csontveli

Bone marrow is the soft, highly vascular tissue found inside the medullary cavities of bones. In Hungarian, the term csontvelő refers to this tissue. Bone marrow is the major site of hematopoiesis, the production of blood cells, including red blood cells, white blood cells, and platelets, throughout most of life.

There are two main types: red marrow and yellow marrow. Red marrow is rich in hematopoietic tissue and is responsible for ongoing blood cell production. In children, red marrow fills much of the spongy bone. In adults, red marrow is limited to the axial skeleton and the proximal ends of some long bones, while the remaining marrow becomes yellow marrow, which consists largely of adipose tissue. Yellow marrow can harbor hematopoietic activity under certain conditions, such as severe blood loss or disease.

Anatomically, bone marrow contains a supportive stromal network of reticular cells, fibroblasts, and extracellular matrix, within a vascular framework of sinusoids. It houses hematopoietic stem and progenitor cells that differentiate into erythroid, myeloid, and lymphoid lineages. The marrow microenvironment also includes macrophages and other immune cells that contribute to development and immune surveillance.

Developmentally, hematopoiesis transitions from fetal sites (yolk sac, liver, and spleen) to the bone marrow around late gestation and after birth. Clinically, bone marrow is accessed via biopsy or aspiration for diagnostic evaluation, and allogeneic or autologous bone marrow or stem cell transplantation is used to treat various hematologic diseases, such as leukemias, lymphomas, and marrow failure syndromes. Aging leads to an increase in yellow marrow and a gradual decline in marrow hematopoietic capacity.