Comprehensive Study Guide for BSC2085: Anatomy and Physiology I
Fundamentals of Anatomy, Physiology, and Homeostasis
Hierarchy of Structural Organization: Life is organized in a sequence of increasing complexity:
Atoms: The basic building blocks of matter.
Molecules: Combinations of atoms.
Cells: The basic unit of life.
Tissues: Groups of similar cells with a common function.
Organ: Composed of multiple tissues performing specific functions.
Organ System: Groups of organs working together.
Organism: The total living being.
Homeostasis: The condition in which the body maintains a relatively stable internal environment within limited ranges. It is not a static state but a dynamic state of equilibrium. Homeostatic imbalance is considered the primary cause of most diseases. Without negative feedback mechanisms, the body's chemistry would fall out of balance.
Homeostatic Control Mechanisms: Regardless of the variable being regulated, all control mechanisms consist of at least three interdependent components:
Receptor: Senses changes in the environment.
Control Center: Processes information (e.g., ADH functions as a thermostat-like control in fluid regulation).
Effector: Executes the response to return to equilibrium.
Feedback Loop Types:
Negative Feedback: The most common mechanism. It works to decrease the original stimulus or prevent sudden severe changes within the body. Examples include the regulation of blood glucose levels and body temperature.
Positive Feedback: These mechanisms tend to increase or enhance the original stimulus. A primary example is the enhancement of labor contractions during childbirth.
Clinical Scenario (Hypertension): If a client has hypertension (high blood pressure) and develops arteriosclerosis (hardening of arteries), the resulting increased peripheral resistance further worsens the hypertension. This creates a positive feedback loop because the initial condition (high pressure) leads to changes that further increase that pressure.
Functional Characteristics of Life:
Maintaining Boundaries: The internal environment must remain distinct from the external environment.
Responsiveness (Irritability): The ability to sense changes (stimuli) in the environment and react/respond to them. The nervous system is the primary responder to environmental stimuli.
Metabolism: All chemical reactions within the body.
Excretion: Removal of metabolic wastes (e.g., increased breathing rate due to buildup is an example of excreting metabolic waste).
Movement: Locomotion and propulsion.
Growth and Reproduction: Essential for species survival.
Note on Decay: Decay is notably not a functional characteristic of life.
Survival Needs:
Nutrients: Chemical substances for energy and cell building.
Oxygen: Required for chemical reactions.
Water: The single most abundant chemical substance in the body, accounting for to of total body weight.
Atmospheric Pressure: Necessary for proper breathing and gas exchange.
Anatomic Terminology and Body Cavities
Anatomical Fields:
Gross Anatomy: The study of structures visible to the naked eye.
Microscopic Anatomy: The study of structures too small to be seen without a microscope.
Cytology: Specifically the study of cells (not to be confused with regional anatomy).
Embryology: Subdivison of anatomy concerning developmental changes occurring from conception to birth.
Body Cavities and Membranes:
Heart Location: Found within the pericardial cavity (part of the mediastinum).
Serous Membranes (Serosa): Thin, double-layered membranes that line closed body cavities and cover organs. Their primary function is to decrease friction between organs using secreted serous fluid.
Parietal Layer: Lines the cavity walls (e.g., Parietal Pleura lines the thoracic cavity; Parietal Peritoneum lines the peritoneal cavity wall).
Visceral Layer: Covers the external surface of the organs (e.g., Visceral Pericardium covers the heart surface; Visceral Pleura covers the lungs).
Medical Imaging: Imaging is essential for discovering obstructed blood supplies in organs and tissues. To localize a brain tumor, an MRI (Magnetic Resonance Imaging) is typically the most effective device.
Cellular Level of Organization
Cell Theory Concepts:
The cell is the basic structural and functional unit of all living organisms.
The activity of an organism depends on both the individual and collective activities of its cells.
Organisms are composed mainly of four elements: Carbon, Hydrogen, Nitrogen, and Oxygen.
Plasma Membrane Structure:
Fluid Mosaic Model: Describes the membrane as a bilayer of phospholipids with embedded proteins.
Phospholipids: Consist of a polar (hydrophilic) head and a nonpolar (hydrophobic) tail. The bilayer is largely impermeable to water-soluble molecules.
Cholesterol: Found in substantial amounts within the plasma membrane to provide stability.
Constituents: Includes glycolipids, phospholipids, and glycoproteins. Messenger RNA () is not a constituent of the plasma membrane.
Specialized Structures:
Microvilli: Fingerlike projections of the plasma membrane that increase surface area for absorption.
Cell Junctions: Tight junctions (impermeable), Desmosomes (anchoring), and Gap junctions (communication). Peroxisomes are organelles, not cell junctions.
Plasma Membrane Functions:
Encloses cell contents.
Acts as a site for cell-to-cell interaction and recognition.
Selective Permeability: It regulates what enters and exits the cell. It does not completely prevent ions like or from crossing but manages their transport to maintain potentials.
Membrane Transport:
Passive Transport: Movement of substances down their concentration gradient without the consumption of ATP. Includes diffusion and osmosis.
Diffusion Rate: Influenced by concentration gradient (greater gradient = faster rate) and temperature (higher temperature = faster rate).
Osmosis: Diffusion of water. Water can move through transmembrane protein channels called aquaporins.
Tonicity:
Isotonic: No net movement of water.
Hypertonic: Cells lose water and shrink (a process called crenation).
Hypotonic: Cells gain water, swell, and may burst (lysis). A red blood cell placed in pure water will swell and burst.
Active and Vesicular Transport:
Phagocytosis: "Cell eating" of solid material. Once inside a vacuole, a lysosome combines with it to digest the contents.
Exocytosis: Discharging particles from the inside of the cell to the outside.
Transcytosis: Moving an endosome from one side of a cell to the other and releasing contents via exocytosis.
Membrane Potential:
Resting Membrane Potential: Maintained by the diffusion of ions (leakage) and active transport.
In a polarized state, the inside of the cell is negative relative to the outside.
Extracellular (Sodium) levels are high, while intracellular (Potassium) levels are high. Sodium is the most common extracellular ion.
Second Messengers: Intracellular signals like Cyclic AMP and Calcium that activate protein kinases.
Subcellular Structures and Organelles
Cytoplasm and Cytosol:
Cytosol: The fluid part of the cytoplasm, mainly composed of water.
Inclusions: Chemical substances like melanin (not organelles).
Organelles:
Mitochondria: Site of aerobic cellular respiration and ATP synthesis. They contain their own DNA and RNA.
Lysosomes: Contain acid hydrolases for digestion; potentially dangerous if they rupture.
Centrioles: Hollow tubes made of tubulins that organize the mitotic spindle during cell division.
Microtubules: Hollow tubes of spherical protein subunits.
Microfilaments: Thin strands of the contractile protein actin (not myosin).
Ribosomes: Site of protein synthesis.
Genetics and Protein Synthesis
DNA and RNA:
Gene: A segment of DNA carrying instructions for one polypeptide chain.
$mRNA$ (Messenger RNA): Carries the template for protein synthesis from the nucleus to the ribosome.
$tRNA$ (Transfer RNA): Brings specific amino acids to the ribosome ("factory site").
$rRNA$ (Ribosomal RNA): Forms part of the ribosome structure.
Transcription/Translation: In transcription, a DNA triplet is coded into an $mRNA$ codon. The $mRNA$ codon is an exact copy of the DNA triplet, except Uracil substituted for Thymine. The $tRNA$ anticodon matches the $mRNA$ codon.
Cell Life Cycle:
Interphase: The metabolic or growth phase where DNA replication occurs.
$G_2$ Phase: Final preparations for cell division.
Mitosis (M Phase): Replication of the nucleus. It produces two daughter cells with the exact same number of chromosomes as the parent cell.
Cytokinesis: The division of the cytoplasmic mass into two parts.
Apoptosis: Programmed cell suicide. Cancer cells are characterized by a failure to undergo apoptosis.
Hyperplasia: Growth of an organ through an increase in the number of cells (differentiated from hypertrophy).
Histology: The Study of Tissues
Epithelial Tissue:
Characteristics: Exhibits polarity (apical/free surface and basal surface), is supported by a basement membrane, and is highly cellular. It is avascular (lacks blood vessels) but innervated.
Classifications:
Simple Squamous: Single layer of flat cells; involved in filtration/diffusion.
Simple Cuboidal: Associated with secretion and absorption.
Simple Columnar: Often possess microvilli in the digestive tract for absorption.
Pseudostratified Columnar: Appears layered but all cells touch the basement membrane; often ciliated in the respiratory tract.
Stratified Squamous: Multiple layers; provides protection from abrasion.
Transitional: Lines the bladder; changes shape between cuboidal and squamous depending on distension.
Glandular Epithelium:
Endocrine Glands: Ductless glands that secrete hormones directly into the blood (e.g., thyroid).
Exocrine Glands: Use ducts to secrete products; classified by structure (e.g., simple, compound, alveolar).
Merocrine: No alteration to the cell during secretion.
Holocrine: Cells accumulate product until they rupture/die.
Apocrine: Apex of cell is pinched off (limited in humans).
Connective Tissue (CT):
Components: Consists of Cells, Fibers, and Ground Substance. Fibers and Ground Substance together form the Extracellular Matrix.
Matrix Fibers:
Collagen: Provides the highest tensile strength (white fibers).
Elastic: Allows for stretch and recoil (yellow fibers).
Reticular: Fine, branched fibers forming internal skeletons.
CT Types:
Connective Tissue Proper: Includes Adipose (nutrient storage; mostly matrix), Tendons (Dense Regular CT), and Ligaments.
Cartilage: Avascular; receives resilience from high water content.
Hyaline: Most abundant; found at bone ends and in embryonic skeleton.
Elastic: Found in the ear and epiglottis.
Fibrocartilage: Shock-absorber; found in intervertebral discs and the knee meniscus.
Bone (Osseous Tissue): Contains lacunae, calcium salts, and blood vessels.
Blood: A unique fluid connective tissue.
Nervous and Muscle Tissue:
Nervous Tissue: Composed of neurons and supporting cells (glia), not collagen fibers.
Muscle Tissue: Highly cellular and well-vascularized; responsible for movement.
The Skeletal System
Functions: Support, protection, movement, mineral storage (calcium/phosphate), blood cell production (hematopoiesis), and fat storage. Communication is notably not a skeletal function.
Gross Anatomy of Long Bones:
Diaphysis: The shaft; contains the medullary cavity (hollow center filled with yellow fat marrow in adults).
Epiphysis: The bone ends, covered by articular (hyaline) cartilage.
Epiphyseal Plate: Growth plate in children (hyaline cartilage); becomes the Epiphyseal Line in adults.
Membranes:
Periosteum: Outer covering; secured by Perforating (Sharpey's) Fibers. The inner layer is osteogenic (containing osteoblasts/osteoclasts).
Endosteum: Membrane lining the internal canals and trabeculae.
Bone Tissue Types:
Compact Bone: Dense outer layer. Structural unit is the Osteon (Haversian System).
Central (Haversian) Canal: Contains nerves and blood vessels.
Volkmann's (Perforating) Canals: Connect blood/nerve supply between osteons.
Lacunae: Small spaces where osteocytes reside.
Canaliculi: Hair-like canals connecting lacunae for cell nutrient transfer.
Spongy Bone: Porous inner layer made of Trabeculae, which align along lines of stress.
Bone Cells:
Osteogenic Cells: Stem cells.
Osteoblasts: Bone-forming cells (secretors of matrix).
Osteocytes: Mature cells that maintain the matrix.
Osteoclasts: Large cells that resorb (break down) bone.
Bone Development and Growth:
Ossification (Osteogenesis):
Intramembranous: Bone develops from fibrous membranes (e.g., cranial bones).
Endochondral: Bone replaces a hyaline cartilage model (most bones).
Growth:
Interstitial Growth: Growth in length at the epiphyseal plate.
Appositional Growth: Growth in width/thickness.
Hormonal Regulation:
Growth Hormone: Stimulates growth during childhood.
Sex Hormones: Trigger adolescent growth spurts and eventual epiphyseal closure. Early elevation can cause premature closure.
Parathyroid Hormone (PTH): Released when blood calcium is low; stimulates osteoclasts to resorb bone and release calcium into the blood.
Calcitonin: Produced by the thyroid; lowers blood calcium.
Wolff's Law: Bone grows or remodels in response to the demands/stresses placed upon it.
Bone Disorders and Fractures:
Osteoporosis: Bone resorption outpaces deposit; bones become porous and thin. Prevention includes Vitamin D, Calcium, and weight-bearing exercise.
Osteomalacia: Soft, poorly mineralized bones.
Osteomyelitis: Bone infection/inflammation.
Fracture Types:
Transverse: Perpendicular to bone axis.
Greenstick: Partial break; common in children due to flexible bone.
Comminuted: Bone fragments into three or more pieces; common in the elderly.
Compression: Bone is crushed (e.g., vertebrae).