Blood and it's Composition
Blood, Blood Composition, Components of Blood and its Functions, Blood Group, Blood Types, Blood pH, Physical Characteristics of Blood, Blood Volume, Blood Discovery Blood physiology, Rh-factor
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| Blood and it's Composition |
What is Blood?
Blood is a constantly circulating fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Blood is a transport liquid and circulates in the blood vessels due to pumped by the heart to all the parts of the body after which it is returned to the heart to repeat the process. Blood is a connective tissue as well as a fluid. Blood is thick viscous fluid with a pH of 7.35-7.45, specific gravity between 1.05 and 1.06 and blood is made up of approximately 78% water and 22% solids.
Blood is a tissue because it is a collection of similar specialized cells that serve particular functions. Blood is fluid having numerous cells and proteins suspended in it, making blood thicker than pure water. Approximately 8% of an adult’s body weight is made up of blood. Females have around 4-5 litres, while males have around 5-6 litres of blood. The presence of haemoglobin in the blood aids to its colour. Oxyhaemoglobin gives blood a brighter Scarlet colour whereas haemoglobin devoid of oxygen attains a bluish colour.
Sir William Harvey was the first person who described the physiology of blood circulation in human body in 1692. Cardiology is the study of heart and and Angiology is the study of blood vessels respectively.
Blood Composition
Human blood is consisting of mainly two components-
1. A fluid matrix called Plasma and
2. Formed elements or Corpuscles
1. Plasma
Plasma is a pale yellow extracellular fluid and is consist of 90% water and 10% of large number of dissolve substances including protein. Plasma makes up about 2/3 of the content of blood. Plasma mainly contains proteins, it helps blood to clot and transport substances through the blood and blood perform various functions within our body. The most abundant solute of plasma is sodium while serum albumins, fibrinogen and globulins form the major proteins.
Types of Plasma Proteins-
There are three types of Plasma proteins-
Albumin:
Fibrinogen:
Fibrinogen is necessary for the clothing of the blood. Fibrinogen can be converted to insoluble fibrin.
Globulin:
Globulin is has many functions. Globulin transport ions, hormones, liquid etc.
2. Formed elements or Corpuscles
Red blood cells (RBCs), or erythrocytes:
They are shaped like slightly indented, flattened or small binocave discs composed of protoplasm lacking nuclei and transport oxygen to and from the lungs. The protoplasm has the pigment called haemoglobin. Haemoglobin is a protein that contains iron and retains the oxygen until its destination. The erythrocyte are formed in the bone marrow and this process of formation is called haemopoeisis. The life span of an RBC is 120 days and are then destroyed in the spleen. Our body replaces RBCs regularly. Our body produces around 2 million blood cells every second in our body. By volume, Red Blood Cells constitute about 45% of whole blood.
The expected number of RBCs in a single drop or microliter of blood is 4.5 to 6.2 million in men and 4.0 to 5.2 million in women. The disintegration of haemoglobin releases iron and organic pigments called Bilirubin and Biliverdin, the latter colour the bile. Iron is stored in liver for freshs haemoglobin Preparation. The decrease in number of erythrocytes is termed anemia and increase in number of erythrocytes is termed polycythemia. The main functions of Erythrocytes is to carry oxygen from the lungs to the rest of the body.
White blood cells (WBCs) or leukocytes:
Leukocytes are basically larger than Erythrocytes. Leukocytes make up less than 1% of blood content and leukocytes form vital defenses against diseases and infections. Leukocytes are produced in liver, yellow bone marrow and lymphoid organs. The normal range of the number of white blood cells in a microliter of blood is between 3,700 and 10,500. By volume, White Blood Cells constitute about 0.7% blood in our body. Higher and lower levels of white blood cells can indicate disease. The increase in the number of leukocytes is termed as leukocytosis and it's decrease is termed as leukopenia while the oozing out of the leukocytes from the capillaries is called diapedesis. The main functions of leukocyts Or WBCs is to help fight infections and aid in the immune process.
Leukocyts are of two types, which are mainly-
1. Agranulocytes (no granules in the cytoplasm) lymphocytes and Monocytes
2. Granulocytes ( granules are presents in the cytoplasm) - basophils, eosinophils and neutrophils.
Platelets, or thrombocytes:
Platelets are small colourless, oval circulating blood, averaging about 3 microns in diameter and formed in the giant bone marrow cell(megakaryocytes). By volume, platelets making up less than 1% blood in our body. Platelets interact with clotting proteins to prevent or stop bleeding. Platelets occur only in mammals. There should be between 150,000 and 400,000 platelets per microliter of blood, reduction below normal is called thrombocytopoenia. In certain forms of haemophilia blood platelets are abnormally stable and fail to released thrombokinase, thus increasing coagulation time.
Their life span is 3-8 days and the main function of platelets is to help in blood clotting.
Blood Group:
The four blood groups are A, B, AB and O depending on the presence of the respective antigens in their RBCs. A, B, O blood group was discovered by Karl Landsteiner in 1900(Nobel Prize in 1930) while the fourth type AB was discovered by Decastrello and Sturli in 1902.
A person with blood group O is termed as Universal Donor as his RBCs don't contain antigens and plasma has antibodies A and B. A person with blood group AB is termed Universal Recipient as it contains no antibodies and A and B antigens in RBC.
When the blood of Donor and recipient do not match, clotting or clumping occures and in such cases the blood of Donor and recipient are said to be incompatible. Thus test of compatibility are carried out before transfusion.
ABO blood groups are based upon the presence of certain proteins in the plasma membrane of RBCs and coded by genes. These proteins are of two types A and Band are called antigens (agglutinogens chemically glycoproteins).
Bernstein discovered the ABO blood grouping is an inherited characteristics which involves multiple allelism. The I gene has three alleles forms viz. IA, IB and I of which IA and IB are codominant.
The Rhesus factor or Rh-factor:
The Rhesus factor or Rh factor is a type of blood protein firstly discovered by Landsteiner and Winer in 1940, in the blood of rhesus Monkey. It is an antigen found on the cell membrane of RBC. If this factor is present in the blood , the blood is Rh positive and if it is absent the blood is Rh negative. Rh factor is inheritable .
If Rh negative pregnant woman carries an Rh positive (inherited from father) baby in her womb, anti Rh agglutinins develop in the blood of Murder in her first pregnancy but are not enough to cause complication .at the time of second pregnancy if the baby is Rh positive again, the anti Rh agglutinin from the mother attrack the RBCs of the embryo causing its death in uterus and this is known as erythroblastosis foetalis.