Capillaries

Definition

Capillaries are the smallest blood vessels in the body, connecting arterioles and venules. They facilitate the exchange of oxygen, nutrients, and waste products between blood and tissues.

5 Must Know Facts For Your Next Test

1. Capillaries have thin walls composed of a single layer of endothelial cells to allow for efficient exchange of substances.
2. They are involved in microcirculation, distributing blood flow to tissues throughout the body.
3. Capillary density varies depending on the metabolic activity of the tissue; muscles have high capillary density.
4. The diameter of capillaries is just large enough for red blood cells to pass through in single file.
5. Capillary function can be influenced by factors such as blood pressure, osmotic pressure, and inflammation.

Review Questions

• What structural feature allows capillaries to efficiently exchange substances with surrounding tissues?
• How does capillary density vary among different types of tissues?
• What factors can influence the function of capillaries?

Related terms

Arterioles: Small branches of arteries leading into capillaries.

Venules: Small vessels that collect blood from capillaries and join to form veins.

Endothelial Cells: Cells lining the interior surface of blood vessels, including capillaries.