Thymus

The thymus is a gland that forms part of the immune system. It is situated in the upper part of the chest, behind the breastbone, and is made up of two lobes that join in front of the trachea. Each lobe is made of lymphoid tissue, consisting of tightly packed white blood cells and fat. The thymus enlarges from about the 12th week of gestation until puberty, when it begins to shrink. Its function is to transform lymphocytes (white blood cells developed in the bone marrow) into T-cells (cells developed in the thymus). These cells are then transported to various lymph glands, where they play an important part in fighting infections and disease. Swelling of lymph glands and fever are a signal that immune cells are multiplying to fight off invaders of the body: bacteria, fungi, viruses or parasites. Edward Jenner showed his faith in vaccination by injecting his own son with cowpox, therefore immunizing the child against smallpox, a deadly disease at that time in history