Biology XI: 18 Body Fluids & Circulation(1 Body Fluids)

Body Fluids, Mechanism of Blood Coagulation, and Blood Groups Blood Connective tissue consisting of fluid matrix, plasma, and formed elements Plasma 55% of blood Plasma = 90-92 % water + 6-8% proteins Proteins presentFibrinogen − blood clottingGlobulins − defence mechanismsAlbumins − osmotic balance Also contain mineral, glucose, amino acids, and lipids in tracesBlood clotting factors are present in inactive form in plasma. Serum = Plasma − Clotting factors Formed Elements Formed elements (45% of blood) Erythrocytes Leucocytes Platelets (thrombocytes) Most abundant: 5 − 5.5 million/ mm3 of blood Relatively lesser in number: 6000 − 8000/ mm3 of blood 1.5 − 3.5 × 105/ mm3 of blood Formed in red bone marrow; average life span is of 120 days; destroyed in spleen, hence spleen is called the graveyard of RBCs Different types of leucocytes have different sites for formation. Formed in megakaryocytes Biconcave and devoid of nucleus Nucleated Nucleated Contain haemoglobin and hence involved in transport of respiratory gases Average value of haemoglobin − 12-16 gm/100 ml of blood They have a major role to play in defence system of body. Involved in blood clotting Lymph Lymph is the fluid released out of blood capillaries leaving behind larger proteins and formed elements. It consists of water and some water soluble substances. It has some mineral distribution as present in plasma. The network of lymph vessels composes lymphatic system. Uses Lymph contains lymphocytes that are involved in immune response. Lymph carries nutrients, hormones, etc. Lymph absorbs fats in lacteals found in intestinal villi. Blood Coagulation Clotting is required to prevent excessive loss of blood from the body. Blood clot − formed by threads of fibrin in which formed elements are trapped Prothrombin (inactive form)thrombin (active form) Fibrinogen (inactive form) fibrin (active form) Mechanism of coagulation is a cascade of reactions involving several clotting factors. Calcium ions play an important role in blood clotting mechanism. Blood groups Widely used blood grouping − ABO and Rh ABO Grouping Surface antigens A and B are present on BRCs. Antibodies are produced against corresponding antigens. Blood Group Antigen on RBC Antibody on plasma Donor’s Group A A Anti B A, O B B Anti A B, O AB A, B Nil AB, A, B, O O Nil Anti A, B O Universal Donor − Blood group ‘O’ Universal recipient − Blood group ‘AB’ Rh Grouping Individuals with Rh antigens present on RBCs are Rh positive and those without it are Rh negative. If Rh −ve mother bears an Rh +ve child during first pregnancy when mother’s blood is exposed to Rh +ve antigens, then anti − Rh antibodies are produced in her blood. During subsequent pregnancies, these antibodies may destroy RBCs of the foetus. This results in severe anaemia and jaundice to new born. This condition is called erythroblastosis foetalis. During Rh incompatibility, the first child is safe or may have anaemia. However, this condition can be avoided for subsequent pregnancies by administering anti-Rh antibodies of mother immediately after delivery of first child.