Source:http://linkedlifedata.com/resource/umls/id/C0006440
MSH: An epithelial outgrowth of the cloaca in birds similar to the thymus in mammals. It atrophies within 6 months after birth and remains as a fibrous remnant in adult birds. It is composed of lymphoid tissue and prior to involution, is the site of B-lymphocyte maturation.,CSP: epithelial outgrowth of the cloaca in birds similar to the thymus in mammals.