THE MALE UEETHRA. 



1309 



ling into the canal, they lie for some distance immediately beneath its mucous 

 niembrane. A number of little pit-like recesses, called the lacunae urethrales, also 

 open into the cavernous part of the urethra, and are so disposed that their openings 

 lead for the most part obliquely into the canal in the direction of its external orifice. 



In some cases a somewhat valve -like fold of the mucous membrane, the valvula fosses 

 navicularis, is found in the upper wall of the urethra in the region of the fossa navicularis. 

 The free edge of this fold is directed towards the external urethral orifice, and may engage 

 the point of a fine instrument introduced into the urethra. 



Structure. The mucous membrane of the urethra contains numerous elastic fibres 

 and varies in thickness in different parts of the canal. In many positions it shows 

 distinct longitudinal folds and also minute depressions or pits the lacunse urethrales, 

 already mentioned. The lining epithelium is composed of many layers of cells, and is 

 continuous through the internal urethral orifice with the epithelium of the bladder, 

 which at first it closely resembles. In the region of the fossa navicularis the lining cells, 

 which throughout the cavernous portion of the canal are of a columnar type, become flat 

 and scaly. 



Numerous minute glands glandulse urethrales open into the urethra. These are 

 most plentiful in the upper, or anterior, wall, but they also occur in smaller numbers in 

 the floor and side walls. They are most numerous in the anterior half of the cavernous 

 portion of the canal, and in the membranous subdivision of the urethra. 



Dorsal vein 

 jrsal artery ! Dorsal nerve 



Corpus cavernosum 

 penis 



Corpus cavernosum 

 urethra; 



Glaus penis 



Corpus cavernosum 

 penis 



Urethra 



G. 1027. A, TRANSVERSE SECTION THROUGH THE BODY OF THE PENIS. B, LONGITUDINAL SECTION 

 OF THE TERMINAL PORTION OF THE PENIS. 



The larger glands are deeply placed beneath the mucous coat, and communicate with 



urethra by long slender obliquely placed branched ducts. The smaller glands lie in 

 the mucous coat and form flask-like depressions with very short ducts. The ducts of some 

 of the glands open into the lacunae, but many of the latter have no connexion with the 

 urethral glands. 



Frequently two or more elongated ducts belonging to some of the larger glands open 

 into the urethra quite close to its termination. These are sometimes spoken of as para- 

 urethral ducts, and may be traced backwards for some distance beneath the mucous 

 membrane forming the roof of the urethra. Morphologically they do not correspond to 

 the ducts which in the female have received the same name. 



The muscular wall in the upper part of the urethra consists of smooth muscle fibres 

 I directed for the most part longitudinally, but some circularly arranged fibres are also 

 present. It is probable that throughout the greater part of the cavernous urethra a 

 muscular coat is not represented. 



Round the beginning of the urethra there is an obliquely placed band of circularly 



arranged smooth muscle fibres, which is continued downwards and forwards from below 



the anterior part of the trigone of the bladder. The lower and anterior fibres of this 



band lie in the anterior wall of the upper part of the prostatic urethra. The band is 



! sometimes spoken of as the sphincter vesicse internus. At a lower level, in front of the 



' prostatic urethra, is a band of striped muscular fibres which is continuous inferiorly with 



the inner circularly disposed part of the sphincter urethrse membranacese. 



Like the latter it is probably to be regarded as a part of a primitive voluntary 

 urogenital sphincter muscle, such as is represented also in the female subject. 



