The diagram given below represents the simplified pathway of the circulation of blood. Answer the questions that follow: The diagram given below represents the simplified pathway of the circulation of blood. Answer the questions that follow:
What is the importance of blood vessel labelled 5?
Topic: Hepatic portal vein
Answer
Vessel 5 is the HEPATIC PORTAL VEIN. It carries blood rich in absorbed FOOD from the small intestine directly to the LIVER, so that the liver can regulate the level of glucose (storing the excess as glycogen) and detoxify any harmful substances BEFORE the blood reaches the rest of the body.
The vessel joins the SMALL INTESTINE to the LIVER, which identifies it at once.
WHAT MAKES IT UNUSUAL: an ordinary vein carries blood straight back to the heart. This one begins in one set of capillaries (in the gut wall) and ENDS in another (in the liver), connecting two capillary beds without passing through the heart between them. That is what a PORTAL vein means.
ITS IMPORTANCE is the point of the question: all absorbed food is taken to the liver FIRST. Without this arrangement, a sudden flood of glucose or a swallowed poison would go straight into the general circulation.