part of part of composed primarily of hematopoietic cell red bone marrow BTO:0001160 SCTID:75330005 FMA:74595 parenchymal red marrow medulla ossium rubra SCTID:328538003 red marrow The red vascular substance consisting of connective tissue and blood vessels, containing primitive blood cells, macrophages, megakaryocytes, and fat cells. Red marrow is found in the cavities of many bones. It manufactures and releases leukocytes and erythrocytes into the bloodstream. parenchyma of none marrow marrow UBERON:0000361 bone marrow hematopoietic tissue