THE ABDOMEit 865 



surface is still covered by the parietal pelvic fascia, which con- 

 structs Alcock's canal. This portion of the muscle lies upon the 

 outer wall of the ischio-rectal fossa. External. — The internal 

 surface of the obturator membrane, and the surrounding bone. 

 For the extrapelvic part of the muscle, see p. 429. 



STRUCTURE OF THE VISCERA OF THE MALE PELVIS. 



The Bladder. 



The wall of the bladder is composed of four coats — serous, 

 muscular, submucous, and mucous. 



The serous coat is formed by the peritoneima, and is confined to 

 the superior surface and upper part of the base. It forms the false 

 ligaments of the viscus. 



The muscular coat consists of plain muscular tissue, which is 

 arranged in three layers — external longitudinal, middle circular, 

 and internal longitudinal. 



The external longitudinal fibres are most apparent on the superior 

 and inferior surfaces. Laterally they are scarce, and are disposed 

 in an interlacing manner. They have an independent bony 

 attachment to the posterior aspects of the bodies of the pubic 

 bones near the lower part of the symphysis, where they constitute 

 the so-called fuho-vesical muscles. They then pass within the 

 pubo-prostatic ligaments to the neck of the bladder, where they 

 are connected with the base of the prostate gland. Having 

 covered the inferior surface as far forwards as the apex, some 

 of them are there prolonged along the urachus for a short 

 distance, whilst others turn to the superior surface over which 

 they pass to the base. Having descended upon the base, they 

 enter the prostate gland, where they blend vnih. its muscular 

 tissue. The longitudinal stratum has been called the detrusor 

 urinse muscle from its supposed fimction in expelling the urine 

 from the bladder. 



The middle circular fibres are somewhat indistinct, and more 

 or less reticular over the greater part of the viscus. In the 

 region where the fundus and inferior surface meet they become 

 more distinct, and around the neck of the bladder, where the 

 urethral opening is situated, they form a tolerably well-marked 

 annular bimdle, knowm as the sphincter vesicae, beyond which they 

 are continuous with the muscular tissue of the prostate gland. 



The internal longitudinal fibres are somewhat indefinite, and are 

 hiefly recognisable on the inferior surface. 



WTien portions of the mucous membrane project between the 

 scattered muscular bundles, the bladder is said to be sacctiluted. 

 When, on the other hand, the muscular bundles become hyper- 

 trophied from any cause, such as enlarged prostate or stricture, 

 they give rise to inward projections of the mucous coat, which are 



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