Download The Pelvis

The Pelvis
The pelvis is the region of
the trunk that lies below the
abdomen; the abdominal and
pelvic cavities are
continuous.
Surface Anatomy
Iliac Crest; Anterior Superior
Iliac Spine; Posterior
Superior Iliac Spine; Tubercle
of Iliac Crest; Pubic Tubercle;
Pubic Symphysis; Pubic Crest;
Spinous Processes Sacrum;
Sacral Hiatus; Coccyx.
Preliminary
Dissection of Male
or female Pelvis
Examine again the division of
the lower part of the abdominal
aorta in front of the fourth
lumbar vertebra into two common
iliac arteries. Follow the
common iliac arteries to their
termination in front of the
sacroiliac joints. Trace the
external iliac artery along the
pelvic brim to the inguinal
ligament.
Identify the inferior
epigastric and deep circumflex
iliac branches. Clean the
origin of the internal iliac
artery and follow it down into
the pelvis, where it ends near
the upper margin of the
greater sciatic foramen by
bifurcating into anterior and
posterior divisions. Identify
the median sacral artery.
Expose and clean the
external, internal
and common iliac
veins.
Identify and clean the
right and left ureters as
they enter the pelvis in
front of the bifurcation
of the common iliac
arteries.
Examine again the lumbaosacral
trunks and the obturator
nerves as they enter the
pelvis. Do not disturb them in
the pelvis at the present time.
Examine again the lower ends of
the lumbar sympathetic trunks
and ganglia. Demonstrate the
continuity of the trunks with
those in the pelvis.
Trace the hypogastric plexus
over the sacral promontory,but
do not disturb it within the
pelvis at this time.
Trace the testicular arteries
to the deep inguinal rings, or
the ovarian arteries to the
pelvic brim.
Examine again the pelvic
colon and identify the
pelvic mesocolon. Follow the
superior rectal artery to
the pelvic inlet and to the
posterior surface of the
rectum.
Examine again the femoral
nerve and the lateral femoral
cutaneous nerve. Trace the
femoral nerve as it emerges
from the lateral border of
the psoas muscle, downward and
laterally in the groove
between the psoas and the
iliacus.
Note that it lies under the
cover of the fascia iliaca and
passes behind the inguinal
ligament to enter the thigh
lateral to the femoral artery.
Follow the lateral cutaneous
nerve of the thigh across the
iliacus muscle and verify that
it enters the thigh behind the
lateral end of the inguinal
ligament.
Dissection of
intact Femal
Pelvis
Peritoneum. Examine the
peritoneum and trace it down
the anterior and lateral
surfaces of the rectum. Follow
the peritoneal reflection from
the rectum onto the upper part
of the posterior surface of
the vagina, which forms the
rectouterine pouch (pouch of
Douglas).
The peritoneal recess on each
side of the rectum is
referred to as the pararectal
fossa. Note that the
pararectal fossa and the
rectouterine pouch are
continuous with one another.
Trace the peritoneum over the
posterior surface of the
uterus, over the fundus, and
down over the anterior surface
of the uterus. It then passes
onto the posterior surface of
the bladder for a short
distance, thus forming the
uterovesical pouch.
Trace the peritoneum over the
upper surface of the bladder
and then forward onto the
anterior abdominal wall. Note
that the outline of the empty
bladder is not easily seen.
Note also that the peritoneum
runs from the superior
surface of the bladder to the
lateral walls of the pelvis.
Observe that the normal uterus
is bent forward so that its
anterior surface faces forward
and inferiorly and overhangs
the bladder (anteverted and
anteflexed).
Note that the peritoneum
almost completely covers the
uterus and extends laterally
on each side of the uterus
as a two-layered fold of
peritoneum to the side wall
of pelvis. This fold is
known as the broad ligament.
Identify in the broad
ligament the following
structures:
1.The uterine tube. This lies
in the free border of the
broad ligament.It opens into
the peritoneal cavity by means
of its funnel-shaped lateral
extremity, the infundibulum.
The free edge of the funnel is
broken up into a number of
finger-like processes known as
the fimbriae,which are draped
over the ovary.
2. The ovary is a small
oval body attached to the
back of the broad ligament
by the mesovarium.
3. The mesosalpinx is that
portion of the broad
ligament which lies between
the mesovarium and the
uterine tube.
4. The suspensory ligament of
the ovary is that part of the
broad ligament which lies
lateral to attachment of the
mesovarium; it contains the
ovarian vessels and nerves.
5. The round ligament of the
ovary produces a ridge of
peritoneum on the posterior
surface of the broad
ligament.
6. The round ligament of the
uterus produces a ridge of
peritoneum on the anterior
surface of the broad ligament
that can be trace from the
lateral edge of the uterus to
the deep inguinal ring.
Dissection of the Left
Half of the Femal Pelvis
With the fingers, carefully
mobilize the rectum from
the anterior surface of the
sacrum. Dissect off the
peritoneum and pelvic
fascia from the posterior
and lateral wall of the
pelvis.
Clean the rectum and observe
that the lower third is
completely devoid of peritoneum,
since it lies below the lowest
part of the rectouterine pouch.
Note that the rectum expands
just above the pelvic floor to
form the ampulla of the rectum.
Once the rectum passes through
the pelvic floor, it becomes
the anal canal.
Follow the superior rectal
artery downward along the
posterior surface of the rectum.
Note that it divides into two
branches that pass down on
either side of the rectum and
anastomose with the right and
left middle rectal arteries,
which are branches of the
internal iliac artery.
Identify the hypogastric and
the left pelvic plexuses. The
hypogastric plexus descends
into the pelvis and divides
into right and left pelvic
plexuses. The fine nerve
threads of the pelvic plexus
will be found in the fascia
surrounding the internal iliac
artery.
Trace the pelvic part of the
sympathetic trunk inferiorly.
Note that above and
posterior to the common
iliac vessels it is
continuous with the
abdominal part of the trunk.
Below it descends posterior to
the rectum and medial to the
anterior sacral foramina. It
has four or five segmentally
arranged ganglia. The trunks
end below by uniting in the
midline anterior to the coccyx
in the ganglia impar. Identify
but do not disturb the sacral
plexus.
Ureter. Identify and clean
the left ureter. Verify that
it enters the pelvis by
crossing the bifurcation of
the common iliac artery in
front of the sacroiliac
joint. It runs downward and
backward in front of the
internal iliac artery and
behind the ovary.
Follow the ureter to the
region of the ischial spine
and trace it forward, beneath
the base of the broad
ligament. Note that the
ureter is crossed superiorly
from lateral to medially by
the left uterine artery at
this point. Note also that
the ureter lies lateral to
the cervix and the left
lateral fornix of the vagina.
Now trace the ureter
forward across the pelvic
floor to the bladder. Insert
a fine probe into the
ureteric orifice within the
bladder and verify its
oblique course through the
bladder wall.
Internal Iliac
Artery.
Clean and study the internal
iliac artery and its branches.
Note that it arises from the
common iliac artery and passes
down into the pelvis medial to
the external iliac vein and
anterior to the internal iliac
vein. The main branches are
visceral and parietal and are
as follows:
Visceral Branches
1. The umbilical artery
gives origin to the superior
vesical artery. The
obliterated remnant then
ascends to the umbilicus as
the lateral umbilical
ligament.
2. The inferior vesical
artery runs forward to the
base of the bladder, which
it supplies and in addition
gives branches to the
ureter.
3. The middle rectal artery
passes medially to the
rectum.
4. The uterine artery runs
forward and medially to
enter the base of the broad
ligament, where it ascends
along the lateral margin of
the body of the uterus.
Note its relationship to
the ureter.
Parietal Branches
1.The iliolumbar artery runs
upward and laterally, deep to
the common iliac vessels, and
terminates by supplying the
iliacus, psoas, and quadratus
lumborum muscles.
2. The lateral sacral artery
or arteries ( there are
usually two ) pass medially to
descend in front of the
anterior sacral foramina.
3. The obturator artery runs
anteriorly with the obturator
vein and nerve to reach the
obturator canal, where it
enters the adductor
compartment of the thigh.
4.The internal pudendal
artery leaves the pelvis
between the piriformis and
coccygeus muscles, through
the lower part of the greater
sciatic foramen. It will be
dissected in the gluteal
region and again in the
perineum.
5. The superior gluteal artery
is the largest branch of the
internal iliac artery. It runs
posteriorly between the
lumbosacral trunk and the first
sacral ramus, passing out of
the pelvis through the greater
sciatic foramen above the
piriformis.
6. The inferior gluteal
artery runs inferiorly
between the anterior ramin of
the first and second sacral
nerves and leaves the pelvis
by passing through the lower
part of the greater sciatic
foramen below the piriformis
muscle.
It must be emphasized
that the origin of
these arteries from the
parent trunk is subject
to considerable
variation.
Pelvic veins.
The main venous drainage of
the pelvis is through the
internal iliac veins ( other
veins are the superior rectal,
ovarain, median sacral, and
the internal vertebral venous
plexus ).
The veins of the pelvis are
large and thin-walled, and
they freely communicate. They
are difficult to dissect and
should be removed, since they
obscure other structures.
Remove them piecemeal with
forceps and scissors.
Sacral Plexus
Expose and clean the
lumbosacral trunk and each of
the five sacral anterior rami.
Trace them inferiorly on the
piriformis muscle, where they
form the sacral plexus.
Identify and clean the
following main terminal
branches of the sacral plexus:
1. Sciatic nerve.
This is the largest nerve
in the body, and it is
easily recognized. It
leaves the pelvis through
the lower part of the
greater sciatic foramen.
2. Pudendal nerve.
This leaves the pelvis
through the lower part of
the greater sciatic foramen
and enters the perineum
through the lesser sciatic
foramen.
3. Nerve to quadratus femoris.
4. nerve to obturator internus.
5. Superior gluteal nerve.
6. Inferior gluteal nerve.
7. Posterior femoral cutaneous
nerve (posterior cutaneous
nerve).
8. Preforating cutaneous nerve.
9. Perineal branch of the
fourth sacral nerve.
Clean the piriformis muscle
and probe the greater and
lesser sciatic foramina.
Understand that there is a
large
amount
of
fatty
areolar tissue between the
peritoneum and the fascia
lining the pelvic walls.
Bladder
Note that, as in the male, the
urinary bladder is situated
immediately behind the pubic
bones. Because of the absence
of the prostate, the bladder
lies at a lower level than in
the male pelvis, and the neck
rests directly on the upper
surface of the urogenital
diaphragm.
The apex of the bladder is
continuous with a fibrous
cord known as the urachus
that passes upward in the
extraperitoneal fat to the
umbilicus, forming the median
umbilical ligament. The base
or posterior surface of the
bladder is triangular in
shape. The superolateral
angles are joined by the
ureters, and the inferior
angle rise to the urethra.
Ovary.
Each ovary is a small oval
body attached to the back of
the broad ligament by the
mesovarium. The ovary lies
close to the lateral wall of
the pelvis in a slight
depression called the ovarian
fossa.
The fossa is bounded by the
external iliac vessels above
and by the internal iliac
vessels and the ureter behind.
The obturator nerve crosses the
floor of the fossa. In a young
woman, the surface of the ovary
is relatively smooth, and you
should look at it carefully for
the possibility of finging a
mature follicle or a corpus
luteum.
After the menopause, the
ovary shrinks in size due to
the loss of stimulation from
the pituitary. In the aged,
the surface of the ovary is
puckered with scars.
Carefully examine the ovary
for the following features:
1. The mesovarium is a twolayered fold of peritoneum
connecting the ovary to the
broad ligament.
2. The suspensory ligament of
the ovary is that part of the
broad ligament extending
between the attachment of the
mesovarium and the lateral
wall of the pelvis. It
contains the ovarian artery,
vein,nerves, and lymphatic
vessels.
3. The round ligament of
the ovary extends from the
upper end of the lateral
wall of the uterus to the
medial margin of the ovary,
between the layers of the
broad ligament.
Uterus.
The uterus is divided up
into the fundus, body, and
cervix. Examine the
different parts:
1.The fundus is the part of
the uterus that lies above the
entrance of the uterine tubes.
2. The body is the part of the
uterus that lies below the
entrance of the uterine tubes.
It narrows below, where it
becomes continuous with the
cervix.
3. The cervis pierces the
anterior wall of the vagina
and is divided into the
supravaginal and vaginal
parts of the cervix.
Note that the broad ligament is
attached to the lateral margins
of the uterus. Identify the
cavity of the uterus and note
that it is slitlike. Note the
relation of the cervix to the
vagina. Identify the anterior,
posterior, and lateral fornices
of the vagina. Relate the
cervix and upper part of the
vagina to the pelvic diaphragm.
Uterine Tube.
Examine the uterine tube as
it lies in the upper free
border of the broad ligament.
Incise the uterine tube
longitudinally with a pair of
scissors and inspect the
following parts:
1.Infundibulum.
This is the funnel-shaped
lateral extremity that
overlies the ovary and opens
into the peritoneal cavity.
The free edge is broken up
into a number of finger-like
processes known as fimbriae.
2. Ampulla.
This is the widest part of
the tube.
3. Isthmus.
This is the narrowest part of
the tube, and it lies just
lateral to the uterus.
4. Interstitial part.
This is the segment that
pierces the uterine wall.
With a probe, trace the
channel from the peritoneal
cavity, through the uterine
tube, uterine cavity, and
cervical canal, to the vagina.
Rectum
Note that the rectum measures
about 13 cm long and begins in
front of the third sacral
vertebra as a continuation of
the pelvic colon. It follows
the curve of the sacrum and
ends 2.5 cm anterior to the
tip of the coccyx by piercing
the pelvic diaphragm and
becoming continuous with the
anal canal.
Observe the following
features after cleaning out
the rectal contents with
moist cheesecloth:
1. The rectal ampulla is the
dilated lower end of the
rectum immediately above the
pelvic diaphragm.
2. The transverse folds of the
rectum are three semicircular
mucosal folds; two are placed
on the left rectal wall and one
on the right wall.
3. The peritoneum covers the
anterior and lateral surfaces
of the first third of the
rectum but only the anterior
surface of the middle third,
leaving the lower third devoid
of peritoneum.
Dissection
of
Intact Male Pelvis
Peritoneum.
Examine the peritoneum and
trace it down the anterior and
lateral surfaces of the rectum.
Follow the peritoneal
reflection from the rectum onto
the upper part of the psoterior
surface of the bladder, to form
the rectovesical pouch.
The peritoneal recess on each
side of the rectum is refered
to as the pararectal fossa.
Note that the pararectal
fossae and the rectovesical
pouch are continuous with one
another. Trace the peritoneum
over the upper surface of the
bladder and then forward onto
the anterior abdominal wall.
Note that the outline of
the empty bladder is not
easily seen. Note also that
the peritoneum runs from
the superior surface of the
bladder to the lateral
walls of the pelvis.
Vas deferens and seminal
vesicle. Identify the vas
deferens at the deep inguinal
ring and follow its course to
the posterior surface of the
bladder. Its course may be
traced by palpating it through
the peritoneum.
If this is found to be
imposible due to hardening of
the tissues, carefully dissect
off the peritoneal covering.
Attempt to identify the upper
ends of the seminal vesicles on
the posterior surface of the
bladder by palpation through
the peritoneum.
Dissection of Left
Half of Male
Pelvis
Prostate.
The Prostate rests on the
superior surface of the
urogenital diaphragm and lies
immediately beneath the neck
of the bladder. It is related
on each side to the anterior
fibers of the levator ani
muscles. Identify the
following features:
1. The prostatic part of the
urethra. This is the widest
and most easily dilatable part
of the male urethra. Note that
it is continuous above with
the cavity of the bladder and
below with the membranous part
of the urethra.
2. The urethra crest is a
longitudinal elevation on the
posterior wall of the
prostatic urethra.
3. The prostatic sinuses are
grooves on either side of the
urethral crest.
4. The prostatic utricle is a
small diverticulum opening into
the prostatic urethra at the
summit of the urethral crest.
5. The ejaculatory ducts pierce
the upper part of the posterior
surface of the prostate to open
into the prostatic urethra at
the lateral margins of the
orifice of the prostatic
utricle.