Form (Anatomy) Determines Function (Physiology)

Definitions and Relationship

Understanding the human body begins with two fundamental sciences: anatomy and physiology. These disciplines are closely linked, as the structure of body parts (anatomy) determines their function (physiology).

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

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

Divisions of Anatomy

Gross (Macroscopic) Anatomy

Gross anatomy examines large body structures visible to the naked eye. It is subdivided into:

• Regional Anatomy: Looks at all structures in a particular area of the body (e.g., the abdomen or leg).

• System Anatomy: Focuses on just one system, such as the cardiovascular, nervous, or muscular systems.

• Surface Anatomy: Studies internal structures as they relate to the overlying skin (e.g., visible muscle masses or veins).

Microscopic Anatomy

Microscopic anatomy deals with structures too small to be seen with the naked eye.

• Cytology: The study of cells.

• Histology: The study of tissues.

Developmental Anatomy

Developmental anatomy traces structural changes that occur throughout the lifespan.

• Embryology: The study of developmental changes that occur before birth.

Divisions of Physiology

Organ System-Based Physiology

Physiology is often divided according to the organ systems being studied. It frequently focuses on events at the cellular or molecular level, emphasizing how chemical reactions in individual cells underpin body functions.

• Renal Physiology: Study of kidney function.

• Neurophysiology: Study of nervous system function.

• Cardiovascular Physiology: Study of heart and blood vessel function.

To study physiology, one must understand basic chemical and physical principles, such as electrical currents, pressure, and lever systems.

The Complementarity of Structure and Function

Principle of Complementarity

Anatomy and physiology are inseparable. The function of a body part always reflects its structure, and what a structure can do depends on its specific form. This is known as the principle of complementarity of structure and function.

• Example: The sharp edges of incisors make them ideal for cutting food, while the flat surfaces of molars are suited for grinding.