Haemoglobin is the protein, which gives red colour present in the red blood cells. It combines with oxygen and carbon dioxide and helps in transporting them to the respective parts of the body. It is an iron protein that imparts red colour to the blood.

Blood is a red coloured fluid connective tissue. The components of blood are plasma, red blood cells, white blood cells, and blood platelets. Platelets are also called as thrombocytes, that is a tiny blood cells that helps in blood clotting, to stop the bleeding. They rush to the site of damage to form a plug (clot) to fix the damage.

The lymphatic system consists of an extensive network of lymphatic vessels and lymph organs (lymph nodes, spleen, and thymus). The fluid present in the lymphatic vessels contains lymphocytes which protect the body by killing the germs of the body tissue by making antibodies. There are three main types of lymphocytes: T cells, B cells, and natural killer cells. The T cells originate in the thymus gland and control the immune response. The B cells originate in the bone marrow and produce antibodies. The natural killer cells are also called cytotoxic cells. These cells have the ability to destroy germs or other cells. The fluid is called lymph.