part of part of Danio rerio Homo sapiens medulla of organ medulla of thymus UBERON:0002124 NCIT:C33775 UMLS:C0229949 Medullary portion of thymus. The reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number, and there are found peculiar nest-like bodies, the concentric corpuscles of Hassall. These concentric corpuscles are composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells. They are the remains of the epithelial tubes, which grow out from the third branchial pouches of the embryo to form the thymus. Each follicle is surrounded by a vascular plexus, from which vessels pass into the interior, and radiate from the periphery toward the center, forming a second zone just within the margin of the medullary portion. In the center of the medullary portion there are very few vessels, and they are of minute size. SCTID:188344009 EFO:0001969 thymus medulla BTO:0004560 MA:0000771 Wikipedia:Thymus#Medulla medulla of thymus gland thymus gland medulla FMA:72206 EMAPA:19305 thymus