Introduction to Anatomy & Physiology

Science, Anatomy, and Physiology

• Science is the systematic observation and measurement of nature to explain phenomena.

• Anatomy is the study of body structure and form.

• Physiology is the study of body function.

• Structure and function are closely related; the form of a body part often determines its function (principle of complementarity).

Levels of Structural Organization

• Chemical level: Atoms and molecules.

• Cellular level: Molecules form cellular structures.

• Tissue level: Groups of similar cells and extracellular matrix (ECM) performing a common function.

• Organ level: Two or more tissue types performing a specialized task.

• Organ system level: Two or more organs performing a broad function.

• Organism level: All organ systems working together.

Organ Systems and Functions

• Integumentary: Protection, vitamin D synthesis, water retention, temperature regulation.

• Skeletal: Support, protection, movement, blood cell production, calcium storage.

• Muscular: Movement, heat production, control of openings.

• Nervous: Rapid regulation via nerve impulses.

• Endocrine: Regulation via hormones.

• Cardiovascular: Transport of blood, nutrients, wastes.

• Lymphatic: Returns tissue fluid, immunity.

• Respiratory: Gas exchange, acid-base balance.

• Digestive: Digestion, absorption, waste removal, fluid/electrolyte/acid-base balance.

• Urinary: Waste removal, fluid/electrolyte/acid-base balance.

• Reproductive (male/female): Gamete production, hormone secretion, sexual function, fetal development (female).

Anatomical Position and Directional Terms

• Anatomical position: Standing upright, feet shoulder-width apart, arms at sides, head and palms facing forward.

• Directional terms:

  • Anterior (ventral): Toward the front

  • Posterior (dorsal): Toward the back

  • Superior (cranial): Toward the head

  • Inferior (caudal): Toward the tail/below

  • Proximal: Closer to point of origin

  • Distal: Farther from point of origin

  • Medial: Toward midline

  • Lateral: Away from midline

  • Superficial: Closer to body surface

  • Deep: Farther below the surface

Body Planes and Cavities

• Sagittal plane: Divides body into right and left (midsagittal = equal halves; parasagittal = unequal).

• Frontal (coronal) plane: Divides body into anterior and posterior.

• Transverse (horizontal) plane: Divides body into superior and inferior.

• Oblique plane: Cut at an angle.

• Body cavities:

  • Posterior: Cranial (brain) and spinal (spinal cord), filled with cerebrospinal fluid.

  • Anterior: Thoracic (pleural, mediastinum, pericardial) and abdominopelvic (abdominal, pelvic, peritoneal).

Homeostasis and Feedback Loops

• Homeostasis: Maintenance of a relatively stable internal environment.

• Feedback loop: A change in a variable produces effects that feed back on the variable.

• Negative feedback: Opposes the initial change to maintain stability (e.g., temperature regulation).

• Positive feedback: Reinforces the initial change (e.g., blood clotting, childbirth).

• Feedback loop steps: Stimulus → Receptor → Control Center → Effector → Response.

Core Principles of A&P

• Feedback loops (negative and positive)

• Structure-function relationship

• Gradients (pressure, concentration, temperature)

• Cell-cell communication (electrical and chemical signals)

The Chemistry of Life

Basic Chemistry Concepts

• Matter: Anything with mass and volume.

• Atom: Smallest unit of matter retaining properties of an element.

• Element: Substance made of identical atoms; defined by number of protons (atomic number).

• Subatomic particles: Protons (+, nucleus), neutrons (0, nucleus), electrons (−, shells).

• Isotope: Same number of protons, different number of neutrons.

• Radioisotope: Unstable isotope that emits radiation.

Major and Trace Elements in the Body

• 96% of body mass: Oxygen, carbon, hydrogen, nitrogen

• Mineral elements (<4%): Na, K, Ca, Cl, Mg, P, S

• Trace elements (0.01%): Fe, Cu, I, Zn, etc.

Types of Mixtures

• Suspension: Large particles, settle out (e.g., blood).

• Colloid: Small particles, do not settle (e.g., milk).

• Solution: Solute dissolved in solvent (e.g., glucose in water).

Chemical Bonds

• Ionic bond: Electron transfer between metal and nonmetal; forms ions (cations and anions).

• Covalent bond: Electron sharing between nonmetals; can be single, double, or triple bonds.

• Nonpolar covalent: Equal sharing (e.g., O2, N2).

• Polar covalent: Unequal sharing; creates dipoles (e.g., H2O).

• Hydrogen bond: Weak attraction between polar molecules (not a true chemical bond).

Acids, Bases, and pH

• Acid: Donates H+; increases H+ concentration.

• Base: Accepts H+; decreases H+ concentration.

• pH: Measures H+ concentration; 7 is neutral, <7 acidic, >7 basic.

• Each pH unit = 10-fold change in H+ concentration.

• Buffer: Resists pH changes (e.g., carbonic acid–bicarbonate system).

Organic Compounds

• Carbohydrates: C, H, O; main fuel; hydrophilic; monomer = monosaccharide (e.g., glucose).

• Lipids: C, H, (some O); hydrophobic; types: fatty acids, triglycerides, phospholipids, steroids.

• Proteins: C, H, O, N; monomer = amino acid; functions: structure, enzymes, movement, defense.

• Nucleic acids: C, H, O, N, P; DNA and RNA; monomer = nucleotide.

Macromolecule Structure and Function

• Carbohydrates: Energy storage (glycogen in animals, starch in plants), cell recognition (glycoproteins).

• Lipids: Energy storage (triglycerides), membrane structure (phospholipids), hormones (steroids).

• Proteins: Structure (collagen), enzymes (amylase), transport (hemoglobin), movement (actin/myosin).

• Nucleic acids: Store and transmit genetic information (DNA, RNA).

ATP and Cellular Energy

• ATP (adenosine triphosphate): Main energy currency; made from ADP + phosphate + energy.

• Energy released by hydrolysis of phosphate bond.

• ATP production requires oxygen and is continuous.

The Cell

Basic Cell Structure

• Three main components: Plasma membrane, cytoplasm, nucleus.

• Cytoplasm: Contains cytosol (fluid), organelles, and cytoskeleton.

• Nucleus: Contains DNA, produces RNA, controls cell activities.

Plasma Membrane

• Phospholipid bilayer: Hydrophilic heads face water; hydrophobic tails face inward.

• Fluid mosaic model: Membrane is dynamic, with proteins, lipids, and carbohydrates.

• Membrane proteins: Integral (embedded), peripheral (surface), transmembrane (span membrane).

• Protein functions: Channels, carriers, receptors, enzymes, structural support, cell linking.

• Other components: Cholesterol (stabilizes), glycoproteins/glycolipids (cell recognition).

Membrane Transport

• Passive transport: No energy required; includes diffusion and osmosis.

• Diffusion: Solute moves from high to low concentration (simple: through bilayer; facilitated: via protein).

• Osmosis: Water moves toward higher solute concentration via aquaporins or between phospholipids.

• Tonicity: Isotonic (no net water movement), hypertonic (cell loses water), hypotonic (cell gains water).

• Active transport: Requires ATP; moves substances against concentration gradient (primary: direct ATP use; secondary: uses existing gradient).

• Vesicular transport: Moves large substances via vesicles (endocytosis, exocytosis, phagocytosis, pinocytosis, receptor-mediated endocytosis).

Cytoskeleton and Organelles

• Cytoskeleton: Microfilaments (shape, movement), intermediate filaments (strength), microtubules (transport, division).

• Organelles:

  • Ribosomes: Protein synthesis (free: cytosol; bound: membranes/secretion).

  • Endoplasmic reticulum (ER): Rough (protein synthesis/modification), smooth (lipid synthesis, detoxification, Ca2+ storage).

  • Golgi apparatus: Modifies, sorts, packages proteins/lipids.

  • Lysosomes: Digestive enzymes; autophagy.

  • Peroxisomes: Break down fatty acids, detoxify.

  • Mitochondria: ATP production (cellular respiration).

Protein Synthesis and DNA Replication

• Central dogma: DNA → RNA → Protein.

• Transcription: DNA to RNA (nucleus).

• Translation: RNA to protein (ribosome).

• DNA replication: Occurs before cell division; produces two identical DNA molecules.

Cell Cycle and Division

• Cell cycle: Interphase (G1, S, G2) + mitotic phase (mitosis + cytokinesis).

• Mitosis: Prophase, metaphase, anaphase, telophase (PMAT).

• Cytokinesis: Division of cytoplasm.

• Result: Two genetically identical daughter cells.

• Checkpoints: Ensure proper division; prevent damaged cells from dividing.

• Apoptosis: Programmed cell death; removes damaged/unnecessary cells.

• Cancer: Uncontrolled cell division; can be benign or malignant (metastasis = spread).

Histology: The Study of Tissues

Introduction to Tissues and ECM

• Tissue: Group of related cells and their environment performing common functions.

• Histology: Study of normal tissue structure.

• Extracellular matrix (ECM): Material surrounding cells; provides strength, support, and regulates cell behavior.

• ECM components: Ground substance (gel with ECF, GAGs, proteoglycans) and protein fibers (collagen, elastic, reticular).

Cell Junctions

• Tight junctions: Zipper-like seals; block passage between cells.

• Desmosomes: Button-like; resist mechanical stress.

• Gap junctions: Channels for communication/transport between cells.

Types of Tissues

• Epithelial: Covers/lines surfaces, forms glands; functions: protection, secretion, transport, sensation.

• Connective: Binds, supports, protects, transports; cells scattered in abundant ECM.

• Muscle: Contracts to generate force; types: skeletal (voluntary), cardiac (heart), smooth (hollow organs).

• Nervous: Sends/receives messages; main cells: neurons (impulse conduction), neuroglia (support).

Epithelial Tissue Classification

• Simple: One layer; for diffusion/transport.

• Stratified: Multiple layers; for protection.

• Pseudostratified: Appears multilayered, but is one layer.

• Cell shapes: Squamous (flat), cuboidal (cube), columnar (tall).

Connective Tissue Types

• Loose (areolar): More ground substance, fewer fibers; wraps/cushions tissues.

• Dense: More fibers; regular (parallel, tendons/ligaments), irregular (random, dermis), elastic (stretch/recoil).

• Adipose: Fat storage, insulation, protection.

• Reticular: Supports cells in organs.

• Cartilage: Chondrocytes in lacunae; types: hyaline (support), fibrocartilage (compression), elastic (flexibility).

• Bone: Osteocytes in mineralized ECM; support, protection, mineral storage.

• Blood: Cells in plasma; transport.

Muscle and Nervous Tissue

• Skeletal muscle: Voluntary, multinucleated, striated.

• Cardiac muscle: Involuntary, branched, intercalated discs, heart only.

• Smooth muscle: Involuntary, spindle-shaped, hollow organs.

• Neurons: Conduct impulses; parts: cell body, axon, dendrites.

• Neuroglia: Support, protect, and nourish neurons.

Glands and Membranes

• Glands: Epithelial structures for secretion; endocrine (ductless, hormones), exocrine (ducts, onto surfaces).

• Membranes: Thin sheets lining surfaces/cavities; types: serous (internal cavities), synovial (joints), mucous (open to outside), cutaneous (skin).

Tissue Repair

• Regeneration: Damaged cells replaced by same type; restores function.

• Fibrosis: Damaged cells replaced by scar tissue (dense irregular CT); function may be lost.

• Repair capacity: Epithelial and most connective tissues regenerate well; cartilage, cardiac, and skeletal muscle often heal by fibrosis.

• Other factors: Nutrition (protein, vitamin C), blood supply.

Table: Comparison of Tissue Types

Example: Feedback Loop in Body Temperature Regulation

• Stimulus: Body temperature rises above normal.

• Receptor: Temperature sensors in brain detect change.

• Control center: Brain processes information.

• Effector: Sweat glands activated, blood vessels dilate.

• Response: Body cools down, temperature returns to normal.

Example: Structure-Function Principle

• Thin lung tissue allows rapid gas exchange; thick tissue would slow exchange.

Key Equations (in LaTeX format)

• pH calculation:

• ATP hydrolysis:

Additional info:

• Study strategies such as spaced repetition, retrieval practice, and dual coding are recommended for mastering A&P content.

• Understanding terminology, body regions, and planes is essential for communication and avoiding medical errors.