Red blood cells:

Red blood cells (RBCs, also called erythrocytes;) are shaped like slightly indented, flattened disks. RBCs contain haemoglobin, a protein that carries oxygen. Blood gets its bright red colour when haemoglobin picks up oxygen in the lungs. As the blood travels through the body, the haemoglobin releases oxygen to the different body parts. Each RBC lives for about four months. Each day, the body makes new RBCs to replace those that die or are lost from the body. RBCs are made in the inside part of bones called the bone marrow.

White blood cells:

The immune system helps the body defend itself against infection. Different types of white blood cells (WBCs) fight germs, such as bacteria and viruses. Some types of WBCs make antibodies, which are special proteins that recognize foreign materials and help the body get rid of them.

Platelets: Platelets (also called thrombocytes) are tiny oval-shaped cells that help in the clotting process. When a blood vessel breaks, platelets gather in the area and help seal off the leak. Platelets work with proteins called clotting factors to control bleeding inside our bodies and on our skin. It survives only about 9 days in the bloodstream and is constantly being replaced by new platelets made by the bone marrow.