Anatomy and physiology

Organ systems, homeostasis, and the physics of the cardiovascular and respiratory systems

What is anatomy and physiology?

Anatomy studies the structure of a living body — its organs, tissues, and how they're arranged. Physiology studies how that structure actually functions — how those same organs and tissues work, individually and together, to keep an organism alive. The two are naturally studied together, since structure and function are closely tied to each other throughout the body.

Organ systems

A body is organized into several major organ systems, each built from multiple organs working together toward a shared function. The skeletal system provides structural support and protection. The muscular system produces movement. The circulatory system moves blood, carrying oxygen, nutrients, and waste throughout the body. The respiratory system exchanges oxygen and carbon dioxide with the environment. The digestive system breaks down food into usable nutrients. The nervous system, covered in more depth in the Neuroscience article, coordinates and controls the rest of the body.

Homeostasis: staying in balance

Homeostasis is the body's ability to maintain a relatively stable internal environment — a fairly constant body temperature, blood sugar level, and much more — despite continuously changing external conditions. This stability is maintained through feedback systems: when a monitored condition drifts away from its target range, the body triggers a response that pushes it back toward that range, the same way a home thermostat detects a temperature change and switches the heating or cooling on to correct it.

How organ systems work together

No organ system operates in isolation — maintaining homeostasis and supporting the body's overall function requires constant coordination between systems. For example, exercising muscles require more oxygen, so the respiratory and circulatory systems both respond together, increasing breathing rate and heart rate to meet that increased demand.

Why anatomy and physiology matter

Anatomy and physiology form the essential foundation for all of medicine — understanding what the body's structures are and how they're supposed to function is the necessary starting point for recognizing disease, understanding how treatments work, and studying how the body responds to injury, illness, and exercise.