8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
1/21
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The hip bone is originally made up of three bones that have fused: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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
2/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
3/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
4/21
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.
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
5/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
6/21
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
7/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
8/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
9/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
10/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
11/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
12/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
13/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
14/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
15/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
16/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
17/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
18/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
19/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
20/21
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
8/14/2019 For Most People, The Bony Pelvis is Very Difficult To
21/21
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.