8. (i) Blood has two broad functions namely protective and transport. Describe how the blood protects the body. (4 marks) (ii) Describe the structural adaptation of the mammalian heart to its function. (16 marks)

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i) White blood cells; – engulf; and destroy bacterial/pathogen;
Produce antibodies; which neutralise bacterial toxins;
Blood platelets; – Cause clotting; on fresh wounds preventing entry of bacteria into tissues prevent loss of blood water; and mineral salts;.


ii) It is muscular/has cardiac muscles; which are myogenic (does not need nervous stimulation) to pump blood;

It is supplied by vagus nerve which has sympathetic and parasympathetic nerves; which controls to rate of heart beat depending on body’s physiological requirements;

It has triscupid; and bicuspid valves between atrium and ventricles which prevent back flow of the blood into the right and left ventricles respectively;.

Presence of valvular tendons attached to the walls of ventricles and to the atria –ventricular walls; to prevent  atria-ventricular valves from turning inside out due to changes in the pressure in the ventricles.

Heart is supplied by coronary artery; which supplies nutrients  and oxygen to the cardiac muscles for their pumping action; the coronary vein in the heart removes metabolic wastes;

The heart is enclosed by the pericardial membrane; that secretes a fluid which lubricates it reducing friction on the walls as it pumps;

The heart is divided into two by the atria –ventricular septum; that prevent mixing of oxygenated blood and deoxygenated blood;

The left ventricles has a thick muscular wall; to pump blood at higher pressure to the distant body tissues;.

Presence of pacemaker which is the origin of the excitatory waves that result into heart beat.

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