Capillaries

Definition

Capillaries are the smallest blood vessels in the body that connect arterioles and venules. They facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and surrounding tissues.

5 Must Know Facts For Your Next Test

1. Capillaries have thin walls composed of a single layer of endothelial cells to allow easy exchange of substances.
2. They form extensive networks called capillary beds throughout the body, ensuring efficient delivery of nutrients and oxygen.
3. Capillary permeability can vary in different tissues; for example, brain capillaries are less permeable compared to those in the liver.
4. The process of nutrient and gas exchange in capillaries occurs primarily via diffusion.
5. Capillaries play a crucial role in regulating blood flow through vasodilation and vasoconstriction influenced by local tissue needs.

Review Questions

• What is the primary function of capillaries?
• How do capillary walls facilitate the exchange of substances?
• In what way do capillaries contribute to homeostasis within tissues?

Related terms

arterioles: Small blood vessels that carry oxygenated blood from arteries to capillaries.

venules: Small blood vessels that collect deoxygenated blood from capillaries and transport it to veins.

diffusion: The movement of molecules from an area of higher concentration to an area of lower concentration.