802 



THE REPRODUCTIVE ORGANS. 



[CH. LVII. 



contains a nucleus which has the usual structure of nuclei ; there 

 is generally one very well-marked nucleolus. The nucleus and 

 nucleolus are still often called by their old names, germinal vesicle 

 and germinal spot respectively. An attraction sphere, not shown 

 in the figure, is also present. 



The ova and the epithelium of the Graafian follicles are 

 developed from the germinal epithelium which in the embryo 

 forms a thick layer over the ovary ; cords of these cells, solid in 

 some animals, tubular in others, grow down into the stroma, and 

 in time these are broken up into nests by ingrowths of the stroma. 

 Each nest represents a primitive Graafian follicle. In this, one 



Fig. 616. Section of the lining membrane of a human uterus at the period of commencing 

 pregnancy showing the arrangement and other peculiarities of the glands, d, d, d, with 

 their orifices, a, a, a, on the internal surface of the organ. Twice the natural size. 



cell in particular becomes enlarged to form the ovum ; the 

 remainder form the epithelium of the follicle. 



The Fallopian tubes have externally a serous coat derived 

 from the peritoneum, then a muscular coat (longitudinal fibres 

 outside, circular inside), and most internally a very vascular 

 mucous membrane thrown into longitudinal folds, and covered 

 with ciliated epithelium. 



The uterus consists of the same three layers. The muscular 

 coat is, however, very thick and is made up of two strata imper- 

 fectly separated by connective tissue and blood-vessels. Of these 

 the thinner outer division is the true muscular coat, the fibres of 

 which are arranged partly longitudinally, partly circularly. The 

 inner division is very thick ; its fibres run chiefly in a circular direc- 

 tion ; the extremities of the uterine glands extend into its internal 

 surface. It is in fact a much hypertrophied muscularis mucosse. 



The mucous membrane is thick, and consists of a corium of soft 

 connective tissue, lined with ciliated epithelium ; this is continued 

 down into long tubular glands which have as a rule a convoluted 

 course. In the cervix the glands are shorter. Near the os 

 uteri the epithelium becomes stratified ; stratified epithelium also 

 lines the vagina. 



