Introduction to Anatomy & Physiology: Core Concepts and Terminology

1. Introduction to Anatomy and Physiology

1.1 Definition and Subdivisions

Anatomy and physiology are foundational sciences that describe the structure and function of the human body. Understanding their subdivisions is essential for further study.

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

  • Gross (Macroscopic) Anatomy: Structures visible to the naked eye (e.g., organs, muscles).

  • Microscopic Anatomy: Structures too small to be seen without a microscope.

    • Cytology: Study of cells.

    • Histology: Study of tissues.

  • Developmental Anatomy: Study of structural changes from conception to adulthood.

    • Embryology: Focus on development before birth.

  • Comparative Anatomy: Compares body structures across species.

• Physiology: The study of body function—how body parts work and carry out life-sustaining activities.

  • Cell Physiology: Functions of cells.

  • Organ Physiology: Functions of organs.

  • Systemic Physiology: Physiology of organ systems (e.g., cardiovascular physiology).

  • Pathophysiology: How disease affects function.

1.2 Relationship Between Anatomy and Physiology

Anatomy provides the structure; physiology explains the function. The structure of a body part determines its function, and function reflects structure.

• Example: The heart’s structure (chambers, valves, and walls) enables it to pump blood efficiently throughout the body.

2. Levels of Structural Organization

2.1 Hierarchical Levels

The human body is organized into a hierarchy of structural levels, each building on the previous one.

1. Chemical Level: Atoms combine to form molecules (e.g., DNA, proteins).

2. Cellular Level: Cells are the basic unit of life.

3. Tissue Level: Groups of similar cells performing a common function (e.g., muscle, nervous tissue).

4. Organ Level: Two or more tissue types working together (e.g., stomach).

5. Organ System Level: Organs working together to perform complex functions (e.g., digestive system).

6. Organismal Level: All organ systems combine to form a living human.

Each level builds on the previous; higher levels cannot function without the proper structure and function of the lower levels.

2.2 The 11 Organ Systems of the Body

The human body is organized into 11 major organ systems, each with specific components and functions.

System	Major Components	Major Function
Integumentary	Skin, hair, nails, sweat/oil glands	Protects body, regulates temperature, sensory reception
Skeletal	Bones, cartilage, ligaments	Supports, protects organs, stores minerals, forms blood cells
Muscular	Skeletal muscles	Movement, posture, heat production
Nervous	Brain, spinal cord, nerves	Controls responses, processes information
Endocrine	Glands (pituitary, thyroid, etc.)	Secretes hormones, regulates growth, metabolism
Cardiovascular	Heart, blood vessels	Transports nutrients, gases, wastes
Lymphatic/Immune	Lymph nodes, vessels, spleen, thymus	Returns fluids, fights infection
Respiratory	Lungs, trachea, bronchi	Gas exchange (O2, CO2)
Digestive	Mouth, esophagus, stomach, intestines, liver, pancreas	Breaks down food, absorbs nutrients, eliminates waste
Urinary	Kidneys, ureters, bladder, urethra	Eliminates waste, regulates water/electrolyte balance
Reproductive	Ovaries, testes, uterus, vagina, penis	Produces gametes, supports offspring development

3. Life Functions and Survival Needs

3.1 Functional Characteristics Necessary to Maintain Life

• Maintaining boundaries: Separates internal from external environments (e.g., skin, cell membranes).

• Movement: Muscles and cells move substances or the body itself.

• Responsiveness: Ability to sense and respond to stimuli.

• Digestion: Breakdown of food into nutrients.

• Metabolism: All chemical reactions in the body.

• Excretion: Removal of wastes.

• Reproduction: Cellular (mitosis) and organismal (offspring).

• Growth: Increase in size or number of cells.

3.2 Survival Needs of the Body

• Nutrients: Carbohydrates, fats, proteins, vitamins, minerals.

• Oxygen: Needed for cellular respiration.

• Water: Medium for chemical reactions, temperature regulation.

• Normal body temperature: ~37°C (98.6°F) for enzyme activity.

• Appropriate atmospheric pressure: Required for breathing and gas exchange.

4. Homeostasis

4.1 Definition and Significance

Homeostasis is the body's ability to maintain a stable internal environment despite external changes. It is essential for survival; imbalance can lead to disease or death.

4.2 Negative vs Positive Feedback

• Negative Feedback: Opposes a change to maintain stability (most common).

  • Example: Blood sugar regulation, body temperature regulation.

• Positive Feedback: Enhances a change to achieve a specific outcome.

  • Example: Blood clotting, labor contractions.

4.3 Homeostatic Imbalances and Disease

• Imbalance: Disrupts homeostasis, leading to disease.

  • Examples: Diabetes (blood sugar), hypertension (blood pressure), dehydration.

4.4 Maintaining Internal Stability

• The body must adapt to physical, chemical, environmental changes, and pathogens.

• Continuous regulation involves survival of cells and organ systems.

5. Anatomical Terminology, Planes, and Cavities

5.1 Human Body Planes

• Sagittal Plane: Divides body into left/right.

• Midsagittal Plane: Exactly midline.

• Frontal (Coronal) Plane: Divides body into anterior/posterior (front/back).

• Transverse (Horizontal) Plane: Divides body into superior/inferior (top/bottom).

5.2 Anatomical Position & Body Directions

• Position: Standing, feet together, arms at sides, palms facing forward.

• Directions:

  • Superior / Inferior

  • Anterior / Posterior

  • Medial / Lateral

  • Proximal / Distal

  • Superficial / Deep

5.3 Anatomical Variability

• Examples: Extra ribs, kidney position differences, varying number of blood vessels.

5.4 Medical Prefixes/Suffixes

• Prefixes: Hypo- (below), Hyper- (high), Brady- (slow), Tachy- (fast)

• Suffixes: -itis (inflammation), -ectomy (removal), -ology (study of)

5.5 Major Body Cavities and Subdivisions

• Dorsal: Cranial (brain), spinal (spinal cord)

• Ventral: Thoracic (heart, lungs), abdominopelvic (digestive organs, bladder, reproductive organs)

• Other Cavities: Oral, nasal, orbital, middle ear

5.6 Serous Membranes

• Pericardium: Heart

• Pleura: Lungs

• Peritoneum: Abdominal organs

• Function: Reduce friction between organs and body wall

5.7 Abdominopelvic Regions & Quadrants

• Nine regions: Right/Left Hypochondriac, Epigastric, Right/Left Lumbar, Umbilical, Right/Left Iliac, Hypogastric

• Four Quadrants: Right Upper, Right Lower, Left Upper, Left Lower

• Contains organs:

  • RUQ: Liver, gallbladder

  • LUQ: Stomach, spleen

  • RLQ: Appendix, cecum

  • LLQ: Descending colon, sigmoid colon