ISSN:
0362-2525
Schlagwort(e):
Life and Medical Sciences
;
Cell & Developmental Biology
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Biologie
,
Medizin
Notizen:
The first mesoderm cells, and therefore the primitive streak, originate from the epiblast in an axial zone of the third quarter of the area pellucida.The primitive streak grows by epiblastic proliferation only, without any forward movement of the epiblast.Presumptive mesoderm cells invaginate during the existence of the streak.The endoderm plays no part in forming the mesoderm and head process.The epiblast cells lose their glycogen when invaginating through the primitive streak or node, to form the mesoderm or head process, both of which are free of glycogen.When invaginating, the epiblast cells show an increase of lipoids (probably sterols) which decrease as they become mesoderm cells, but are retained in the head process. The higher lipoid content is correlated (1) with the organizing effect of the primitive streak, node and head process; (2) with the behavior of Nile blue marks, which when reaching the streak, node or head process are retained and no longer follow the movements of the individual cells.The shortening of the primitive streak is effected by the approximation of the epiblast from either side, which begins at the cranial end of the streak and spreads caudally. There is no backward migration of the cells of the primitive node.The arrangement of the presumptive embryonic material in the epiblast at the end of the blastula stage is described.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jmor.1050620305
