Bone Marrow Cells and Connective Matrix

‭Bone marrow cells and connective matrix‬ -‭ ‬ ‭Fibroblasts‬‭called reticular or stellate cells because‬‭the cytoplasmic expansions are‬ ‭important, they are large cells. In the cytoplasm we find myofilaments, therefore cells with‬ ‭contractile capacity. These cells are connected together by Gap junction type systems. They will‬ ‭develop the reticulin fibers found in the framework and the important thing is that the fibroblasts‬ ‭come into contact with the hematopoietic stem cells via integrin and they will regulate the growth‬ ‭of these stem cells by the secretion of growth factors.‬ ‭The fibroblasts which are located in contact with the sinusoidal capillaries are called adventitial‬ ‭cells which will participate in the regulation of the passage of the elements of the MOH towards the‬ ‭circulatory torrent.‬ ‭-‬ ‭Adipocytes:‬‭are filler cells but with particular characteristics‬‭compared to other adipocytes‬ ‭in the body. There we have the medullary adipocytes and the other white adipocytes that are found‬ ‭scattered throughout the body. The difference between these medullary adipocytes and the others is‬ ‭the cytochemical activity with the expression of esterases which are more or less fluoro resistant:‬ ‭there is no esterase.erase in disseminated white adipocytes and in addition when there are‬ ‭butiratesterases, they are fluorolabiles. These adipocytes participate in the regulation of‬ ‭hematopoiesis while the others mainly participate in energy homeostasis. Medullary adipocytes‬ ‭are not not sensitive to insulin which is used for storage while disseminated white adipocytes are‬ ‭very sensitive to insulin. These adipocytes are more or less present depending on the age of the‬ ‭individual. When we carry out a myelogram, that is to say a puncture at the level of the MOH, we‬ ‭can highlight other cell types such as osteoblasts, osteoclasts.‬ -‭ ‬ ‭Innervation:‬‭This organ is innervated, the fibroblasts‬‭are in relation to the fibers‬ ‭unmyelinated nerves which they surround in a cytoplasmic groove and the simulations nerves cause‬ ‭the contraction of these fibroblasts which are for example in contact with the sinusoid capillaries so‬ ‭these elements can contract and we will have a regulation of the migration of mature elements‬ ‭towards the circulatory torrent. So the innervation of this organ is not only a vasotropic action but‬ ‭also an action on the exchange capacities of the tissue. towards the blood.‬ -‭ ‬ ‭The medulla-blood barrier‬‭:it is made up of the wall‬‭of the sinusoidal capillaries and‬ ‭therefore the endothelial cells. These rest on a basal membrane which is discontinuous here, which‬ ‭is made essentially of reticulin fibers, sometimes the basal is absent and at this time we have the‬ ‭endothelial cells which can be in contact with the adventitial cells without there being any GAP‬ ‭junction systems between these two types cellular therefore simply a contact but no junction‬ ‭system.‬