Involved in the early development of the immune system, the thymus is a large structure in the child, begins to atrophy after puberty, and shows considerable size variation in the adult. In the elderly adult, it’s barely identifiable as an organ, consisting mostly of fatty tissue which is sometimes arranged as 2 lobed fatty structures.
Arteries to the thymus contain small branches originating from the internal thoracic arteries. Venous drainage is generally into the left brachiocephalic vein and possibly into the internal thoracic veins.
Lymphatic drainage returns to multiple groups of nodes at 1 or more of the following locations:
- along the internal thoracic arteries (parasternal);
- at the tracheal bifurcation (tracheobronchial); and
- in the root of the neck.
Ectopic Parathyroid Glands In The Thymus
The parathyroid glands develop from the third pharyngeal pouch, which also creates the thymus. The thymus is for that reason a common site for ectopic parathyroid glands and, potentially, ectopic parathyroid hormone production.