RKGNANCY 



71 



uterine mucosa wliere it forms an implantation cavity containing 

 maternal blood, which escapes from the capillaries in the process 

 of boring. The developing embryo becomes completely buried 

 in the uterine tissue and lies bathed in maternal blood, from 

 which it absorbs nourishment probably through the trophoblast. 



SyncytiotTO'phohlast 



Cytotrophoblast 



Maternal 

 blood-vessels 



Uterine 

 epithelium 



Blood-clot 



Fig. 52. — Section (semi-diagrammatic) through developing ovum 

 embedded in the uterine dec'idua. (After Peters, from 6'/'ay'.s' 

 A/U(tom//.) 



The uterine mucous membrane undergoes extensive changes 

 as a result of pregnancy. In the immediate neighbourhood 

 of the ovum the connective tissue cells become transformed 

 into large oval or polygonal epithelioid cells containing large 

 nuclei. These are called decidual cells. The process rapidly 



