What organ's blood circulation is the exception to the rule of parallel flow, and one capillary bed between artery and vein?

Question

Quizplus · Accepted Answer

The kidney has a unique blood circulation system where there are two sets of capillary beds between the artery and vein. The first capillary bed (glomerulus) filters blood to form urine, and the second capillary bed reabsorbs necessary nutrients back into the bloodstream. This is known as a "portal system" and is an exception to the typical pattern of parallel blood flow in the body.

What Organ's Blood Circulation Is the Exception to the Rule