Biology · Body Fluids and Circulation · NEET
It is a VEIN. The hepatic portal vein carries blood, but unlike a normal vein it does NOT go straight to the heart. It connects two capillary beds: capillaries of the gut (stomach, intestine) drain into the hepatic portal vein, which then breaks into capillaries again inside the liver. Only after the liver does the blood collect into the hepatic vein and go to the heart. So it is a vein by structure but 'portal' by function (two capillary sets).
After a meal, blood from the intestine is loaded with absorbed glucose, amino acids and other nutrients. The liver acts as a checkpoint: it stores excess glucose as glycogen, detoxifies harmful substances, and regulates nutrient levels. If this blood went straight to the heart and body, sugar and toxins would flood the whole body at once. The hepatic portal system forces the blood through the liver first for processing.
No. This is a very common NEET trap. Even though the heart chambers are full of blood, the thick cardiac muscle wall cannot absorb enough oxygen and nutrients directly from that blood by diffusion. The heart has its OWN dedicated supply called coronary circulation. Coronary arteries branch off the aorta right where it leaves the heart and spread over the heart muscle to feed it.
Both are portal systems (two capillary beds). The hepatic portal system connects the intestine to the liver and is present in humans and frogs. The renal portal system connects the lower body/tail region to the kidney and is present in frogs (and many lower vertebrates) but is ABSENT in humans/mammals. NCERT states both are seen in frogs; for humans only the hepatic portal system is relevant.
If a coronary artery is narrowed or blocked (by fat, cholesterol and calcium deposits = atherosclerosis / coronary artery disease), the cardiac muscle beyond the block does not get oxygen. This causes chest pain (angina) and can lead to a heart attack (myocardial infarction) where that part of the heart muscle dies. This links coronary circulation directly to CAD in the NCERT disorders section.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A blood pathway in which blood passes through two capillary beds, connected by a vessel (usually a vein), before returning to the heart.
No. The renal portal system is present in frogs and lower vertebrates but is absent in humans. Humans have only the hepatic portal system.
The hepatic portal vein. It carries nutrient-rich blood from the digestive tract to the liver before it reaches the heart via the hepatic vein.
Coronary arteries arise from the base of the aorta, just as it leaves the left ventricle, and supply oxygenated blood to the cardiac muscle.
It is the basis of coronary artery disease (atherosclerosis), angina and heart attack, which are directly asked in the Body Fluids and Circulation disorders section.
