Bone marrow

Bone marrow is a semi-solid tissue found within the spongy or cancellous portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production or hematopoiesis. It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells. In adult humans, bone marrow is primarily located in the ribs, vertebrae, sternum, and bones of the pelvis. Bone marrow comprises approximately 5% of total body mass in healthy adult humans, such that a man weighing 73 kg (161 lbs) will have around 3.65 kg (8 lbs) of bone marrow.

Composition

Bone marrow is composed of a variety of different types of cells, including stem cells, which are responsible for the production of new blood cells. These stem cells divide and differentiate into the various types of blood cells, including red blood cells, white blood cells, and platelets. In addition to stem cells, bone marrow also contains stromal cells, which support the function of the stem cells, and adipose cells, which store fat.

Function

The primary function of bone marrow is to produce blood cells, a process known as hematopoiesis. This process is essential for life, as blood cells perform a variety of critical functions in the body, including carrying oxygen to tissues (red blood cells), fighting infections (white blood cells), and aiding in clotting to prevent excessive bleeding (platelets).

Diseases and Disorders

There are a number of diseases and disorders that can affect the bone marrow, including leukemia, a type of cancer that starts in the bone marrow and leads to the production of abnormal white blood cells. Other conditions include anemia, which can be caused by a decrease in the production of red blood cells, and thrombocytopenia, which is characterized by a decrease in the production of platelets.

Bone Marrow Transplant

In some cases, diseases or disorders of the bone marrow can be treated with a bone marrow transplant. This procedure involves replacing the patient's diseased bone marrow with healthy bone marrow from a donor. This can be a life-saving treatment for conditions such as leukemia, but it also carries significant risks, including the risk of infection and graft-versus-host disease.

See Also

• Hematopoiesis
• Stem cell
• Leukemia
• Bone marrow transplant