Blood consists of fluid called plasma (60%) and a very large number of blood cells called corpuscles (40%). Plasma has water along with proteins and inorganic salts. Organic products such as glucose, amino acids, fats, urea, hormones and enzymes, are found in plasma.

tussles are of two kinds, red and white. Red corpuscles are made in the spleen . They form the majority of blood corpuscles and contain the protein pigment haemoglobin which givens the red colour to blood. It also has iron White corpuscles are much less in number compared to red corpuscles These are of different kinds, some of which destroy disease germs entering the blood. Haemoglobin is a protein pigment in red blood cells. If combines readily with oxygen in lungs to form a loose compound called oxy haemoglobin which is transported to tissues where it changes up into haemoglobin and oxygen. The oxygen is taken up by tissues for oxidation and carbon dioxide formed is carried away by the blood. Tit

Blood group means the grouping of people whose blood can be mixed without clumping of blood corpuscles. A, B, AB and O are the four main blood groups. When blood of any two different groups is mixed, agglutination or clotting of blood corpuscles occurs resulting in dangerous consequences and so only blood of the same group is used in blood transfusion.

Heart: A strong muscular organ in the chest between the right and left lungs and enclosed in bag called the pericardium. It is placed behind the breast bone and the ribs, slightly to the left. It has two auricles in the upper halt and two ventricles in the lower half, separated from each other by partitions. These partitions have valves between them.


Circulation of our Blood: Auricles and ventricles present in the heart contract and expand alternately. The right auricle receives impure blood from a large vein and the left auricle takes pure blood from the lungs. Both types of blood are fed into two ventricles by the contraction of two auricles. Now the two ventricles contract, Non-return valves close the opening between auricles and ventricles (systole) and so no blood can return back into the auricles. Thus the pure blood from the left ventricle goes into a large aorta and the impure blood from the right ventricles goes into the pulmonary artery. The aorta trabsoirts blood to various parts of the body. The pulmonary artery feeds impure blood to the lungs. When ventricles relax (diastole) the auricles are again filled with blood repeating same process.

Veins: Veins have valves and carry blood to the heart. The backward flow of blood (away from the heart) by the pulsation of heart is controlled by these valves.