Anatomy Physiology


Bone marrow is the lifeline for cellular elements in many parts of the body including the cells present in the blood stream. The bone marrow is located in the substance of most of the bones and it is usually located in the central portion of these bones. In general, there are two main types of bone marrow, namely the ‘red marrow’ and the ‘yellow marrow’. Among them, the red marrow is the place where hype of activity takes place and the yellow marrow usually acts the role of a reserved part of the marrow for body requirement leading to acute and intense marrow activity. Overall, the bone marrow is said to account for almost 4% of the body weight.

Red marrow:

Red marrow is the most active segment of the bone marrow as many of the cell production takes place in these types of marrow. Red marrow is present mainly in flat bones such as the ribs, breast bone, hip bones, shoulder blades, clavicle as well as in the vertebras. Apart from these sites, it is also present in the epiphysial ends of the long bones as well.

When looking at its function, red marrow will produce red blood cells, white blood cells as well as platelets which makes it an enormously vital section of tissue to sustain life.

Yellow marrow:

In contrast, the yellow marrow would not perform a function similar to the red marrow although they play a vital part in the structural integrity and the overall composition of the bone marrow. This area of the bone marrow will contain cells which contains fat deposits and these cells will have the ability to transform into red marrow if the need arise. In an adult, most of the marrow will be of the yellow marrow type whereas in a newborn, almost all marrow will belong to red marrow category. When looking at the location of yellow marrow, they tend to concentrate in the shaft of the long bones.

But, it should be remembered that, the yellow marrow which forms the main part of the stroma contributes to the hematopoeisis indirectly by providing the necessary environment and the factors necessary to stimulate blood cell formation. Among the other constituents of the stroma, apart from the yellow marrow, fibroblasts, macrophages, adipocytes, osteoblasts, osteoclasts as well as endothelial cells can be taken as the main constituents.

Apart from the red marrow, the yellow marrow as well as the stroma, there will be numerous numbers of blood vessels and lymphatic tissues present in the marrow substance.