Class 7 Science - Chapter Transportation in Animals and Plants NCERT Solutions | What are the components of blood?
What are the components of blood?
The average adult person has about 4 to 6 litres of blood and the study of blood is known as haematology. Four component of blood are as follows:
1. PLASMA: Plasma is pale yellow in colour, slightly alkaline and viscous fluid. It has fixed chemical composition: 90% water and 1% inorganic salts; and inorganic salts and 7 to 8% proteins. The remaining 1- 2% of the plasma is formed by food materials and waste products, dissolved gases, regulatory substances, anticoagulants cholesterol and the antibodies.
2. RED BLOOD CELLS (RBC): Red blood cells are red in colour due to the presence of a red, oxygen carrying pigment called haemoglobin; in the cytoplasm and are most abundant cells in the human body. Their shape varies in different vertebrate classes. In some like fishes, amphibians, reptiles, they are oval, biconvex and nucleated. In mammals, they are circular, biconcave, de-nucleated discs etc.
3. WHITE BLOOD CELLS (WBC): The white blood cells are also known as leucocytes; it fights from the infection and protect us from diseases that may occurs from the pathogens. White blood cells make chemicals ‘antibodies’ which usually fights against infection. They lack haemoglobin and are rounded irregular shaped cells which changes their shape and capable of doing amoeboid movement.
4. PLATELETS: Platelets are pale yellow in colour and are also called thrombocytes; are the tiny fragments of megakaryocyte cells in which cytoplasm remains enclosed by the piece of plasma membrane but lacks nuclei. Thrombopoietin hormone is produced by the liver which increases the number of megakaryocytes in the bone marrow and which automatically stimulates platelets production. Platelets are mainly involved in blood clotting (transformation of blood from liquid into solid gel). They helps to stop blood loss from the damaged blood vessels by forming platelet plus (thin layer). Their granules contains chemical when they released which promotes blood clotting.
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