374 



HISTOLOGY 



amnion is seen on the upper surface of the section, having its simple cu- 

 boidal or flat epithelium toward the embryo, and its mesodermic connec- 



Amnion. 



Com pa 



Cave-nous layer. <j*if^' 



land 



Vein 



Muscularis. 



Pic. 373. VERTICAL SECTION THROUGH THB WALL OF A UTERUS ABOUT SEVEN MONTHS PREGNANT 

 WITH THE MEMBRANES IN SITU. X 3o. (Schaper.) 



live tissue toward the chorion. Adhesions in the form of slender strands 

 bind it to the connective tissue of the chorion. The chorionic epithelium 



forms a layer over the surface of the vera; it 

 presents slight irregularities but is without 

 villi. The superficial uterine epithelium has 

 degenerated; it disappeared in an earlier 

 stage. The modified mucosa. or decidua 

 vera, is divisible into a superficial compact 

 layer and a deep cavernous layer. After the 

 epitheb'um of the glands in the compact 

 layer had degenerated and was resorbed, the 

 connective tissue came together obliterating 

 the gland cavities. The compact layer is 

 therefore without glands. The cells of the 

 tunica propria have enlarged, and become 

 decidual cells (Fig. 374). These cells, which 

 occur only in pregnancy, are flattened, round, 

 oval or branched structures of large size (0.03 

 to o.i mm.). Usually they contain a single nucleus but often there are 

 two or more, and in giant forms there may be thirty or forty. The 



FIG. 374. DECIDUAL CELLS FROM 

 THE Mucous MEMBRANE OF A 

 HUMAN UTERUS ABOUT SEVEN 

 MONTHS PREGNANT. One cell 

 shows a mitotic figure. X 250 

 (Schaper.) 



