part of has part bone marrow cell Homo sapiens tissue bone element bone marrow consider placement of NCIT:C53466 medullary bone TODO - create superclass for bone marrow / head kidney. both are portions of tissue in the hematopoetic system. also consider adding as subclass of zone of bone organ for consistency with FMA. See also: Leydig and epigonal organs hematopoietic system immune system hematopoietic tissue