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The Pelvis

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The pelvis is the region of

the trunk that lies below the

abdomen; the abdominal andpelvic cavities are

continuous.

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Surface AnatomyIliac Crest; Anterior SuperiorIliac Spine; Posterior

Superior Iliac Spine; Tubercleof Iliac Crest; Pubic Tubercle;Pubic Symphysis; Pubic Crest;

Spinous Processes Sacrum;Sacral Hiatus; Coccyx.

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Preliminary

Dissection of Maleor female Pelvis

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Examine again the division ofthe lower part of the abdominal

aorta in front of the fourthlumbar vertebra into two common

iliac arteries. Follow thecommon iliac arteries to theirtermination in front of thesacroiliac joints. Trace theexternal iliac artery along thepelvic brim to the inguinalligament.

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Identify the inferior

epigastric and deep circumflexiliac branches. Clean theorigin of the internal iliacartery and follow it down intothe pelvis, where it ends nearthe upper margin of thegreater sciatic foramen by

bifurcating into anterior andposterior divisions. Identifythe median sacral artery.

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Expose and clean the

external, internal andcommon iliac veins.

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Identify and clean theright and left ureters as

they enter the pelvis infront of the bifurcation

of the common iliacarteries.

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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.

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Examine again the lower ends of

the lumbar sympathetic trunks

and ganglia. Demonstrate the

continuity of the trunks with

those in the pelvis.

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Trace the hypogastric plexus

over the sacral promontory,but

do not disturb it within the

pelvis at this time.

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Trace the testicular arteries

to the deep inguinal rings, or

the ovarian arteries to the

pelvic brim.

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Examine again the pelviccolon and identify the

pelvic mesocolon. Follow the

superior rectal artery to

the pelvic inlet and to the

posterior surface of therectum.

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Examine again the femoral

nerve and the lateral femoralcutaneous nerve. Trace thefemoral nerve as it emerges

from the lateral border ofthe psoas muscle, downward andlaterally in the groove

between the psoas and theiliacus.

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Note that it lies under the

cover of the fascia iliaca andpasses behind the inguinalligament to enter the thigh

lateral to the femoral artery.Follow the lateral cutaneousnerve of the thigh across the

iliacus muscle and verify thatit enters the thigh behind thelateral end of the inguinalligament.

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Dissection of

intact FemalPelvis

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Peritoneum. Examine the

peritoneum and trace it downthe anterior and lateralsurfaces of the rectum. Follow

the peritoneal reflection fromthe rectum onto the upper partof the posterior surface ofthe vagina, which forms therectouterine pouch (pouch of

Douglas).

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The peritoneal recess on each

side of the rectum is

referred to as the pararectal

fossa. Note that thepararectal fossa and the

rectouterine pouch arecontinuous with one another.

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Trace the peritoneum over the

posterior surface of theuterus, over the fundus, and

down over the anterior surface

of the uterus. It then passes

onto the posterior surface of

the bladder for a shortdistance, thus forming the

uterovesical pouch.

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Trace the peritoneum over theupper surface of the bladderand then forward onto theanterior abdominal wall. Note

that the outline of the emptybladder is not easily seen.Note also that the peritoneum

runs from the superiorsurface of the bladder to thelateral walls of the pelvis.

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Observe that the normal uterusis bent forward so that its

anterior surface faces forwardand inferiorly and overhangs

the bladder (anteverted andanteflexed).

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Note that the peritoneumalmost completely covers theuterus and extends laterallyon each side of the uterusas a two-layered fold of

peritoneum to the side wallof pelvis. This fold isknown as the broad ligament.

Identify in the broadligament the followingstructures:

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1.The uterine tube. This liesin the free border of thebroad ligament.It opens intothe peritoneal cavity by means

of its funnel-shaped lateralextremity, the infundibulum.The free edge of the funnel isbroken up into a number offinger-like processes known asthe fimbriae,which are drapedover the ovary.

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3. The mesosalpinx is that

portion of the broad

ligament which lies between

the mesovarium and the

uterine tube.

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4. The suspensory ligament ofthe ovary is that part of the

broad ligament which lieslateral to attachment of the

mesovarium; it contains theovarian vessels and nerves.

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5. The round ligament of the

ovary produces a ridge of

peritoneum on the posterior

surface of the broad

ligament.

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6. The round ligament of theuterus produces a ridge of

peritoneum on the anteriorsurface of the broad ligament

that can be trace from the

lateral edge of the uterus to

the deep inguinal ring.

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Dissection of the Left

Half of the Femal Pelvis

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With the fingers, carefully

mobilize the rectum from

the anterior surface of the

sacrum. Dissect off theperitoneum and pelvic

fascia from the posterior

and lateral wall of the

pelvis.

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Clean the rectum and observethat the lower third iscompletely devoid of peritoneum,since it lies below the lowestpart of the rectouterine pouch.Note that the rectum expandsjust above the pelvic floor toform the ampulla of the rectum.

Once the rectum passes throughthe pelvic floor, it becomesthe anal canal.

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Follow the superior rectalartery downward along the

posterior surface of the rectum.Note that it divides into twobranches that pass down on

either side of the rectum andanastomose with the right andleft middle rectal arteries,which are branches of theinternal iliac artery.

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Identify the hypogastric and

the left pelvic plexuses. Thehypogastric plexus descendsinto the pelvis and divides

into right and left pelvicplexuses. The fine nervethreads of the pelvic plexus

will be found in the fasciasurrounding the internal iliacartery.

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Trace the pelvic part of the

sympathetic trunk inferiorly.

Note that above and

posterior to the commoniliac vessels it is

continuous with the

abdominal part of the trunk.

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Below it descends posterior to

the rectum and medial to theanterior sacral foramina. Ithas four or five segmentally

arranged ganglia. The trunksend below by uniting in themidline anterior to the coccyx

in the ganglia impar. Identifybut do not disturb the sacralplexus.

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Ureter. Identify and clean

the left ureter. Verify thatit enters the pelvis bycrossing the bifurcation of

the common iliac artery infront of the sacroiliacjoint. It runs downward and

backward in front of theinternal iliac artery andbehind the ovary.

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Follow the ureter to theregion of the ischial spineand trace it forward, beneaththe base of the broadligament. Note that the

ureter is crossed superiorlyfrom lateral to medially bythe left uterine artery atthis point. Note also that

the ureter lies lateral tothe cervix and the leftlateral fornix of the vagina.

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Now trace the ureter

forward across the pelvicfloor to the bladder. Insert

a fine probe into the

ureteric orifice within the

bladder and verify its

oblique course through thebladder wall.

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Internal Iliac

Artery.

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Clean and study the internaliliac artery and its branches.Note that it arises from thecommon iliac artery and passesdown into the pelvis medial tothe external iliac vein andanterior to the internal iliac

vein. The main branches arevisceral and parietal and areas follows:

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Visceral Branches

1. The umbilical artery

gives origin to the superior

vesical artery. Theobliterated remnant then

ascends to the umbilicus as

the lateral umbilical

ligament.

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2. The inferior vesicalartery runs forward to the

base of the bladder, which

it supplies and in addition

gives branches to the

ureter.

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3. The middle rectal artery

passes medially to therectum.

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ParietalBranches1.The iliolumbar artery runs

upward and laterally, deep to

the common iliac vessels, andterminates by supplying the

iliacus, psoas, and quadratuslumborum muscles.

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2. The lateral sacral artery

or arteries ( there are

usually two ) pass medially to

descend in front of the

anterior sacral foramina.

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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.

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4.The internal pudendal

artery leaves the pelvisbetween the piriformis and

coccygeus muscles, through

the lower part of the greater

sciatic foramen. It will be

dissected in the glutealregion and again in the

perineum.

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5. The superior gluteal artery

is the largest branch of theinternal iliac artery. It runs

posteriorly between the

lumbosacral trunk and the first

sacral ramus, passing out of

the pelvis through the greatersciatic foramen above the

piriformis.

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6. The inferior gluteal

artery runs inferiorlybetween the anterior ramin of

the first and second sacral

nerves and leaves the pelvisby passing through the lower

part of the greater sciaticforamen below the piriformis

muscle.

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It must be emphasized

that the origin of these

arteries from the parent

trunk is subject to

considerable variation.

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Pelvic veins.The main venous drainage of

the pelvis is through the

internal iliac veins ( otherveins are the superior rectal,

ovarain, median sacral, and

the internal vertebral venous

plexus ).

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The veins of the pelvis are

large and thin-walled, andthey freely communicate. They

are difficult to dissect and

should be removed, since they

obscure other structures.

Remove them piecemeal withforceps and scissors.

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Sacral Plexus

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Expose and clean thelumbosacral trunk and each ofthe five sacral anterior rami.

Trace them inferiorly on thepiriformis muscle, where theyform the sacral plexus.

Identify and clean thefollowing main terminalbranches of the sacral plexus:

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1. Sciatic nerve.

This is the largest nerve

in the body, and it is

easily recognized. Itleaves the pelvis through

the lower part of thegreater sciatic foramen.

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2. Pudendal nerve.

This leaves the pelvis

through the lower part of

the greater sciatic foramenand enters the perineum

through the lesser sciaticforamen.

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3. Nerve to quadratus femoris.

4. nerve to obturator internus.5. Superior gluteal nerve.6. Inferior gluteal nerve.

7. Posterior femoral cutaneousnerve (posterior cutaneousnerve).

8. Preforating cutaneous nerve.9. Perineal branch of thefourth sacral nerve.

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Clean the piriformis muscle

and probe the greater and

lesser sciatic foramina.

Understand that there is alarge amount of fatty

areolar tissue between the

peritoneum and the fascia

lining the pelvic walls.

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BladderNote that, as in the male, theurinary bladder is situated

immediately behind the pubicbones. Because of the absenceof the prostate, the bladderlies at a lower level than inthe male pelvis, and the neckrests directly on the uppersurface of the urogenitaldiaphragm.

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The apex of the bladder iscontinuous with a fibrous

cord known as the urachusthat passes upward in theextraperitoneal fat to theumbilicus, forming the medianumbilical ligament. The baseor posterior surface of thebladder is triangular in

shape. The superolateralangles are joined by theureters, and the inferiorangle rise to the urethra.

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Ovary.Each ovary is a small ovalbody attached to the back of

the broad ligament by themesovarium. The ovary lies

close to the lateral wall of

the pelvis in a slightdepression called the ovarian

fossa.

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The fossa is bounded by theexternal iliac vessels above

and by the internal iliacvessels and the ureter behind.The obturator nerve crosses the

floor of the fossa. In a youngwoman, the surface of the ovaryis relatively smooth, and you

should look at it carefully forthe possibility of finging amature follicle or a corpus

luteum.

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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.

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Carefully examine the ovary

for the following features:

1. The mesovarium is a two-

layered fold of peritoneum

connecting the ovary to the

broad ligament.

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2. The suspensory ligament of

the ovary is that part of thebroad 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.

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3. The round ligament of

the ovary extends from the

upper end of the lateral

wall of the uterus to themedial margin of the ovary,

between the layers of the

broad ligament.

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Uterus.The uterus is divided up

into the fundus, body, and

cervix. Examine the

different parts:

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1.The fundus is the part of

the uterus that lies above theentrance 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 itbecomes continuous with the

cervix.

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3. The cervis pierces theanterior wall of the vagina

and is divided into thesupravaginal and vaginal

parts of the cervix.

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Note that the broad ligament isattached to the lateral margins

of the uterus. Identify thecavity of the uterus and notethat it is slitlike. Note the

relation of the cervix to thevagina. Identify the anterior,posterior, and lateral fornices

of the vagina. Relate thecervix and upper part of thevagina to the pelvic diaphragm.

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Uterine Tube.Examine the uterine tube asit lies in the upper free

border of the broad ligament.Incise the uterine tube

longitudinally with a pair of

scissors and inspect thefollowing parts:

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1.Infundibulum.This is the funnel-shaped

lateral extremity that

overlies the ovary and opensinto the peritoneal cavity.

The free edge is broken up

into a number of finger-like

processes known as fimbriae.

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2. Ampulla.

This is the widest part ofthe tube.

3. Isthmus.

This is the narrowest part of

the tube, and it lies just

lateral to the uterus.

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4. Interstitial part.

This is the segment thatpierces the uterine wall.

With a probe, trace thechannel from the peritoneal

cavity, through the uterine

tube, uterine cavity, andcervical canal, to the vagina.

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RectumNote that the rectum measures

about 13 cm long and begins infront of the third sacralvertebra as a continuation of

the pelvic colon. It followsthe curve of the sacrum andends 2.5 cm anterior to thetip of the coccyx by piercing

the pelvic diaphragm andbecoming continuous with theanal canal.

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Observe the following

features after cleaning outthe rectal contents with

moist cheesecloth:

1. The rectal ampulla is the

dilated lower end of the

rectum immediately above thepelvic diaphragm.

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2. The transverse folds of therectum are three semicircular

mucosal folds; two are placedon the left rectal wall and oneon the right wall.3. The peritoneum covers theanterior and lateral surfaces

of the first third of therectum but only the anterior

surface of the middle third,leaving the lower third devoidof peritoneum.

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Dissection ofIntact Male Pelvis

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The peritoneal recess on eachside of the rectum is referedto as the pararectal fossa.Note that the pararectal

fossae and the rectovesicalpouch are continuous with oneanother. Trace the peritoneum

over the upper surface of thebladder and then forward ontothe anterior abdominal wall.

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Note that the outline of

the empty bladder is not

easily seen. Note also that

the peritoneum runs fromthe superior surface of the

bladder to the lateralwalls of the pelvis.

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Vas deferens and seminal

vesicle. Identify the vas

deferens at the deep inguinal

ring and follow its course tothe posterior surface of the

bladder. Its course may be

traced by palpating it through

the peritoneum.

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Dissection of Left

Half of MalePelvis

P t t

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Prostate.

The Prostate rests on thesuperior surface of theurogenital diaphragm and lies

immediately beneath the neckof the bladder. It is relatedon each side to the anterior

fibers of the levator animuscles. Identify thefollowing features:

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1. The prostatic part of the

urethra. This is the widestand most easily dilatable part

of the male urethra.Note thatit is continuous above with

the cavity of the bladder and

below with the membranous partof the urethra.

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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

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4. The prostatic utricle is asmall diverticulum opening into

the prostatic urethra at thesummit of the urethral crest.5. The ejaculatory ducts pierce

the upper part of the posteriorsurface of the prostate to openinto the prostatic urethra at

the lateral margins of theorifice of the prostaticutricle.

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