Circulatory System - Sample Question (2)

Here is another sample question on the human circulatory system:

The diagram below shows the circulation of blood in the human body.

(a) Name the organs that X and Y represent. (1 m)

X: Lungs
Y: Heart

Comment: The heart will have to pump blood to and from all parts of the body, including the lungs.

(b) Which part, P, Q, R or S, represents blood vessels that have the highest level of oxygen? Give a reason for your answer. (1 m)

Q. Blood vessel Q transports blood from the lungs where oxygen from the inhaled air passes through the walls of the air sacs into the blood.