Knochenmarksinusoidendurchläufe

Bone marrow is a soft, vascular tissue located inside the cavities of most bones. In adults, it is classified as red marrow, which produces blood cells, and yellow marrow, which stores fat. Red marrow is predominantly found in the pelvis, spine, ribs, sternum, skull, and the proximal ends of the femur and humerus; as people age, much of it is gradually replaced by yellow marrow.

Hematopoiesis, the formation of blood cells, occurs in the red marrow. Hematopoietic stem cells differentiate into red blood cells, various white blood cells, and megakaryocytes, which give rise to platelets. The marrow's microenvironment includes stromal cells, adipocytes, endothelial cells, and an intricate network of blood vessels that support the development, maturation, and release of blood cells into the circulation. Immune cells also originate and mature within the marrow.

Clinical relevance: The marrow is routinely sampled with bone marrow biopsy and aspiration to diagnose hematologic disorders such as leukemia, lymphoma, myeloma, aplastic anemia, and metastatic cancers. Bone marrow transplantation, including autologous and allogeneic transplants, is used to treat a range of hematologic diseases and some solid tumors. Aging commonly leads to a gradual replacement of red marrow with yellow marrow, reducing hematopoietic reserve and potentially affecting the body’s ability to respond to stress or infection.

Assessments of marrow function employ imaging and laboratory tests, and therapeutic interventions may include growth factors to stimulate specific blood cell production. Procedures carried out to obtain or treat marrow typically require appropriate anesthesia and carry risks such as pain, bleeding, or infection.