332 ANATOMY FOR NURSES [Chap. XVll 



2. The areolar coat connects the mucous and muscular. It 

 permits freedom of movement such as is essential in an organ 

 subject to change in size and shape. 



3. The muscular coat has three layers, an inner longitudinal, 

 middle circular, and outer longitudinal. The circular fibres are 

 collected into a layer of some thickness around the cervix or 

 neck, where the bladder becomes continuous with the urethra. 

 These circular fibres around the neck form a sphincter muscle 

 which is normally in a state of contraction, only relaxing at 

 intervals, when the accumulation of urine within the bladder 

 renders its expulsion necessary. 



4. The serous coat is a reflection of the peritoneum, and only 

 covers the upper portion of the fundus. 



Function. — The bladder serves as a reservoir for the reception 

 of urine. When moderately distended, it holds about one pint 

 (about one-half litre). 



THE URETHRA 



The urethra is a narrow, membranous canal, about an inch 

 and a half (38 mm.) in length in the female. Its normal diameter 

 is about one-quarter of an inch (6.3 mm.), but it admits of consid- 

 erable dilatation. It extends from the neck of the bladder to the 

 external orifice, which is named the meatus urinarius. It is placed 

 behind the symphysis pubis, and is embedded in the anterior wall 

 of the vagina. Its direction is obliquely downward and forward, 

 its course being slightly curved, with the concavity directed for- 

 ward and upward. Its external orifice is the narrowest part and 

 is located between the clitoris and the opening of the vagina. (See 

 Fig. 207.) 



The wall of the urethra consists of three coats : — 



(1) An inner or mucous coat which is continuous with that of 

 the bladder. 



(2) A submucous coat which contains a network of veins. 



(3) An outer muscular coat which is continuous with that of the 

 bladder. 



MICTURITION 



Urine is secreted continuously by the kidneys. It is carried 

 to the bladder by the ureters, and at intervals is expelled from the 



