IGCSE Biology 0610: Blood Vessels, Capillaries and Named Vessels

A patient with kidney failure is connected to a dialysis machine. A tube inserted into a blood vessel in the patient's arm carries blood out to the machine, which removes waste substances from the blood, before a second tube returns the cleaned blood to the same arm. Meanwhile, the patient's own diseased kidneys still receive a blood supply directly from the body's circulatory system.

(a) State two functions of capillaries. [2]

(b) Name the blood vessel that carries blood to the kidney, and the blood vessel that carries blood away from the kidney. [2]

(c) Name the blood vessel that carries blood from the heart to the lungs, and the blood vessel that carries blood from the lungs back to the heart. [2]

(d) State one feature of the structure of a vein that is not found in an artery. [1]

Part (a): Functions of capillaries

Capillaries are the smallest blood vessels in the body. Any two of the following functions are creditable: they allow substances such as oxygen, carbon dioxide, glucose, urea and other dissolved substances to be exchanged between the blood and the surrounding body cells; and they link the arterioles (the smallest arteries) to the venules (the smallest veins), connecting the arterial part of the circulation to the venous part.

Part (b): Vessels to and from the kidney

The renal artery carries blood to the kidney. The renal vein carries blood away from the kidney, back towards the heart. This is separate from the tubing connecting to the dialysis machine, which is not a blood vessel of the body at all.

Part (c): Vessels to and from the lungs

The pulmonary artery carries blood from the heart to the lungs. Although it is an artery, it carries deoxygenated blood, which is unusual. The pulmonary vein carries blood from the lungs back to the heart, and although it is a vein, it carries oxygenated blood.

Part (d): A feature unique to veins

Veins contain valves at intervals along their length. These valves prevent the backflow of blood, which is important because blood in veins is at lower pressure and often has to travel against gravity, for example back up from the legs. Arteries do not have valves.

Final answers

(a) Any two of: exchange of substances (oxygen, carbon dioxide, glucose, urea, other dissolved substances) between blood and cells; linking arterioles to venules.
(b) To the kidney: renal artery. Away from the kidney: renal vein.
(c) To the lungs: pulmonary artery. From the lungs: pulmonary vein.
(d) Veins have valves (to prevent backflow); arteries do not.