4. Pantothenic acid (vitamin B5)

         1. Pantothenic acid functions as part of coenzyme A; thus, it is essential for energy-releasing mechanisms

         2. Most diets provide sufficient amounts; deficiencies are rare

      5. Vitamin B6

         1. Vitamin B6 is a group of compounds that function as coenzymes in metabolic pathways that synthesize proteins, certain amino acids, antibodies, and nucleic acids

         2. Its requirement varies with protein intake

      6. Biotin (vitamin B7)

         1. Biotin is a coenzyme required for the metabolism of amino acids and fatty acids, and for nucleic acid synthesis

         2. It is stored in metabolically active organs, including the brain, liver, and kidneys.

      7. Folacin (vitamin B9 or folic acid)

         1. Liver enzymes catalyzed reactions that convert folacin to physiologically active folinic acid

         2. It is a coenzyme needed for the metabolism of certain amino acids, DNA synthesis, and the production of normal red blood cells

      8. Cyanocobalamin (vitamin B12)

         1. The cyanocobalamin molecule contains cobalt.

         2. Its absorption is regulated by the secretion of intrinsic factor from the gastric glands

         3. It functions as part of coenzymes needed for nucleic acid synthesis and for the metabolism of carbohydrates and fats

         4. It is important to erythrocyte production and myelin formation in the central nervous system

   3. Ascorbic acid (vitamin C)

      1. Vitamin C is similar chemically to monosaccharides

      2. It is required for collagen production, the metabolism of certain amino acids, and iron absorption.

      3. It is not stored in large amounts; excess is excreted in the urine.

18.8 Minerals

1. Characteristics of minerals

   1. Minerals account for about 4% of body weight

   2. Minerals are usually incorporated into organic molecules, although some are in inorganic compounds or are free ions

   3. They compose structural materials, function in enzymes, and play vital roles in various metabolic processes

   4. Homeostatic mechanisms regulate mineral concentrations

   5. The physiologically active form of minerals is the ionized form

2. Major minerals

   1. Calcium

      1. Calcium is essential for forming bones and teeth, neurotransmitter release, contracting muscle fibers, the cardiac action potential, clotting blood, and activating various enzymes

      2. Existing calcium concentration, vitamin D, protein intake, and motility of the digestive tract affect calcium absorption

   2. Phosphorus

      1. Phosphorus is incorporated into the salts of bones and teeth

      2. It participates in nearly all metabolic reactions as a constituent of nucleic acids, proteins, and some vitamins.

      3. It also is in the phospholipids of cell membranes, in ATP, and in phosphates of body fluids.

   3. Potassium

      1. Potassium is concentrated inside cells

      2. It maintains osmotic pressure, regulates pH, and plays a role in impulse conduction in neurons

   4. Sulfur

      1. Sulfur is incorporated into two of the 22 amino acids

      2. It is also in thiamine, insulin, biotin, and mucopolysaccharides

   5. Sodium

      1. Most sodium is in extracellular fluids or is bound to the inorganic salts of bone

      2. The kidneys, under the influence of aldosterone, regulate the blood concentration of sodium 

      3. Sodium helps maintain solute concentration and regulates water balance

      4. It is essential for impulse conduction in neurons and moving substances through cell membranes

   6. Chlorine

      1. Chlorine is closely associated with sodium as chloride ions

      2. It acts with sodium to help maintain osmotic pressure, regulate pH, and maintain electrolyte balance.

      3. Chlorine is essential for hydrochloric acid formation and for carbon dioxide transport by red blood cells

   7. Magnesium

      1. Magnesium is abundant in the bones as phosphates and carbonates

      2. It functions in ATP production and in the breakdown of ATP to ADP

      3. A reserve supply of magnesium is stored in the bones; excesses are excreted in the urine

3. Trace Elements

   1. Iron

      1. Iron is part of hemoglobin in red blood cells and myoglobin in muscles

      2. A reserve supply of iron is stored in the liver, spleen, and bone marrow

      3. It is required to catalyze vitamin A formation; it is also incorporated into various enzymes and the cytochrome molecules

   2. Manganese

      1. Most manganese is concentrated in the liver, kidneys, and pancreas

      2. It is necessary for normal growth and development of skeletal structures and other connective tissues; it is essential for the synthesis of fatty acids, cholesterol, and urea.

   3. Copper

      1. Most copper is concentrated in the liver, heart, and brain.

      2. It is required for hemoglobin synthesis, bone development, melanin production, and myelin formation.

   4. Iodine

      1. Iodine is most highly concentrated in the thyroid gland

      2. It is an essential component of thyroid hormones

      3. It is often added to foods as iodized table salt

   5. Cobalt

      1. Cobalt is widely distributed throughout the body

      2. It is an essential part of cyanocobalamin and is required for the synthesis of several enzymes

   6. Zinc

      1. Zinc is most concentrated in the liver, kidneys, and brain.

      2. It is a component of several enzymes that take part in digestion, respiration, and metabolism

      3. It is necessary for normal wound healing.

   7. Fluorine

      1. The teeth concentrate fluorine

      2. It is incorporated into enamel and prevents dental caries

   8. Selenium

      1. The liver and kidneys store selenium

      2. It is a component of certain enzymes

   9. Chromium

      1. Chromium is widely distributed throughout the body

      2. It regulates glucose use

18.9 Healthy Eating

1. An adequate diet provides sufficient energy and essential nutrients to support optimal growth, as well as maintenance and repair, of tissues.

2. Individual needs vary so greatly that it is not possible to design a diet adequate for everyone

3. Devices to help consumers make healthy food choices include recommended daily allowances, recommended dietary allowances, food group plans such as MyPlate, and food labels.

4. Malnutrition 

   1. Poor nutrition is due to lack of foods or failure to wisely use available foods

   2. Primary malnutrition is due to poor diet

   3. Secondary malnutrition is due to poor diet

   4. Secondary malnutrition is due to an individual characteristic that makes a normal diet inadequate

5. Starvation

   1. A person can survive 50-70 days without food

   2. A starving body digests itself, starting with carbohydrates, then fats, then proteins.

   3. Symptoms include low blood pressure, slow pulse, chills, dry skin, hair loss, and poor immunity. Finally, vital organs cease to function

   4. Marasmus is undernutrition involving a lack of calories and protein

   5. Kwashiorkor is protein starvation

   6. Anorexia nervosa is a self-starvation eating disorder

   7. Bulimia is an eating disorder characterized by binging and purging

18.10 Life-Span Changes

1. Basal metabolic rate rises in early childhood, declines, then peaks again in adolescence, with decreasing activity during adulthood

2. Weight gain, at any age, occurs when energy in exceeds energy out, and weight loss occurs when energy out exceeds energy in

3. Changing nutrition with age reflects medical conditions and social and economic circumstances.