for most people, the bony pelvis is very difficult to

8/14/2019 For Most People, The Bony Pelvis is Very Difficult To

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Pelvis

For most people, the bony pelvis is very difficult to visualize three-dimensionally. Even artists have a difficult time getting it right. For thisreason, it becomes important for anatomy students to spend some timeidentifying and memorizing the various parts of the pelvis before learningabout the contents. In knowing the bony pelvis well, you will be moreconfident in visualizing how structures enter and leave the pelvis and howmuscles of the pelvic floor are attached. You should look at the pelvisfrom all possible aspects.

The hip bone is originally made up of three bones that have fused:

1)ilium, 2)ischium and 3)pubis. These come together at the acetabulum.

Bony Pelvis

From the superior view ofthe pelvis, you should beable to identify thefollowing:

1. iliac crest

2. anterior superior iliac

spine3. anterior inferior iliac

spine

4. acetabulum

5. obturator foramen

6. ischiopubic ramus

7. pubic tubercle

8. pectineal line of the

pubis9. pubic crest

10.pubic symphysis

11.pelvic brim(separates the truefrom the false pelvis)

12.iliac fossa

13.sacral promontory

14.sacrum

anterior sacral


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foramen

ala of sacrum

15.coccyx

16.ischial spine

The pelvic brim extends from promontory of the sacrum, arcuate line ofthe ilium, pectineal line (pectin of pubis) and pubic crest. Some peopledivide the pelvis into a greater (or false) pelvis and lesser (or true) pelvis.They are separated by using the pelvic brim as the limiting line. Thegreater pelvis is located above the pelvic brim and the lesser pelvis belowthe brim.

No muscle crosses the pelvic brim. If they did, they would be in the way

during childbirth.

Turn the pelvis over andidentify the structures onthe back:

1. sacrum

posterior

sacral foramen

2. coccyx

3. posterior superioriliac spine

4. iliac crest

5. anterior superioriliac spine

6. tubercle of the crest

7. ischial tuberosity

8. acetabulum

9. ischiopubic ramus

10.pubic symphysis

11.obturator foramen

12.ischial spine

13.greater sciatic notch

14.lesser sciatic notch


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From the lateral view,identify the:

1. sacrum

2. posterior superior

iliac spine

3. iliac crest

4. tubercle of the crest

5. anterior superior

iliac spine

6. anterior inferior iliacspine

7. pubic tubercle

8. inferior pubic ramus9. superior pubic

ramus

10.ischial tuberosity

11.greater sciatic notch

12.ischial spine

13.lesser sciatic notch

14.obturator foramen

(not labeled)In this image, the pelvis isshown as it would be inthe erect posture. Theanterior superior iliacspine and pubic tubercleare in the same verticalplane.Looking at the pelvis fromthe inside, you should be

able to identify thefollowing items:

1. anterior superioriliac spine

2. anterior inferior iliacspine

3. pectineal line ofpubis

4. pubic tubercle

5. pubic symphysis


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6. obturator foramen

7. ischial tuberosity

8. lesser sciatic notch

9. ischial spine10.greater sciatic notch

11.articulation ofsacrum

12.posterior superioriliac spine

13.iliac fossa

14.pelvic brim - not

labeled

Ligaments of the Pelvis

Strong ligaments arenecessary to hold thehip bone to thesacrum. These arefound anteriorly andposteriorly. Anteriorly,you can identify theanterior sacroiliacligaments.

Posteriorly, there areeven strongerligaments:

sacrotuberous

sacrospinous

posteriorsacroiliac

The fifth lumbarvertebra also has astrong tie-in with theilium through theiliolumbar ligament.


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The sacrotuberous and sacrospinous ligamentscomplete the greater and lesser sciatic foraminae.

View of Pelvic Structures on Sagittal Section

The best way to get a good idea of how the structures of the male andfemale pelvis are arranged is to view them on a sagittal section. That wayyou can see the way the different midline structures relate to oneanother.

Male Pelvis


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symphysis andrepresents the pelvicoutlet. Below this line isthe region called theperineum. Between thetwo lines is the true (orlesser) pelvis. This is thearea we are interested infor now.

Female Pelvis

In the sagittal sectionof the female pelvis,identify the followingitems, staring again

from the front:

pubic symphysis

retropubic space

urinary bladder

urethra

uterus

vagina

rectouterinepouch of Douglas

rectum

presacral space

Again the pelvic inletand outlet isrepresented as twolines. You can see

exactly what structuresare within the lesserpelvis. Again, they aremidline structures.Since, in both male andfemale, the organs arecentrally located, thatmeans that their bloodand/or nerve supplymust come in from

laterally or posteriorlyand we will find this to


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be true when weexamine thevasculature of thepelvis. We will alsonote that most of themuscles found in thepelvis lie laterally.

These midlinestructures aresupported by amusculature pelvicdiaphragm which wewill discuss in amoment.

Muscles of the Pelvis

Muscles of the female pelvis arethe:

pelvic diaphragm

pubococcygeus

puborectalis

iliococcygeus

coccygeus

piriformis

iliacus

psoas major


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The male pelvic muscles are thesame as the female except thatthere is no vagina to support in themale.Identify the following:

pelvic diaphragm

pubococcygeus

puborectalis

iliococcygeus

coccygeus

piriformis

iliacus

psoas major

The puborectalis is actually a partof the pubococcygeus muscle thatwraps around the posterior aspectof the rectum forming a sling thatholds the rectum forward in thepelvis.

The pubococcygeus and

iliococcygeus muscles make up thelevator ani. The muscles of thelevator ani are importantsupportive muscles for the midlineorgans of the pelvis. Any weaknessin these muscles can cause clinicalproblems of urinary or fecalincontinence.

Arteries of the Pelvis


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With one exception,the arteries of thepelvis are branches ofthe internal iliacartery. The exceptionis the superior rectalartery which is abranch of the inferiormesenteric artery.

Starting posteriorly,the branches of theinternal iliac artery areas follows:

iliolumbar superior gluteal

lateral

sacral

inferior gluteal

internalpudendal

middle rectal

inferior vescical(the uterine inthe female)

obturator

superior vesical

terminal part ofthe internal iliacis occluded andbecomes thelateral umbilical

ligament of thelower anteriorabdominal wall.

Nerves of the Pelvis


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The nerves of the pelvisare derived from the:

1. lumbosacralplexus

2. inferiormesenteric plexus

3. sympathetic chain

The lumbosacral plexusis made up of:

L4

L5

L4 and L5merge toform thelumbosacraltrunk

S1

S2

S3

L4, L5, S1,

S2, S3forms thesciatic nerveand othercombinations form thesuperior andinferiorgluteal

S4

S2, S3, S4

join to formthepudendalnerve thatsuppliesstructures intheperineum.

The inferior mesentericplexus starts out in the


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abdomen at the point oforigin of the inferiormesenteric artery andpasses along the aortato the presacral region.As the plexus drops intothe pelvis, it usuallysplits up into a right andleft hypogastric plexusthat lies behind therectum.

The sacral sympatheticchain is the continuationof the lumbar chain.

The sacral part of theparasympatheticnervous system arisesfrom S2, S3, S4 andsupplies the pelvicstructures as well as theleft colic flexure,descending colon andsigmoid colon.

Urinary bladder

Compare the male andfemale bladders.

Male bladder

This image displays themale urinary bladderopened from the top andfront and defining the:

trigone of thebladder

interureteric fold

opening of the ureter

uvula of the vesical(beginning of theurethra)

urethral crest

seminal

colliculus


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opening of

prostatic utricle

prostatic sinus(opening of

ejaculatory ductsenter here)

membranous urethra

ureter

vas deferens

Female bladder

In the female bladder,identify:

ureter

interureteric fold

opening of theureters

trigone

internal opening ofurethra

vesical sphincter

Prostate Gland

The prostate gland is acone-shaped gland aboutthe size of a chestnut and ismade up of connectivetissue and smooth muscle.Parts of relations of thegland are:

the base is cephaladagainst the neck ofthe bladder

the apex is directedcaudad against theurogenital diaphragm

the posterior surfaceis separated from therectum by the

rectovesical septum


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the anterior surface isseparated from thepubic symphysis bythe the retropubic

space, that is filledwith a venous plexus

the lateral surfacesface the levator aniand a venous plexus

it is made up of 5lobes

two lateral

lobes

anterior lobe -in front of theprostaticurethra

middle lobe -

behind theprostaticurethra andbetween thetwo ejaculatory

ducts

posterior lobe

If the prostate is opened upfrom the front, you canidentify the following:

urethral crest

seminal colliculus - aslightly enlarged partof the urehtral crestwhich open theejaculatory ducts andan embryonicremnant, theprostatic utricle.

prostatic sinus - smallvalleys along side the

crest into which theprostatic ducts open


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Clinical Considerations

1. middle lobe: important clinically because enlargement of themucous glands in this lobe leads to obstruction. Adenomas arefrequent in this lobe and they encroach into the urethra, blockingthe internal urethral orifice.

2. posterior lobe: adenomas are rare; this lobe can be felt on rectalexamination

3. anterior lobe: adenomas are rare; there is not encroachment on theurethra when this lobe enlarges

4. lateral lobe: enlargement of lateral lobes can cause obstruction tothe urethra

Uterus and Broad Ligament


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The uterus is a midlineorgan and is held to thelateral walls of the truepelvis by a double layer ofperitoneum, called the broadligament. The broadligament also encloses theuterine tube in its upper freeborder, the ovarian artery,the round ligament of theuterus, uterine artery,ovary, and the ovarianligament. A betterunderstanding of therelationships to the broad

ligament can be gained ifyou also look at a sectionthrough the broad ligament.In the first image, you arelooking at the posterioraspect of the broad ligamentand the posterior wall of thevagina has been opened up.These items should be foundin relation to the broad

ligament.

uterus

uterine tube (oviduct,Fallopian tube)

fimbriated end

ovarian artery

ovary

ovarian ligament

mesovarium

mesosalpinx

opening of cervix

cervix

vagina

opening of urethra

bladder


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In the section through thebroad ligament payattention to the:

broad ligament

uterine tube - in theupper free margin ofthe broad ligamentand connected to theroot of themesovarium by themesosalpinx

ovary - attached tothe posterior part ofthe broad ligament by

the mesovarium

ovarian ligament - infree margin of themesovarium

anterior layer of thebroad ligament

posterior layer of thebroad ligament

round ligament of theuterus - beneath theanterior layer of thebroad ligament

uterine artery - nearthe root of the broadligament

The ovary is also describedas having a suspensoryligament but this is nothing

more the a fold ofperitoneum near where theovarian artery and veinscross the pelvic brim toenter the true pelvis.

Rectum and Anal Canal


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The rectum andanal canal areclinicallyimportant parts ofthe intestinaltract because, byeither palpationor rectoscope orsigmoidoscope,they can be easilyexamined in aroutine physical.Tumors,hemorrhoids orabscesses are

frequent in thispart of the GItract.

The rectum is thecontinuation ofthe sigmoid colonand at the pointof their junction,the rectum

becomes coveredby peritoneumonly on itsanterior surface,and thereforebecomesretroperitoneal.

The rectumterminates

approximately atthe attachment ofthe levator ani toits borders. Alsoat this point, isthe pectinate linewhich,anatomically, isthe anorectaljunction.

The inside of the


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rectum is throwninto folds calledrectal valves.These maintainthe fecal materialuntil water isremoved and abowel movementoccurs. At thatpoint the rectumelongates and thevalves becomeless prominent.

At the lower end

of the rectum, aseries ofrectalcolumns encirclethe rectum.Between thecolumn are rectalsinuses. Outsideof the columns isfound the internalrectal plexus of

veins. It is herethat internalhemohhroids arefound.

At the junction ofthe rectum andanal canal, thecolumns andsinuses form a

dentate orpectinateappearance. Thisis called thepectinate line andis the startingpoint of the analcanal which isabout 2.5-4.0 cmlong.

The lining of the


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anal canal iscontinuous withthe skin at thewhite line ofHilton (orintersphinctericline). This line canbe felt with thefinger as a smallindentationbetween theinternal analsphincter (circularmuscle of therectal wall) and

the subcutaneousexternal analsphincter. Theexternal analsphincter is muchstronger to thetouch than theinternal. Notethat the externalanal sphincter

consists of threeparts, the deep,superficial andsubcutaneous.

Arteries to the rectum

There are three sources of arterial supply to the rectum and anus:

1. superior rectal artery - from the inferior mesenteric artery

2.

middle rectal arteries - either directly from the internal iliac artery orfrom a common branch with the inferior vesical artery

3. inferior rectal arteries - from the internal pudendal artery.

Veins of the Rectum and Anus

Surrounding the rectum and anus is a very dense rectal plexus of veins.The upper part of the plexus will send tributaries to form the superiorrectal vein which then goes into the inferior mesenteric vein.

From the middle part of the plexus, along with tributaries from the

bladder, prostate and seminal vesicle pass to the internal iliac vein


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From the inferior part of the plexus, drainage is into the internal pudendalvein.

Lymphatic Drainage

From the rectum, lymphatics pass eventually into the inferior mesenteric

group ofpreaortic lymph nodes.

From the anal canal, lymphatics pass along the middle rectal artery to endin the internal iliac nodes and from these to the common iliac nodes andthen to the lateral aortic group of nodes.

From the anus, below the white line of Hilton, the lymphatics join those ofthe perineum and scrotum and pass into the superficial inguinal nodes

Clinical Considerations Internal hemorrhoids are found above the pectinate line and outside

the rectal columns.

external hemorrhoids are below the pectinate line and are the morecommon clinically and can be seen when enlarged.

Both types of hemohhroids can be sources of bleeding whenabraded. This type of bleeding is bright red compared to bleedinghigher up in the GI tract where the blood is occult and must beidentified by chemical tests.

for most people, the bony pelvis is very difficult to

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