374 THE ORGANS 



cous membrane is thicker and presents numerous folds — the plicce 

 palmatcB. The epitheUum is higher than in the body of the organ. 

 In addition to glands like those found in the body of the uterus, the 

 cervical mucosa contains peculiar short, sac-like invaginations, lined 

 , with a continuation of the surface epithelium, which secrete a glairy 

 I mucus. Closure of the mouths 



of some of these sacs frequently 



r. .^ l--r-»' ^ occurs, leading to the formation 



. _^ of retention cysts, the so-called 



ovula Nabothi. At about the 



^ .. .^. . " ^ '' junction of middle and lower 



5 .. .- d thirds of the cervical canal a 



I change takes place in the epi- 



^ '' , thelium. Here the simple 



.. - columnar ciliated epithelium 



/ ; " ii of the upper part of the cervix 



Fig. 266.-From Section of Dog's Cervix, gradually paSSeS OVer into a 



X4- (Technic 2, p. 385.) a, Cervical canal; stratified SquamoUS epithe- 



b, mucosa; c, folds of mucosa: (plicas pal- . "XT +>i f 1 



matae); d, muscle layers of cervix; e, epithe- lium. JNI ear tne external OS 



Hum of vagina and vaginal surface of cervix; p^piH^ appear, the vaginal 



/, vagmal epithelium; g, vaginal mucosa; h, ^ ^ ^ ^ ^ ° _ 



sub mucosa and muscularis of vagina; I, blood- surface of the cervix being 



''®^^^^^- covered with a stratified 



squamous epithelium with underlying papillae similar to and con- 

 tinuous with that of the vagina. 



Near the external os the epithelium changes over into the strati- 

 fied squamous epithelium with underlying papillae, similar to that 

 of the external surface of the cervix. 



2. The Mucosa of the Menstruating Uterus 



This consists of the same structural elements as the mucosa of 

 the resting uterus: stroma, glands, and lining epithelium. These, 

 however, undergo certain changes which may be conveniently 

 divided into three stages : 



{a) The stage of preparation. 



{h) The stage of menstruation proper. 



{c) The stage of reparation. 



(a) The Stage of Preparation. — This begins several days 

 before the actual flow of blood, and is marked by an intense 

 hyperaemia determining a swelling and growth of the entire mucosa. 



