Introduction to Anatomy and Physiology

Overview of Anatomy and Physiology

Anatomy and physiology are closely integrated fields that study the structure and function of the human body. Mastery of foundational terminology and concepts is essential for success in this course.

• Anatomy: The study of the structure of body parts and their relationships to one another.

• Physiology: The study of the function of the body’s structural machinery.

• Gross Anatomy: Study of structures visible to the naked eye.

• Cytology: Study of cells.

• Histology: Study of tissues.

• Tissues: Groups of similar cells performing a common function.

• Organs: Structures composed of at least two tissue types that perform specific functions.

Levels of Organization

The human body is organized into hierarchical levels, each with increasing complexity.

1. Chemical (atoms and molecules)

2. Cellular (cells and their organelles)

3. Tissue (groups of similar cells)

4. Organ (contains two or more types of tissues)

5. Organ System (organs that work closely together)

6. Organismal (the human body as a whole)

Organ System Overview

Each organ system has a specific function and set of main organs.

• Integumentary: Protects body, regulates temperature (skin, hair, nails).

• Skeletal: Supports and protects organs, stores minerals (bones, joints).

• Muscular: Movement, posture, heat production (skeletal muscles).

• Nervous: Fast-acting control system (brain, spinal cord, nerves).

• Endocrine: Hormone production, regulates processes (glands such as thyroid, pancreas).

• Cardiovascular: Transports blood (heart, blood vessels).

• Lymphatic: Returns fluid to blood, immunity (lymph nodes, spleen).

• Respiratory: Gas exchange (lungs, trachea).

• Digestive: Breaks down food, absorbs nutrients (stomach, intestines).

• Urinary: Eliminates waste, regulates water (kidneys, bladder).

• Reproductive: Produces offspring (ovaries, testes).

Medical Terminology and Anatomical Terms

Understanding medical terminology and anatomical terms is crucial for describing body regions and positions.

• Terminologia Anatomica: International standard for anatomical terminology.

• Anatomical Position: Body standing upright, facing forward, arms at sides, palms facing forward.

• Directional Terms: Used to describe locations of structures (e.g., superior, inferior, anterior, posterior, medial, lateral, proximal, distal, superficial, deep).

Body Cavities and Serous Membranes

The body contains several cavities that house organs, lined by serous membranes.

• Ventral Body Cavity: Includes thoracic and abdominopelvic cavities.

• Serous Membranes: Double-layered membranes that reduce friction between organs and cavity walls.

• Parietal Layer: Lines cavity walls.

• Visceral Layer: Covers organs.

• Cavity: Space between layers filled with serous fluid.

Homeostasis

Homeostasis is the maintenance of a stable internal environment. It is regulated by physiological processes and feedback mechanisms.

• Negative Feedback: Opposes deviations from normal (e.g., body temperature regulation).

• Positive Feedback: Enhances deviations (e.g., blood clotting).

The Cellular Level of Organization

Cell Structure and Function

Cells are the basic units of life, each containing specialized structures called organelles that perform distinct functions.

Plasma (Cell) Membrane Structure

The plasma membrane separates the cell from its environment and controls movement of substances.

• Phospholipid Bilayer: Hydrophilic heads face outward, hydrophobic tails inward.

• Integral Proteins: Embedded in membrane, form channels for ions and water.

• Peripheral Proteins: Attached to membrane surface, often act as enzymes.

• Functions of the Cell Membrane:

  1. Physical isolation

  2. Regulation of exchange with environment

  3. Sensitivity to environment

  4. Structural support

Membrane Transport Mechanisms

Substances move across the cell membrane by passive or active processes.

• Permeability: The property of a membrane that determines which substances can pass through.

• Types:

  • Impermeable: Nothing passes through.

  • Freely Permeable: Anything can pass through.

  • Selectively Permeable: Some substances can pass, others cannot.

Passive Transport

• Diffusion: Movement of molecules from high to low concentration until equilibrium is reached.

• Osmosis: Diffusion of water across a selectively permeable membrane toward higher solute concentration.

• Facilitated Diffusion: Carrier proteins help large molecules (e.g., glucose) cross the membrane without energy use.

• Factors Influencing Diffusion Rate:

  1. Distance

  2. Ion and molecule size

  3. Temperature

  4. Concentration gradient

  5. Electrical forces

Osmosis and Tonicity

• Isotonic Solution: Same solute concentration as cell; no net water movement.

• Hypotonic Solution: Lower solute concentration than cell; water enters cell, may cause hemolysis (cell bursts).

• Hypertonic Solution: Higher solute concentration than cell; water leaves cell, may cause crenation (cell shrinks).

• Osmotic Pressure: The force with which water moves toward a higher solute concentration.

• Hydrostatic Pressure: The pressure exerted by a fluid due to gravity.

Active Transport

• Active Transport: Movement of substances against their concentration gradient using ATP.

• Sodium-Potassium Exchange Pump: Moves 3 Na+ out and 2 K+ into the cell per ATP used, maintaining ion gradients essential for cell function.

• Vesicular Transport:

  • Endocytosis: Import of materials via vesicles (includes phagocytosis and pinocytosis).

  • Exocytosis: Export of materials via vesicles.

ATP: The Energy Molecule

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

• ATP Cycle Equation:

• ATP is regenerated from ADP by phosphorylation.

Cell Life Cycle and Division

Cells undergo a life cycle that includes growth, DNA replication, and division.

• Interphase: Period of cell growth and normal function; includes G0, G1, S, and G2 phases.

• Mitosis: Division of the nucleus into two identical daughter cells. Stages include prophase, metaphase, anaphase, and telophase.

• Cytokinesis: Division of the cytoplasm.

Tumors, Cancer, and Differentiation

• Tumor: Mass of abnormal cells.

• Malignant Tumor: Cancerous, invades tissues.

• Invasion: Spread of cancer into surrounding tissues.

• Metastasis: Spread of cancer cells to distant sites.

• Oncogenes: Genes that can cause cancer when mutated.

• Mutagens: Agents that cause mutations.

• Carcinogens: Cancer-causing substances.

• Cellular Differentiation: Process by which cells become specialized in structure and function.

Key Terminology

• Plasma (cell) membrane, phospholipid bilayer, peripheral proteins, integral proteins, channels, cytoplasm, cytosol, organelles, centriole, cilia, flagella, ribosomes, mitochondria, nucleus, chromosomes, nucleoli, endoplasmic reticulum, Golgi apparatus, lysosomes

• Permeability, diffusion, concentration gradient, osmosis, osmotic pressure, hydrostatic pressure, tonicity, isotonic/hypotonic/hypertonic solutions, hemolysis, crenation, carrier proteins, facilitated diffusion, active transport, ion pumps, sodium-potassium exchange pump, endocytosis, pinocytosis, phagocytosis, pseudopodia

• Cell division, mitosis (all stages), chromosome, histone, nucleosome, chromatin, nucleoli, gene, G0, G1, S, G2 phases, interphase, DNA replication, centromere, spindle fibers, daughter chromosomes, telophase, cytokinesis, ATP <--> ADP cycle

Additional info: Some explanations and definitions have been expanded for clarity and completeness based on standard Anatomy & Physiology textbooks.