THE URETHRA. 



221 



spongy portion. They are most abundant and best developed in the upper 

 wall of the spongy portion distal to the openings of the ducts of the bulbo- 

 urethral (Cowper's) glands. Their ducts often extend several millimeters 

 obliquely backwards, more or less parallel to the urethra, and divide into 

 several slightly expanded alveoli, lined with columnar epithelium. In addi- 

 tion to the foregoing true, although small glands, the urethral mucosa is 

 beset, along its upper wall, with small diverticula, the lacuna urethrales, 

 which are little more than tubular depressions, or crypts, within the mucous 

 membrane and can not be regarded as glands, although they often receive 

 the ducts of the extramucosal glandules. One crypt of exceptional size 



Surface epithelium 



Crypt 



Blood-vessels 

 in mucosa 



Venous spaces 

 of cavernous 

 tissue 



FIG. 271. Section of wall of urethra, spongy portion, showing crypts and blood-spaces in mucosa. X 35- 



(4-12 mm. in depth) is commonly found on the roof of the navicular fossa, 

 its orifice being guarded by a fold of mucous membrane. 



The Female Urethra. The wall of this canal, much shorter than 

 the urethra in the male, consists essentially of a mucous membrane supple- 

 mented by a robust outer muscular tunic. The mucous membrane, 

 thrown into longitudinal folds, is composed of a tunica propria, rich in elastic 

 fibres, wandering cells and plexiform veins, and a layer of epithelium. The 

 latter resembles that of the bladder above and that of the vestibule, into 

 which the canal opens, below, but in places the stratified squamous epithe- 

 lium gives way to one approaching the simple columnar in type. In the 

 female the urethral glands are represented by small tubular alveoli that open 

 by minute ducts on the mucous surface and correspond to Littre"'s glands in 

 the male. They are most plentiful in the upper part of the urethra and in 

 aged subjects may contain concretions. The mucosa is also pitted with 

 small crypts, similar to those in the male canal, into which the ducts of the 

 glands often open. 



The intrinsic muscular tissue of the female urethra is disposed as an 

 inner layer of longitudinal and an outer one of circular fibres, the two being 

 separated by a thin connective tissue stratum with many elastic fibres. At 

 the internal urethral orifice, in conjunction with fibres from the trigonum ot 



