The Thymus
Situation
The gland lies in the upper part of the mediastinum
behind the sternum
extends upwards into the root of the neck.
10 to 15 g. at birth, grows puberty
Then atrophies
Structure
Maximum weight 30 - 40g by the age of 40
Consists of two lobes connected by areolar tissue.
Fibrous capsule - septae divide the gland into lobules
Lobules consist of epithelial cells and lymphocytes.
Function
Lymphocytes originate in red bone marrow.
Enter the thymus
Mature and develop into activated T-lymphocytes
Then divide into two groups :
- those that enter the blood, some lodge in other lymphoid tissue
- those that remain in the thymus gland - source of future generations of T-lymphocytes.
Thymus is stimulated by thymosin
Thymosine is secreted by the epithelial framework of the thymus gland.
Involution of the gland begins in adolescence.
