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Essay on Blood
Essay Contents:
- Essay on the Blood and Its Composition in Humans
- Essay on the Blood Plasma
- Essay on the Blood Cells in Humans
- Essay on the Coagulation of Blood in Humans
- Essay on the Functions of Blood in Humans
- Essay on the Blood Groups
Essay # 1. Blood and Its Composition in Humans:
The blood is a fluid connective tissue which plays an important role in supplying oxygen to all tissues and cells of the body and removing carbon dioxide from the body. The total volume of blood forms about 1/12th of the body weight or about 5 to 6 liters of blood. Blood is heavier than water with a specific gravity of 1.04 – 1.07. It is slightly alkaline in nature.
Composition of Blood:
Blood is composed of two components:
1. Blood Plasma:
A fluid which forms about 55% of the total volume of blood.
2. Blood Cells:
Which are floating freely in the blood plasma. The amount is about 45% of the total volume of blood.
Essay # 2. Blood Plasma in Humans:
Blood plasma or serum is a non-cellular fluid, of yellow colour and alkaline in nature. It is mainly consisting of water and other solid substances.
1. Water-90 to 92%
2. Solid substances – 8 to 10%
Solid substance of blood plasma include the following material:
(a) Protein 7.0%:
The important plasma proteins are Albumin (4.7 – 5.7%), Globulin (1.3 – 2.5%), Fibrinogen (0.2 – 0.4%), Prothrombin (0.1 -1.0)
(b) Inorganic constituents – 0-9%:
These are salts of sodium potassium, calcium magnesium, phosphorous, iron, copper etc.
(c) Organic constituents like protein nitrogenous substances:
Urea, uric acid, creatinine, ammonia, amino acids, xanthine etc.
(d) Fat:
Phospholipids, natural fat, cholesterol etc.
(e) Carbohydrates, Glucose etc.
(f) Other substances:
Internal secretions or hormones antibodies, enzymes etc.
(g) Colouring matter:
Bilirubin, carotene etc. which gives yellow colour to plasma.
(h) Heparin is present in plasma which is an anticoagulant released by the liver cells.
3. Plasma carries gases like oxygen and carbon dioxide.
Plasma Proteins:
In normal individuals the total amount of plasma protein varies from 6.5 – 7.5 % average is about 7%.
The followings are the plasma protein:
Albumin:
There are normally 4.7 – 5.7% of albumin in the plasma. They are the smallest blood proteins formed in liver. It has three functions.
(1) It is responsible for the osmotic pressure which maintains the blood volume.
(2) Many special substances are carried which combines with the albumin.
4. It provides protein to the tissues.
Globulin:
The amount of serum globulin is about 1.3 – 2.5%. It is insoluble in distilled water but soluble in salt solution. Globulin is much more variable than albumin in composition. They are carrier proteins and also maintain osmotic pressure. This comprises a large number of different proteins. They act as the antibodies and protect the body against the attack of disease germs.
Fibrinogen:
The amount of fibrinogen in blood plasma is about 0.2 – 0.4%. It is essential for clotting of blood during which fibrinogen is converted to fibrin.
Prothrombin:
0.1% of prothrombin are present in Blood plasma. They act as blood clotting factor. Vitamin K helps in the formation of prothrombin in the liver.
Functions of Blood plasma:
1. Plasma acts as the medium for transmission and circulation of nutrients, salts, fats, glucose, amino-acids, vitamins, oxygen, hormones etc. to the tissues.
2. It is the medium for removal of waste materials like urea, uric-acid, carbon dioxide, excess water and other such things.
3. It maintains the PH of blood. (Hydrogen ion concentration)
4. It maintains the acid base balance in the body.
5. Plasma helps in maintaining the immunity power of the body.
6. It takes active part in the clotting of blood.
Essay # 3. Blood Cells in Humans:
There are three types of blood cells which are floating in blood plasma. The amount is about 45% of the total blood volume.
These cells are:
(1) Erythrocytes or Red Blood Cells
(2) Leukocytes or White Blood Cells
(3) Thrombocytes or Blood Platelets.
1. Erythrocytes:
The erythrocytes are minute circular discs, both sides of which are concave. The central part of the cell is thinner than the circumference. Each cubic millimeter of blood contains five millions of red blood cells. They are so small that if placed flat edge to edge, about 10 millions of R.B.C. can be kept in one square inch.
The number of R.B.C. varies in human body according to physiological and pathological conditions. When examined under the microscope they are individually seen to be pale yellow in colour, but in masses appear red and give the colour to the blood.
Composition of Erythrocytes:
It is composed of 65% water, 35% solids of which 33% is haemoglobin bound with 2% of protein, phospholipids, cholesterol, neutral fat and organic substances.
Structure of Erythrocytes:
The red blood cells resemble a sponge. They consists of an outer elastic envelop which encloses a red pigment called haemoglobin. R.B.C is covered by a very thin plasma membrane made up of lipid and protein complex. Mature erythrocytes do not have any nucleus. The red cells need protein and iron for their structure. So a balanced diet containing some iron is necessary for the replacement of R.B.C.
The Red Blood cells originate in bone marrow. In process of development in the bone marrow the red cells pass through several stages. At first, they are large and the edges are uneven. They contain a nucleus but no haemoglobin. When the R.B.C are matured, they are charged with haemoglobin and finally lose their nucleus. These cells are then passed out for circulation in the blood.
The normal life span of R.B.C is about 120 days, then they are destroyed. These cells are disintegrated in the spleen and liver. The globin of the haemoglobin is broken down into amino acids to be used as protein in the tissues.
The iron in the haem is removed for the formation of new R.B.C. The rest of the haem is converted into bilirubin, an yellow pigment and biliverdin, a green pigment. During severe bleeding, red-cells with haemoglobin are lost. In moderate hemorrhage these red cells are replaced when balanced diet is taken.
Functions of Erythrocytes:
1. Erythrocytes have respiratory function. Haemoglobin of R. B. C. attracts oxygen from the air sacs and converted into oxy-haemoglobin in the lungs. So that the blood is purified. Thus Red cells supply oxygen to the tissues and cells remove the waste product like carbon dioxide.
2. The Red cells maintain acid-base balance. It is carried out by the buffering action of haemoglobin.
3. It maintains ion-balance in the blood.
4. Red cells help to maintain the viscosity of blood.
5. Various pigments like bilirubin and biliverdin are produced after the disintegration of Red cells.
Haemoglobin:
Haemoglobin is the red pigment present in Red blood cells. It is a complex protein rich in iron. It is consisting of two parts – 96% of globin, a protein substance and 4% of Hoem, an iron containing pigment. Haemoglobin is synthesized inside the redcells in the bone marrow. The content of haemoglobin present in normal blood is 15 gms per 100 ml of blood and this amount is usually called hundred percent. The amount over 90% is considered normal. In the foetus the concentration is highest. At birth it is 23 gms per 100 ml.
In females, the amount of haemoglobin is slightly lower than in males. The average is 13.7% in females. At higher altitude haemoglobin-percentage rises. Exercise, excitement, adrenaline injections etc. increase the amount of haemoglobin. In Anaemia, the amount of haemoglobin present in the blood is diminished. Sometimes in serious cases it may fall below 30% that is 5gms per 100 ml.
Functions of Haemoglobin:
1. It is essential for oxygen carriage.
2. It plays an important part in carbon dioxide removal.
3. It constitutes one of the important buffers of blood and helps to maintain the acid-base balance.
4. Various pigments of bile, stool urine etc. are formed from it.
Anaemia:
Anaemia is a condition in which there is a reduction in the total circulating haemoglobin. In some severe forms of Anaemia, the haemoglobin level may fall below 30% that is 5gms per 100 ml. Deficiency of R.B.C. in blood causes anaemia.
Causes of Anaemia:
Causes of Anaemia are:
1. Excessive Blood loss due to hemorrhage, delivery, menstruation etc.
2. Increased destruction of R.B.C. is another cause. In the disease like sickle cell. Thalassemia, continuous malaria, syphilis, there is increased destruction of R.B.C. and haemoglobin is reduced.
3. Failure of function of bone marrow is due to enormous exposure to X-Ray, cancer in bone marrow, poisoning through toxins, kidney disease etc. This is an important cause of reduction of R.B.C and thereby causing Anaemia.
4. Anaemia is caused due to the defective for motion of RBC. Deficiency of Vitamin B12, Folic acid and gastric intrinsic factors help in defective R.B.C. formation.
Types of Anaemia:
Anaemia may be of different types:
i. Hypochromic Anaemia or iron deficiency Anaemia.
ii. Pernicious Anaemia or Vitamin B12 deficiency Anaemia.
iii. Megaloblastic Anaemia or Folic Acid deficiency Anaemia.
i. Hypochromic Anaemia:
This is also known as iron deficiency anaemia. Iron deficiency follows a specific sequence. First the iron reserves drop to lower levels. At the last stage, there is no iron reserves and plasma iron continue to fall and the cells are pale and reduced in size.
The term nutritional anaemia is sometime applied to iron deficiency anaemia. Iron deficiency anemias are widely prevalent throughout the world. Generally, the incidence is high in infants and pregnant woman of low economic status and higher in black than in white individuals. In better economic circumstances the incidence is lower.
The following factors are responsible for iron deficiency anaemia:
1. Blood loss due to accidental, hemorrhage, chronic disease like tuberculosis, ulcers, intestinal disorders, excessive menstrual losses, excessive blood donation, parasites such as hook worm etc.
2. Deficiency of iron in the diet during the period of infancy, adolescent girls, pregnancy, lactation etc.
3. Inadequate absorption of iron during diarrhea pellagra.
4. Nutritional deficiencies like protein Calory Malnutrition.
The main symptoms are skin pallor, weakness, easy fatigability, headache, dizziness, sensitivity to cold, loss of appetite, the heart rate increases, palpitation occurs and there is shortness of breath.
Anaemia can be prevented by consumption of foodstuff like green leafy vegetables, bread and cereals, daily administration of iron salts etc. Ascorbic acid rich juices improve the absorption of iron. Dry milk, egg yolk and other animal foods are essential.
ii. Pernicious Anaemia:
It is caused by a lack of intrinsic factor in the gastric juice and therefore Vitamin B12 cannot be absorbed. With the absence of Vitamin B12 the synthesis and maturation of R.B.C. are arrested. This anaemia occurs chiefly in middle aged to elderly persons and may be a genetic defect.
National Institute of Nutrition (NIN) Hyderabad showed that vitamin B12 deficiency, anaemia can be seen even in breast fed babies, because of the poor vitamin B12 content of mother’s milk. The vitamin content of breast milk can be improved by supplementation of the mother’s diet with vitamins.
Symptoms:
Patients have a pale yellow colour body anorexia, glossitis, abdominal discomfort, frequent diarrhoea, weightloss, and general weakness. There is also neurological change like coldness of the extremities and difficulty in walking.
Vitamin B12 deficiency can be corrected only through intake of foods of animal origin such as milk, fleshy foods, eggs etc. The Vitamin becomes ineffective when given orally, because of the absence of intrinsic factor. The diet must be corrected for adequate calories and for protein. A soft or even liquid diet is preferable. High protein, high calorie beverages two or three times daily should be given.
iii. Megaloblastic Anaemia:
A deficiency of folic acid leads to arrest of the synthesis and maturation of the red blood cells thus leading to megaloblastic anaemia. A high incidence of folic acid deficiency has been noted in elderly patients co-related with a poor intake of milk, fresh fruits and vegetables. This type of anaemia in babies is more frequent in those born to mothers who also have a folic acid deficiency.
Anaemia is present in infants who have scurvy because lack of ascorbic acid reduces conversion of folic acid to its active form. Women who have used oral contraceptives for a long time may have this type of anaemia.
Consumption of adequate amount of green leafy vegetables and pulses which are rich in folic acid corrects folic acid deficiency. Among the nutritional disorders affecting women in child bearing age, anaemia is one of the most important disease. The cause for this in most cases is iron deficiency. Pregnancy aggravates anaemia in women and anaemia in turn may affect the course of pregnancy. It has been observed that directly or indirectly, anaemia is a major cause of much of the maternal mortality in the country.
2. Leucocytes:
Leucocytes are transparent, colourless and irregular is shape. Nucleus is present in white blood cells. The cells are larger in size and fewer in number than erythrocytes. The size of W.B.C. varies from 8 to 15 microns. Each cubic millimeter of blood contains 6000 -10000 of white cells with an average of 8000. The ratio of WBC and R.B.C. is 1:500 or 600 i.e. for one W.B.C., there are 500 or 600 RBC.
White Blood cells are constantly changing their shape and thus resemble a minute microscopic animal amoeba found in pond water. By means of these movements they are capable of moving from one place to another and even if come out through the thin walls of the smallest blood vessels. They are able to take up the foreign particle, disease germs etc. and protect the body.
Types of Leucocytes:
The leucocytes are broadly classified into two categories:
A. Granulocytes or granular leucocytes.
B. Agranulocytes or Agranuller leucocytes.
A. Granulocytes:
These are also known as polymer pronuclear Leucocytes. All types of granulocytes are formed and stored in the bone marrow until they are required in the circulatory system. The cytoplasm of these cells contains specific granules and the nucleus is divided into many lobes. They form almost 70% of the total white cell count.
These granulocytes are classified into three according to the stain:
(i) Neutrophil Cells:
The cyloplasm of neutrophil cells are packed with granules. They have affinity towards neutral dyes. It is a mixture of both acid and alkaline stain. So it appears purple. The nucleus of this cell has 3 -5 lobes. The amount of these cells is 66% which are phagocytic in action.
(ii) Eosinophil Cells:
These cells are up to 3%. The granules of these cells stain red with acidic dyes. The nucleus is bilobed. In allergic conditions the number of Eosinophil cells increases considerably which is a disease condition known as “Eosinophilia.”
(iii) Basophils:
These cells take the basic dyes and stain blue. The number of these cells is 1% in the blood. The nucleus is lobed and ‘S’ shaped in these cells. These Basophils have amoeboid movement. These cells contain histamine, heparin and serotonin.
B. Agranulocytes or Agranular Leucocytes:
These cells are a clear cytoplasm with a single large nucleus. So it is called Mononuclear leucocytes.
These cells are of two types:
(i) Monocytes:
About 5% of these cells are present in the blood. These are the largest cells of the body. The nucleus is like kidney shaped or horseshoe shape. They are also formed in the bone marrow. These cells have amoeboid movement and are phagocytic in action. They can live for months and even year unless destroyed by performing phagocytic function.
(ii) Lymphocytes:
They form about 25% of the total white cells count. They are smaller than monocytes but larger than R.B.C. They have a large nucleus. These cells are developed in the lymph glands, the spleen, liver, lymphatic tissues and bone marrow. They have no power of amoeboid movement. They do not ingest bacteria but make valuable antibodies to protect the body against chronic infection and maintaining the immunity power.
Functions of Leucocytes:
i. Phagocytosis:
The granulocytes and monocytes play an important role in protecting the body from microorganisms. They ingest foreign particles and living bacteria from the blood. This action of W.B.C. is called phagocytic action (Phago -I eat) or phagocytosis. By their power of amoeboid movement they can move freely in the blood vessels take in living organisms and destroy them.
ii. Antibody Formation:
Lymphocytes play an important role in the defensive mechanism of the body. They make valuable antibodies in the blood for protecting the body.
iii. Formation of Fibroblasts:
W.B.C. can surround any area which is infected or injured. Lymphocytes are converted into fibroblasts in the area of inflammation and helps in the process of repair.
iv. Removal of Foreign Articles:
W.B.C. removes the foreign particles like bits of dirt, splinters of wood etc.
v. Manufacture of Trephones:
Leucocytes manufacture a substance called trephone from plasma protein which have great influence on the nutrition, growth and repair of tissues.
vi. Secretion of Heparin:
The basophil leucocytes secrete “heparin” which prevents the clotting of blood inside the blood vessels.
vii. Promoting Healing process:
The granulocytes posses a protein splitting ferment which enables them to act on living tissue, break it down and remove it. In this way diseased or injured tissue can be removed and healing process becomes quicker.
3. Thrombocytes or Blood Platelets:
Blood platelets are small, round or oval and biconvex discs like cells. The size of these cells is about one third the size of a Red blood cell. Platelets have no nucleus. There are 300,000 of these platelets in each cubic millimeter of blood. The average life span of platelets is about 5-9 days. They are produced in the bone marrow and destroyed in the spleen. They have the properties like easy clumping and easy disintegration.
Functions:
i. Blood Clotting:
Clotting or coagulation of blood is the main function of Blood platelets. At the time of bleeding the platelets disintegrate and liberate thromboplastin which converts prothrombin into thrombin. When thrombin is combined with fibrinogen, fibrin results and there is clotting of blood.
ii. Repair Capillary Endothelium:
When blood platelets are coming in contact with the damaged endothelial lining of the capillaries, they bring about rapid repair.
iii. Protection against Certain Diseases:
They contain some substances which are like ABO blood antigens. They increase the immunity power by the production of antibodies. Blood platelet prevents the disease “purpura” in which hemorrhage occurs beneath the skin and mucous membrane.
Essay # 4. Coagulation of Blood in Humans:
At the time of injury, there is shedding of blood from the blood vessels. It quickly becomes sticky. By losing its fluidity, it turns into a red jelly like substance. This process is called coagulation or clotting of blood. After few minutes, this jelly or clot contracts and a straw coloured fluid called serum.
The formation of a blood clot is called coagulation of blood. It is a complicated process. If shed blood is microscopically examined, very fine threads will be seen. These insoluble fibrin threads are formed form the fibrinogen in the blood plasma by the action of the ferment thrombin.
These threads entangle the blood cells and form the clot together with them. Thrombin is not present in normal unshed blood but its precursor pro-thrombin is present and is converted into the active ferment thrombin by the action of thrombokinase.
Thrombokinase of thromboplastin is an activating agent liberated on injury to the blood cells. Calcium salts are present in the blood which help in the conversion of prothrombin into thrombin. Prothrombin is made in the liver. Vitamin K is necessary for its production. The active thrombin converts fibrinogen into fibrin. The fibrin threads surround the platelets, blood cells and plasma to form a clot. This clot covers the injured part of blood vessels. So that further loss of blood is prevented.
The following factors are necessary for clotting of blood:
1. Calcium salts normally present in blood.
2. Thrombin formed from pro-thrombin in the presence of thrombokinase.
3. Cell injury which liberates thrombokinase.
4. Fibrin formed from fibrinogen in the presence of thrombin.
Blood does not clot under normal condition inside blood vessels. When there is a rupture in a blood vessel the blood comes in contact with the damaged epithelial tissues and collagen fibers. The procoagulants become active and then the blood clot develops.
Formula of Blood Clotting:
Pro-thrombin + Calcium + Thrombokinase = Thrombin
Thrombin + Fibrinogen = Fibrin
Fibrin + Blood cells = Blood clot
Factors Hastening Coagulation of Blood:
The following factors are responsible for the quickening of the process of coagulation of blood:
1. Heat, a little higher than the body temperature.
2. Contact with rough surface, such as rough edge of a damaged blood vessel or a surgical dressing.
3. Addition of foreign bodies into a sample of blood.
4. Addition of thrombin.
5. Addition of thromboplastin.
6. Vitamin K injection or oral administration increases the pro-thrombin content of blood.
7. Addition of calcium chloride.
8. Adrenaline injection produces contraction of blood vessels and helps in blood clotting.
Factors Preventing Coagulation:
The following factors are responsible for the retardation of coagulation of blood:
1. By lowering temperature, coagulation can be prevented.
2. By avoiding contact with rough surface which prevents thrombokinase action.
3. Contact with oil, grease or paraffin wax, ointment and greasy materials prevent coagulation.
4. By the addition of potassium citrate or sodium citrate, which remove the calcium salts normally present.
5. Precipitation of fibrinogen.
Symbols and Name of Blood clotting Factors:
Essay # 5. Functions of Blood in Humans:
1. Transport of Gases:
Blood carries oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.
2. Transport of Nutrients:
It carries nutrients to the different tissues and cells which are required for the nourishment of the body, so that the normal functions are performed.
3. Transport of Soluble Organic Compounds:
It transports the soluble organic compounds like glucose, amino acids, fatty acids, glycerol etc. from small intestine to various parts of the body for their assimilation and utilization.
4. Carriers of Internal Secretions:
The internal secretions, hormones and enzymes are conveyed from one place to another inside the body through blood.
5. Transport of Other Essential Substances:
It acts as the vehicle through which vitamins, essential chemicals metabolic byproduct are brought to their places of activity.
6. Drainage of Waste Products:
Blood carries the soluble excretory materials like carbon dioxide, urea, uric acid, and other waste products to the excretory organs as lungs, kidneys, skin etc.
7. Regulation of Body Temperature:
Blood regulates the body temperature by evaporation from the skin and by contraction and dilation of skin. It distributes heat from deeply seated organs to all parts of the body. The water content of the blood, possess high specific heat. So it can absorb a large amount of heat and there by prevent sudden change of body temperature.
8. Maintenance of Water Balance and Ion Balance:
Blood maintains water balance of the body and ion balance between the cells and the surrounding fluids.
9. Maintenance of Acid-Base Equilibrium:
Blood helps in the maintenance of Acid base equilibrium with the help of kidney, skin and lungs. The inorganic salts maintain a constant blood osmotic pressure and constant PH.
10. Defensive Action:
Blood acts as the defense system of the body. The white blood cells provide many protective substances and are called as soldiers of the body. By their amoeboid movement and phagocytic action, they engulf the bacteria’s entering into the blood and protect the body against the disease germs. It also develops the antibodies for defensive action. The lymphocytes and antibodies provide immunity to the body.
11. Coagulation of Blood:
The blood protein pro-thrombin and fibrinogen help in clotting or coagulation of blood by maintaining hemostasis. By this property it guards against hemorrhage.
12. Distribution of Protein:
The blood plasma distributes proteins needed for tissue formation. It also acts as the store house of proteins for the tissues.
Essay # 6. Blood Groups in Humans:
Blood transfusion is necessary when there is a loss of blood. In some cases blood plasma cannot accept this outside blood where the agglutination is formed in the plasma. The cause of this agglutination means if blood of an incompatible group is transfused, it cause clumping and hemolysis (breakdown) of R.B.C. which prevents normal flow of blood in the blood vessels resulting in death of the person.
The clumping of RBC inside the blood vessels after blood transfusion is called transfusion reaction. The cause of this reaction was discovered by Landsteiner in the year 1900. Blood grouping and tests of incompatibility are carried out in order to ensure safety before blood transfusion.
Landsteiner observed two types of antigens on the surface of the red blood cells. He named them as A-antigen and B-antigen. A person may possess A-antigen or B-antigen. Some people may have both A and B antigen. On the basis of this, human beings may be classified into four Blood Groups. These are also called as ABO Group.
1. ‘A’ Blood Group:
‘A’ antigen on the surface of RBC and B antibody in plasma. Group A is subdivided into A1 and A2.
2. ‘B’ Blood Group:
‘B’ antigens on the surface of RBC and A antibody in plasma.
3. ‘AB’ Blood Group:
Both A and B antigen on the surface of RBC and no antibodies in plasma. Group AB is subdivided into A1B and A2B.
4. ‘O’ Blood Group:
Both A and B antigens are absent on the surface of RBC but both A and B antibodies are present in plasma. Besides these groups thirty different types of blood groups have been reported to be present in man now-a-days. But this ABO group and RH group of antigens are responsible for the transfusion reaction in the body.
Donors of Blood:
Group AB may give blood to AB
Group A to A and AB
Group B to B and AB
Group O is a universal donor for all Groups.
Recipients of Blood:
Group AB is a universal Recipient
Group A may receive blood from Group A and O.
Group B may receive blood from Group B and O.
Group O may receive blood from Group O.
The terms universal donors and universal recipients are not always applicable, as Rh blood group also plays an important role in transfusion reaction. So it is safe to transfuse blood of the same group. Group A and B can give blood to their own groups and also to AB group and can take blood from their own group and from the Group O. Other combinations are not compatible. Before blood transfusion, it is necessary to take precautions of testing the serum of the recipient against the RBC of the donor to confirm that the mixture is compatible.
Rh Factor:
In the year 1940 Landsteiner and Weiner discovered a type of antigen on the surface of RBC of Rhesus monkey. They discovered the same antigen on the red cells of 85% of human being. They named this antigen as Rhesus factor or Rh factor. This can be divided into two groups. Persons with Rh factor are known as Rh-positive (85%) and without this factor are called Rh-negative (15%).
There are six types of Rh antigens such as C, D, E and c, d, e. The type D antigen is present in most of the human population. So person with ‘D’ antigen is said to be Rh positive. Those people who do not have type ‘D’ antigen are called to be Rh negative. When a Rh-negative person is given Rh-positive blood, there is no immediate transfusion reaction, because the Rh-negative person have no Rh antibodies in his plasma to cause agglutination of RBC. But gradually after two to four months he develops Rh antibodies in his blood and the subsequent transfusion of Rh positive blood to the same Rh negative person causes severe transfusion reaction.
Rh factor plays an important role in prenetal development. If the parents are Rh positive, their offspring will be Rh positive. If there is difference between the blood types of the foetus and its mother they may be biochemically incompatible. For e.g. the child’s RBC may contain a substance which makes his blood agglutinate or clump in response to a specially prepared serum, while his mother’s blood may lack this substance.
In this case the child is Rh positive and his mother Rh negative. Rh negative mother with Rh positive father may have a Rh positive child. The Rh positive foetus produces certain substances called antigen which enter into the mother’s circulation through the placentae barrier. The mother develops anti Rh-antibodies which are passed back into the foetus circulatory system.
They may do a great deal of damage by destroying the RBC and preventing them from distributing oxygen normally. There may be miscarriages, still birth or death shortly after birth. Sometimes the baby may be partially paralyzed or mentally retarded as a result of brain damage from inadequate oxygen supply during the prenetal developmental period.
This disease of the foetus and the new born infants is known as “Erythroblastosis Fetalis”. These disastrous consequences do not occur in every case of mother child Rh incompatibility. First born children are not usually affected because it takes certain time for the mother to develop anti Rh-antibodies but in subsequent pregnancies these Rh-antibodies may cause transfusion reaction like abortion and death also. It is observed that Erythroblastosis occurs only in about one out of every 200 pregnancies. The incompatibility between the blood of mother and the child is caused by the irritancy of the Rh factor.
