a. The urinary bladder (see figure 3-5) is a musculomembranous sac situated in
the pelvic cavity behind and below the symphysis pubis, in front of the rectum, and
above the prostate gland in the male. The bladder lies in front of the neck of the uterus
and the anterior wall of the vagina in the female. When the bladder becomes full and
distended, it begins to ascend above the symphysis pubis, pushes its peritoneal
covering ahead of it, and partially becomes an abdominal structure.
b. The bladder is connected to the pelvic wall by fascial attachments that extend
from the back of the pubic bones to the front of the bladder. Other muscular fibers also
pass from the base of the bladder to the sides of the rectum.
c. The bladder consists of a thick muscular wall with outer adventitial and inner
mucosal layers. In addition, a peritoneal layer partially covers and is attached to the
bladder dome. The blood supply of the bladder is derived from branches of the anterior
trunk of the hypogastric artery.
d. As a result of the peristaltic muscular contraction of the renal pelvis and
ureter, the urine is actively propelled from the kidney to the bladder and expressed from
the ureteral orifice.
e. The size, position, and relation of the bladder to the intestines, rectum, and
reproductive organs vary according to the amount of fluid it contains. The process of
emptying the bladder appears to be initiated by nerve cells from the sacral divisions of
the autonomic nervous system. These sacral reflex centers are controlled by higher
voluntary centers in the brain. Stimulation from the sacral centers results in contraction
of the bladder muscle and relaxation of the bladder outlet sphincters. Muscle tone
maintains closure of the sphincters when the bladder is at rest.
The male urethra (see figure 3-5) is a tube about 20 cm (8 inches) in length that
forms an S curve. It is the terminal portion of both the urinary and reproductive tracts.
The male urethra has three divisions: the prostatic urethra, which passes through the
prostate gland, the membranous urethra, which contains the external sphincter of the
bladder, and the remainder, called the bulbous urethra. The male urethra is composed
of mucous membrane that is continuous with that of the bladder and merges with the
submucous tissue, which in turn connects the urethra with other structures that it
The female urethra (see figure 2-2 of Lesson 2) is a narrow membranous hollow
tube about 4 cm (1/2 inches) in length and 6 mm (1/4 inch) in diameter. When it is not
in use, however, its walls collapse. This structure lies behind and beneath the