Function of Bone Marrow

The main function of bone marrow is to produce the different types of blood cells that make up a healthy blood cell count. Leukemia, a cancer of the blood, affects cells in the bone marrow, causing red bone marrow to produce large amounts of fast-growing, abnormal blood cells.

Bone Structure

Bones are not the solid structures they appear to be. The hard outer surface of bones conceals and protects the bone marrow. Bone marrow is a fibrous tissue that contains fluid, blood vessels, fat cells and blood-forming stem cells.

Yellow bone marrow has a high concentration of fat cells. Red bone marrow contains hematopoietic cells, which are responsible for creating new blood cells.

A newborn’s bone marrow is entirely composed of red bone marrow. As he ages, yellow bone marrow develops. In adults, bone marrow is divided between red bone marrow and yellow bone marrow.

Blood Cells and the Function of Bone Marrow

Red bone marrow in the large bones is responsible for the bulk of new blood cell production. Bones that produce the most blood cells in adults include the:

• Arm bones
• Breastbone
• Leg bones
• Ribs
• Spine.

Stem cells within the bone marrow divide to form blood cells. The new cells come in two types:

• Pluripotential cells continue to divide, creating new stem cells.
• Unipotential cells form one single type of blood cells.

Different "colonies" of unipotential cells divide at different times, ensuring a steady supply of unipotential cells at different maturity levels. When unipotential cells interact with substances called poietins, they develop into "blasts," or young blood cells.

Blood Cell Count

A healthy blood cell count contains different types of blood cells, which each have a specific function. Types of blood cells produced by bone marrow include:

• Erythrocytes (red blood cells): Red blood cells contain hemoglobin, which can bind with oxygen. Erythrocytes transport oxygen from the lungs to the rest of the body, and give blood its characteristic red color.
• Granulocytes: Granulocytes are a group of white blood cells that include neutrophils, basophils and eosinophils. Granulocytes are designed to destroy bacterial invaders.
• Lymphocytes: Lymphocytes are a type of white blood cells, including B cells and T cells. B cells target bacteria and toxic substances, while T cells destroy virally infected or cancerous body cells.
• Monocytes: Monocytes are large white blood cells that surround and consume foreign particles.
• Platelets: Platelets originate in the bone marrow and play an important role in blood clotting.

Leukemia and Bone Marrow

Leukemia occurs when the function of bone marrow is disrupted. Bone marrow produces abnormal white blood cells that remain immature, but reproduce rapidly. Leukemia cells disrupt the normal blood cell count, crowding out healthy blood cells.

Resources

MedicineNet. (1998). Definition of lymphocyte. Retrieved March 17, 2010, from http://www.medterms.com/script/main/art.asp?articlekey=4220.

Oncology Channel. (2007). Bone marrow and blood formation. Retrieved March 16, 2010, from http://www.oncologychannel.com/leukemias/bonemarrow.shtml.

Oncology Channel. (2007). Types of blood cells. Retrieved March 16, 2010, from http://www.oncologychannel.com/leukemias/blood-cell-types.shtml.

University of California San Francisco Children’s Hospital. (2010). What is bone marrow? Retrieved March 16, 2010, from http://www.ucsfchildrenshospital.org/education/what_is_bone_marrow/index.html.