CHAPTER X. 



DEVELOPMENT OF THE DECIDUA, AND ATTACHMENT 

 OF THE FCETAL MEMBRANES TO THE UTERUS. 



IN the human species, where the embryo is developed within the 

 uterus, it depends for its nutrition upon materials derived from 

 the female parent. The immediate source of this supply is the mucous 

 membrane of the uterus, which becomes unusually developed during 

 gestation, and, when thus modified in structure, is known as the 

 decidua. It has received this name from the fact that it is thrown 

 off and discharged at the same time that the foetus and its membranes 

 are expelled from the uterus. 



The mucous membrane of the body of the uterus, in the unimpreg- 

 nated condition, presents a smooth internal surface. There is no dis- 

 tinct layer of connective tissue between it and the muscular substance 

 beneath ; so that the mucous 



membrane cannot here, as in FIG. 203. 



most other organs, be read- 

 ily separated by dissection 

 from the subjacent parts. 

 Its structure, however, is 

 well marked. It consists, 



FIG. 202. 



UTERINE Mucous MEMBRANE, from 

 the unimpregnated uterus, in verti- 

 cal section, a. Free surface. 6. At- 

 tached surface. Magnified about 10 

 diameters. 



UTERINE TUBULES, from the mucous membrane of an 

 unimpregnated human uterus. Magnified 125 diam- 

 eters. 



throughout, of tubular follicles, arranged side by side, perpendicularly 

 to its free surface. Near this surface they are nearly straight ; but 

 toward the deeper part of the membrane, where they terminate in 

 blind extremities, they become more or less wavy or spiral in their 

 course. They are about 0.05 millimetre in diameter, and are lined 

 with columnar epithelium. They occupy the entire thickness of the 



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