Lecture Notes
Ch. 1: Orientation to the Human Body
Overview
Anatomy - study of structure (shape of the body and its parts)
Physiology - study of function (how the body and its parts work or function)
A & P are always related
Structure determines function
Pathology - study of structural changes that lead to disease
Levels of Study
Gross (macroscopic) Anatomy
Study of large structures that are easily visible to the naked eye
Subdivisions include regional, systemic, and surface anatomy
Microscopic Anatomy
Study of very small structures that can only be viewed with a microscope
Subdivisions include cytology (study of cells) and histology (study of tissues)
Developmental Anatomy
Study of structural changes that occur in the body throughout the lifespan
Subdivisions include embryology
Physiology has many subdivisions as well
Renal physiology, neurophysiology, cardiovascular physiology, etc.
Levels of Structural Organization (Hierarchy)
Chemicals → Organelles → Cells → Tissues → Organs → Organ Systems → Organism
Chemical Level: Atoms and molecules
Cellular Level: Cells are formed from organelles
Tissue Level: Tissues from similar cells
Organ Level: Organs formed from different tissues
Organ System Level: 11 organ systems work together
Organism: Complete human body
Maintaining Life
Necessary Life Functions
Maintaining boundaries
Movement
Locomotion
Transport of substances throughout the body
Responsiveness
Ability to sense changes (stimuli) and respond to them
Digestion
Breakdown and absorption of nutrients
Metabolism - all chemical reactions within the body
Catabolism breaks things down
Anabolism builds things up (makes body structures)
Production of energy (ATP)
Excretion
Elimination of wastes from metabolic reactions
Reproduction
Production of offspring
Growth
Increase in cell size and number
Survival Needs
Nutrients
Chemicals for energy and cell building
Includes carbohydrates, proteins, lipids, vitamins, and minerals
Oxygen
Required for chemical reactions
Water
60-80% of body weight
Involved in metabolic reactions
Normal body temperature
Appropriate atmospheric pressure
Homeostasis - maintaining a stable internal environment within narrow limits, regardless of environmental changes
Must be maintained for normal body functioning and to sustain life
Maintaining Homeostasis
The body communicates through neuronal & hormonal control systems
Receptor
Respond to changes in the environment (stimuli)
Sends information to the control center
Control Center
Determines the set point - the normal value the body is designed to maintain for a variable
Ex: Body temp. 37°C or 98.6°F
The body usually operates within a normal range (slight increases and decreases around the set point)
Analyzes information
Determines the appropriate response or course of action
Effector (only in muscles or glands)
Executes response
Feedback Mechanisms
Negative Feedback
Includes most homeostatic control mechanisms
Ex: heart rate, blood pressure, body temp., rate of respiration, blood glucose, oxygen, and carbon dioxide levels, etc.
Shuts off the original stimulus or reduces its intensity
Ex. moves the variable back toward the set point
Works like a household thermostat
Positive Feedback
Has an amplifying effect that increases the original stimulus to push the variable further away from the set point
Only normal occurrences are in blood clotting, the birth of a baby, and sexual response
Others are the result of pathology and are harmful
Ex: heart attack due to restricted blood flow to the heart eventually results in less cardiac output, which again decreases blood flow
Homeostatic Imbalance
A disturbance in homeostasis resulting in disease
It may be caused by infection, injury, or genetic abnormality
The Language of Anatomy
Special terminology is used to prevent misunderstanding
Exact terms are used for:
Position
Direction
Regions
Structures
Orientation and Directional Terms
Proper Anatomical Position
A point of reference
Directional Terms
Superior (above)/Inferior (below)
Anterior (front)/Posterior (back)
Medial (toward the midline)/Lateral (away from the midline)
Proximal (closer to the point of attachment)/Distal (further from the point of attachment)
Superficial (near body surface)/Deep (further from body surface)
Regional Terms
Axial
Head
Neck
Trunk
Thorax, Abdomen, Pelvis
Appendicular
Specific body areas
Body Planes and Sections
Frontal (divides anterior/posterior)
Transverse (superior/inferior)
Sagittal (left/right)
Midsagittal (perfect left/right)
Oblique
Body Cavities and Membranes
Dorsal Cavity
Composed of the cranial and vertebral (spinal) cavities
Ventral Cavity
Contains visceral organs
Composed of the thoracic, mediastinum (pericardial), and abdominopelvic cavities
Membranes
Lines the cavities and covers the outside of the organs
Named by location + the cavity word
The thoracic cavity is lined by parietal+pleura - parietal pleura
Thoracic organs are covered by the visceral pleura
The abdominopelvic cavity is lined by parietal peritoneum
Abdominopelvic organs are covered by visceral peritoneum
The pericardial cavity is lined by the parietal pericardium
The pericardial organ (heart) is covered by the visceral pericardium
Other body cavities
Oral and digestive, nasal, orbital, middle ear, synovial, etc.
Abdominal Regions and Quadrants
9 regions (specific anatomical areas)
Right hypochondriac region
Epigastric region
Left hypochondriac region
Right lumbar region
Umbilical region
Left lumbar region
Right iliac region
Hypogastric region
Left iliac region
4 quadrants (common clinical use)
Right upper quadrant (RUQ)
Left upper quadrant (LUQ)
Right lower quadrant (RLQ)
Left lower quadrant (LLQ)
Ch. 2: Chemistry (Organic & Inorganic)
Matter
Anything that occupies space and has mass (weight)
Ex. The physical (living and non-living) "stuff" of the universe
Can exist as a solid, liquid, or gas
Weight (mass)
We quantify the amount of a substance by its mass. Under the influence of gravity on the Earth's surface, mass is equal to the more familiar term "weight".
Composition of matter
Elements
Fundamental units of matter
They cannot be broken down into other substances
96% of life is made up of 4 elements
C, H, O, N
Atoms
Building blocks of elements
Atomic Structure
Nucleus
Protons (p+)
Neutrons (n0)
Outside of the nucleus
Electrons (e-)
Identifying Elements
Elements differ in the number of subatomic particles in their atoms
Chemical Symbol
Atomic Number
Number of p+ that the atom contains
Mass Number/Atomic Mass
protons + neutrons
Isotopes
Same number of p+ and e-
Vary in the number of neutrons
Ex. 12C, 13C, 14C
Radioisotope
Heavy isotope
Tends to be unstable
Decomposes to a more stable isotope
Radioactivity
Process of spontaneous atomic decay
As some isotopes adjust to a more stable form, they will emit a measurable energy. This energy release is called "radiation".
We can make use of radioactive isotopes in medicine (low-level radiation)
Normally, cells (epithelial tissue) in the thyroid gland (organ) take up the element iodine I) from your diet to make a thyroid hormone. If we want to check the activity of your thyroid gland, we can feed you radioactive iodine. As your thyroid cells take up the radioactive iodine, energy emitted from your thyroid gland is captured by a machine (scanned) and used to make an image (picture) of your gland. We may see cancer tumors, an underactive, overactive, or normal gland. This procedure is often called a "thyroid scan".
Electrons & Chemical Bonding
Electrons occupy energy levels called electron shells
Electrons closest to the nucleus are most strongly attracted
Each shell has distinct properties
The number of e- held has an upper limit
Rule of 8s (octet rule)
Shell 1 holds 2 e-
Shell 2 holds 8 e-
Shell 3 holds 8 e- (for bonding purposes)
Shells closest to the nucleus fill first
Bonding involves interactions between e- in the outer shell (valence shell)
Full valence shells do not form bonds
Inert Elements
Have complete valence shells and are stable
Ex. He, Ne
Reactive Elements
Valence shells are not full and are unstable
Tend to gain, lose, or share electrons
Allows for bond formation, which produces a stable valence shell
Ex. C, H, O, N
Chemical Bonds
Ionic Bonds
The attractive force between oppositely charged ions
Ions
Charged particles (elements)
Ex. NaCl
Will dissociate in water and form + and - ions
NaCl → Na+ + Cl-
Chemicals that are made up of atoms with ionic bonds are called salts or electrolytes
Ions with a positive charge are called cations: examples H+, K+
Ions with a negative charge are called anions: examples HCO, ОН-
Covalent Bonds
Atoms become stable through shared e-
Single covalent bonds share one e-
Double covalent bonds share two e-
Ex. CH4, O2
Polarity
Covalent-bonded molecules
Some are nonpolar
Electrically neutral as a molecule, as electrons are evenly shared
Ex. CO2
Some are polar
Electrons are unevenly shared
Results in a positive and a negative side
Ex. H2O
Hydrogen bonds
Weak chemical bonds
Hydrogen is attracted to the negative portion of a polar molecule
Provides attraction between molecules
Molecules, Compounds, and Solutions
Molecules: two or more atoms (same or different) joined together by chemical bonds
Ex. O2, N2, H2O
Compounds: substances composed of two or more different elements
Ex. H2O, CH4, NaCl, C6H12O6 (glucose), etc.
Exceptions: Note that because electrolytes are electrically attracted and not chemically combined, we do not use the term "molecule" to describe NaCl, etc.
Solutions: two or more components physically intermixed (not chemically bound)
Ex. saline solutions [table salt (NaCl) and water], blood plasma, interstitial fluid, urine, etc.
Solvent: dissolving medium
Present in the greatest amount
Ex. water
Solute: the dissolved substance
Present in smaller amounts
Ex. NaCl, glucose, O2, CO2, Ca2+, etc.
Concentrations
The amount (concentration) of a solute in the total solution is usually measured as one of the following:
Percent of the solute in the total solution (parts per 100)
Milligrams per deciliter (mg/dL)
Note: A deciliter is 100 mL
Molarity (moles per liter), indicated by M
Chemical Reactions
Terminology
Reactants: reacting substances
Products: end product (result)
Ex. 4 H + C → CH4
Three major types of reactions:
Atoms, molecules, ions, and compounds are built into more complicated forms (anabolism)
Always involves bond formation: A + B → AB
Ex. building of human muscle cells or amino acids into proteins
Decomposition reactions
Breaking down large molecules into smaller units (catabolism)
Bonds are broken: AB → A + B
Ex. dietary intake of animal protein or glycogen into glucose
Reversible reactions
Some chemical reactions don't just proceed in one direction but seek "equilibrium" and may proceed in both directions
Arrows indicate the direction of the reaction.
An important example of how the body maintains CO2 and acid-base balance is the carbonic acid buffering system:
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
Inorganic Compounds
Lacks carbon
Exception: CO2, HCO3-
Tend to be simpler than organic compounds
Ex. H2O, NaCl (inorganic) vs. C6H12O6 (organic)
Important Inorganic Compounds in Living Matter
Water (H2O)
Most abundant inorganic compound (60-80% of our body weight)
Vital properties
High heat capacity
High heat of vaporization
Polar solvent properties
Often called the "universal solvent"
Biological molecules do not react unless they are in solution, so this is crucial to sustain life
Will also form hydration layers to shield charges
Serves as a transport medium
Chemical reactivity
Hydrolysis reactions
Dehydration synthesis
Cushioning
Stabilizes the structure of all macromolecules
Hydrophobic interactions
Oxygen (O2)
Approximately 20% of the air you breathe is oxygen
O2 is essential for cells to extract energy from other compounds
Without O2, many cells die quickly as they run out of internal energy compounds (ATP)
Carbon dioxide (CO2)
As energy is extracted from molecules with long chains of carbon atoms, bonds are broken, and carbon atoms must be removed from the body. CO2 is formed.
Salts
Ionic compounds that contain cations other than H+ and anions other than OH-
Ex. NaCl, CaCO3, KCl, etc.
Easily dissociate into ions in the presence of water
Form electrolytes, which conduct electrical currents
Salts (and electrolytes) are vital to many body functions
Ex. Nerve cell communication, muscle contraction, etc.
If ionic balance in our body is not maintained (a function of the kidneys), the physiological activities listed above and thousands of others will become disrupted and stop. Virtually nothing in the body will then work, and death will quickly ensue.
The antidepressant Lithium Chloride:
LiCl → Li+ + Cl-
Acids and Bases
Note: Like salts, acids, and bases are electrolytes. They ionize and dissociate in water and can then conduct an electrical current.
Acids
Proton donors
H+ (hydrogen ion) = proton
Electrolytes are called acids if they yield H+ in water
Example of partial dissociation: (weak acid) H2CO3
Note: The body uses the decomposition part of this reversible reaction to form CO, for removal from the body
H2CO3 → H+ + HCO3-
Example of complete dissociation: (strong acid) HCl
Note: The stomach uses this dissociation to create a very acidic stomach environment
HCl → H+ + Cl-
Bases
Proton acceptors
They attract and combine with H+ in water
Examples:
NH3 + H+ → NH4+
H+ + HCO3- → H2CO3
The kidney uses the synthesis reaction above to get rid of excess acid (H+)
pH: Acid-Base Concentration
Measures H+ (proton) concentration
Scale runs from 0-14
pH = 7 neutral
pH < 7 = acid
pH > 7 = base
Concept of physiological pH
The normal pH range for human blood is 7.35-7.45
Therefore, <7.35 = acidosis and > 7.45 = alkalosis in humans
Buffers
Chemicals that can regulate pH change
Ex. carbonic acid-bicarbonate system
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
Properties of Organic Compounds
The Molecules of Life
Carbohydrates, lipids, proteins, & nucleic acids
Binding Properties of Carbon
Can covalently bind up to 4 different atoms
Can bind itself
Creates an infinite variety of carbon skeletons with energy-rich covalent bonds
Can form single, double, and triple bonds
Result: Infinite diversity and complexity of organic molecules
Hydrocarbons
Composed entirely of C and H atoms
Very strong
Form stable portions of most biological molecules
Functional Groups
Bind the carbon backbone and convey specific chemical properties to the compound
Ex. Estrogen vs. Testosterone
How do Cells Build Organic Compounds?
Overview: monomers → polymers
Cells join monomers into chains called polymers via dehydration reactions
Results in the covalent linkage of the monomer to the chain through the loss of an H2O molecule
Cells break polymers down into monomers via hydrolysis reactions
Biological Molecules
Carbohydrates (Polysaccharides /Sugar)
Functions:
Energy-yielding fuel stores
Extracellular structural elements & signals
Bulk in feces
Composition
Building blocks of monosaccharides
Ex. glucose, fructose, ribose, deoxyribose
Disaccharides
2 monosaccharides covalently linked
Examples:
Sucrose (table sugar)
Lactose (milk sugar)
Maltose (grain sugar)
Polysaccharides (aka complex carbohydrates)
Many sugar units (same or different) are covalently linked
Examples:
Starch
Energy storage in plants
Polymer of glucose subunits
Amylase is an enzyme that breaks starch into monosaccharides usable by humans
Glycogen
Energy storage in animal cells
Polymer of glucose subunits
Cellulose
Polymer of glucose
Humans do not have cellulase, so linkages cannot be hydrolyzed
Therefore, the “fiber” or bulk in feces
Lipids
Intro:
Characterized by their inability to dissolve in H2O
All hydrophobic
Functions: Protection, insulation, regulation, vitamins, structure (like membranes, steroids, etc.), energy
Types:
Fats (aka triglyceride)
Building blocks
An alcohol (glycerol) + 3 fatty acids
Unsaturated fatty acids
Liquid at room temp.
Contains double bonds
Saturated fatty acids
Solid at room temp.
No double bonds
Stored in adipose cells
Phospholipids
Phosphate replaces one of the fatty acids
Forms a lipid bilayer with hydrophobic and hydrophilic molecular ends
Steroids
Very different from fats in structure and function, but still a lipid (hydrophobic)
The carbon skeleton forms 4 fused rings
Different steroids arise from different functional groups
Cholesterol
Serves as a “base steroid” or building block
Ex. Cholesterol, bile salts, estrogen, progesterone, testosterone
Anabolic steroids
Proteins
Intro
Protein = Polymer of amino acid monomers
Each protein has a unique 3D structure that corresponds to a specific function
Functions: Regulation, transport, protection, contraction, structure, energy
The Monomers: Amino Acids (AA)
All proteins are constructed from the same 20 amino acids
Each AA differs only in the “R group”
Gives each AA its special chemical behavior
AAs are grouped together according to their side-chain properties
Hydrophobic, hydrophilic, acidic, basic
Proteins as Polymers
Amino acids are linked together by dehydration reactions, forming a peptide bond
Protein Shape
A functional protein is 1 or more polypeptides precisely folded into a unique 3D shape
Its final 3D conformation facilitates its specific function
Proteins have at least 3 levels of structure. If the protein has more than 1 polypeptide, it has a 4th level: 4° structure
1° structure (Primary)
The sequence of amino acids held together by peptide bonds
Sequence is determined by inherited genetic info
Even a slight change in the 1° structure may affect the structure and function of the protein
Ex. Sickle-cell anemia
2° Structure (Secondary)
Hydrogen bonds between the backbone of the 1° structure
The result is a helical coil (α-helix) or sheet-like array (β-pleated sheet)
3° Structure (Tertiary)
Final 3D conformation of a protein that results from weak interactions (hydrogen bonds, ionic bonds, hydrophobic interactions, etc.) between the R groups
Hydrophobic regions congregate in the interior, away from H2O
Hydrophilic regions congregate toward the exterior, in contact with H2O
Chemical bonding (hydrogen bonds, ionic bonds, etc.) between different parts of the polypeptide reinforces the shape
4° structure (Quadernary)
Complexing of 2 or more polypeptide chains through weak interactions
Ex. Hemoglobin
Protein Classifications
Fibrous (structural) proteins
Extended and strand-like
Insoluble in water and very stable
Ideal for mechanical support and tensile strength
Ex. Collagen, keratin, etc.
Globular (functional) proteins
Compact and spherical
Water soluble and chemically active
Play crucial roles in virtually all biological processes
Ex. Antibodies, peptide hormones, enzymes, chaperones, etc.
Protein Denaturation
Fibrous proteins are stable (some exhibit only 2º structure), but globular proteins are not (most exhibit 3° or even 4°structure) and are therefore highly dependent on weak bonds to maintain their final, 3D conformation and ultimate function.
Since weak bonds are fragile, they are easily broken by chemical and physical factors (high temperatures, chemicals, extreme pH, etc.)
Causes protein to unravel & lose its normal 3D conformation; therefore, normal functioning is lost (which is often irreversible)
Enzymes
Globular proteins that speed up chemical reactions (catalysts)
Lock and key or hand-in-glove-induced fit models
Usually ends in “-ase”
Ex. Lipase, proteases, etc.
Clinical: Lactose intolerance
Nucleic Acids
Nucleotides
Composed of:
5-carbon sugar (pentose)
Ribose in RNA
Deoxyribose in DNA
A base
A
T
C
U
G
A phosphate group
Nucleic Acids
Provides instructions for building proteins (blueprints for life)
DNA
Double-stranded; forms a double helix
Sugar-phosphate backbone
Bases are hydrogen-bonded between strands
A, T, C, G
Genetic messages are encoded in the base sequence
In a gene, the sequence of nucleotide bases is translated into an amino acid sequence to make a specific protein
RNA
Single-stranded
A, U, C, G
The function is the assembly of proteins
Adenosine Triphosphate (ATP)
Chemical energy is used by all cells
ATP/ADP Cycle
Energy is released by breaking a high-energy phosphate bond
A-P-P-P → A-P-P + P + Energy for anabolism and cellular activities
Restoration of energy bonds for future use
A-P-P + P + Energy (from catabolism) → ATP
How ATP Drives Cellular Work
Transport work
Mechanical work
Chemical work
Ch. 3: Cells
Introduction to Cells
Smallest living units in biology
They carry out all chemical activities needed to sustain life
Basic structural and functional unit of living organisms
Microscopic but vary in shape, size, and function
Humans have several trillion cells organized into groups of tissues in organs
The human body is based on proper cell function. We can study normal life functions as well as disease states by examining what happens at the cellular level.
Likewise, we can study cellular activity of the body by measuring clinical "vital signs"
Cells can link elements like C (carbon), H (hydrogen), and O (oxygen) into molecules like carbohydrates (C6H12O6), proteins, and lipids.
Cells produce enzymes that perform many chemical reactions in the body, including not only the assembly but also the breakdown of molecules and chemicals.
O2 + C6H12O6 → CO2 + H2O + energy for life activities (ATP)
Many different cell types share common structures that we study as the generalized cell model.
Anatomy of the Cell
The generalized cell
3 main parts:
Plasma membrane
Cytoplasm with organelles
Nucleus
Plasma membrane
The cell membrane divides the intracellular and extracellular environments
Produces a charge difference (called membrane potential) across the membrane by regulation of intracellular and extracellular ion concentrations
Inside is negatively charged with respect to the outside
Construction: double (bilayer) of phospholipids with embedded proteins
Fluid Mosaic Model
Membrane is neither rigid nor static in structure, but instead highly flexible and can change its shape and composition through time
3 major components:
Phospholipids
Hydrophilic head groups face water in the interior and exterior of the cell
Hydrophobic tails face each other on the interior of the membrane
Can keep some substances from flowing directly through the membrane
Lipid-soluble substances can get through (some hormones, drugs, etc.), while other substances cannot
Proteins
Integral (transmembrane) vs. peripheral proteins
Function as transport channels, receptors for signal transduction, attachment to cytoskeleton and extracellular matrix (ECM), enzymatic activity, intercellular joining, cell-cell recognition, etc.
Cholesterol
Stabilizes membrane
Amount determines how fluid the membrane will be
Selective permeability
Some substances (small, hydrophobic, not charged) can cross more easily than others
Membrane transport - movement of substances into and out of the cell
Transport of small molecules
Simple diffusion
Movement of molecules down their concentration gradient (high conc. → low)
Solutes are lipid-soluble materials and small enough to pass through membrane pores (e.g., O2, CO2, H2O, etc.)
No energy required
Facilitated diffusion (helps by membrane transport)
Diffusion with transport/carrier proteins
Mechanism for glucose, amino acids, and ion transport
Characteristics:
Specificity for a single type of molecule
Competition among molecules of similar shape
Saturation - rate of transport limited to the number of available transport proteins
Active transport
Movement of solutes against their concentration gradient (low → high conc.)
Requires energy (ATP) and a carrier protein
Example: Na+/K+ exchange pump that creates electrical potentials across membranes
Vesicular Transport - transport of large particles and macromolecules across plasma membranes
Endocytosis - bulk or large molecule transport into the cell
Phagocytosis
Ex: White blood cells (WBC) engulf invaders or cell debris and take it into the cell
Pinocytosis ("cell drinking")
Receptor-Mediated Endocytosis - When protein receptors are activated on the surface, the membrane takes in substances from the outside
Clinical: hypercholesterolemia
Exocytosis - bulk or large molecule transport out of the cell
Osmosis
Diffusion of water across a selectively permeable membrane
Affected by the total concentration of all solute particles in a solution (called osmolarity)
Hypotonic: low solute concentration compared to the human body plasma compartment
Hypertonic: high solute concentration compared to the human body plasma compartment
Isotonic: same solute concentration compared to the human body plasma compartment
H2O always moves from hypotonic to hypertonic
Important because large volume changes caused by water movement disrupt normal cell function
The cytoplasm
Fluid matrix like jello (cytosol) with embedded organelle structures
Organelles are small, separate, membrane-bound structures within the cell with distinct functions
Mitochondria: ATP synthesis
Provides all energy for cellular work
The number will increase in a cell when energy requirements increase
A small amount of mitochondrial DNA is present
Two energy-releasing pathways:
Both start with glycolysis in the cytoplasm
Anaerobic respiration/glycolysis
Occurs in the cytoplasm
Does not require oxygen
Results in very little ATP production
Aerobic respiration
Occurs in mitochondria
Requires oxygen
Results in a large amount of ATP production
Ribosomes: protein synthesis
Free ribosomes suspended in the cytosol synthesize proteins that will stay inside the cell
Attached ribosomes (to the endoplasmic reticulum) will synthesize proteins destined for secretion outside of the cell
Endoplasmic Reticulum (ER)
Smooth ER: drug detoxification, lipid and cholesterol production, steroid hormone production, etc.
Phenobarbital resistance
Rough ER: preparation of proteins for transport and secretion, and "membrane factory" (produces integral membrane proteins and phospholipids)
Golgi apparatus: packages, modifies, and segregates proteins
Secretory pathway: RER → Golgi → vesicle → exocytosis
Lysosomes: site of intracellular digestion
Filled with hydrolyzing enzymes
Peroxisomes: detoxification
Detoxifies harmful substances like alcohol and formaldehyde and neutralizes dangerous free radicals
Inclusions: temporary storage of pigments, fat droplets, etc.
Cytoskeleton: small internal rods that determine cell shape and structure, support organelles, and provide machinery needed for transport and cell division
Composed of microtubules, microfilaments, and intermediate filaments
Centrioles within the centrosome structure produce fibers (microtubule spindle) necessary for cells to divide and replicate
Barrel-like structure
Cellular Extensions
Cilia
Hair-like projections used to propel substances across the cell surface
Beat in only one direction
Flagella
Single tail-like projection used to propel the entire cell forward only
Example: sperm cell
Microvilli
Finger-like projections on the surface of some cells that increase surface area for absorption (such as in the intestine)
The nucleus (contains DNA and all life-sustaining things)
Control center for cell activities (life)
Recipes for life are stored in the chemical form of DNA
All cells have at least one nucleus at some point.
Structural organization
Nuclear envelope with nuclear pores
Chromatin (uncoiled DNA)
Chromosomes (tightly coiled DNA)
Nucleolus (RNA for ribosome assembly)
Inside the nucleus
The Cell Cycle
Overview
Comparison of Mitosis and Meiosis
Mitosis
Meiosis
Primary function: growth and repair/replacement
Occurs in all of the somatic cells of the body (normal body cells like skin, liver, kidney, etc.)
One (1) round of cell division
Produces 2 genetically identical daughter cells
Each daughter cell has 46 chromosomes
Primary function: gametogenesis
Occurs only in the glands (testes in males; ovaries in females)
Two (2) rounds of cell division
Meiosis I and Meiosis II
Produces 4 (haploid) daughter cells, each with half the number of chromosomes
Each daughter cell has 23 chromosomes
Interphase
The phase between cell divisions
Period of cell growth and normal ongoing metabolic (chemical) activities
G1 (Gap 1): Normal metabolic activities (e.g., producing proteins, energy, interacting with the environment) and vigorous growth
The cell is just being a cell and doing its job
Virtually no activities related to cell division occur here
Although this is where the cell spends most of its time, G1 usually lasts only minutes to hours
S (Synthesis): DNA replication (exact duplication of all genetic material)
G2 (Gap 2): Growth and final preparations for cell division
Usually brief, but ensures everything is ready for entry into M phase
G0 (Resting Phase): Cells stop dividing and exit the cell cycle
Mature cardiac muscle cells, nerve cells, and often multinucleated skeletal muscle cells enter G0 and never re-enter the cell cycle
Mitosis
Process necessary for cell division into two identical cells (used for growth and replacement)
Goal: Exact and equal division of replicated DNA
Stages (PMAT):
Prophase
Chromosomes condense
Nuclear envelope breaks up
Microtubule spindle forms
Metaphase
Spindle microtubules attach to sister chromatids
Sister chromatids align at the metaphase plate
Tension builds for separation
Anaphase
Attachments between sister chromatids break
Chromatids migrate to opposite poles
Independent daughter chromosomes are now present
Telophase
Chromosomes arrive at opposite poles
They decondense
Spindle breaks down
Nuclear envelope reforms
Cytokinesis
Cleavage furrow and contractile ring form (via microfilaments)
Cytoplasm divides
Two genetically identical daughter cells are formed
If there’s any disruption in these phases, the cell is arrested in that phase and cannot proceed until corrected
Some chemotherapy drugs target these mitotic stages to stop cancerous cells from completing division
Developmental Aspects of Cells
Life After Mitosis
Differentiation - taking on a cellular fate
All cells originate from one fertilized egg
Cells respond to different chemical signals to form:
3 germ layers: endoderm, mesoderm, ectoderm
4 major tissue types: epithelial, connective, muscle, nervous
Once differentiated, cells divide and carry out specialized functions
The issue with aging: Why cells quit doing their jobs
Cellular clock: Cells die after a certain number of divisions
Apoptosis: Programmed cell death
Free radical detox slows with age, speeding up cell death
Telomeres break down during mitosis, limiting the number of divisions
Understanding Cancer: Uncontrolled division and spread of cells in the body
Neoplasm: Abnormal mass of growing cells
Benign Tumor
Encapsulated, not spreading
Can function normally, but in the wrong place
Often removable via surgery
Malignant Tumor (Cancer)
During mitosis, tumor-suppressor genes should stop cells with errors
If these genes fail, cells with faulty DNA can survive and divide uncontrollably
Causes of Gene Damage (Mutations)
Carcinogens (cancer-causing agents):
Radiation
Mechanical trauma
Certain viral infections
Chemicals (e.g., tobacco tars, saccharine)
Unregulated Growth
Cells ignore normal regulatory signals
No longer respond to contact inhibition or growth factor depletion
Begin metastasis (spreading throughout the body)
Cancer kills by disrupting, displacing, and starving normal tissues
Diagnosis & Treatments
Biopsy: Tissue sample examined for malignancy
Surgical Removal: Physical removal of the tumor
X-ray Therapy: Targets local cancer cells
Chemotherapy: Circulates throughout the body to kill escaped cells
DNA Replication
Structure of DNA
Double helix
Sugar-phosphate backbone (covalently bound)
2 strands held together by hydrogen bonds between bases (nucleotides)
4 nucleotides:
Adenine (A)
Cytosine (C)
Thymine (T)
Guanine (G)
Base pairing:
A = T
C = G
DNA Replication
Exact duplication of a cell's genetic material (DNA)
Semiconservative DNA Replication:
DNA helicases separate the 2 strands of the double helix.
Stretches of nucleotide bases are exposed.
The companion strand is assembled via DNA polymerases:
Parent strand serves as a template.
Complementary bases come in and base pair with the single-stranded template.
Nucleotides then connect to form the sugar-phosphate backbone.
Results in 2 identical daughter DNA molecules, each with one parent strand and one daughter strand (semi-conservative).
DNA Repair
DNA polymerases proofread.
DNA ligases glue pieces together.
Protein Synthesis
Overview
DNA contains the information to produce proteins.
Transcription of a gene (DNA segment for a protein) results in mRNA (mirror image copy).
mRNA leaves the nucleus and goes to a ribosome.
Amino acids are carried to the ribosome by tRNAs.
Translation uses mRNA information to determine the number, kinds, and arrangement of amino acids in the protein.
Transcription (DNA → mRNA)
Structure of mRNA:
Single-stranded.
4 nucleotides:
Adenine (A)
Cytosine (C)
Uracil (U)
Guanine (G)
Base pairing:
A = U
C = G
Sugar-phosphate backbone with ribose sugar (instead of deoxyribose).
3 types of RNA: mRNA, tRNA, rRNA.
Mechanism of Transcription:
Initiation:
RNA polymerase binds to the DNA promoter and unwinds the DNA.
A transcription bubble is formed.
Elongation:
RNA polymerase catalyzes base-pairing of RNA nucleotides to DNA bases (A-U and C-G).
Termination:
A termination signal is reached.
mRNA is released and travels out of the nucleus to the cytoplasm.
DNA returns to its original structure.
Translation (mRNA → protein)
Deciphering mRNA transcripts:
mRNA message is translated from nucleotides to amino acids (protein "language").
Every 3 nucleotides = a CODON.
One codon specifies a single amino acid.
The Genetic Code represents all possible codon combinations and their corresponding amino acids.
Steps in Translation:
Initiation:
The ribosome binds to mRNA and moves to the AUG start codon (binding site #1).
"Start" codon signals the beginning of a protein.
Elongation:
tRNA brings the appropriate amino acid to the binding site #1 based on the mRNA codon (codon-anticodon matching).
Binding site #2 on the ribosome is open.
The next tRNA with the corresponding amino acid binds to the open binding site #2.
The ribosome catalyzes the formation of a peptide bond between the two amino acids.
tRNA in binding site #1 is released, and the ribosome shifts down the mRNA by one codon.
Binding site #2 becomes the new binding site #1, and binding site #2 is now open for the next tRNA.
This process repeats until a stop codon is reached in the mRNA.
Termination:
A "Stop" codon is reached on the mRNA.
There is no tRNA anticodon for a stop codon.
mRNA and the polypeptide are released from the ribosome.
What happens next?
mRNA is recycled.
The new protein enters the cytoplasm or the rough ER (for processing in the Golgi apparatus and potential secretion).
Mutations
Mutations are changes in the genetic material of a cell.
Mutations can be beneficial, neutral, or harmful.
Harmful mutations can lead to genetic disorders or hereditary diseases.
Example: Sickle-cell anemia is caused by a single base pair mutation in the hemoglobin gene, leading to an abnormal protein and associated symptoms.
The Science Behind Genetically Inherited Diseases:
DNA change → mRNA change → codon change(s) → amino acid sequence change → altered protein folding → change in 3D conformation → altered protein structure → altered protein function.
What causes mutations?
Spontaneous: Errors during DNA replication, repair, or recombination that are not corrected.
Mutagens:
Physical agents: X-rays and other high-energy radiation (like UV light).
Chemical agents: Accutane, etc.
Types of mutations:
Silent mutations:
Result from the redundancy of the genetic code (different codons can code for the same amino acid).
Substitution mutations:
One or more bases are replaced by others.
Example: Sickle cell anemia.
Frame-shift mutations:
Insertions (addition of one or more bases).
Deletions (loss of one or more bases).
Ch. 4: Tissues & Membranes
Overview
Tissues - A “fabric” or group of cells with similar structure and function
Four primary types
Epithelium (covering)
Connective (support)
Muscle (movement)
Nervous (control)
The importance of the microscopic study of tissue
Histology
Biopsy
Autopsy
Epithelial Tissues and Glands
Definition: A Sheet of cells that covers all free body surfaces (inside and out), forming an interface or boundary between two environments.
Functions
Protection
Absorption - Intake of molecules and substances
Filtration - Closely fitted cells can form a “strainer” with small holes
Secretion - Release of molecules and substances
Sensory reception
Special Characteristics
Cellularity
Specialized contacts
Polarity (1 free surface; 1 bound surface)
Apical surface (free surface)
Basal surface (bound surface)
Supported by connective tissue
Avascular but innervated
Regeneration
Special Structural Features
Apical surface
Microvilli
Fingerlike extensions of epithelial cells lining some parts of the digestive tract or the kidney. The surface area is increased, increasing absorption and secretion. It may also create adhesion points for secreted mucus.
Cilia
Microtubules project from cell membranes as hairs that move uniformly in one direction (wave-like). They can move substances along the surface of a sheet of epithelial cells.
Clinical note: Nicotine decreases ciliary action
Lateral cell junctions
Desmosomes
Anchoring junctions linking proteins) between cells that prevent cells subjected to mechanical stress (such as skin cells) from being pulled apart
Confers strength
Tight junctions
Rivets that securely fuse adjacent plasma membranes together into leakproof sheets; seal the extracellular space
Gap junctions
Allow substances to leak between cells
Basal surface
Basal Lamina
A noncellular, adhesive sheet of glycoproteins secreted by epithelial cells toward the neighboring connective tissue layer.
Functions:
Selective filter
Scaffold to which epithelial cells can migrate or grow upon
Combines with fibers from the CT layer to form a basement membrane
Basement Membrane
Located just deep into the basal lamina
Reinforces the epithelial sheet and defines the epithelial boundary
Classification of Epithelium
Two names followed by “epithelium”
1st name: # of cell layers
Simple - One layer
Stratified - More than one layer
Pseudostratified - Looks like more than one layer, but isn't
2nd name: Shape of cells
Squamous - Flat, plate or scale-like
Nucleus: Flat & disc-like
Cuboidal - Cube-shaped or box-like
Nucleus: Large & round; spherical
Columnar - tall and column-shaped
Nucleus: Oval and elongated, located in the basal ⅓
Glandular Epithelium
Glands - One or more epithelial cells organized to make and secrete (export) a particular product (often an aqueous fluid that contains proteins)
Secretory pathway:
RER → Golgi → vesicles → exocytosis
Two major gland types
Endocrine glands
Ductless (secretion into the bloodstream)
Secretions are chemical messenger molecules called hormones
Each messenger (hormone) is a regulatory chemical manufactured to react with a specific “target” organ(s) in some specific way
Ex. The pancreas has an endocrine function where some of its glandular cells produce the hormone insulin, which affects the energy pathways used by many organs of the body
Exocrine glands
Secret products onto a body surface or into body cavities
Unicellular
Ex. Single goblet cell secretes a protein called mucin
Mucin + H2O = Slimy, viscous mucus
Multicellular
Secretory unit + duct
Ex. Sweat and oil glands, salivary glands, liver, pancreas (both endocrine and exocrine), etc.
Connective Tissue
4 main classes (several subclasses)
Connective tissue proper
Cartilage
Osseous tissue (bone)
Blood
Functions
Binding (connection) and support
Protection
Insulation
Transportation
Structural Elements
Cell type
Fibrocyte
Chondrocyte
Osteocyte
Red Blood Cells (RBCs)/White Blood Cells (WBCs)
Extracellular Matrix (ECM) is composed of:
Ground substance
Holds water and ranges from liquid to jelly to firm
Composition:
Water
Adhesion proteins
Polysaccharide molecules
Fibers
Produced by the cells
3 types
Collagen fibers
Extremely tough; high tensile strength
Elastic fibers
Stretch and recoil
Reticular fibers
Fine collagen, but more give
Muscle Tissue
Highly cellular, well-vascularized tissue that functions to produce movement
Cells are also called muscle fibers
Contains internal myofilaments (actin and myosin) for contraction
3 types:
Skeletal muscle
Cardiac muscle
Smooth muscle
Nervous Tissue
Main component of the Nervous System (brain, spinal cord, nerves, etc.)
2 major cell types:
Neuroglia (nerve support cells that protect, insulate, etc.)
Neurons (nerve cells)
Functions:
Irritability
Conductivity (send impulses to other areas of the body)
Common structural components
Dendrites
Cell body
Axon
Axonal (presynaptic) terminals
Tissue Repair
Overview
The body has many techniques for protecting itself against pathogens and/or injury:
External Defenses
Mechanical
Intact skin
Mucous membranes
Chemical
Fatty acids - Lower pH on skin
Enzymes (lysozyme & pepsin)
Stomach acid
Vaginal secretions
Urine
Microbiological
Internal Defenses
Inflammatory Response
Nonspecific
Develops quickly
Specific Immune Response
Targets specific pathogens
Takes longer
When tissue injury occurs, external barriers are penetrated, and internal defenses are therefore activated.
Repair occurs in two major ways: Regeneration and fibrosis
Regeneration: replacement of destroyed tissue with the same kind of tissue (i.e., epithelium with epithelium)
Fibrosis: replacement of destroyed tissue with fibrous connective tissue (called scar tissue)
Steps
Inflammation sets the stage
Severed blood vessels bleed, and inflammatory chemicals are released.
Local blood vessels become more permeable, allowing white blood cells, fluid, clotting proteins, and other plasma proteins to seep into the injured area.
Clotting occurs; the surface dries and forms a scab.
The organization restores the blood supply
The clot is replaced by granulation tissue, which restores the vascular supply.
Fibroblasts produce collagen fibers that bridge the gap.
Macrophages phagocytize cell debris.
Surface epithelial cells multiply and migrate over the granulation tissue.
Regeneration and fibrosis affect permanent repair
The fibrotic area matures and contracts; the epithelium thickens.
A fully regenerated epithelium with an underlying area of scar tissue results.
Note: The repair process described above follows the healing of a wound (cut, scrape, puncture, etc.) that breaches an epithelial barrier. In simple infections (i.e., pimples, sore throats, etc.), healing is solely by regeneration. There is usually no clot formation or scarring. Only severe (destructive) infections lead to scarring.
Regenerative Capacity of Different Tissues
Epithelial tissues, bone, areolar, and blood-forming tissue regenerate extremely well
Smooth muscles and dense, regular connective tissue have a moderate capacity for regeneration
Skeletal muscle and cartilage have a weak regenerative capacity
Cardiac muscle and nervous tissue in the brain and spinal cord have virtually no functional regenerative capacity and are routinely replaced by scar tissue
Simplest Organs: Membranes
Continuous multicellular sheets composed of epithelial + connective tissue
3 types:
Cutaneous membranes (skin)
Mucous membranes
Cover all portals to the inside
Produces mucus
Serous membranes
Lines close internal cavities & cover the outside of organs
Produces slippery serous fluid
Named by lining location + the cavity word
The thoracic cavity is lined by parietal + pleura = parietal pleura
Thoracic organs are covered by the visceral pleura
The abdominopelvic cavity is lined by parietal peritoneum
Abdominopelvic organs are covered by visceral peritoneum
The pericardial cavity is lined by the parietal pericardium
The heart (inside the pericardial cavity) is covered by the visceral pericardium
Connective Tissue only
Synovial membranes
Line the inside of freely movable joints
Produces synovial fluid
Ch. 5: The Integumentary System
Overview
Composition
Skin (integument)
Skin derivatives (appendages)
Sweat (sudoriferous) glands
Sebaceous (oil) glands
Hairs and hair follicles
Nails
Skin functions
Protection
The skin consists of at least three types of barriers: chemical, physical, and biological
Protects deeper tissue from:
Mechanical damage
Chemical damage
Bacterial damage
Thermal damage
UV radiation
Desiccation
Body temperature regulation
Cutaneous sensation
Metabolic functions (synthesizes vitamin D precursor, etc.)
Blood reservoir
It can hold about 5% of the body's total blood volume, which can then be shunted into general circulation for use by vigorously working muscles and/or other body organs
Excretion
Eliminating nitrogen-containing wastes (ammonia, urea, uric acid), NaCl, H2O, etc.
Skin Structure
Epidermis (5 strata)
Stratified squamous epithelium with keratin
Cells are tightly connected by desmosomes
Keratinocytes form several layers
Layers of the epidermis
Stratum basale
Single row of cells that serve as the origin of keratinocytes for all superficial strata
High mitotic activity
Contains melanocytes
Accounts for about 10-25% of stratum basale cells
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
20-30 cell layers thick, and accounts for three-quarters of epidermal thickness
Located on the exposed surface of the skin
Protective barrier of dead, durable, and expendable cells
Cells are filled with keratin (keratin-filled plasma membranes)
Helps give the epidermis its protective properties, etc.
The thickness will vary depending on use
Calluses can develop on the palms of hands and soles of feet
Glycolipids secreted between cells provide waterproofing and preserve some permeability characteristics of the skin
Allows for transdermal medications (nicotine patches, birth control patches, etc.)
Melanin
Pigment produced by melanocytes
Gets packaged in melanosomes and then deposited into the keratinocytes in more superficial layers
Melanin granules then position themselves on the superficial (or sunny) side of the keratinocyte nucleus to protect against UV radiation
The amount produced depends on genetics and exposure to sunlight
Cell production of tyrosinase (acts on the amino acid tyrosine) is critical for melanin production
Albinism - failure to produce tyrosinase is the most common form
Dermis
Strong, flexible connective tissue
Two layers
Papillary layer
Thin, superficial layer of areolar connective tissue
Accounts for about 20% of dermis thickness
Supports and nourishes the overlying epidermis through blood vessels (dermal capillaries)
Has nipple-like projections called dermal papillae
Has ridges that increase surface area for things like fingerprints
Pain receptors
Capillary loops
Reticular layer
Accounts for about 80% of dermis thickness
Dense irregular connective tissue with a meshwork of collagen and elastic fibers
Blood vessels
Glands
Nerve receptors
Hypodermis (subcutaneous)
Technically, it's not part of the skin
Anchors skin to the underlying organs
Composed mostly of adipose tissue (accounts for half of the body's stored fat)
Appendages of the Skin
Sebaceous glands
Produces oil (sebum)
Softens and lubricates the hair and skin
Most have ducts that empty into hair follicles
Distributed body-wide except for palms of hands and soles of feet
Glands are activated at puberty (under hormonal control)
Clinical: Acne
Accutane is teratogenic (birth defect)
Sweat (sudoriferous) glands
Widely distributed in the skin (up to 3 million body wide)
Comes in two types:
Eccrine
Coiled, tubular portion in the dermis with an opening via a duct to the pore on the skin’s surface
Distributed body-wide (most numerous)
Helps dissipate excess heat through evaporative cooling
Apocrine
Ducts empty into hair follicles
Localized to axillary and pubic (anogenital) areas
Only about 2000 in number
Activated by stress, pain, and sexual excitement, not temperature
Fatty acid and protein secretion
Bacteria breakdown produces body odor
Modified sweat glands
Ceruminous glands
Found in the lining of the external ear canal
Secretion mixes with sebum to produce cerumen (earwax)
Mammary glands
Hair
Distributed body-wide except for palms, soles, lips, nipples, and part of the external genitalia
Strand of dead, hard keratinized epithelial cells projecting from an invaginated tunnel in the epidermal and dermal layers called the hair follicle
Hair follicle
Tubular invaginations of the epidermis
Formed by mitotically active stratum basale cells
Melanocytes provide pigment for hair color
Dermal capillaries provide the blood supply
3 major parts:
Bulb - growth zone at the inferior end of the hair follicle
Root - part of the hair enclosed in the hair follicle
Shaft - visible part of hair; projects from the surface of the skin
Arrector pili (smooth muscle)
Clinical: Minoxidil (Rogaine)
Nails
Nail structures
Nail fold (lateral and proximal skin coverings)
Eponychium (cuticle)
Nail body
A sheet of hard keratin attached to the nail bed
Lanula - crescent-shaped vascular area at the proximal end of the nail bed and visible through the nail. Used for visual checks of oxygen status in patients.
Clinical: Eponychiitis, ingrown toenail
Clinical Applications
Injection Sites
Intradermal (ID)
Subcutaneous (“subcue” or SQ)
Intramuscular (IM)
Intravenous (IV)
Blisters
Fluid-filled pocket between epidermis and dermis
Lines of Cleavage
Formed by uniform alignment of collagen and elastic fibers
Stretch marks
Decubitus ulcers or "bed sores"
Blood supply restricted → ischemia (O2 reduced) → necrosis (tissue death)
Bacterial infections result, difficult-to-heal, secondary intention
Areas of highest risk are least padded (elbow, heels, backbone)
Patients of high risk: elderly (less body fat for padding) in care homes
The importance of rotating patient positions, artificial padding, and clean bedding
Burns
Tissue damage inflicted by heat, electricity, UV radiation, or chemicals that denature proteins and cause cell death in affected areas
Associated dangers
Catastrophic loss of body fluids can lead to:
Dehydration
Electrolyte imbalance
Renal failure
Circulatory shock
Infection
Sepsis (widespread bacterial infection) is the leading cause of death in burn victims
Rule of Nines
A way to approximate the extent of burns
Special tables are used when greater accuracy is desired
Severity of burns
1st degree
Only the epidermis is damaged
Redness, pain, and swelling (inflammation)
Usually heals in 2-3 days
2nd degree
Damage to the epidermis and dermis
Same symptoms as 1st degree, but also blistering
Usually requires 3-4 weeks to heal
3rd degree
Total tissue destruction (epidermis, dermis, and even hypodermis)
Tissue becomes discolored, but no edema, pain, etc.
Usually requires a skin graft
Skin Cancer
The most common type of cancer
3 types of skin cancer:
Basal cell carcinoma
Least malignant but most common type
Accounts for about 80% of all skin cancers
Arises from stratum basale cells that then go on and invade the underlying dermis and hypodermis
Results in a shiny, dome-shaped nodule most commonly found in sun-exposed regions of the face
Slow growth and, therefore, metastasis seldom
Full cure by surgical excision in 99% of cases
Squamous cell carcinoma
Arises from the stratum spinosum
Results in a scaly, reddened papule, most commonly on the head (scalp, ears, and lower lip) and hands
Tends to grow rapidly and will metastasize if not removed
The chance of a complete cure is good if the condition is caught early and removed by surgery or radiation
Malignant melanoma
Most deadly of skin cancers
Accounts for only about 5% of all skin cancers, but 90% of skin cancer deaths are due to metastasis and resistance to chemotherapy
Cancer of melanocytes
Metastasizes rapidly to the lymph and blood vessels
Can occur body-wide
Most appear spontaneously, but about 1/3 appear from pre-existing moles (wherever there is pigment)
The key to survival is early detection, so it is strongly encouraged to evaluate moles regularly using the ABCDE rule:
A = Asymmetry
B = Irregular border
C = Color
D = Larger than 6mm in diameter (about the size of a pencil eraser)
E = Elevation above the skin surface and evolution (changes over time)