The oxygen-rich blood enters the capillaries where the oxygen and nutrients are released. The waste products are collected and the waste-rich blood flows into the veins in order to circulate back to the heart where pulmonary circulation will allow the exchange of gases in the lungs. During systemic circulation, blood passes through the kidneys. This phase of systemic circulation is known as renal circulation. During this phase, the kidneys filter much of the waste from the blood.
Blood also passes through the small intestine during systemic circulation.
This phase is known as portal circulation. During this phase, the blood from the small intestine collects in the portal vein which passes through the liver. The liver filters sugars from the blood, storing them for later.