Introduction to Anatomy & Physiology

Definitions and Scope

Anatomy and physiology are foundational sciences for understanding the structure and function of the human body. Anatomy focuses on the body's structures, while physiology examines how those structures work.

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

• Microscopic anatomy: Study of structures requiring magnification, including histology (study of tissues).

• Human physiology: Study of the functions and processes of the human body.

Organization of the Human Body

Levels of Organization

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

• Chemical level: Atoms (smallest particles of elements) and molecules (particles of two or more atoms joined by chemical bonds).

• Cellular level: Cells made of molecules; basic unit of life.

• Tissue level: Aggregation of similar cells performing a common function.

• Organ level: Two or more tissue types integrated to perform specific functions.

• Organ system level: Groups of organs with related functions (e.g., integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, urinary, male and female reproductive systems).

• Organismal level: All organ systems functioning together to form an individual.

Major Organ Systems and Their Functions

Overview of Organ Systems

Each organ system has specialized functions essential for maintaining life.

• Integumentary system: Protection, sensory reception, temperature regulation.

• Skeletal system: Support, movement (levers), mineral storage.

• Muscular system: Movement, regulation of organ volume.

• Nervous system: Rapid communication, control, and integration.

• Endocrine system: Hormone production and regulation.

• Cardiovascular system: Transport of nutrients, gases, and wastes.

• Lymphatic system: Immune response, return of leaked fluids to cardiovascular system.

• Respiratory system: Gas exchange (oxygen and carbon dioxide).

• Urinary system: Elimination of waste, regulation of fluid balance.

• Male reproductive system: Production and transfer of sperm.

• Female reproductive system: Production of ova, sites for fertilization and fetal development, delivery, milk production for newborn.

Maintaining Life: Essential Processes and Survival Needs

Life Processes

To sustain life, the body must perform several essential functions:

• Maintain boundaries: Separation between internal and external environments.

• Movement: Locomotion and movement of substances.

• Responsiveness: Ability to sense and respond to stimuli.

• Metabolism: All chemical reactions in the body, including anabolism (building up) and catabolism (breaking down).

• Excretion: Removal of wastes.

• Reproduction: Production of offspring.

• Growth: Increase in size and number of cells.

Survival Needs

Certain factors must be present for cells and the body to survive:

• Nutrients: Energy source, vital for cell structure and function, protection (cushioning), insulation.

• Vitamins & minerals: Required for chemical reactions, often acting as cofactors.

• Oxygen: Essential for chemical reactions that release energy.

• Water: Makes up 60-80% of body weight; necessary for chemical reactions and maintaining environment.

• Normal body temperature: (); required for optimal chemical reaction rates.

• Atmospheric pressure: Necessary for breathing and gas exchange.

Homeostasis

Definition and Mechanisms

Homeostasis is the ability to maintain a stable internal environment despite external changes.

• Body fluids: Intracellular and extracellular fluids are regulated.

• Feedback systems: Mechanisms that maintain homeostasis, consisting of:

  • Variable: The factor being regulated.

  • Receptor: Detects changes.

  • Control center: Processes information and initiates response.

  • Effector: Carries out the response.

• Negative feedback: Response reduces the original stimulus (e.g., temperature regulation).

• Positive feedback: Response enhances the original stimulus (e.g., blood clotting).

Medical Terminology

Anatomical Position and Directional Terms

Standardized terms are used to describe locations and directions in the body.

• Anatomical position: Body upright, feet together, arms at sides, palms forward.

• Directional terms: Cranial, caudal, medial, lateral, proximal, distal, superior, inferior, posterior/dorsal, anterior/ventral, superficial/external, deep/internal, palmar, plantar.

Body Planes & Sections

• Sagittal plane: Divides body into left and right parts; midsagittal is exactly in the midline.

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

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

• Oblique plane: Cuts at an angle.

Body Cavities

Body cavities are confined spaces within the axial region that house organs.

• Dorsal body cavity: Includes cranial cavity (brain) and spinal (vertebral) cavity (spinal cord).

• Ventral body cavity: Contains thoracic cavity (pleural, mediastinum, pericardial) and abdominopelvic cavity (stomach, intestines, spleen, pancreas, kidneys, liver, urinary bladder, reproductive organs, rectum).

• Serous membranes: Parietal serosa (lines cavity walls), visceral serosa (covers organs), serous cavity (space between).

Chapter 4: Tissues

Overview of Tissues

Tissues are groups of cells similar in structure and function. Histology is the study of tissues using a microscope. There are four basic types of tissues: epithelial, connective, muscle, and nervous.

Epithelial Tissue

Epithelial tissue covers body surfaces, lines cavities, and forms glands.

• Functions: Protection, absorption, filtration, excretion, secretion, sensory reception.

• General categories: Lining/covering epithelium and glandular epithelium.

• Characteristics: Mostly cells, apical border, basement membrane, supported by connective tissue, innervated but avascular, highly reproductive.

• Classification:

  • Number of cell layers: Simple (one layer), stratified (multiple layers).

  • Cell shape: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

  • Types:

    • Simple squamous: Lines capillaries, glomeruli, alveoli.

    • Stratified squamous: Nonkeratinized (mouth, esophagus, vagina), keratinized (skin).

    • Simple cuboidal: Kidney tubules, small gland ducts.

    • Simple columnar: Digestive tract, may be ciliated and contain goblet cells.

    • Transitional: Ureters, bladder, parts of urethra; can stretch without damage.

    • Pseudostratified columnar: Respiratory tract (trachea, bronchi), often ciliated with goblet cells.

Connective Tissue

Connective tissue supports, protects, and binds other tissues together.

• Characteristics: Derived from mesenchyme, varying degrees of vascularity, extracellular matrix.

• Structural components:

  • Ground substance: Fills space between cells, contains protein fibers.

  • Fibers: Provide support and flexibility (collagen, elastic, reticular).

  • Cells: Fibroblasts (produce fibers), chondrocytes (cartilage), osteocytes (bone), hemocytes (blood), adipocytes (fat).

• Types of connective tissue:

  • Connective tissue proper: Loose (areolar, adipose, reticular) and dense (regular, irregular).

  • Cartilage: Hyaline (most common), elastic (flexible), fibrocartilage (compression resistance).

  • Bone: Hard matrix due to collagen fibers and calcium salts.

  • Blood: Functions in transportation and protection.

Nervous Tissue

Nervous tissue is specialized for communication via electrical impulses.

• Neurons: Generate and conduct impulses.

• Neuroglia: Non-conducting cells that support neurons.

Muscle Tissue

Muscle tissue is responsible for movement and consists of cells containing contractile protein fibers.

• Skeletal muscle: Striated, multinucleated, voluntary; attached to bones.

• Smooth muscle: Non-striated, mononucleated, involuntary; found in walls of hollow organs.

• Cardiac muscle: Striated, mononucleated, branching, involuntary; found only in the heart.

Integumentary System and Skin

Structure and Functions

The integumentary system includes skin, hair, nails, glands, and sensory receptors. It provides protection, regulates temperature, and enables sensation.

• Functions of skin: Protection, temperature regulation (via blood vessels), sensation (touch, pressure, warmth, coolness), excretion (water, wastes), absorption (fat-soluble vitamins, gases, toxins).

• Layers of skin: Epidermis (outermost, thinnest), dermis (deeper, thicker), hypodermis (subcutaneous layer).

Epidermis

• Specialized cell types: Keratinocytes (produce keratin), melanocytes (produce melanin), Langerhans cells (immune function), Merkel cells (sensory function).

• Layers (from deep to superficial):

  • Stratum basale: Deepest, single cell layer, mitotically active, contains melanocytes.

  • Stratum spinosum: Several cell layers, many Langerhans cells.

  • Stratum granulosum: 3-5 cell layers, keratinization begins.

  • Stratum lucidum: Only in thick skin, thin band of flattened cells.

  • Stratum corneum: Outermost, 20-30 cell layers, 3/4 of epidermis thickness.

Dermis

• Thicker than epidermis, contains blood vessels, nerves, glands, and sensory receptors.

Table: Comparison of Major Tissue Types

Additional info: Some content was expanded for clarity and completeness, including definitions, examples, and the table comparing tissue types.