The Circulatory system helps in preventing desiccation of body cells by providing each cell with nutrients and water.

Fibrinogen is a protein that helps in clotting of blood. Thrombin converts fibrinogen into fibrin (clot).

A cockroach has a 13 chambered heart corresponding to 3 thoracic and 10 abdominal segments.

These are granulocytes. Their cytoplasmic granules contain heparin, which gives them their anti-coagulating function.

Erythrocytes are the red blood cells. They contain the respiratory pigment, haemoglobin, which binds oxygen and help in carrying it to different cells of the body. Granulocytes are the white blood cells whose cytoplasm is granular. They are devoid of any pigment.

The mitral valve is the bicuspid valve found between the left atrium and the ventricle. The function of the valve is to prevent back flow of blood into the left atrium.

Inferior venacava is responsible for pumping blood into the right atrium of the human heart.

The left and the right ventricles are separated from each other by a partition called the interventricular septum. Bundle of His is situated in the interventricular septum. It branches and forms a network of fibres throughout the walls of ventricles. These fibres are called the Purkinjee fibres.

Leucocytes are produced in the spleen or yellow bone marrow and when worn out, they disintegrate in the blood stream and get engulfed by phagocytes.

Sphygmomanometer is the instrument used for measuring blood pressure in humans.

The fibres of SA (Sinu-atrial) node express the ability of self excitation and control the rate of the entire heart beat. Hence, they are also called pacemakers. So, artificial pace makers are used when the SA node gets defected.

Pericardium is the outer covering of the heart.

The pulmonary vein carries oxygenated blood from the lungs and opens into the left atrium. This oxygenated blood is then supplied to the entire body through the aorta.

80 mm of Hg is considered as the normal diastolic blood pressure.

The coronary artery is the blood vessel that supplies blood to the heart muscles.

Malphigi discovered capillaries in 1661, Harvey could not detect them as there were no microscopes at that time.

Earthworm is an annelid. The blood flows throughout the body in closed circuit formed by heart and blood vessels( arteries, veins and capillaries) in annelids.