Article: Bone marrow

Gray's Anatomy illustration of cells in bone marrow.

Bone marrow (or "medulla ossea") is the tissue comprising the center of large bones. It is the place where new blood cells are produced. Bone marrow contains two types of stem cells: hematopoietic (which can produce blood cells) and stromal (which can produce fat, cartilage and bone). Stromal stem cells have the capability to differentiate into many kinds of tissues, such as nervous tissue. Hematopoietic stem cells give rise to the three classes of blood cell that are found in the circulation: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes).

The tissue of bone marrow, where pluripotential hematopoietic stem cells produce blood cells, is called "myeloid tissue".

"Long bones", like the femur are tubular in structure, and the hollow middle is filled with yellow marrow. While the majority of long bones are formed of cortical ("compact") material; at the ends are the epiphysis, which are generally composed of cancellous ("spongy") material and red marrow. Large amounts of red bone marrow can also be found in flatter bones like those of the pelvis and skull.

Bone marrow as a food

Though once used in various preparations, including pemmican, bone marrow has fallen out of favor as a food. Now, it is commonly used only as a flavoring for soups and sauces, although dishes with intact bone marrow can still be found in some European restaurants. Bone marrow is a source of protein and high in monounsaturated fats. These fats are known to decrease LDL cholesterol levels. Some believe this results in a reduced risk of coronary heart disease, prompting them to make bone marrow a dietary staple. The actual health effects of the addition of bone marrow to the diet remain unknown.

See also

• Leukemia
• Bone marrow transplant
• Aplastic Anemia