(i) Blood plasma is liquid in nature
(ii) Blood is derived from embryonic mesenchymal cells like other connective tissue
(iii) Matrikara (liquid in nature) is very high in blood like other connective tissue
(iv) It maintains communication between different cells, tissues and organs.

1. Nutrient transport: Nutrients and vitamins are transported to different parts of the body through the blood.
2. Oxygen transport: Blood carries oxygen from the heart to different parts of the body.
3. Carbon Dioxide Transport: Blood carries carbon dioxide from different parts of the body to the heart.
4. Acid-base balance: Blood maintains the body’s acid-base balance with the help of phosphate and carbonate compounds.
5. Blood coagulation: When a wound occurs anywhere in the body, the microcirculation stops blood flow by coagulation.
6. Temperature Balance: Heat balance is regulated throughout the body through the blood.
7. Self-defense: When a microbe enters the body, the blood protects the body by eating the microbe in the process of phagocytosis.
8. Immunity: Blood makes the body immune to diseases by making antibodies.
9. Wound healing: Blood produces fibroblasts to heal wounds in the body.
10. Storage: Plasma proteins act as storage of proteins in the body. When the amount of protein in the body decreases, the tissues take protein from the storage.
11. Homeostasis: Blood balances the internal environment of the body. This is called homeostasis.
12. Water balance: Water balance in the body is controlled through the blood.
13. Ion Balance: It maintains ion balance in the body.
14. Diagnosis: When there is any change in the body, there is a change in blood composition. Therefore, diagnosis is made by analyzing blood components.
15. Transport of metabolic substances: Blood carries chemical substances such as hormones, vitamins, antibodies etc. to the site of action. These substances regulate metabolism.
16. Transport of waste products: Blood carries the body’s urea, uric acid, bilirubin, CO2, etc. to organs such as kidneys, liver, lungs, sweat glands etc. These organs then excrete the wastes.

Cells contain organelles such as nucleus, mitochondria, ribosomes, lysosomes, Golgibodies, centrioles etc. Blood cells do not contain any organelles. Cells divide to form new cells. Blood cells do not divide. They originate from the bone marrow. Cells join together to form layers. Blood cells float in fluid. For these reasons, blood cells are not called blood cells.

1. Blood coagulation: Microcyclines induce blood coagulation at the wound site and stop bleeding by forming a hemostatic plug.
2. Vasoconstriction: It produces serotonin which causes vasoconstriction.
3. Destruction of microbes: They eat carbon particles and viruses by the process of phagocytosis.
4. Reconstruction: It repairs and reconstructs the lining of blood vessels.
5. Protein content: They have folds in the mantle that contain collagen and fibrinogen proteins.
6. Enzyme production: They are easily broken down and produce thrombokinase enzyme for blood clotting.
7. Clotting Factor Secretion: Clotting Factors are secreted by the molecule. It accelerates blood clotting.
8. Growth Factor Secretion: Cytokines secrete growth factors. It protects the inner wall of the endothelium.
9. Dissolving blood clots: Helps in dissolving blood clots when needed.
10. Heart disease: If the number of molecules is higher than normal, it can lead to heart attack and stroke.

Microcytes are the smallest blood cells. It is spherical, ovoid, rod-shaped and without a nucleus. Their diameter is 1-4 µm. Their cytoplasm contains pinocytic cavities and contractile cavities. The number of platelets per cubic milliliter of blood is 1.5-3.0 lakhs. But its number is more in diseased body. Their average lifespan is 8-12 days. It contains proteins and phospholipids called cephalin. It is stored only in the spleen. They originate from megakaryocyte cells in the bone marrow and are destroyed in the liver and spleen. About 200 billion (20 thousand crore) molecules are produced every day. Glycoproteins located in the molecular membrane bind to vascular lesions and large amounts of phospholipids are released from the membrane. It accelerates blood clotting.

White blood cells are the body’s independent guards and loyal soldiers. Monocytes and neutrophils protect the body by destroying microbes in the process of phagocytosis. Lymphocytes make antibodies and make the body immune to disease. In addition, white blood cells produce histamine and increase the body’s immune system. For all these reasons white blood cells are called microscopic soldiers.

1. Phagocytosis: Monocytes and neutrophils destroy microbes in the process of phagocytosis.
2. Destruction of microbes: Neutrophils contain toxic granules that destroy microbes.
3. Immunity: Lymphocytes make the body immune to disease by producing antibodies.
4. Removal of dead cells: They remove dead cells from the body.
5. Prevention of blood clotting: Basophils prevent blood clotting by producing heparin.
6. Histamine: Granular white blood cells produce histamine and increase the body’s immune system.

(i) Acts as a natural drain
(ii) Ingests viruses and bacteria
(iii) causes phagocytosis.

Monocytes are the largest white blood cells. Its nucleus is kidney-shaped or horseshoe-shaped. Its diameter is 12-20 µm. Their number is 280 per cubic milliliter. 4% of white blood cells are monocytes. Lifespan 2-5 days. It originates from red bone marrow (monoblast cells), liver, spleen and lymph nodes. 30-40 hours after generation it transforms into macrophage.

(i) Produces antibodies and destroys germs
(ii) Acts as a memory cell
(iii) Attacks the virus directly
(iv) Destroys cancer cells.