PELVIS 611 



the two left folds are situated, one an inch and a half above 

 the right fold, and the other the same distance below it 

 (Birmingham). 



The Structure of the Walls of the Bladder. The bladder 

 possesses the following five coats : 



i. Serous. 2. Subserous. 3. Muscular. 4. Submucous. 5. Mucous. 



The serous or peritoneal covering has already been 

 examined. The subserous coat is a thin stratum of areolar 

 tissue which connects the peritoneum with the muscular coat. 



The Muscular Coat. The fibres of the muscular wall of 

 the bladder are arranged in three layers : 



i. External longitudinal fibres. 2. Circular fibres. 3. Internal longi- 

 tudinal fibres. 



The external longitudinal fibres^ frequently spoken of as 

 the detrusor urina, spring from the back of the pubic bones, 

 the pubo-prostatic ligaments, and the base of the prostate. 

 They ascend from these attachments over the anterior border 

 and the medial parts of the infero-lateral surfaces of the 

 bladder. At the apex a few pass into the urachus, but 

 the majority pass backwards over the superior surface and 

 the base of the bladder to the prostate, to which they are 

 attached. On the lateral parts of the infero-lateral surfaces 

 and on the lateral borders of the bladder this layer is less 

 complete, and the fibres take a more oblique direction. 



The circular fibres are arranged in coarse bundles, which 

 run obliquely as well as circularly round the bladder and 

 constitute the greater part of its muscular coat. At the 

 internal urethral orifice the bundles become finer and are 

 massed together to form a sphincter, the fibres of which are 

 more or less continuous with those of the prostate. 



The internal longitudinal fibres are absent on the fundus, 

 and form only an incomplete layer on the other walls of the 

 bladder. 



The Submucous Coat is a layer of loose areolar tissue 

 which forms a loose connection between the mucous and 

 muscular coats, except in the region of the trigone where the 

 connection is much closer. The blood-vessels and nerves 

 ramify in the submucous layer before they enter the mucous 

 coat. 



The Mucous Coat was examined when the bladder was 

 opened (p. 571). 



! 39 n 



