The thymus gland is actually composed of lymphoid tissue and is located in the mediastinal cavity, in front of and above the heart.
The thymus gland is a two-lobe primary lymphoid organ which has an important role in immune function. It secretes thymosin hormone which stimulates the maturation of T cells. So, the thymus is a place where T cells mature. This organ is most active during the neonatal and pre-adolescent periods.
