Positioned in the upper chest cavity, the thymus gland is actually a two-lobed structure that extends partially into the neck region. It is precisely located right about the pericardium of the heart, below the thyroid and between the lungs. The thymus has two lobes, each of which has smaller divisions known as lobules.
The medulla is the inner area of the lobule, whereas the outer area is called the cortex. Immature T-lymphocytes stay in the cortex region, whereas the medulla region contains the mature T-lymphocytes. Only the mature cells can identify foreign cells.
The gland has a thin outer covering and consists of three different types of cells–lymphocytes, epithelial cells, and neuroendocrine cells. Epithelial cells give structure to the thymus, neuroendocrine cells release hormones, and lymphocytes protect you against infections.