Bone marrow

Fig. 1. Distribution of red bone marrow in the skeleton (painted black).

Bone marrow is one of the blood-forming organs, producing cells of the blood myeloid series (erythrocytes, granular leukocytes). Its basis is reticular fabric, penetrated by a large number of blood vessels, mainly capillaries, extended in the form of sinusoidal. In the adult human body there are red and yellow bone marrow. Red bone marrow is actually blood-forming part of the bone marrow, it fills in the cells of the spongy substance flat bones, vertebrae and epiphyses tubular bones (Fig. 1). Yellow bone marrow is found in bone marrow cavities of divisov tubular bones. He is a reborn reticular tissues, cells which contain fat inclusion (Fig. 2).
In children entire bone marrow red. After 3-4 years of age in bone marrow cavities of divisov bones red bone marrow gradually replaced by yellow. The total mass of the bone marrow in adults is an average of 2.6 kg, of which about half are presented in red bone marrow. The ratio of yellow and red bone marrow may vary depending on the conditions of supply, nervous, endocrine and other factors. Red bone marrow has a dark red color and semi-fluid consistency, which gives the opportunity to prepare a thin smears on the glass.

yellow bone marrow
Fig. 2. Yellow bone marrow: 1 - bone; 2 - artery; 3 - Vienna; 4 - the fat cells.
red bone marrow
Fig. 3. Red bone marrow: 1 - erythrocytes; 2 - fat cell; 3 - acidophilus plasmic order has been revealed; 4 - neutrophilic plasmic order has been revealed; 5 - reticular cell; 6 - erythroblast; 7 - genocidally.

In red bone marrow distinguish stroma, formed reticular cells star-shaped with large kernels and network reticulin fibers, and parenchyma, which are maturing cellular elements of blood (Fig. 3). Among them maternal cells red blood cells - erythroblast and in a smaller number of maternal cells, which develop different forms of granular leukocyte - myeloblaste.
The major function of bone marrow is the blood (see). Along with other blood-forming organs, bone marrow involved in maintaining a constant number of formed elements of blood. This is achieved by the fact, that instead of dead blood cells are formed new ones.
The blood supply to the bone marrow is the feeding arteries that form two systems capillaries: supply and sinusoidal. In the yellow bone marrow sinusoidal capillaries are missing. Venules, receiving blood from the capillaries, merge in collecting and Central veins. Together with blood vessels in the bone marrow penetrate the nerve fibers which control it.
Cm. also Blood-forming organs.