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Cyto ‐epitheliochorial placenta of the viviparous lizard Pseudemoia entrecasteauxii : A new placental morphotype
Author(s) -
Adams Susan M.,
Biazik Joanna M.,
Thompson Michael B.,
Murphy Christopher R.
Publication year - 2005
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.10314
Subject(s) - biology , lamina propria , placenta , placentation , epithelium , apocrine , lumen (anatomy) , chorioallantoic membrane , cuboidal cell , pinocytosis , uterus , anatomy , microbiology and biotechnology , endocrinology , cell , pregnancy , fetus , endocytosis , embryo , genetics
The structural features of the uterine epithelium of the chorioallantoic placenta and omphalloplacenta in the viviparous Australian skink, Pseudemoia entrecasteauxii , were investigated using SEM and TEM techniques. In particular, the structural characteristics that would allow interpretation of function were analyzed, particularly those of gas exchange in the chorioallantoic placenta and histotrophy in the omphaloplacenta. Pseudemoia entrecasteauxii has a complex placenta consisting of a placentome, paraplacentome, and omphaloplacenta. The paraplacentome has a well‐vascularized lamina propria in which projecting uterine capillaries displace the overlying uterine epithelial cells, reducing them to attenuated cytoplasmic extensions. Associated cell nuclei and organelles are lost from this region, to provide a capillary lumen to uterine lumen barrier of 0.5–1.0 μm. Hence, the paraplacentome is likely a prominent site for gaseous exchange via simple diffusion. The omphaloplacenta has a similar cytology to that of the placentome, but the uterine epithelial cells are hypertrophied and the apical plasma membrane actively secretes vesicles into the uterine lumen. The omphaloplacenta shows features that are associated with histotrophic transport of nutrients via vesicle secretion, very similar to that of lipid apocrine secretion. The placentome consists of cuboidal cells in the uterine epithelium, with large centrally located nuclei overlying the well‐vascularized lamina propria. Although the placentome has a similar cytological structure to that of the omphaloplacenta, granules or active vesicle secretion were not observed. Thus, the placentome may be associated with histotrophy, but not via apocrine secretion. Squamate placentation is epitheliochorial; however, we propose a new term be used to describe the type of placentation in P. entrecasteauxii : “ cyto‐ epitheliochorial,” because of the extreme attenuation of uterine epithelial cells of the paraplacentome. J. Morphol. © 2005 Wiley‐Liss, Inc.