1098 UROGENITAL SYSTEM. - 
elmpty, it extends upwards into the abdominal cavity. Its anterior aspect is m 
contact with the posterior surface of the anterior abdominal wall. At birth the 
peritoneum forming the recto-vesical pouch covers the whole of the posterior sur- 
face of the bladder, and reaches as low as the upper limit of the prostate. The 
internal urethral orifice is placed at a high level, and sinks gradually after 
birth (Fig. 746, A). In the newly-born child this opening hes on a level with the 
upper margin of the 
sy mphysis pubis, 
and the openings 
of the ureters le 
almost on a level 
with the plane of 
the pelvic brim. 
The obliterated 
hypogastric arteries 
are more intimately 
related to the 
bladder in the foetus 
J Becca and child than in 
Bladder 
Symphysis DUIS a 
Corpus cavernosun 
; ay | Internal sphincter ani the adult, and lie 
Bulb of urethr yyy #——|— Extern alisphineber/anl sees : : 
Bulbo-cayernosus i \ So Anal canal close against its 
muscle 3 
= <2 External sphincter ani sides as they pass 
upwards towards 
the umbilicus 
Hig. 757): 
Interior of 
the Bladder.—The 
mucous membrane 
lining the bladder 
is but loosely con- 
nected to the mus- 
cular coat,and when 
the bladder is con- 
Uterus tracted the mucous 
lining is thrown 
into a number of 
prominent wrinkles 
or folds (Fig. 747). 
SETBIE TIR EESS Z ne \ W@ 7 | , / enone sphincter ani At one place only 
XC ae . ~ | Anal canal the mucous mem- 
———7- External sphincter ani brane 1s firmly con- 
nected to the sub- 
jacent muscular 
coat, and the inner 
surface of this part 
of the bladder wall 
is smooth and free 
from wrinkles. 
This smooth area, called the trigonum vesice, corresponds to a triangular surface 
behind the urethral orifice and to the part of the bladder wall which immediately 
surrounds the opening. The base of the triangle is formed by a line drawn 
between the openings of the ureters into the bladder, and the apex hes at the 
beginning of the urethra. Just behind the urethral opening the bladder wall 
bulges slightly into the cavity, owing to the presence beneath it of the middle 
lobe of the prostate. When well marked, as it often is in old people, this elevation 
is termed the uvulavesice. Stretching across between the openings of the ureters 
there is usually to be seen a smooth curved ridge, which is due to the presence of 
a bundle of transversely-disposed muscle fibres within this part of the bladder wall, 
beneath the mucous membrane. The lateral portions of this ridge are called the 
Bladder —j7 
= a———= 
a 
—Rectum 
Symphysis pubis 
Vagina 
Urethra 
Internal sphincter ani 
B 
Fra. 746.—MESIAL SECTION THROUGH THE PELVIS OF NEWLY-BORN CHILD. 
A, Male, and B, Female. From preparations in the Anatomical Department, 
Trinity College, Dublin. 
