The thymus is considered an actual organ, and can be located in the upper mediastinum, behind the manubrium of the sternum, and just in front of the aorta. It is a bi-lobed organ that varies in size. It is known to be quite large in perspective during the first few years of life and then shrinks considerably as the body grows. As it shrink, the adult body’s thymus is then infiltrated with various fatty tissues and strands of fibrous connective tissue.
The thymus is associated equally with the lymphatic system as it is with the endocrine system. Lymphocytes known as T-cells are administered via the thymus and while these are known to contribute to immunity. The T-cell count is vital to determining the health of the human immune system. The thymus administers a hormone known as thymosin, which is responsible for continued stimulation of T-cells once they leave the confines of the thymus.