Bone marrow – Structure and function of bone marrow
Bone marrow It is the main blood-forming organs; total weight of it is 1,6-3,7 kg (average 2,6 kg), half of it falls on the active red brain.
Red bone marrow It stored in the cancellous Stuff flat bones, vertebrae and metaphyses of long bones, Yellow - is enclosed in the diaphysis of long bones.
The total amount of bone marrow It depends on gender, age, the nature of the pathological process. It is believed, that women have the amount of red bone marrow less, than men. In newborns all the bones are red bone marrow.
With the growth of the body's red bone marrow in the long bones gradually turns into fat. This process begins at the age of 3-4 years and ends in 14-16 years.
Bone marrow is the basis of connective tissue - stroma, provided reticulum, parenchyma (blood cells) and blood vessels.
Reticular bone marrow tissue Located between the vessels and bone marrow crossbeams (beams), covered endosteum, which forms a fibrous capsule. Bone marrow is rich in blood vessels, penetrating from the bone and forming it closed network, wherein arterioles pass directly into the venous sinuses (sinusoidы). The walls are composed of sinusoidal reticulum.
The venous sinuses are formed blood cells, that, reaching maturity, enter the peripheral blood. The mechanism of this process has not been studied. Immature cells normally remain in the bone marrow (apparently, endothelium of the venous sinuses) and not in the peripheral blood received. Under pathological conditions of bone marrow function or the enhanced (in leukemia), or attenuated (when Hypersplenism).
In the bone marrow it takes a large number of nerve fibers. Nerve endings are not only in the walls of blood vessels, but in the brain tissue. Influence of the nervous system on the blood is now considered an established fact. So, irritation of the sympathetic part of the autonomic nervous system stimulates the maturation and release of cells in the blood, and irritation of parasympathetic part inhibits these processes.
The main function of bone marrow – hematopoietic. Besides, bone marrow involved in immunobiological and protective processes, bone formation, intermediate, protein, fat, carbohydrate and mineral metabolism, development of lecithin, protein bodies, Deposit phosphatides, cholesterol, ascorbic acid, and in iron metabolism. Besides, bone marrow serves as a depot: if necessary, it increases the amount of circulating blood 60 %, while reducing to 20 %.
The life of each red blood cell short. According to, obtained by the tracer, the life of red blood cells 120-125 days, wherein the period of maturation in the bone marrow is 2-3 days. The longevity of neutrophils 14-15 days. Time of maturation in the bone marrow 5-6 days, and the circulation in the blood stream - from 30 minutes to 2 Nights, 6-7 Days they are located in the tissues. Maturing lymphocytes occurs within 2-3 days, their life cycle is not yet completely - from 2-3 weeks to 100- 200 day and even more. Maybe, that there are two kinds of lymphocytes - a short and a long lifecycle. The normal life span of platelets 10 days.
In the bone marrow occur processes of blood cells, their further maturation and washing out the mature cells in the peripheral blood. Of great importance in these processes give hematopoietins, in particular erythro, lejko- and trombotsitopoetinam. The most studied erythropoietin - physiological stimulants erythrogenesis. They stimulate the activity of the bone marrow germ erythroblastic, cause an increase in reticulocytes and erythrocytes in peripheral blood.
Education erythropoietin primarily due to hypoxia of any origin. Most researchers believe, what erythropoietin are parathormone, and recognize their protein (polypeptide) origin. Basically erythropoietins complexes formed in juxtaglomerular kidney; in adult liver detected erythropoietin profaktor.
Regulation and leukopoiesis thrombocytopoiesis remains poorly understood.
