Capillaries

Definition

Capillaries are the smallest blood vessels in the body, connecting arterioles to 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.
2. They are involved in microcirculation, allowing for efficient gas and nutrient exchange.
3. The diameter of capillaries is typically 5-10 micrometers, small enough for red blood cells to pass through in single file.
4. There are three types of capillaries: continuous, fenestrated, and sinusoidal.
5. Capillary beds can regulate blood flow using precapillary sphincters.

Review Questions

• What is the primary function of capillaries?
• Name the three types of capillaries and describe one characteristic of each.
• How do capillary walls facilitate exchange between blood and tissues?

Related terms

Arterioles:

Small arteries that lead into capillary beds.

Venules: Small veins that receive blood from capillary beds.

Endothelial Cells: The thin layer of cells lining the interior surface of blood vessels including capillaries.