Form and Function of Anatomy & Physiology

Anatomy

Anatomy is the study of the structure of body parts and their relationships to one another. It provides the foundational knowledge for understanding how the human body is organized.

• Definition: Anatomy examines the physical structures of organisms.

• Applications: Used in medical imaging, surgery, and diagnostics.

Physiology

Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities.

• Definition: Physiology focuses on the mechanisms and processes that allow organisms to live.

• Applications: Understanding disease processes, pharmacology, and homeostasis.

Topics of Anatomy

Subdivisions of Anatomy

Anatomy is divided into several branches, each focusing on different aspects of body structure.

• Gross (Macroscopic) Anatomy: Study of large, visible structures.

  • Regional Anatomy: Looks at all structures in a particular area of the body.

  • System Anatomy: Examines one system at a time (e.g., cardiovascular, nervous).

  • Surface Anatomy: Studies internal structures as they relate to the overlying skin.

• Microscopic Anatomy: Deals with structures too small to be seen with the naked eye.

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Developmental Anatomy: Studies anatomical and physiological development throughout life.

  • Embryology: Study of developments before birth.

Topics of Physiology

Subdivisions of Physiology

Physiology is often based on organ systems and focuses on cellular and molecular levels.

• Examples: Renal physiology (kidney function), cardiovascular physiology (heart and blood vessels).

• Physiology explains how body systems work together to maintain life.

Complementarity of Structure and Function

Anatomy and physiology are inseparable; function always reflects structure. What a structure can do depends on its specific form. This is known as the principle of complementarity of structure and function.

• Example: Bones can support and protect body organs because they contain hard mineral deposits.

Structural Organization of the Human Body

The human body is organized from the smallest chemical level to the whole organism level.

• Chemical Level: Atoms, molecules, and organelles.

• Cellular Level: Single cells.

• Tissue Level: Groups of similar cells.

• Organ Level: Contains two or more types of tissues.

• Organ System Level: Organs that work closely together.

• Organismal Level: All organ systems combined to make the whole organism.

Requirements for Life

Necessary Life Functions

To maintain life, organisms must perform several essential functions.

• Maintaining Boundaries: Separation between internal and external environments (e.g., plasma membranes separate cells, skin separates organism from environment).

• Movement: Muscular system allows movement; contractility refers to movement at the cellular level.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex prevents injury).

• Digestion: Breakdown of ingested foodstuffs, followed by absorption of simple molecules into blood.

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

• Excretion: Removal of wastes from metabolism and digestion (e.g., urea, carbon dioxide, feces).

• Reproduction: Cellular level: division of cells for growth or repair; organismal level: production of offspring.

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

Survival Needs

Humans need several factors for survival that must be in the appropriate amounts.

• Nutrients: Chemicals for energy and cell building.

  • Carbohydrates: Major source of energy.

  • Proteins: Needed for cell building and chemistry.

  • Fats: Energy storage.

  • Minerals and Vitamins: Involved in chemical reactions and structural purposes.

• Oxygen: Essential for release of energy from foods; survival only a few minutes without oxygen.

• Water: Most abundant chemical in the body; provides environment for chemical reactions and base for secretions/excretions.

• Normal Body Temperature: If body temperature falls below or goes above 37°C, rates of chemical reactions are affected.

• Appropriate Atmospheric Pressure: Specific pressure of air is needed for adequate breathing and gas exchange in lungs.

Homeostasis

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

Homeostatic Controls

Body variables must be monitored and regulated to maintain homeostasis. The nervous and endocrine systems play a major role in maintaining homeostasis.

• Components of Homeostatic Control:

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

  • Control Center: Determines set point at which variable is maintained, receives input from receptor, and determines appropriate response.

  • Effector: Receives output from control center and provides the means to respond. Response either reduces stimulus (negative feedback) or enhances stimulus (positive feedback).

Negative Feedback

Most-used feedback mechanism in the body. Response reduces or shuts off original stimulus. Variable changes in opposite direction of initial change.

• Examples:

  • Regulation of body temperature (nervous system mechanism).

  • Regulation of blood glucose by insulin (endocrine system mechanism).

Positive Feedback

Response enhances or exaggerates the original stimulus. May exhibit a cascade or amplifying effect as feedback causes variable to continue in the same direction as initial change. Usually controls infrequent events that do not require continuous adjustment.

• Examples: Enhancement of labor contractions by oxytocin, platelet plug formation and blood clotting.

Homeostatic Imbalance

Disturbance of homeostasis increases risk of disease and contributes to changes associated with aging. If negative feedback mechanisms become overwhelmed, destructive positive feedback mechanisms may take over (e.g., heart failure).

Summary Table: Levels of Structural Organization

Summary Table: Necessary Life Functions

Key Equations

• Body Temperature Regulation:

  • Homeostasis maintains body temperature at approximately .

• Metabolism:

  • Catabolism:

  • Anabolism: