DISSECTION 32
The Pelvis
References: M1 327-402; N240, 340-356, 380-383, 390-393, 481; N248, 352-371, 400-403, 410-413, 499; R
327-334, 338-347, 352-355, 419-424, 456-457
AT THE END OF THIS LABORATORY PERIOD YOU WILL BE RESPONSIBLE FOR THE
IDENTIFICATION AND DEMONSTRATION OF THE STRUCTURES LISTED BELOW:
1. Bones and bony features: sacrum: (promontory, ala, anterior sacral foramina), coccyx, bony pelvis:
(ilium, ischium, pubis, obturator foramen, iliac crest, anterior superior iliac spine, arcuate line, pubic
symphysis, ischial tuberosity, ischial spine, greater sciatic notch, lesser sciatic notch).
2. Viscera: urinary bladder (trigone, ureteral orifice, urethral orifice), rectum, ureter, ovary, uterus,
uterine tube.
3. Peritoneal folds and fossae: paravesical fossa, pararectal fossa, ureteral fold, rectovesical fold,
rectovesical pouch, rectouterine fold, rectouterine pouch, vesicouterine pouch.
4. Mesenteries and ligaments: mesovarium, round ligament of uterus, ovarian ligament, broad ligament
(and its subdivisions), suspensory ligament of the ovary, medial umbilical ligament.
5. Muscles: levator ani, coccygeus, arcus tendineus, obturator internus, piriformis.
6. Vessels: external iliac, inferior epigastric, deep circumflex iliac, abnormal obturator from inferior
epigastric, common iliac, internal iliac, umbilical, superior vesical, internal pudendal, obturator,
inferior gluteal, uterine, iliolumbar, lateral sacral, superior gluteal arteries, external and internal iliac
veins.
7. Nerves: femoral, obturator, lumbosacral trunk.
YOU SHOULD ALSO BE ABLE TO DO THE FOLLOWING THINGS:
1. Describe the peritoneal reflections in the male and female pelvis.
2. Discuss the lymphatic drainage of each of the pelvic organs.
3. Demonstrate the parts of the bony pelvis.
4. Relate the pelvic organs to the skeleton of the pelvis.
5. Explain the innervation of the pelvic organs and describe the fiber composition and distribution of the
pelvic splanchnic nerves. List the results of sectioning the hypogastric plexus or the pelvic splanchnic
nerves.
6. List the principal structures which support the uterus.
7. Name and identify the subdivisions of the broad ligament.
8. List 3 differences between the male bony pelvis and the female bony pelvis.
9. Name the subdivisions of the uterine tube.
10. Describe the pelvic diaphragm and its attachments.
11. Give the relationship of the uterine artery to the ureter.
12. Identify structures on cross-sectional drawings, C-T scans, or tissue sections through the pelvis.
Dissection 32, The Pelvis
Page 2
The Pelvic Skeleton
Understanding the pelvic structures and
perineum is facilitated by a familiarity with the
pelvic skeleton. This consists of the SACRUM, the
COCCYX, and the two hip bones (os coxae) which
in turn consist of the ILIUM, the ISCHIUM, and the
PUBIS (G3.2; N340, 341; N352, 353; A395, 398).
Also the function and attachments of the pelvic
diaphragm should be understood (G3.4, 5, Table
3.1; N343, 346; N356, 359; A365). Identify the
OBTURATOR FORAMEN, the ILIAC CREST, the
ANTERIOR SUPERIOR ILIAC SPINE, the ARCUATE
LINE, the PUBIC SYMPHYSIS, the ISCHIAL
TUBEROSITY, the ISCHIAL SPINE, the GREATER
SCIATIC NOTCH, the LESSER SCIATIC NOTCH,
and the SACRAL PROMONTORY, ALA OF THE
SACRUM and ANTERIOR SACRAL FORAMINA
(G4.16, 17, 3.2; N340, 341; N352, 353; A395398).
Study the pelvic contents and the reflections
of the peritoneum noting the following (G3.8A,
28; N340-341; N352-353; A353-354, 377-378):
MALE
rectovesical pouch
rectovesical fold
MALE & FEMALE
urinary bladder
rectum
ureter (pelvic part)
paravesical fossa
pararectal fossa
ureteral fold
FEMALE
ovary
mesovarium
round ligament
(of uterus)
ovarian ligament
uterus
uterine tube
broad ligament
rectouterine fold
rectouterine pouch
vesicouterine pouch
suspensory ligament
of the ovary
In some bodies, especially when much fat is
present external to the peritoneum, identification
of folds and fossae may be difficult. You will
then need to study them from an atlas or on
another body and note where they should have
appeared on your own specimen.
Arteries of the Pelvis
Remove the peritoneum from the pelvic
organs and clear away the extraperitoneal fat.
Clean the EXTERNAL ILIAC VESSELS, which
traverse the brim of the pelvis, and note the
origins of the INFERIOR EPIGASTRIC and DEEP
CIRCUMFLEX ILIAC ARTERIES (N351; N364).
Look for an unusual origin of the OBTURATOR
ARTERY from the external iliac or inferior
epigastric. Clean the COMMON ILIAC and the
INTERNAL ILIAC (BNA, hypogastric) vessels and
their branches, and trace them as far as may be
practical in the intact pelvis (N328, 382, 383;
N341, 402, 403). The internal iliac often has two
major branches, an anterior branch and a posterior
branch, with all of the visceral branches coming
from the anterior branch along with the obturator
and inferior gluteal. The first large branch is
usually the UMBILICAL ARTERY, which in turn
gives off one or more SUPERIOR VESICAL
ARTERIES to the bladder. Beyond this point the
umbilical artery is obliterated and continues to the
umbilicus as the MEDIAL UMBILICAL LIGAMENT.
The anterior division of the internal iliac also
usually, but not always, gives rise to the following
arteries: INTERNAL PUDENDAL, OBTURATOR,
INFERIOR GLUTEAL, and UTERINE (female only).
Using G3.19 or N382, 383; N402, 403 or A355,
364, identify as many of the above as you can.
From the posterior branch of the internal iliac
look for the ILIOLUMBAR, LATERAL SACRAL,
and the SUPERIOR GLUTEAL ARTERIES. Note
that the superior and inferior gluteal arteries pass
out of the pelvis above and below the
PIRIFORMIS MUSCLE respectively and the muscle
can be identified on this basis.
Considerable variation in the pattern of
branching of the internal iliac artery is to be
expected; hence, positive identification of a given
vessel must be made according to what organ or
region it supplies, rather than on its manner of
origin. These vessels may be grouped into
visceral and parietal arteries, of which the
vesicals, middle rectal, deferential (male),
UTERINE and vaginal (female) are typically
visceral, and the remainder are classified as
parietal.
The
INTERNAL
PUDENDAL
(predominantly parietal) has visceral branches.
Any vessel that cannot be identified positively
Dissection 32, The Pelvis
while the pelvis is still intact should be reviewed
and traced after the pelvis is divided (G3.19;
N382, 383; N402, 403; A364).
The Pelvic Diaphragm
Identify the superior surface of the pelvic
diaphragm. This is the internal layer of fascia
that invests the LEVATOR ANI and the
COCCYGEUS MUSCLES. Look for the ARCUS
TENDINEUS where the lateral border of the levator
ani crosses the upper part of the OBTURATOR
INTERNUS MUSCLE. This arch is attached to the
superior pubic ramus anteriorly and to the spine
of the ischium posteriorly. Superiorly, its fascia
is continuous with that of the iliacus muscle
(G3.5; N343, 345, 351; N356, 358, 364; A359,
365).
The Lumbar Plexus
ON THE RIGHT SIDE ONLY, remove the
veins, including the common iliac; free the
arteries enough to give access to the anterior rami
of lumbar and sacral nerves.
Trace the
sympathetic trunks into the pelvis. Remove the
medial part of the psoas major muscle, but spare
nerves that pierce it, the genitofemoral in
particular. Identify by number, lumbar nerves 15; the lumbar part of the lumbosacral plexus
which gives rise to the FEMORAL, lateral femoral
cutaneous and OBTURATOR NERVES; then trace
Page 3
these and the genitofemoral to their sites of exit
from abdominal or pelvic cavities (N259, 327;
N267, 340). Trace the LUMBOSACRAL TRUNK,
formed by part of the 4th and most of the 5th
lumbar nerves, to its junction with the lst sacral.
Further dissection of the sacral portion of the
plexus may be deferred until the pelvis is divided
(G3.24A; N478-480; N496-498).
Plexuses of autonomic nerves are well
represented about the walls of organs and arteries
of the pelvis. A satisfactory display of them is
not ordinarily required in routine dissection, but
their presence should not be forgotten.
Sympathetic nerves from the caudal part of the
sympathetic trunks and parasympathetic nerves
(craniosacral division of the autonomic system)
from S2, S3, and S4 (pelvic splanchnics) go to the
pelvic autonomic plexuses. Their study from a
textbook is recommended (M1 358-361, H752756). The pelvic splanchnic nerves can be seen
better after the pelvis is divided.
The interior of the bladder can be observed by
cutting a window through the anterosuperior wall
to observe the TRIGONE (G3.16; N353; N366;
A356) and the URETERAL and URETHRAL
ORIFICES.
Dissection 32, The Pelvis
Page 4
STUDY QUESTIONS
1.
Name the bones that make up the
bony pelvis.
1.
The two hip bones, the sacrum, and the coccyx.
Each hip bone, or os coxae, has three parts: the
ilium, the ischium, and the pubis.
2.
How are the bones which form the
bony pelvis held together?
2.
By ligaments and by two synovial joints, the
sacroiliac joints, and by two symphyses, the
symphysis pubis and the sacrococcygeal joint.
3.
What is the pelvic brim?
3.
The pelvic brim is a line or ridge that extends
from the sacral promontory posteriorly around the
lateral margin of the superior pelvic aperture to
the top of the symphysis pubis anteriorly.
4.
What are the three parts of the
pelvic brim?
4.
1) the promontory and anterior border of the
ala of the sacrum,
2) the arcuate line of the ilium,
3) the pecten and crest of the pubis.
5.
Define the terms major pelvis,
minor pelvis, true pelvis, false
pelvis, greater pelvis, lesser pelvis,
and obstetric pelvis.
5
The major pelvis (also greater or false pelvis) is
that part of the bony pelvis above the pelvic brim.
The minor (also true, lesser, or obstetric pelvis) is
that part of the bony pelvis below the pelvic brim.
6.
What is the pelvic inlet?
Pelvic outlet?
6.
The pelvic inlet, or superior pelvic aperture, is the
opening surrounded by the pelvic brim. The
pelvic outlet is the inferior pelvic aperture.
7.
List major ways in which the
female pelvis differs from the
male pelvis.
7.
1) Females have a broader sacrum, and thus
the hip bones are farther apart.
2) Females have a wider subpubic angle and
thus the ischial tuberosities are farther apart.
3) Females have a less curved sacrum, which
also increases the size of the inferior pelvic
aperture.
8.
List the muscles that cross
the pelvic brim.
8.
9.
List the muscles that line the
walls of the true pelvis.
9.
10. Name the muscles that form
the pelvic diaphragm.
The piriformis and the obturator internus.
10. The levator ani and the coccygeus.
Dissection 32, The Pelvis
Page 5
11. What part of the levator ani muscle
is important in maintaining the angle
between the rectum and the anal canal?
11. The puborectalis.
12. Name the nerves that cross the
pelvic brim.
12. The lumbosacral trunk, the obturator nerve and the
sympathetic trunk on each side.
13. Name the arteries that cross the
pelvic brim.
13. Internal iliac, median sacral, superior rectal, and
ovarian.
14. What is the relationship of the
uterine artery to the ureter?
14. The uterine artery passes anterior and superior to
the ureter where they cross near the lateral fornix
of the vagina. "Water runs under the bridge."
15. Describe the course of the internal
pudendal artery.
15. After branching from the internal iliac artery, it
passes inferiorly along the lateral wall of the minor
pelvis to the cleft between the piriformis and the
coccygeus where it passes through the wall. It then
passes superficial to the ischial spine or the
sacrospinous ligament and enters the pudendal
canal in the lateral wall of the ischiorectal fossa.
The pudendal canal is located in the fascia of the
obturator internus muscle.
16. What are the terminal branches of
the internal pudendal artery?
16. The deep artery of the penis (clitoris) and the
dorsal artery of the penis (clitoris)
17. Name the pelvic venous plexuses:
17.
a. in the male.
a.
external rectal plexus
internal rectal plexus
prostatic plexus
vesical plexus
b. in the female.
b.
external rectal plexus
internal rectal plexus
vesical plexus
vaginal plexus
uterine plexus
18. In general, what is the lymphatic
drainage of the pelvic viscera?
18. Lymph from the pelvic organs drains either to
internal iliac nodes, to external iliac nodes, or to
sacral nodes. Efferents from the external and
internal iliac nodes and from sacral nodes drain to
common iliac nodes. The common iliac nodes
drain to lumbar nodes.
Dissection 32, The Pelvis
Page 6
19. What is the main importance of
the prostatic venous plexus?
19. The prostatic venous plexus drains into the vesical
plexus and from it into the internal iliac veins.
The internal iliac veins also receive blood from
the lateral sacral veins which communicate with
the external and internal vertebral venous
plexuses. Since none of these veins is valved,
any increase in intraabdominal pressure can
force blood from the pelvic veins into the
vertebral venous plexus. Valsalva maneuvers
associated with straining, coughing, etc., can
cause the spread of prostatic tumor cells through
the blood to the vertebral column, the brain, and
elsewhere by this route. By this means
metastatic tumors from the prostate can reach
distant sites without passing through the lungs.
20. For the bladder: what is its base,
its apex, its neck?
20. The bladder has four surfaces: a superior surface,
two inferolateral surfaces, and a posterior
surface. The posterior surface is the base of the
bladder, and it is this surface that is in contact
with the seminal vesicles. The apex is opposite
the base and is at the point of attachment of the
median umbilical ligament (urachus). The neck
of the bladder is the inferior narrowed portion
just above the opening of the urethra.
What is the fundus of the bladder?
The term fundus is sometimes applied to the base
of the bladder. The two terms are synonymous.
21. Discuss the nerve supply to the
bladder.
21.
22. Locate the cell bodies of nerve fibers
which:
22.
The pelvic splanchnic nerves supply afferent
fibers and preganglionic efferent fibers to the
bladder. Postganglionic neurons (terminal
ganglia) are located in the bladder wall. Cell
bodies of afferent fibers are located in the dorsal
root ganglia of the midsacral (S2, S3, S4) nerves.
a. innervate smooth muscle which
contracts the bladder;
a.
Ganglia of the outer and submucous coats
of the bladder (parasympathetic terminal
ganglia).
b. innervate blood vessels in the wall
of the bladder;
b.
Ganglia of the pelvic portion of the
sympathetic trunk (lateral ganglia) or
sympathetic ganglia of the pelvic plexus
(collateral ganglia).
c. are activated by stretch of bladder
muscle (detrusor) fibers;
c.
Dorsal root ganglia at S2, S3, and S4.
d. initiate and interrupt micturition.
d.
Anterior gray column of the second,
third, and fourth sacral segments of
the spinal cord.
Dissection 32, The Pelvis
Page 7
23. What deleterious effect on body
functions is produced by enlargement
of the prostate?
23. Obstruction of the flow of urine from the bladder
(urinary retention).
24. List the structures supporting the
uterus.
24. The broad ligament, the cardinal ligaments, the
uterosacral ligaments, and the round ligaments;
probably the most important structure supporting
the uterus, however, is the pelvic diaphragm.
25. Name the subdivisions of the uterine
tube.
25. The fimbriated end, the infundibulum, the
ampulla, the isthmus, and the intramural or uterine
part.
What prevents peritoneal fluid
from leaking out the vaginal orifice?
The walls of the cervix usually remain in close
opposition as do the walls of the vagina,
preventing the cavity of the uterus from "opening"
directly to the outside; in addition, the volume of
peritoneal fluid is usually very small.
How can a physician determine if at
least one tube is patent?
Both tubes?
26. Trace lymphatic drainage from
the uterus.
Why is this important?
By instilling a small amount of air into the uterus.
The air will ascend through a patent uterine tube
and escape into the peritoneal cavity to collect
beneath the diaphragm.
By radiographic demonstration of bilateral
leakage into the peritoneal cavity of radio-opaque
material placed in the cavity of the uterus.
(G3.33B)
26. Most efferent vessels from the cervix and lower
body end in nodes of the pelvis: internal iliac,
external iliac; and sacral. Most efferent vessels
from the fundus and upper body drain to nodes of
the lumbar chain, although a few drain along the
round ligament to end in superficial inguinal
nodes.
The pattern of lymphatic drainage of the uterus is
important because of the prevalence of cancer of
the uterus and because of the tendency of these
cancers to spread by way of the lymphatics.
Dissection 32, The Pelvis
27. What is a cystocele?
Page 8
27. A bulging of the bladder into the anterior wall of
the vagina (and sometimes out the vestibule!)
What types of trauma produce this
defect?
This results from tearing of the connective tissue
fibers of the anterior vaginal wall when the vagina
is stretched during childbirth.
What deleterious effects on body
functions result from a cystocele?
Distortion of the shape of the bladder allows the
bladder sphincter to leak, especially under stress
such as sneezing, etc.; this is called urinary
incontinence. Another problem frequently
associated with a cystocele is failure to empty the
bladder, i.e. residual urine, which favors the
development of infection.
What is prolapse of the uterus?
Relaxation of the supports of the uterus, allowing
the organ to descend into the vagina; in severe
cases the cervix may appear through the vestibule
and become chronically inflamed.
28. In what clinical situations are the
venous anastomoses around the
rectum important?
28. In cases of portal hypertension the connections of
the superior rectal veins may serve as an
important communication of the portal with the
caval system to relieve, somewhat, the portal
hypertension.
What is the route of lymphatic
drainage from the rectum?
From upper rectum to inferior mesenteric nodes;
from middle and lower rectum to internal iliac
nodes.
Abnormality of what embryonic
structure results in imperforate anus?
Cloacal membrane
At what time in development does
this defect occur?
7 or 8 weeks
29. What is the neural hypogastric
plexus (presacral nerve)?
29. Preganglionic and postganglionic sympathetic
fibers, small sympathetic ganglia (collateral), and
a few afferent fibers.
What are the results of presacral
neurectomy?
Loss of ability by the male to ejaculate; possibly
relief of pain in dysmenorrhea (female).
What types of fibers are contained
in the pelvic plexus?
Preganglionic and postganglionic sympathetic
fibers, preganglionic and postganglionic
parasympathetic fibers, and afferent fibers.
What results from interruption of
the nervi erigentes (pelvic splanchnic
nerves)?
Loss of muscle tone in the wall of the bladder
(atonic bladder) reduced peristalsis in the rectum,
loss of sensation (pain, fullness) from pelvic
organs, and, in the male, loss of the ability to
produce an erection.
Dissection 32, The Pelvis
Page 9
30. What is the relation of the ovarian
artery to the ureter at the pelvic brim?
30. The artery is lateral to the ureter.
31. What remains of the umbilical artery
after birth?
31. It remains patent as far as the superior vesical
artery and becomes the medial umbilical ligament
distal to this.
32. Where is the vagina in relation
to the peritoneum?
32. Posterior fornix
33. What are the subdivisions of the
broad ligament?
33. The mesovarium extending between the ovary and
the major part of the broad ligament, the
mesosalpinx between the attachment of the
mesovarium and the uterine tube, and the
mesometrium below the attachment of the
mesovarium.
LJ:bh
revised
06/19/09