Red Bone Marrow vs. Yellow Bone Marrow
Key Differences
Comparison Chart
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Other Name
Occurrence
Function
Color
Cells
Development
Location in the skeleton
Red Bone Marrow vs. Yellow Bone Marrow
Red bone marrow which is also called myeloid tissue is highly vascularized and initially produces hematopoietic stem cells (HSCs) which differentiate into progenitor cells that generate red blood cells, white blood cells, and platelets. These differentiated cells then enter into the blood circulation through sinusoids. In contrast, Yellow bone marrow is formed from the red bone marrow which is converted into yellow marrow throughout an individual life. In this marrow, adipocytes are the primary cell type in yellow marrow. The lipid droplets within these cells contain carotenoids.
What is Red Bone Marrow?
Red bone marrow contains hematopoietic tissue. The main function of red bone marrow is to produce all types of blood cells such as RBCs, WBCs, and platelets. At the time of birth, all bone marrow is red, but with the passage of age, it is replaced by the yellow bone marrow. With age, the level of red bone marrow decreases. Almost 2.6 kg of bone marrow is present in adults and half of it is red bone marrow. Red bone marrow can be found in the spongy bones of the skull, spine, ribs, shoulder blades, sternum and at the end of the long bones in legs and arms in adults. Red bone marrow is filled in the spaces of the trabeculae plates in the spongy bones.
Two types of the stem cells are produced by the hematopoietic stem cells of the bone marrow which are lymphoid stem cells and myeloid stem cells. Lymphoid stem cells are differentiated into red blood cells whereas myeloid stem cells are differentiated into white blood cells. Red bone marrow has all developmental stages of most of the blood cells. When these blood cells become mature, they are released into the circulation. Red bone marrow also assists as filters for damaged and aged blood cells and removes them from the blood circulation. All blood cells are produced in the red bone marrow, so it is richly supplied with the blood.
What is Yellow Bone Marrow?
Yellow bone marrow is riched with fat. It primarily occurs in the marrow cavity of the long bones. The yellow bone marrow is formed from red bone marrow. At the age of five years, red bone marrow in the marrow cavity is converted into the yellow bone marrow. With age, the level of yellow bone marrow increases. The fat is stored in the cell called adipocytes and can be consumed in extreme hunger. The fat of the yellow bone marrow is the last source of the body’s energy. It helped to provide sustenance and maintained a balanced environment for the bone to function, but in certain conditions such as in significant blood loss, yellow bone marrow is converted into the red bone marrow to produce blood cells. It can also be converted into cartilage and compact bones. It has an inadequate blood supply compared with the red bone marrow.
The lipids which are stored in the yellow bone marrow are called marrow fats and are physiologically different from brown and white adipose tissue and enhance with age, in a gender-specific manner and various disease conditions such as spinal cord injury and starvation. This increase in marrow fat levels decreases the ratio of HSCs t adipocytes which is called bone marrow cellularity. In some conditions such as sickle cell disease or high altitude, the count of HSCs is upregulated increasing bone marrow cellularity.
