Download The Pelvic Cavity and Contents

The Pelvic Cavity and Contents
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The pelvic cavity, or cavity of the true pelvis, can be defined as the area between the pelvic
inlet and the pelvic outlet. The pelvic contents or viscera include the distal parts of the
urinary system, digestive tract, and the reproductive system.
Sigmoid Colon
The sigmoid colon is 10 to 15 in. (25 to 38 cm) long and begins as a continuation of the
descending colon in front of the pelvic brim. Below, it becomes continuous with the
rectum in front of the third sacral vertebra. The sigmoid colon is mobile and attached to the
posterior pelvic wall by the fan-shaped sigmoid mesocolon.
Relations
•
•
Anteriorly: In the male, the urinary bladder; in the female, the posterior surface of
the uterus and the upper part of the vagina
Posteriorly: The rectum and sacrum.
Blood Supply
Arteries
Sigmoid branches of the inferior mesenteric artery.
Veins
The veins drain into the inferior mesenteric vein, which joins the portal venous system.
Lymph Drainage
The lymph drains into nodes along the course of the sigmoid arteries; from these nodes, the
lymph travels to the inferior mesenteric nodes.
Nerve Supply
The sympathetic and parasympathetic nerves from the inferior hypogastric plexuses.
Rectum
• The rectum is about 5 in. (13 cm) long and begins in front of the third sacral vertebra as
a continuation of the sigmoid colon and ends in front of the tip of the coccyx and
becoming continuous with the anal canal. The lower part of the rectum is dilated to
form the rectal ampulla.
• The peritoneum covers the anterior and lateral surfaces of the first third of the rectum
and only the anterior surface of the middle third, leaving the lower third devoid of
peritoneum.
• The muscular coat of the rectum is arranged in the usual outer longitudinal and inner
circular layers of smooth muscle. The three teniae coli of the sigmoid colon, however,
come together so that the longitudinal fibers form a broad band on the anterior and
posterior surfaces of the rectum.
Relations
• Posteriorly: The rectum is in contact with the sacrum and coccyx; the piriformis,
coccygeus, and levatores ani muscles; the sacral plexus; and the sympathetic trunks.
• Anteriorly: the upper two thirds of the rectum, is related to the sigmoid colon and coils
of ileum. The lower third of the rectum is related to the posterior surface of the bladder,
the termination of the vas deferens and the seminal vesicles on each side, and to the
prostate (the posterior surface of the uterue and vagina in the female).
Blood Supply
Arteries
The superior, middle, and inferior rectal arteries supply the rectum.
• The superior rectal artery is a direct continuation of the inferior mesenteric artery.
• The middle rectal artery is a small branch of the internal iliac artery.
• The inferior rectal artery is a branch of the internal pudendal artery in the perineum. It
anastomoses with the middle rectal artery at the anorectal junction.
Veins
The veins of the rectum correspond to the arteries. The superior rectal vein is a tributary of
the portal circulation and drains into the inferior mesenteric vein. The middle and inferior
rectal veins drain into the internal iliac and internal pudendal veins, respectively. The union
between the rectal veins forms an important portal-systemic anastomosis .
Lymph Drainage
The lymph vessels of the rectum drain first into the pararectal nodes and then into inferior
mesenteric nodes. Lymph vessels from the lower part of the rectum follow the middle
rectal artery to the internal iliac nodes.
Nerve Supply
The nerve supply is from the sympathetic and parasympathetic nerves from the inferior
hypogastric plexuses. The rectum is sensitive only to stretch.
Urinary Organs
Ureters
• The ureters are muscular tubes, 25-30 cm long, that connect the kidneys to the urinary
bladder. The ureters are retroperitoneal.
• the ureters cross the bifurcation of the common iliac artery or the beginning of the
external iliac artery, thus leaving the abdomen . The pelvic parts of the ureters begin
when entering the lesser pelvis by passing over the pelvic brim, in male; each ureter
then runs down the lateral wall of the pelvis in front of the internal iliac artery to the
region of the ischial spine and turns forward to enter the lateral angle of the bladder.
Near its termination, it is crossed by the vas deferens.
• In female; it runs downward and backward in front of the internal iliac artery and
behind the ovary until it reaches the region of the ischial spine. It then turns forward and
medially beneath the base of the broad ligament, where it is crossed by the uterine
artery .The ureter then runs forward, lateral to the lateral fornix of the vagina, to enter
the bladder.
• In both sexes; the ureter passes obliquely through the wall of the bladder for about 0.75
in. (1.9 cm) before opening into the bladder.
Blood Supply
Arteries
The arterial supply to the pelvic parts of the ureters is variable, with ureteric branches
extending from the common iliac, internal iliac artery or its branches, especially the vesical
(superior and inferior vesical) and uterine arteries, but also from the middle rectal and
vaginal arteries.
Veins
The venous drainage from the pelvic parts of the ureters generally parallels the arterial
supply, draining to veins with corresponding names.
Lymph Drainage
Lymphatic vessels pass primarily to common and internal iliac nodes.
Nerve Supply
The ureter receives preganglionic sympathetic input from the T10-L2 spinal segments.
Postganglionic fibers arise from several ganglia in the aorticorenal, superior, and inferior
hypogastric autonomic plexuses. Parasympathetic input is received from the S2-S4 spinal
segments.
Urinary Bladder
• The urinary bladder is situated immediately behind the pubic bones within the pelvis.
The empty bladder in the adult lies entirely within the pelvis; as the bladder fills, its
superior wall rises up into the hypogastric region.
• The empty bladder is pyramidal, having an apex, a base, and a superior and two
inferolateral surfaces; it also has a neck.
The apex of the bladder points anteriorly and lies behind the upper margin of the
symphysis pubis .
The base, or posterior surface of the bladder, faces posteriorly and is triangular. The
superolateral angles are joined by the ureters, and the inferior angle gives rise to the
urethra.
• The muscular coat of the bladder is composed of smooth muscle and is arranged as
three layers of interlacing bundles known as the detrusor muscle. At the neck of the
bladder, the circular component of the muscle coat is thickened to form the sphincter
vesicae (internal urethral sphincter).
In the male; the two vasa deferentia lie side by side on the posterior surface of the bladder
and separate the seminal vesicles from each other.
The upper part of the posterior surface of the bladder is covered by peritoneum, which
forms the anterior wall of the rectovesical pouch.
The superior surface of the bladder is covered with peritoneum and is related to coils of
ileum or sigmoid colon.
The lower part of the posterior surface is separated from the rectum by the vasa deferentia,
the seminal vesicles, and the rectovesical fascia.
The neck of the bladder lies inferiorly and rests on the upper surface of the prostate.
In the female; because of the absence of the prostate, the bladder lies at a lower level than
in the male pelvis, and get close relation to the uterus and the vagina .
The base, or posterior surface, is separated by the vagina from the rectum.
The superior surface is related to the uterovesical pouch of peritoneum and to the body of
the uterus.
The neck of the bladder rests on the upper surface of the urogenital diaphragm.
Blood Supply
Arteries
The superior and inferior vesical arteries, branches of the internal iliac arteries.
Veins
The veins form the vesical venous plexus which drains into the internal iliac vein.
Lymph Drainage
Internal and external iliac nodes.
Nerve Supply
The inferior hypogastric plexuses.
Urethra
The male urethra originates at the bladder neck and terminates at the urethral meatus on
the glans penis. It is roughly 15-25 cm long in the adult male. The male urethra is often
divided into 3 segments on the basis of its investing structures: prostatic urethra,
membranous urethra, and spongy (or penile) urethra.
The urethra can be separated simply into anterior and posterior urethra.
Prostatic urethra
The prostatic urethra is the portion of the urethra that traverses the prostate. It originates in
the region of the bladder neck, courses roughly 2.5 cm inferiorly, and terminates at the
membranous urethra. It lies in a retropubic location
The posterior wall of the prostatic urethra contains the verumontanum, where the paired
ejaculatory ducts and the opening of the prostatic utricle opened into the lumen of the
urethra.
Membranous urethra
The shortest and least distensible portion of the urethra is the membranous urethra. This
region spans from the apex of the prostate to the bulb of the penis. It is invested in the
external urethral sphincter muscle and the perineal membrane.
Spongy urethra
The spongy urethra is the region that spans the corpus spongiosum of the penis. It is
divided into the pendulous (or penile) urethra, the bulbous (or bulbar) urethra and fossa
navicularis.
The pendulous urethra is invested in the corpus spongiosum of the penis in the pendulous
portion of the penis.
In the distal urethra lies the fossa navicularis, a small dilation of the urethra just proximal
to the urethral meatus.
The bulbous urethra is invested in the bulb of the penis. The ducts of Bulbourethral
(Cowper) glands empty into the bulbous urethra.
The female urethra is approximately 4 cm long and 6 mm in diameter and passes
anteroinferiorly from the the urinary bladder( posterior and then inferior to the pubic
symphysis) to the external urethral orifice. The external urethral orifice is located in the
vestibule, the cleft between the labia minora of the external genitalia.
The female urethra is divided as anterior and posterior parts or as proximal and distal
portions.