528 THE EEPEODUCTIVE SYSTEM 



are distributed to the muscular coat, and to the mucous membrane in 

 which they form a rich subepithelial capillary plexus. The veins follow 

 a similar course, and like the arteries, form an extensive plexus in the 

 muscular coat. The abundance of vessels in the muscular wall of the 

 oviduct has led to the description of this coat as the vascular layer of 

 the organ. 



The lymphatics arise by anastomosing plexuses in the mucosa, from 

 which vessels pass to the serous coat and enter valved lymphatics by 

 which the lymph is conveyed to the lymph nodes of the lumbar region. 



The nerves, which are chiefly sympathetic, are distributed from a 

 plexus in the serous coat, to the muscular wall, and to the mucosa, in 

 which they form a terminal subepithelial plexus. 



The Uterus 



The uterus is a hollow pear-shaped organ, divisible into a deepest or 

 fundus portion, the body, and the cervix ~, about 3 inches in depth, 1% 

 in width and 1 in thickness. The cervix opens into the body through 

 the internal os, into the vagina through the external os. Its wall consists 

 of a mucous membrane, a muscular coat, and an outermost serous coat 

 which is derived from the peritoneum and invests the body of the organ. 

 The cervix uteri projects into the vaginal canal and the serous coat is 

 there replaced by a reflection of the vaginal mucosa. 



The serous coat, or perimetrium, of the uterus consists of meso- 

 thelium which rests upon a thin subepithelial layer of connective tissue. 

 It presents no peculiarities. 



The muscular coat, or myometrium, of the uterus consists of 

 smooth muscle whose fibers are of large size (40 to 60 ju. in length) and 

 which are disposed in interlacing bundles. In the lower mammals these 

 form quite regular layers an outer longitudinal, a thick inner layer, 

 most of whose fibers are circular, and an innermost, but less distinct, 

 submucous portion containing oblique and longitudinal fibers. The outer 

 longitudinal and circular layers are separated by a fibromuscular stratum 

 containing a rich plexus of large blood-vessels. 



In the human uterus the arrangement of muscle fibers is much less 

 regular, but follows a similar plan, though there is no distinct sub- 

 division into layers. Nevertheless, careful examination reveals three indis- 

 tinct strata which are intimately blended with one another. The outer- 

 most of these indistinct layers consists of irregularly disposed longitudi- 

 nal fibers, the stratum supravasculare. This layer is in most parts very 



