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. [ http://medical-dictionary.thefreedictionary.com/red+marrow ]
Synonyms: red marrow medulla ossium rubra parenchymal red marrow