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TOPOGRAPHIC ANATOMY
OF THE PELVIC CAVITY
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The bony pelvis is composed of four bones: the two innomiÂnate bones or
hip bones form the lateral and anterior walls, and the sacrum and the coccyx form
the back wall. The pelvis is diÂvided into two parts by the pelvic brim. Above the
brim is the false pelvis or greater pelvis, which forms part of the abdomiÂnal cavity.
Below the brim is the true pelvis or lesser pelvis. The true pelvis is a bowl-shaped
structure that contains and protects the lower parts of the intestinal and urinary tracts
and the internal organs of reproduction. The true pelvis has an inlet, an outlet and a
cavity.
The pelvic inlet, or pelvic brim, is bounded posteriorly - Âby the sacral
promontory, laterally – by the iliopectineal lines, and anteriorly – by the
symphysis pubis.
The pelvic outlet is bounded posteriorly – by the coccyx, laterally – by
the ischial tuberosities, and anteriorly – by the pubic arch. Laterally there are the
sciatic notches. The sciatic notches are divided by the sacrotuberous and
sacrospinous ligaÂments into the greater and lesser sciatic foramina.
The pelvic cavity lies between the inlet and the outlet. It is a short, curved
canal, with a shallow anterior wall and a much deeper posterior wall.
The walls of the pelvis are formed by bones and ligaments that are partly
lined with muscles covered with fascia and parietal peritoneum. The pelvis has
anterior, posterior and lateral walls and it also has an inferior wall or floor.
The piriformis muscle arises the front of the lateral masses of the sacrum and
leaves the pelvis to enter the gluteal region by passing laterally through the greater
sciatic foramen. It is inserted into the upper border of the greater trochanter of the
femur.
The obturator membrane is a fibrous sheet that almost completely closes the
obturator foramen, leaving a small gap, the obturator canal for the passage of the
obturator nerve and vessels as they leave the pelvis to enter the thigh.
The sacrotuberous ligament is strong and extends from the lateral part of the
sacrum and coccyx and the posterior inferior iliac spine to the ischial tuberosity.
The sacrospinous ligament is strong and triangular in shape. It is attached by
its base to the lateral part of the sacrum and coccyx and by its apex to the spineof the
ischium. The two ligaments convert the greater and lesser sciatic notches into
foramina, the greater and lesser sciatic foramina.
The obturator internus muscle arises from the pelvis surface of the obturator
membrane and the adjoining part of the hip bone. The muscle fibers converge to a
tendon, which leaves the pelvis through the lesser sciatic foramen and isinserted into
the greater trochanter of the femur.
The floor of the pelvis supports the pelvis viscera and is formed by the pelvic
diaphragm and the urogenital diaphragm.
The pelvic diaphragm is formed by the important levatores ani muscles and
the small coccygeus muscles and their covering fasciae.
The levator ani is the important muscle and the integrity of the pelvis floor
depends upon its function. It is particularly liable to damage during difficult
deliveries and this damage may by followed by urinary incontinence prolapse of the
bladder, and prolapse of the uterus through the vagina. The muscle has a linear origin
from the pelvic wall. This origin starts anteriorly on the inner aspect of the body of
the pubis, extends across the surface of the oturator fascia from an overlying
condensation of the pelvic fascia called the arcus tendineus, and terminates at the
spine of the ischium where its most posterior fibers lie parallel with the lower fibers
of coccygeus. The levator ani can be described in two parts according to the origin
of their fibers. Those fibers arising from the pubis are known as pubococcygeus and
those from the arcus tendineus and the spine of the ischium as iliococcygeus. The
coccygeus muscle is a small muscle that arises from the spine of the ischium and is
inserted into the lateral margin of the lower sacrum and coccyx.
The urogenital diaphragm lies below the anterior part of the floor and the
genital hiatus between the medial margins of the levator ani muscles. The diaphragm
consists of a layer of striated muscle sandwiched between two fascial layers. The
deep layer or superior fascia of the urogenital diaphragm is an inÂsubstantial layer
which blends posteriorly with the perineal boÂdy and perineal membrane. The
muscular layer consists of the deÂep transverse perineal muscles. The more
superficial fascial laÂyer is known as the inferior fascia of the urogenital diaphragm,
or more commonly the perineal membrane.
The pelvic fascia
The pelvic fascia is the continuation of the endoabdominal fascia below the
pelvic brim.
The pelvic fascia may be divided into the parietal and visceral layers.
The parietal pelvic fascia lines the walls of the pelvis. It is formed arcus
tendineus on boundary between the superior half and inferior half of the obturator
internus muscle, from which the fibers of the levator ani arise. The pelvic fascia is
formed the two ligaments between the symphysis pubis and the prostate in the male
and between the symphysis pubis and the urinary bladder in the female. They are
puboprostatic and pubovesical ligaments, respectively.
The visceral pelvic fascia covers all the pelvic viscera.
The pelvic fascia is formed the two sagittal plates in passage from walls to
pelvic organs. They spread between the pubic bone and the sacrum. Thus the pelvic
viscera are located into space, which is limited anteriorly - by the pubic bones,
posteriorly - by the sacrum and the coccyx and laterally - by the sagittal plates. This
space is divided into two parts anterior and posterior by septum, which is located in
frontal plane between the peritoneum and the urogenital diaphragm. This septum is
called the peritoneoperineal aponeurosis Dennonvillier. The peritoneoperineal
aponeurosis separates the rectum from urinary bladder and the prostate in the male.
The anterior parts of space in the male contains the urinaÂry bladder, the
prostate, the seminal vesicle and ampulla of vas deferens. The anterior part of
space in the female contains the urinary bladder and vagina.
The posterior part of space contains the rectum in the male and female. The
peritoneoperineal aponeurosis Dennonvillier seÂparates the rectum from the
vagina. The fascial sheath of some pelvic organs were described as capsules. The
fascial sheath of the prostate is called capsule Pirogov-Retziy. The fascial sheÂath
of the rectum is called capsule Amuse. The organs of the pelvic cavity are separated
from the walls by the fat spaces.
The relation of the peritoneum to pelvic viscera
The peritoneum is formed the transverse vesical fold in passage from the
anterior abdominal wall to the superior wall of the urinary bladder. Further in the
male the peritoneum covers part of the lateral and posterior wall of urinary bladder
and the medial borders (margins) of the ampullas of vas deferenses and the apexes
of the seminal vesicle. Then, the peritoneum passes on rectum, forming the rectovesical pouch. Laterally this pouch is limited by the recto-vesical folds of the
peritoneum which pass in sagittal direction from the urinary bladder to the rectum.
The recto-vesical pouch contains the coils of small intestine in norm, but it may
contains the blood, the pus, the exudate in pathology.
In female, the peritoneum is formed the two pouches in passage from the
urinary bladder to the uterus and from the uterus to the rectum. They are
vesicouterine pouch and the rectouterine pouch.
The recto-vesical pouch in the male and the rectouterine pouch in the female
are called pouchs of Duglas. The vesicouteÂrine pouch may contain the greater
omentum in norm.
The rectouterine pouch may contain the coils of small intestine in norm, but
it may contain the blood, the pus, the exudate in pathology. This pouch may drain
by means the puncture through the posterior fornix of the vagina. Laterally, the
rectouterine pouch is limited by the rectouterine folds of the peritoneum, which pass
in sagittal direction from the uterus to the rectum.
THREE FLOORS OF PELVIC CAVITY
The pelvic cavity is divided into three parts or floors: peritoneal pelvic cavum,
subperitoneal pelvic cavum and subcutaÂneous pelvic cavum.
The first floor or peritoneal pelvic cavum - is the inferior part of the
abdominal cavity and is limited by plane which passes through the pelvic brim. Here
the organ or parts of organs of the pelvic cavity which cover by peritoneum are
contained. The superior and partially the posterolateral and anterior walls of the
urinary bladder and part of the rectum are located in the peritoneal pelvic cavum in
the male.
The such parts of urinary bladder and the rectum and the more part of the
uterus and its appendages (ovaries and uterine tubes), the broad ligaments and also
the most superior part of the vagina (posterior fornix of the vagina) are located in
the peritoneal pelvic cavum in the female.
The second floor or subperitoneal pelvic cavum is contained between the
peritoneum and the parietal layer of the pelvic fasÂcia, which covers the superior
surface of the levator ani muscÂle. Here, the extraperitoneal parts of the uprinary
bladder and the rectum, the prostate, the seminal vesicles, the pelvic parts of the vas
deferenses with their ampullas, the pelvic parts of ureters are located in the male.
The such parts of the ureters, urinary bladder and rectum and also the cervix of the
uterus, the part of the vagina are located here in the female. All orÂgans, which are
located in the subperitoneal pelvic cavum are surrounded by the fascial sheath and
the fat spaces. Besides of the organs the fat layers contain the nerves, blood vessels
and lymph nodes.
The third floor or subcutaneus pelvic cavum is located betÂween the
inferior surface of the pelvic floor and the skin. This floor is the perineum. It contains
the parts of organs of the urogenital system, the final part of the rectum and the
ischioÂrectal fossa.
The vessels, nerves and lymph nodes of pelvis
Common iliac artery ends at the pelvic inlet in front of the sacroiliac joint
by dividing into the external and internal iliac arteries.
The external iliac artery runs along the medial border of the psoas muscle,
following the pelvic brim and gives off the inferior epigastric and deep circumflex
iliac branches. It leaÂves the false pelvis by passing under the inguinal ligament, to
became the femoral artery.
The following arteries enter the pelvic cavity:
1. Internal iliac artery.
2. Superior rectal artery.
3. Ovarian artery.
4. Median sacral artery.
The internal iliac artery passes down into the pelvis to the upper margin of
the greater sciatic foramen, where it diviÂdes into anterior and posterior divisions.
The branches of these divisions supply the pelvic viscera, the peritoneum, the pelvic
walls and the buttocks. The branches of the anterior division may be divided into
parietal and visceral branches.
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Anterior division of the internal iliac artery Posterior division of
the internal iliac
Parietal branches
visceral branches
artery
Obturator artery, superior vesical artery,
iliolumbal artery
Internal pudendal inferior vesical artery,
lateral sacral artery,
artery,
artery to the ductus superior gluteal artery
Inferior
gluteal deferens,
artery
middle rectal artery,
vaginal artery,
uterine artery
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Parietal veins accompanying the parietal branches of the internal iliac arteries
drain into the internal iliac veins. Visceral veins form the venous plexuses which
surround the pelÂvic organs. They are the rectal venous plexuses, the vesical veÂnous plexuses, the uterine venous plexuses, the vaginal venous plexuses and the
prostatic venous plexuses. The venous plexuses drain into the internal iliac veins.
The pelvic venous plexuses also communicate with the external and internal
vertebral plexuÂses. These communications play an important part in the spread of
disease from the pelvis. It should also be remembered that the middle rectal veins
communicate with the superior rectal veÂins which form part of the portal venous
system.
Nerves of the pelvis
The sacral plexus lies on the posterior pelvic wall in front of the piriformis
muscle. It is formed from the anterior rami of the fourth and fifth lumbar nerves and
the anterior rami of the first, second, third and fourth sacral nerves. Note that the
contribution from the fourth lumbar nerve joins the fifth lumbar nerve to form the
lumbosacral trunk.
...
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