They help to control the level of glucose in the blood stream. Parathyroid Is one of four small organs in the neck. There are two each side of the thyroid gland in the front of the neck. It releases a hormone that controls the level of calcium in the blood. Blood transports food and oxygen to all living cells in the body, and takes away waste matter from them.
Blood consists mainly of a watery liquid called plasma.
Red cells, white cells and platelets float in the plasma. The disc-shaped red blood cells take oxygen from the lungs to the tissues. White blood cells help to fight infection by attacking harmful bacteria. Small particles called platelets are important for blood clotting. There are approx.