Lymphoid organ

alt=3D medical animation still showing structure of as well as location of the spleen in human body|thumb|A 3D medical animation still of spleen structure and exact location

cells and soft materials in the hollow space of long bones

The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule.

organ of the lymphatic system

diffuse system of lymphoid tissue found in various mucosal sites

a ringed arrangement of lymphoid tissue in the pharynx.