- The Thymus is located in the anterior part of the superior mediastinum and extends into the anterior mediastinum. It is located immediately deep to the superior part of the sternum and superficial to the cardiac pericardium.
- The thymus appears as a delicate lymphoid tissue which may be easily missed upon dissection. The organ is at its most obvious during childhood after which it begins a slow involution into adult age. By the elder years the organ is almost completely absent, replaced largely by adipose tissue.
- The thymus develops from the third pharyngeal pouch.