Capillary Beds

A capillary bed is a network of 10 to 100 capillaries that run between an arteriole and a venule, facilitating microcirculation.

The oxygenated blood first enters the terminal arteriole and flows into the capillary bed.

While passing through the capillary bed, oxygen, nutrients, and waste products from the blood are exchanged with the interstitial fluid.

The oxygen-poor blood later drains into the postcapillary venule.

The amount of blood passing through the capillary bed varies based on the tissue requirements.

For instance, after a meal, blood flows through the capillary bed, exchanging the nutrients released from digestion.

However, once digestion is complete, the capillary pathways close, and blood bypasses the capillary bed to drain directly into the postcapillary venule.

This redirection is achieved through the contraction of the precapillary sphincters, which are composed of smooth muscle fibers. They are located at the junctions of metarterioles — the short vessels connecting arterioles and capillaries.

Once the precapillary sphincters are closed, blood flows through the metarteriole and the thoroughfare channel, directly reaching the postcapillary venule.