01 / Location & anatomical relationships
In tiny networks within most body tissues.
02 / Structure & organization
A capillary wall consists mainly of endothelium and its basal lamina. Continuous, fenestrated and sinusoidal capillaries have different permeability characteristics. Their large collective surface area and short diffusion distances facilitate exchange.
03 / Function
Oxygen, nutrients and wastes pass between blood and body tissues here.
04 / Mechanism
Their very thin walls put blood close to cells. Materials move across these walls according to local conditions: oxygen and nutrients can enter tissues, while carbon dioxide and other wastes enter blood. Capillaries connect the arterial and venous sides of circulation.
Working together: circulatory system
Your heart pumps blood to your lungs to collect oxygen. Blood then delivers oxygen to body cells and carries carbon dioxide back to your lungs.
Meet this body system →FOR DEEPER STUDY
Connect structure with function
Exchange depends on concentration gradients, hydrostatic forces and barrier properties. Different organs use capillary structures suited to filtration, absorption or protective control.
Check your understanding
Locate the capillary in relation to its neighbors. Explain how the structural features described above support its function, then distinguish it from a nearby structure with a different role.
Keep learning
Further reading: NHLBI: How the Heart Works.
Continue with OpenStax Anatomy and Physiology for system-level study. This atlas is educational and has not undergone independent medical peer review.