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Assertion: The reduction in number of platelets can lead to clotting disorders. Reason: Platelets release a variety of sustances most of which are involved in the clotting of blood.

Assertion: Body has the ability to alter cardiac output. Reason: Body has the ability to alter the stroke volume as well as the heart rate.

Assertion: WBCs accumulate at the site of wounds by diapedesis. Reason: It is the squeezing of leucocytes from the endothelium.

Assertion: Opening of pulmonary trunk and aorta are guarded by valves. Reason: These valves prevent backward flow of blood in ventricles

Assertion: SA node is called pacemaker of heart. Reason: It is responsible for initiating and maintaining the rhythm of heart

Assertion: The wall of left ventricle is thickest among all four chambers of heart. Reason: The left ventricle has to pump blood to whole body.

Assertion: The velocity of flow of blood is minimum in capillaries. Reason: The surface area of capillaries are maximum among all blood vessels.

Assertion: Human heart is myogenic. Reason: Normal activities of heart are regulated intrinsically by specialized muscle.

Assertion: Circulation in amphibians and reptiles is called incomplete double circulation. Reason: Deoxygenated and oxygenated blood get mixed up in the single ventricle pumps out mixed blood.

Assertion: Individual with ' \(\mathrm{O}\) ' blood group is considered to be universal donor. Reason: Blood of 'O' blood group individual do not contain antigens on their RBCs.