(a)(i) Draw and label.the mammalian heart. (ii) Explain briefly pulmonary circulation in mammals. (b) State five processes by which the mammalian body reduc...

(a)(i) Longitudinal section of a mammalian heart

Labels: aorta, pulmonary artery, pulmonary veins, superior vena cava, inferior vena cava, right atrium, left atrium, right ventricle, left ventricle, tricuspid valve, bicuspid (mitral) valve, semilunar valves and septum.

(a)(ii) Pulmonary circulation

Deoxygenated blood is pumped from the right ventricle through the pulmonary semilunar valve into the pulmonary artery. The pulmonary artery carries it to the capillaries of the lungs, where carbon dioxide diffuses out of the blood and oxygen diffuses into it. The oxygenated blood then returns to the left atrium through the pulmonary veins.

(b) Processes by which the mammalian body reduces its temperature

1. Increased sweating: Sweat is secreted onto the skin. Its evaporation absorbs heat from the body and cools it.
2. Vasodilation: Skin arterioles widen, allowing more warm blood to flow through surface capillaries, where heat is lost to the surroundings.
3. Relaxation of hair erector muscles: Body hairs lie flat, reducing the layer of trapped insulating air and increasing heat loss.
4. Reduced muscular activity: Less heat is produced by muscle contraction.
5. Reduced metabolic activity: The rate of heat-producing chemical reactions in the body is lowered.