Differentiation of the embryonic disc, amnion, and yolk sac in the rhesus monkey

Allen C. Enders, Sandra Schlafke, Andrew G Hendrickx

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

The inner cell mass of the blastocyst has differentiated into epiblast and hypoblast (primitive endoderm) prior to implantation. Since endoderm cells extend beyond the epiblast, it can be considered that both parietal and visceral endoderm are present. At implantation, epiblast cells begin to show marked evidence of polarity. They form a spherical aggregate with their basal ends toward the basal lamina and apical ends toward the interior. The potential for an internal space is formed by this change in polarity of the cells. No cytological evidence of separation of those cells that will form amniotic epithelium from the rest of the epiblast is seen until a cavity begins to form. The amniotic epithelium is originally contiguous with overlying cytotrophoblast, and a diverticulum remains in this position during early development. Epiblast forms a pseudostratified columnar epithelium, but dividing cells are situated toward the amniotic cavity rather than basally. The first evidence of a trilaminar disc occurs when a strand of cells contiguous with epiblast is found extending toward visceral endoderm. These presumptive mesoderm cells are undifferentiated, whereas extraembryonic mesoderm cells are already a distinct population forming extracellular materials. After implantation, visceral endoderm cells proliferate forming an irregular layer one to three cells thick. Visceral endoderm cells have smooth apical surfaces, but very irregular basal surfaces, and no basal lamina. At the margins of the disc, visceral endoderm is continuous with parietal endoderm and reflects back over the apices of the marginal visceral endoderm cells. This sacculation by visceral endoderm cells precedes pinching off of the secondary yolk sac from the remaining primary yolk sac.

Original languageEnglish (US)
Pages (from-to)161-185
Number of pages25
JournalAmerican Journal of Anatomy
Volume177
Issue number2
DOIs
StatePublished - 1986

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Yolk Sac
Amnion
Endoderm
Macaca mulatta
Germ Layers
Epithelium
Mesoderm
Basement Membrane
Blastocyst Inner Cell Mass
Cell Polarity
Cell Separation
Diverticulum
Trophoblasts

ASJC Scopus subject areas

  • Anatomy

Cite this

Differentiation of the embryonic disc, amnion, and yolk sac in the rhesus monkey. / Enders, Allen C.; Schlafke, Sandra; Hendrickx, Andrew G.

In: American Journal of Anatomy, Vol. 177, No. 2, 1986, p. 161-185.

Research output: Contribution to journalArticle

Enders, Allen C. ; Schlafke, Sandra ; Hendrickx, Andrew G. / Differentiation of the embryonic disc, amnion, and yolk sac in the rhesus monkey. In: American Journal of Anatomy. 1986 ; Vol. 177, No. 2. pp. 161-185.
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