ISSN:
0362-2525
Schlagwort(e):
Life and Medical Sciences
;
Cell & Developmental Biology
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Biologie
,
Medizin
Notizen:
In hematopoietic marrow, sinuses form a system of vessels running radially from the periphery toward the central longitudinal vein. Hematopoietic tissue, having the form of cords, lies between the sinuses.The wall of the vascular sinus of the marrow, in fullest development, is trilaminar. It consists of a lining cell, basement membrane and adventitial cell. It may, however, consist of lining cell alone. Occasionally, the wall is bilaminar, made up of lining cell and basement membrane, or lining cell and adventitial cell. The adventitial cell and lining cell are reticular cells and may exactly resemble one another. But often the adventitial cell, and occasionally, the lining cell of a sinus may be very voluminous and rarefied, extending among the hematopoietic cells. The mural reticular cells, particularly the adventitial cells, may be phagocytic. The adventitial cells, moreover, contain fat droplets, and may accumulate the unilocular fat deposit characteristic of a fatty marrow.Megakaryocytes lie outside the sinus discharging platelets through mural apertures. In places, fairly large segments of sinus wall may become attenuated, pierced by apertures and, perhaps, drop out, with the result that the sinus is enlarged. Normo-blasts, reticulocytes and myelocvtes enter the circulation by passing into a sinus. Three mechanisms are present: (1) They may pass through existing apertures or (2) create an aperture by pressing into a sinus wall. (3) A segment of wall may drop out setting heretofore extravascular cells into the circulation.Adventitial spurs or processes extend from the sinus into the perisinus tissue. These spurs are of the same structure as the sinus wall. The perisinus tissue, present as cords between sinuses, is typically filled with hematopoietic and other free cells. The adventitial processes, together with the reverse surface of the sinus walls, incompletely bound the intersinus hematopoietic cords. The intersinus space may thereby have the same contour as sinuses. They differ from sinuses in containing many hematopoietic cells and in being less completely bounded by wall.It is postulated that the sinuses and intersinal cords form a reciprocating system wherein portions may become vascular (sinal) or extravascular (cordal) depending upon the requirements for hematopoiesis, blood flow, blood storage and delivery of cells to the blood. The reciprocation is effected by the ready capacity of sinal walls and adventitial spurs to take form, change disposition and break down.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jmor.1051170308
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