THYMUS GLAND

1. Flat, bilobed gland located in the mediastinal space in front of heart.
2. Well developed in new born child and grows upto puberty but starts degenerating thereafter at 25 years of age, it disappears.
3. Parenchyma contains numerous lymphocytes undergoing proliferation and maturation forming different types of T- Iymphocytes which later migrate to spleen, lymph nodes, Peyer's patches etc. and remain stored there or some are also retained in circulating blood.
4. Secretes a hormone, thymosin, which activates lymphocytes.