Download ANATOMY (7). INTRODUCTION TO THE PELVIS. MOHAMMAD

ANATOMY (7).
INTRODUCTION TO THE PELVIS.
MOHAMMAD ALLOUH.
BNB
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Introduction to the Pelvis:
Pelvic Wall & Pelvic Cavity
pelvis (L, basin, sink ), is The region of the trunk that lies
inferoposterior to abdomen & its cavity is continuous above with
the abdominal cavity (abdominopelvic cavity).
# physiological functions :
1- Bears the weight of upper body when
standing or sitting on a chair ( because your body
will be on a slope, so the whole weight of the body will not be
on the lower limbs , it will be resting on the pelvis
).
Why we said it’s located
inferioposterior to the abdomen:
if you go through the thoracic
cavity, abdominal cavity, and
pelvic cavity  you see its tilted
backward a little bit, so it’s not on
the same side as the thoracic
and abdominal cavities .
2- Transmits weight from axial skeleton To
lower appendicular skeleton During standing & walking.
3- Protects & supports pelvic viscera (i.e: Urinary Bladder, urethra,
lower part of the ureter & internal. reprod. Organs: ovaries and uterus
in female, seminal vesicles & prostate gland in males).
4- (imp) Provides attachments for muscles of:
. locomotion (that produce the movement as you walk mainly the
major flexors of the hip the iliopsoas that is attached to the iliac fossa,
and extensors of the hip the gluteus attached to the iliac bone).
. & posture (muscles of trunk)  ext.oblique, int.oblique, transversus
abdominis ).
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the pelvis just like the thorax and the abdomen is made up of
A WALL & A CAVITY .
The human body wall is made up of 4 imp
However, the main specialty in this
structures:
type of walls is that it’s mainly made
skin, fascia (superficial & deep), muscles
by bones  PELVIC GIRDLE
and bones.
You see specialty of one of these
and some muscle & some fascia &
structures in each area you move, for ex:
skin.
Pelvic Wall:
In the ABDOMEN the majority of its wall is
made up by muscles and fascia .
In the THORAX  muscles and bones.
In the PELVIS  mainly by bones.
1- Pelvic girdle (bony pelvis) made up of:
.TWO HIP BONES,(anterolateral), each one is made of 3 bones:
The V-shaped one is PUPIS.
The L-shaped one is ISCHIAM.
The largest one with a wing is  ILIUM.
. SACRUM & COCCYX (the tail bone), which
are the two bones of the vertebral column posteriorly.
2- Pelvic Muscles (inferolat. Wall), they
are imp in forming the floor of the pelvic cavity
(the inferior wall of the pelvis), and some of the
posterior & lateral wall.
*P.S: the bones will be located all around
anterior, lateral and posterior wall,
while the inferior wall is mostly made of
muscles.
3- Pelvic Fascia & Ligaments
the deep fascia covering over the muscles (tough membranous fascia) the fascia will
take the name of the muscle it covers.
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Pelvic cavity, divided into two areas, the greater and the lesser pelvis:
1- the greater (false) pelvis
2- the lesser (true) pelvis
.the upper funnel-shaped area
.called false because it’s a misnomer
.it’s actually the lower part of the
. the lower part (the inside part).
abdominal cavity
.locatedbetween the two iliac wings
within the iliac fossa.
However it’s not part of the pelvic
cavity
The light upper green area, that’s wedged in btw
the 2 iliac wings
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. smaller
# The real pelvic area that
contains the pelvic viscera
(UB, ureter, uterus …)
#clinically  has a major
obstetrical & gynecological
Significance.
the darker lower green area,
P.S: how to distinguish btw the false & the true
pelvis?!
By a bony landmark  the
pelvic brim.(the red
dashed line).
above the pelvic brim  the false pelvis.
below the pelvic brim  the true pelvis.
PELVIC BRIM:
A bony edge (rim) that surrounds & define the PELVIC INLET (entrance to
pelvis) and separates False from True pelvis. (Pelvic brim = pelvic inlet).
Formed by:
posteriorly  Promontory & ala of sacrum .
anteriorly Upper edge of symphysis pubis.
laterally  linea terminalis/iliopectineal line.
iliopectineal line is made of 2 lines:
(plz chick the pic in colors)
1- Arcuate line of ilium:
that separate the body of the ilium
from the wing of the ilium
posteriolateral side of pelvic brim.
2- Pectineal line of the pubis:
sup. Border of sup. Ramus & body
of pubis.
anteriolateral side of pelvic brim.
# it’s the line where the pectineal
ligament of cooper is attached.
# Also it’s an attachment site
for  pectineus muscle (‫)المشطية‬
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Promontory means: the prominent part
anteriorly of the upper margin of the first
sacral vertebrae.
Once you entered through the 1st sacral
vert. now you are in the true pelvis.
At the level of L5  the false pelvis
(abdominal cavity).
How does the pectineal ligament
form over the pectineal line?
The inguinal ligament as it goes
from anterior superior iliac spine
 all the way to the pubic tubercle,
at the pubic tubercle, some of its
fibers that reflected will separate
again, and flatten to give the
lacunar ligament.
The lacunar ligament has a very sharp medial edge, that forms the medial
border of femoral canal.
Some of the fibers of the lacunar ligament will extend over the upper margin of the
pubic bone (the superior pubic ramus), these fibers as they attach to the bone, they
will form a linear elevation now it’s called the pectineal ligament of cooper.
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The greater (false) pelvis:
the lesser (true) pelvis:
#Lower part of abdominal cavity that
funnels in at its lower end to form the
True pelvis.
It has an inlet, outlet &
cavity: (plz chick the pic below)
1- Pelvic inlet
bounded by the pelvic brim.
# BOUNDARIES:
posteriorly  the lumbar vertebrae
( mainly L5 & part of L4).
laterally  iliac fossae & iliacus muscle.
Anteriorly  the hypogastric region of the
anterior abdominal wall.
# CONTENTS:
lower abdominal viscera (ilium & colon).
2- pelvic outlet
ant lower boarder of pubic arch
Latischial tuberosity &
Sacrotubular.lig
posttip of the coccyx
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Pelvic outlet (cont):
some books refer to the
sacrospinal ligament &
sacrotubular ligament as
part of the pelvic outlet.
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If you want to draw the exact areas of
pelvic outlet start from:
tip of the coccyxto the ischial
tuberosity (laterally) then anteriorly
to the lower margin of pub,sym .
plz chick the pic again :”)
this area in the pic (bounded by the red line) is the area of the true pelvis
“ look, I’m not gonna say it’s the pelvic cavity now ,
it is the area of the true pelvis, this
is the space within the true pelvis,
remember this “ the doctor said .
#the space of the true pelvis:
Ant  very shallow, demarcated by
(upper & lower) borders of
pubic symphysis.
Post  widen and deepen more &
more to become the sacrum
and the coccyx.
Shallow  anteriorly
Deep  posteriorly
#clinical relations: (chick the pic above plz)
usually in clinics, the obstetrician, when
they ask you to determine the borders of pelvis you just draw a line to simplify 
first:
a line from the promontory of the sacrum  to the upper margin of pubic
symphysis, that is :
(the PELVIC INLET = the upper border of the true pelvis)
Second:
a line from tip of the coccyx  to lower border of pubic symphysis , that’s called:
( the PELVIC OUTLET = the lower border of the true pelvis ).
Third:
draw a curve line from midpoint of the pelvic inlet  to the midpoint of the pelvic
outlet, this curved line is called: (imp) (chick the pic in the following pg)
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(THE AXIS OF THE PELVIS ), it’s very imp in obstetrics because, this is the
bath that the child will take as it descends through the true pelvis during delivery.
Another imp line is :
the DIAGONAL CONJUCATE line:
(diagonal means oblique)
#from the promontory of the sacrum to
the lower margin of the pub.sym.
#it’s around (5-inch/ 12-13cm)
# during the vaginal examination
(in pregnancy), when you insert your
fingers with your thump attached to
the pubic symphysis , your index finger
should not reach the promontory of the
sacrum.
#If the diagonal conjugate was much shorter
so you can palpate the promontory of the
sacrum, this indicates that the true pelvis
is narrow(contracted), this will lead to problems during
delivery or labor, and by this the obstetrician may indicate cesarean section.
So 2 important clinical landmarks: (remember them)
1- The axis of the pelvis.
2- The diagonal conjugate.
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 The shape of the space of the true pelvis:
4 diff shapes :
1. Gynecoid (like female):
# Typical female pelvis
#around half of females (41%) of females.
# It’s more wide laterally, than the anteriopost.
dimension.
2. Android (has nth to do with the shape of gynacoid):
# Typical male pelvis.
#funnel-shaped & contracted outlet.
#more common in white females.
at transverse view looks heart-shaped
at vertical (ant)veiw  looks like a funnel
3. Anthropoid
#long narrow oval shaped pelvis
#more common in black women
# more wide in anteriopost dimension.
4. Platypelloid
(platy=plade, pelloid=like a pillow).
#wide flattened pelvis.
# v.rare less than 2% of women.
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In 1933 the two physician
( Caldwell and moloy) indicated the
shapes of the true pelvis, into 4 diff
shapes.
Clinically imp  because they
determine the nature of delivery .
--------------------------Gynecoid means like gynae (female)
that’s why we call it gynecology
) ‫(علم النسائية‬
 Review, the bony pelvis or pelvic girdle it’s composed of 4 bones:
 2 hip bones
 sacrum
 coccyx
we have 4 joints:
1) Anteriorly: which demarcating the border of the true pelvis, which is the
symphysis pubis (or pubic symphysis).
 Pubic symphysis is a secondary cartilaginous joint; it is a cartilaginous
because there is a fibro
cartilaginous disc
between the 2 pubic
bones.

This is a secondary
cartilaginous joint
between the 2 pubic bone
anteriorly.
(inside the circle)
 Why it is secondary not primary cartilaginous?
 The joint is 3 types:
1- Bone to bone with some collagen fibers, we call it fibrous.
2- Bone –cartilage- bone, we call it cartilaginous (this joint is 2 types):
A. Primary with no movement, like (xiphisternal joint).
B. Secondary with limited movement, like (sternal angle).
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So,
 The pubic bones can move or they can a little bit spread from each other especially
during delivery.
 the ligaments and the joints are very important because they provide a
mechanism of expansion during delivery  then the joints will get back togather
again like spring ) ‫(مثل الزنبرك‬, so it’s a secondary cartilaginous not primary.
3- bone - space - bone, called synovial joint free range of movement (the types
of the synovial joint regarding to the surfaces : saddle shape, gliding joint.. )
2) Posteriorly: sacroiliac joint
(right & left) important joint in
expansion.
 it is a compound joint (2 joints):
1. Anteriorly : synovial joint, between
iliac bone and sacrum, we call it the
auricular surfaces like auricle ,but
this auricular is rough ) ‫)خشن‬, so its
covered by articular cartilage that
make smoothness .
2. Posteriorly: fibrous (sendesmosis).
 The fibrous have 2 types:
1- Fixed (suture).
2- Movable, the one that allow limited movement, called syndesmosis. so its
combined joint.
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3) Posteroinferior: The sacro-coccygeal joint. 
something special about the bony girdle :
in a LATERAL VIEW  you
will see it’s tilted forward
this tilting will make the:
ant. surface  facing ant.inf .
post. Surface  become post.sup .
That’s why when you look at the 2nd pic
you will see that the pelvis as it tilts, it will
go a little bit post. ; (that’s why the pelvic
cavity is not in the same axis with the abd
cavity, it’s a little bit inf.post).
This tilting will allow the ant.sup iliac
spine to be in the same vertical plate with
the upper margin of pubic symphysis.
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Anterior pelvic wall:
#The shallowest
#tilted forward
#bears the weight of the visceral organs
that lies on it (specially urinary bladder).
#Formed by:
1-pubic bones (body & rami).
2- Symphysis pubis.
#Bears the weight of urinary bladder.
# The only separation btw the urinary bladder and the pubic bones is retropubic
fat.
(imp) So clinically  any fracture or damage to the pubic bone or diastasis of the
pubic sym (separation)  that will lead most commonly to injury in the urinary
bladder.
so ant pelvic wall  pubic bone & pubis sym.
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posterior pelvic wall:
sacrum & coccyx & (imp) Piriformis muscle & fascia(piriformis facscia).
Sacrum (sacred bone):
Single wedge-shaped bone with forward concavity
that formed by fusion of the 5 sacral vertebrae.
-wider and less curved in female
Coccyx (bird beak):
Small triangular-shaped bone that formed by fusion
of the 4 coccygeal Vertebrae.
Piriformis (L, pear shaped)
Origin: ant. surface of Sacrum, lat. To the sacral foramina.
Passage: lat. through the greater sciatic foramen into the Gluteal Region
so it goes from the true pelvis to the buttock region.
Insertion: upper border of greater trochanter of femur.
Action: lat. rotation of femur(thigh) at the hip joint.
*it’s an imp Landmark muscle of gluteal region:
it separates the gtuteal reg. into superior and inferior
compartments.
So,
 Anterior pelvic wall are  pubic symphysis & pubic bone.
 Posterior pelvic wall are  sacrum, coccyx and piriformis.
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Now,
 Lateral pelvic wall :
o Made of bony landmark, mostly part of the sacral and part of the ilium.
o Along with these landmarks, Sacro-tuberous and sacrospinous ligaments are seen.
o Obturator foramen covered by obturator membrane  and it covers all the
foramen except the superior par, called obturator canal (it allows the passage of
veins, arteries and nerves).
o Lateral wall formed of ischium, ilium bony component  along with them the
obturator internus muscle and the fascia covering it.
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 Obturator internus muscle :
o Originates from the inner surface of the obturator membrane and the bony
margins of obturator foramen. Imp
o It is a large muscle, form the most of the lateral wall of true pelvis.
o From the origin point, it will move backward and converge (like triangle and it
well give a small tendon)
 This tendon will leave the pelvis through lesser sciatic foramen
 Then it will turn at right angle laterally and
move to obturator region (so it will move
vertically and the tendon goes laterally)
 Then the tendon will accompanied with
gemellus muscles into the medial border or
surface of greater trochanter of the femur.
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So, this muscle is separated into
upper and lower part by a
thickening of the fascia covering
it, coming from the pubic body
to the ischial spine, this is called
the tendinous arch
In this picture you can see the greater
sciatic foramen separated from greater
sciatic foramen by
sacrospinous ligament.
You can see also the twin muscle
( the gemellus muscle)
o Its action  lateral rotation of the thigh.
o Innervation: nerve to obturator internus muscle (L5, S1), it also supply the
gemellus muscle.
o It's covered by obturator fascia if you draw a line from the pubic body all the
way until the area of ischial spine you will see the obturator fascia there,( is
thickened), here it's called tendinous arch obturator fascia.
 Very important to know that this tendinous arch will form the attachment
for the muscle that will form the inferior pelvic wall.
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 inferior pelvic wall (pelvic floor) :
o We refer it as pelvic diaphragm. ( all of them has the same meaning )
The fascia in green color that extend from
the pubic to ischial spine is thickened and
will become the tendinous arch of
obturator fascia that will allow the
attachment of levator ani muscle.
- you can see here the superior part
(upper part) of obturator internus ( the
star).
- between the upper and lower part of
obturator internus the inferior pelvic
wall hold them.
in this part
o It formed by 2 muscles, the important one called levator ani muscle (elevate the
anus) the other one from the back called coccygeus muscle (ischiococcygeus,
it come from ischial spine  go to the sacrum and coccyx mainly).
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o Levator ani will attach to the tendinous arch of obturator fascia and it will
separate the true pelvis into 2 cavities:
1. The main pelvic cavity (superior or above).
2. The perineum (below).
o Pelvic diaphragm is very important because the tone of these muscles will carry
all the contents of abdomen and pelvic cavity especially during downward
pressure of inspiration.
 coccygeus muscle :
o Its action  help in flexing the coccyx  so there is a movement between
sacrum and coccyx.
LEVATRO
ANI
Coccygeus
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 Levator ani :
o Divided into 3 main part :
1. Anterior part : are slips of muscles.
 these slips will go around the vagina forming a sphincter in female, called
pubovaginalis or sphincter vaginae.
 and around prostate in male, called puboprostetae or levator prostatae .
 Very important, the is a gap or space anterior the
levator ani allowing communication between the
pelvic cavity and perineum called UROGENITAL
HIATUS  allowing of the passage of urethra and
vagina.
DSOME BOOKS LIKE SNELL,
DON'T TALK ABOUT THE
OTHER PARTS, HE JUST TALK
ABOUT THE ANTERIOR PART
ONLY CONSIDER IT AS THE
MAIN PART.
2. Middle part: from pubic bone to the coccyx called pubococcygeus
In addition, it has another part called puborectalis (doctor didn't mention it
but it's in slides)
3. Posterior part: from ilium to
coccyx called iliococcygeus.
Here you can see the slips of muscle.
o In levator ani there are 2 masses of fibers :
 Anterior the anal canal called perineum
body.
 Posteriorly called anococcygeus body.
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