All the living cells in the human body require a constant supply of nutrients, oxygen and other essential substances. Also for the healthy functioning of the body and the tissues, the wasteful substances needed to be removed constantly. Therefore a mechanism is a must that helps in transporting nutrients and other substances from one cell to another. In simple organisms, water is present as a means of transport. But in complex organisms, blood is the commonly used body fluid. The lymph can also serve special purposes in transporting some nutrients. As blood is present in human beings, this blood in every individual is not the same. It has certain factors that make the blood different. On the types of antigens present on the red blood cells, there is an Rh blood group and an abo blood group. We will study more about the Rh blood group system below. First, let us learn about blood.
It is specialized connective tissue. It consists of a fluid matrix, plasma and also has formed elements that form the cellular portion. Plasma makes 55% of the blood and the rest 45% is made up of formed elements. Plasma is the fluid that forms the matrix of the blood. It is straw coloured. The plasma is composed of water, proteins, minerals and other amino acids. The water makes 90% of the plasma. Fibrinogen, globulin and albumins are the proteins that are present in plasma. Fibrinogen helps in the clotting of blood. Globulins help in the defence mechanism of the body and albumins help to maintain the osmotic balance. Glucose, amino acids and lipids are also present in the plasma and these substances enter and leave the plasma at regular intervals. The formed elements that make the rest of the composition are erythrocytes, leukocytes and platelets. Erythrocytes are the red blood cells that give blood its red colour and also help in transporting oxygen from one cell to another. The leukocytes are the white blood cells and they are known as soldiers of the body. They are named so because they help in fighting the body with infections. The leukocytes are lymphocytes, monocytes, eosinophils, basophils and neutrophils. The platelets in the blood are colourless and non-nucleated fragments of the cells. They are produced by the bone marrow and help in blood clotting.
Antigens are the molecules that are present on the surface of cells and thus they are recognised as foreign cells by the immune system and thus they can induce an immune response. To counter these antigens, the human body produces certain chemicals to fight against them and destroy them. These are known as antibodies. They get bonded to the antigens in a special fashion. The membranes of the red blood cells also contain some antigens. The ABO and Rh blood group system is done on this basis only.
Rh blood group discovered by Karl Landsteiner. Rh in Rh blood group stands for Rhesus monkey. They are named so because they were first discovered in monkeys. The Rh system is a group of antigens that are present on the red blood cells. The people that possess these Rh system factors are known as Rh blood group positive and the people that do not have these factors are known as Rh blood group negative. A person that has Rh-ve factors, when exposed to Rh+ve blood, then it will form antibodies against the Rh antigen. Therefore Rh factors should also be taken care of when matching blood groups are taking place. In the Rh blood group system, Rh compatibility is also taken care of. This condition is observed when the Rh- blood of a mother who is pregnant with an Rh+ foetus. As the Rh- a mother is not exposed to Rh antigen of the foetus in her first pregnancy because the placental barriers keep a check on that but at the time of birth, there is a possibility of slight mixing of blood. When this happens the mother’s body makes appropriate antibodies to fight it. And these antibodies can cross the placenta and then if the same condition happens in the second pregnancy, they can destroy the foetus as this foetus for the mother’s cells is foreign. Erythroblastosis foetalis is the name of this condition.
Karl Landsteiner gave this system in 1901. This blood group is based on the presence and absence of two surface antigens which are A and B and are present on the RBC. The individual plasma also contains anti-A and anti-B antibodies. According to him, if an antigen is present in the blood then its corresponding antibody will be present in the individual. Also, if the antigen is absent in the RBC, then the antibody must be present in the plasma. To its own antigens of red blood cells, the immune system exhibits tolerance. So a person who has an A blood group will have B antibodies and not A-antibodies. The same applies to the B blood group. For the AB blood group, no antibodies are produced and for the O-blood group, both the antibodies that are anti-A and anti-B are present.
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1. What are Thrombocytes?
Answer: These are known as blood platelets and they are the smallest of the formed elements. They are 150000-350000 per meter cubic of blood. They are not true cells and are cell fragments. They have a round shape and have a disc-like body. Megakaryocytes from the bone marrow are responsible for producing these cells. They last for about a week and are destroyed in the spleen and liver. A variety of substances are released by them that help in the coagulation of blood. These platelets are responsible for making the most of the mass of the clot. It also activates clotting factors in plasma and results in the formation of threads of fibrin. Thrombocytopenia is the condition in which the amount of platelets is reduced. This can lead to the loss of blood from the body. Purpura is the name of the diseases caused by this condition.
2. What are Granulocytes?
Answer: They are of three types: Eosinophils, basophils and neutrophils. The eosinophils have a two-lobed nucleus. They have granules present in them and also hydrolytic enzymes. They have antihistamine properties. The basophils have a three-lobed nucleus. Serotonin and heparin are secreted by these cells. Neutrophils are the most abundant of the WBCs and these are phagocytic.