590 ABDOMEN 



spherical form or, in some cases, an ovoid form with the 

 large end above (Fig. 236). In the latter case its long axis 

 is no longer horizontal, but oblique, being directed from above 

 downwards and backwards. 



When the urine is ejected from the bladder, the superior 

 wall descends till it becomes approximated to the infero- 

 lateral walls and the fundus. The viscus, therefore, becomes 

 flattened from above downwards, and comes to lie again 

 entirely within the cavity of the small pelvis. When such a 

 bladder is examined in medial section, in a subject from 

 whom the urine was expelled shortly before death, the walls 

 of the bladder are thick and firm, and the lumen of the 

 viscus may be reduced to a mere slit. The part of the 

 lumen which lies behind the internal urethral orifice is called 

 the posterior limb, and the part in front of the orifice, 

 bounded by the approximated superior and infero -lateral 

 walls, is called the anterior limb of the cavity. The anterior 

 limb is long and nearly horizontal. The posterior limb is 

 short and sometimes barely recognisable ; further, it is oblique 

 or vertical, and joins the anterior limb at an angle. Viewed 

 in medial section, therefore, the lumen of the perfectly empty 

 bladder usually forms two limbs of a Y, the stem being 

 the urethra. 



In other cases the empty bladder is firm and rounded, 

 and when divided in the medial plane its cavity is seen to 

 present only the one limb or slit which is directly continuous 

 with the urethra. 



Relation of the Peritoneum to the Bladder. In the empty 

 bladder only the superior surface is directly covered by 

 peritoneum. The membrane is separated from the upper 

 part of the fundus by the seminal vesicles and the deferent 

 ducts. The infero -lateral surfaces are entirely devoid of 

 peritoneum. 



When the bladder fills it rises into the hypogastric region, 

 and it is important to note that the peritoneal reflection from 

 the apex is raised along with the organ, and, as a result, a 

 considerable area of the bladder wall, below the ligamentum 

 umbilicale medium (iirachus] becomes applied directly to the 

 anterior abdominal wall without the intervention of peri- 

 toneum. Consequently, in those cases of retention of urine 

 in which a catheter cannot be passed into the bladder 

 through the urethra, relief can be given, without fear of 



