What is blood? Describe its composition.

Blood:

1. Blood is the fluid connective tissue of the body.
2. It helps in the transportation of nutrients, gases, and waste materials in the body.

Composition of blood:

1. Blood contains plasma as its fluid component whereas blood corpuscles as its solid component.
2. The plasma contains 90-92% of water, proteins that include 7% of hormones, globulins, fibrinogen, antibodies etc.
3. Plasma also contains food nutrients, metabolites like enzymes, lactic acid, urea, etc. and inorganic salts like calcium chloride, sodium chloride, etc.
4. The solid part of the blood includes the three types of blood cells named erythrocytes, leucocytes, and thrombocytes.
5. The total count of erythrocytes or red blood cells is about 5 million in adult human males and 4.5 million in adult human females.
6. Red blood cells contain haemoglobin, a pigment responsible for the red color of the blood and the oxygen-carrying capacity of the red blood cells.
7. There are about 5000 leucocytes or white blood cells in 1 cubic millimetre of blood.
8. There are five different types of white blood cells present in the blood which are broadly divided into- granulocytes and agranulocytes.
9. Granulocytes include basophils, eosinophils, and neutrophils.
10. Agranulocytes include lymphocytes and monocytes.
11. The white blood cells play a vital role in the defense mechanism of the body.
12. The third cellular component of blood is the thrombocytes or the platelets.
13. There are around 2,50,000 to 4,00,000 platelets in 1 cubic millimetre of blood.
14. These play a vital role in coagulation or clotting of blood.