CIE iGCSE Co-Ordinated Science B9.1 Circulatory systems Exam Style Questions Paper 3

(a)(i) A – aorta; C – renal artery

Vessel A carries oxygenated blood away from the heart towards the lungs’ side and down to the body.
In Fig. 1.1, A leaves the heart to supply the liver, intestines, kidneys and other organs, so it is the aorta.
Vessel C leads directly into the kidneys, so it is the renal artery.

(a)(ii) B – artery; D – vein; E – artery

Vessel B carries blood towards the intestines (away from the heart, oxygenated), so it is an artery.
Vessel D carries blood away from the liver back towards the heart, so it is a vein.
Vessel E carries blood away from the heart towards the lungs, so it is an artery.

(a)(iii) Valves

Valves are flap-like structures found in the heart and in veins.
They close to prevent the backflow of blood.
This ensures blood always flows in one direction only.

(a)(iv) Septum

The septum is the muscular wall inside the heart.
It separates the left side (oxygenated blood) from the right side (deoxygenated blood).
This prevents the two types of blood from mixing.

(b) 

Arteries have the thickest walls to withstand the high pressure of blood pumped from the heart.
Veins have thinner, less muscular walls since blood flows at lower pressure.
Capillaries have walls only one cell thick (\(0.0005\,\text{mm}\)) to allow efficient exchange of substances.

(c) Exchange of substances between blood and tissue cells

Capillaries have very thin, permeable walls (one cell thick).
This allows oxygen, glucose, and other substances to diffuse from the blood into tissue cells.
Waste products such as carbon dioxide diffuse from cells back into the blood.

(d) Any two from: red blood cells, white blood cells, plasma, platelets

Blood is made up of several components with different functions.
Red blood cells transport oxygen, white blood cells fight infection, plasma carries dissolved substances, and platelets help clotting.
Any two of these four components are accepted.