Introduction to Anatomy & Physiology

Definition and Scope

Anatomy and physiology are foundational sciences for understanding the human body.

• Anatomy: The study of structure and organization of living organisms.

• Physiology: The study of how the body functions, including chemical and physical processes.

• Approaches include teleological (purpose-driven), mechanistic (process-driven), and the concept of emergent properties (complexity arising from interactions).

Core Concepts of Physiology

• Structure and Function: Closely related; molecular interactions and compartmentation are key.

• Energy: Essential for life processes.

• Gradients and Flow: Concentration, pressure, and electrical gradients drive physiological processes.

• Communication: Coordinates body functions.

• Homeostasis: Maintains internal stability.

Tissues & Histology

Formation and Types of Tissues

Tissues are groups of cells assembled by cell junctions and extracellular matrix (ECM).

• Extracellular Matrix (ECM): Synthesized and secreted by cells; includes proteoglycans and insoluble protein fibers (collagen, fibronectin, laminin).

• Cell Junctions: Hold cells together; include cell adhesion molecules (CAMs) such as cadherins, integrins, immunoglobulin superfamily, and selectins.

• Types of cell junctions: communicating (gap), occluding (tight), and anchoring (adherens, desmosomes, hemidesmosomes, focal adhesions).

Types of Tissue

• Epithelial: Covers surfaces, regulates exchange.

• Connective: Supports, protects, stores energy.

• Muscular: Movement, posture, heat.

• Nervous: Detects and responds to environment.

Epithelial Tissue

Structure and Function

Epithelial tissue protects internal environments and regulates material exchange.

• Classified by number of layers (simple, stratified) and cell shape (squamous, cuboidal, columnar).

• Functional categories: exchange, transporting, ciliated, protective, secretory.

Development of Endocrine and Exocrine Glands

• Exocrine glands: Form ducts to secrete substances to the surface.

• Endocrine glands: Lose connecting cells, secrete hormones directly into the bloodstream.

Connective Tissue

Structure and Components

Connective tissue is characterized by abundant ECM and diverse cell types.

• Functions: Support, strength, insulation, transport, fat storage.

• Composition: Cells (mobile and fixed) and matrix (ground substance and protein fibers).

Organ Systems Overview

Major Organ Systems and Functions

The human body is organized into systems that perform specialized functions.

• Integumentary: Protection

• Respiratory: Gas exchange

• Digestive: Nutrient absorption

• Urinary: Waste removal, water balance

• Reproductive: Species perpetuation

• Musculoskeletal: Support, movement

• Circulatory: Material transport

• Immune: Defense

• Nervous: Coordination via electrical signals

• Endocrine: Coordination via regulatory molecules

Homeostasis

Principles and Regulation

Homeostasis is the maintenance of a stable internal environment.

• Factors under control: Temperature, pH, fluids, gases, nutrients, electrolytes, hormones.

• Mass balance: Input must equal output for stability.

• Mass flow: Rate of movement of substances.

Feedback Mechanisms

• Negative feedback: Reverses changes, stabilizes variables.

• Positive feedback: Reinforces changes, requires external intervention.

• Feedforward: Anticipates changes.

Regulation Pathways

• Control systems: Input signal, integrating center, output signal.

• Reflex control: Long-distance pathways using nervous/endocrine systems.

Body Compartments

Anatomical and Functional Compartments

The body is divided into cavities and fluid compartments.

• Anatomical compartments: Cranial, thoracic, abdominopelvic cavities.

• Functional compartments: Intracellular fluid (ICF), extracellular fluid (ECF: interstitial fluid and plasma).

Chemical Disequilibrium

• ICF and ECF have distinct ion concentrations.

Cell Chemistry & Cell Components

Cell Membrane Structure and Function

The cell membrane is a phospholipid-protein boundary layer.

• Functions: Physical isolation, regulation of exchange, communication, structural support.

• Composition: Phospholipids, cholesterol, glycolipids, proteins (integral, peripheral, glycoproteins).

• Selective permeability: Nonpolar molecules pass easily; ions and large polar molecules require channels or transporters.

Nervous Tissue and Nervous System

Organization and Cell Types

The nervous system is divided into central (CNS) and peripheral (PNS) systems.

• Neurons: Excitable cells transmitting signals.

• Glial cells: Support and protect neurons; types include oligodendrocytes, microglia, astrocytes, ependymal cells (CNS), Schwann cells, and satellite cells (PNS).

Neuron Anatomy and Functional Categories

• Structural types: Pseudounipolar, bipolar, anaxonic, multipolar.

• Functional types: Sensory (afferent), interneurons, motor (efferent).

Axonal Transport

• Motor proteins (kinesin, dynein) move cargo along microtubules.

• Fast axonal transport moves vesicles and organelles; slow transport moves soluble proteins.

Resting Membrane Potential

Cellular Properties and Ion Gradients

• Conductors (cytosol, ECF) allow ion flow; insulators (membrane) create charge separation.

• Resting membrane potential is established by ion gradients and selective permeability.

• Key ions: Na+, K+, Cl-.

Na+/K+ ATPase

• Maintains concentration gradients by pumping 3 Na+ out and 2 K+ in per ATP hydrolyzed.

Electrical Excitability of Neurons

Graded and Action Potentials

• Graded potentials: Local, variable amplitude, decremental.

• Action potentials: Long-distance, all-or-none, propagate without loss of strength.

Action Potential Steps

• Resting state: VG Na+ channels resting, VG K+ closed.

• Depolarization to threshold opens VG Na+ channels (fast), VG K+ (slow).

• Na+ influx, then K+ efflux restores resting potential.

Refractory Periods

• Absolute refractory: No new action potential possible.

• Relative refractory: Action potential possible with stronger stimulus.

Summary Table: Functional Categories of Epithelia

Summary Table: Connective Tissue Types

Summary Table: Glial Cell Types