Overview of Anatomy and Physiology

Definitions and Scope

Anatomy is the study of the structure of body parts and their relationships to one another, focusing on what they are and where they are located. Physiology is the study of the function of the body—how the body parts work and carry out their life-sustaining activities.

• Anatomy answers: Where is it? What does it look like?

• Physiology answers: How does it work?

Topics of Anatomy

Major Subdivisions

• Gross (Macroscopic) Anatomy: Study of large body structures visible to the naked eye (e.g., regional, systemic, surface anatomy).

• Microscopic Anatomy: Study of structures too small to be seen without a microscope (e.g., cytology—the study of cells, and histology—the study of tissues).

• Developmental Anatomy: Study of structural changes throughout the lifespan.

To study anatomy, mastery of anatomical terminology, observation, manipulation, palpation, and auscultation are essential skills.

Topics of Physiology

Major Subdivisions

• Renal Physiology: Kidney function and urine production.

• Neurophysiology: Functioning of the nervous system.

• Cardiovascular Physiology: Operation of the heart and blood vessels.

• Muscular Physiology: Muscle function and movement.

Studying physiology requires understanding processes at multiple levels (systemic, cellular, molecular) and applying basic physical and chemical principles.

Principle of Complementarity of Structure and Function

The function of a body part depends on its structure, and the structure is formed to serve its function. For example, bones can support and protect body organs because they contain hard mineral deposits.

Levels of Structural Organization in the Human Body

Hierarchy of Complexity

• Chemical Level: Atoms combine to form molecules and organelles.

• Cellular Level: Cells are made up of molecules.

• Tissue Level: Tissues consist of similar types of cells.

• Organ Level: Organs are made up of different types of tissues.

• Organ System Level: Organ systems consist of different organs that work together closely.

• Organismal Level: The human organism is made up of many organ systems.

Necessary Life Functions

Key Functions for Survival

• Maintaining Boundaries: Separation between internal and external environments (e.g., cell membranes, integumentary system).

• Movement: Muscular system allows movement of body parts and substances.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex, control of breathing).

• Digestion: Breakdown of food and absorption of nutrients.

• Metabolism: All chemical reactions in the body, including catabolism (breakdown) and anabolism (synthesis).

• Excretion: Removal of wastes from the body.

• Reproduction: Cellular division for growth and repair; production of offspring.

• Growth: Increase in size of a body part or organism.

Organ Systems of the Human Body

Major Systems and Their Functions

Survival Needs

• Nutrients: Chemicals for energy and cell building (carbohydrates, fats, proteins, minerals, vitamins).

• Oxygen: Essential for ATP production.

• Water: Most abundant chemical in the body; solvent for reactions.

• Normal Body Temperature: 37°C; necessary for proper metabolic reactions.

• Appropriate Atmospheric Pressure: Required for adequate breathing and gas exchange.

Homeostasis

Definition and Importance

Homeostasis is the maintenance of relatively stable internal conditions despite continuous changes in the environment. It is a dynamic state of equilibrium, maintained by all organ systems.

Homeostatic Control Mechanisms

• Receptor (Sensor): Monitors environment and responds to stimuli.

• Control Center: Determines set point, analyzes input, determines response.

• Effector: Carries out response to restore homeostasis.

Feedback Mechanisms

• Negative Feedback: Most common; response reduces or shuts off original stimulus (e.g., regulation of body temperature, blood glucose).

• Positive Feedback: Response enhances original stimulus; usually controls infrequent events (e.g., labor contractions, blood clotting).

Homeostatic Imbalance

Disturbance of homeostasis increases risk of disease, contributes to aging, and may result in destructive positive feedback mechanisms (e.g., heart failure).

Examples and Clinical Correlations

• Duchenne Muscular Dystrophy (DMD): Genetic disorder affecting dystrophin production, leading to muscle degeneration.

• Celiac Disease: Autoimmune disorder causing intestinal damage after gluten ingestion, resulting in poor nutrient absorption.

• Gout: Accumulation of uric acid crystals in joints, causing pain and inflammation.

• Alzheimer’s Disease: Impaired brain glucose metabolism contributes to neurodegeneration.

Functional Grouping of Organ Systems

• Connecting Systems: Cardiovascular, Lymphatic

• Movement of Matter: Digestive, Respiratory, Urinary

• Control of Body: Endocrine, Nervous

• Support and Movement: Skeletal, Muscular

• Protection: Integumentary, Lymphatic

• Continuity of Species: Reproductive