Thymus gland. Light micrograph of a section through tissue from the thymus gland, part of the lymphoid system. The dense areas are the thymic cortex, which produces lots of lymphocytes. The lighter areas, the thymic medulla, produce less lymphocytes. In-between are blood vessels. This gland is located in the throat. Its role is to produce and mature T-lymphocytes (a specialised form of white blood cell), as well as other, more basic lymphocytes. It also controls the development of lymph nodes and the spleen. Magnification: x20 when printed 10 centimetres wide.