- Blood is a fluid tissue in our body and it is the medium in which dissolved gases, nutrients, hormones and waste products are transported. Blood along with the heart and the blood vessels comprises the circulatory system of the blood.
- Cells present in the blood are called corpuscles. They are of three types.
3. Blood platelets
RBC (RED BLOOD CELLS)
- Red blood cells are also known as erythrocytes are red in colour. They have a red coloured protein called haemoglobin.
- Because of haemoglobin blood is red in colour, which helps in the transport of oxygen and carbon dioxide. 1ml of human blood has about 5 millions of red blood cells which survive for 120 days in blood.
- Red blood cells formed in the liver and spleen in the embryonic stage.
- After birth, these RBC are generated from the bone marrow of long bones. All mammals except Camel and Ulama have red blood cells without a nucleus.
WBC ( WHITE BLOOD CELLS )
- The second type of cells present in the blood is white blood cells. These cells do not have haemoglobin, hence they are colourless cells or leukocytes and they have a nucleus. These cells are less in number when compared to the RBC.
- There are two types of cells in WBC
- Granulocyte cells are of three types
2. Basophils and
- These cells attack and destroy the microorganisms that enter the blood. These dead WBC come out of wounds. This is generally called ‘Pus’.
- Agranulocytes are of two types
1. Lymphocytes and
- Lymphocytes secrete antibodies to guard against foreign material that enters into the blood.
- Monocytes move like amoeba and along with granulocytes. They attract foreign materials and engulf them. The foreign materials are destroyed inside these cells. They are called ‘scavengers’.
- Blood platelets are a separate group of cells which do not have a nucleus. They are disk-like projections.
- In blood platelets whenever a blood vessel is injured, platelets accumulate at the site of injury and help in the formation of a blood clot. The clot seals the wound in blood vessels and prevents further blood loss.