1002 THE URINARY ORGANS. 



but the bladder suddenly contracts to the opening of the urethra. In the male its 

 direction is oblique in the erect posture, and it is surrounded by the prostate gland. 

 In the female its direction is obliquely downward and forward. 



The urachus is the obliterated remains of the tubular canal of the allantois, 

 which exists in the embryo, and a portion of which becomes expanded to form the 

 bladder (see section on Embryology). It passes upward, from the apex of the 

 bladder, between the transversalis fascia and peritoneum, to the umbilicus, becom- 

 ing thinner as it ascends. It is composed of fibrous tissue, mixed with plain mus- 

 cular fibres. On each side of it is placed a fibrous cord, the obliterated portion 

 of the hypogastric artery, which, passing upward from the side of the bladder, 

 approaches the urachus above its summit. In the infant, at birth, it is occasion- 

 ally found pervious, so that the urine escapes at the umbilicus, and calculi have 

 been found in its canal. 



Ligaments. The bladder is retained in its place by ligaments, which are divided 

 into true and false. The true ligaments are five in number : two anterior, two 

 lateral, and the urachus. The false ligaments, also five in number, are formed by 

 folds of the peritoneum. 



The anterior true ligaments (pubo-pro static) extend from the back of the ossa 

 pubis, one on each side of the symphysis, to the front of the neck of the bladder, 

 over the anterior surface of the prostate gland. These ligaments are formed by 

 the recto-vesical fascia, and contain a few muscular fibres prolonged from the 

 bladder. 



The lateral true ligaments, also formed by the recto-vesical fascia, are broader 

 and thinner than the preceding. They are attached to the lateral parts of the 

 prostate and to the sides of the base of the bladder. 



The urachus is the fibro-muscular cord already mentioned, extending between 

 the summit of the bladder and the umbilicus. It is broad below, at its attachment 

 to the bladder, and becomes narrower as it ascends. 



The false ligaments of the bladder are two posterior, two lateral, and one 

 superior. 



The two posterior pass forward, in the male, from the sides of the rectum ; in 

 the female, from the sides of the uterus, to the posterior and lateral aspect of the 

 bladder : they form the lateral boundaries of the recto-vesical fold of the perito- 

 neum, and contain the obliterated hypogastric arteries, and the ureters, together 

 with vessels and nerves. 



The two lateral ligaments are reflections of the peritoneum, from the iliac fossae 

 and lateral walls of the pelvis to the sides of the bladder. 



The superior ligament (ligamentum suspensoriuni) is the prominent fold of 

 peritoneum extending from the summit of the bladder to the umbilicus. It is 

 carried off from the bladder by the urachus and the obliterated hypogastric arteries. 



Structure. The bladder is composed of four coats serous, muscular, sub- 

 mucous, and mucous. 



The serous coat is partial, and derived from the peritoneum. It invests the 

 superior surface and the upper part of the lateral surfaces and base, and is reflected 

 from these parts on to the abdominal and pelvic walls. 



The muscular coat consists of three layers of unstriped muscular fibre : an 

 external layer, composed of fibres having for the most part a longitudinal arrange- 

 ment ; a middle layer, in which the fibres are arranged, more or less, in a circular 

 manner ; and an internal layer, in which the fibres have a general longitudinal 

 arrangement. 



The fibres of the external longitudinal layer arise from the posterior surface of 

 the body of the os pubis in both sexes (musculi pubo-vesicalis), and in the male from 

 the adjacent part of the prostate gland and its capsule. They pass, in a more or 

 less longitudinal manner, up the anterior surface of the bladder, over its apex, 

 and then descend along its posterior surface to its base, where they become 

 attached to the prostate in the male and to the front of the vagina in the female. 



