196 



UKOGENITAL SYSTEM 



The epithelial lining of the Miillerian ducts gives rise merely to the epithelium of 

 the genital tracts. The muscular and connective- tissue elements of the mucous 

 membrane, and of the wall of the uterus and vagina, are derived from the genital cord, 

 which undergoes a progressive development as compared with that of the male. The 

 lower part surrounding the ends of the ducts grows downwards, and apparently 

 in the process occasions the shortening of the urogenital sinus already referred to. 

 By the fifth month the muscular wall of the uterus begins to differentiate, and the 

 mucous membrane to thicken. It is noticeable that during the later months of foetal 

 life the cervix bears a very large proportion to the body (fig. 249), which is very 

 short, and it is not till puberty that the body begins to assume its proper relative 

 proportions. 



FIG. 248. SECTION THROUGH A HUMAN EMBRYO OF 30 MM. ABOUT THE BEGINNING OF THE 

 THIRD MONTH. (T. H. Bryce.) 



Below the spinal cord is seen the body of a sacral vertebra ; on each side the lateral part of the 

 sacrum and a portion of the ilium ; between the body and the lateral cartilages a pair of spinal nerves. 

 The section passes through the hip- joints ; between these ventrally the pubic cartilages. Between the 

 two ischial cartilages the rectum, below this the urogenital sinus with the Wolffian ducts opening into 

 it ; between the Wolffian ducts the Miillerian eminence, in which is seen the irregular blind end of the 

 fused Miillerian ducts ; between the pubic cartilages the urethra. 



Descent of the ovaries and testes. In both sexes the genital glands 

 undergo a displacement from their primitive position in the lumbar region and 

 come to lie above the brim of the pelvis. From this situation in the later months 

 of pregnancy the testicles descend into the scrotum, while the ovaries retain their 

 secondary position until ultimately, with the enlargement of the pelvis, they sink 

 to the definitive position. The descent of the glands is chiefly effected by the 

 agency of a fold, in which muscular fibres develop, called the plica gubernatrix 

 (fig. 247). 



The change in position of the different structures is best understood by referring 

 back to a stage reached about the end of the second month (fig. 251). The Wolffian 

 body, on each side, is seen to be attached to the posterior abdominal wall by the 



