ANATOMY OF THE
PELVIS
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pelvis
Two hip bones, which form the anterior and lateral walls.
Sacrum and coccyx, which form the posterior wall.
composed These 4 bones are connected by 4 joints and lined by 4 muscles.
of 4 bones The bony pelvis with its joints and muscles form a strong basin-shaped structure (with multiple foramina),
The pelvis contains and protects the lower parts of the alimentary & urinary tracts & internal organs of reproduction
Anteriorly: Posteriolateraly: Posteriorly:
Symphysis pubis (cartilaginous Two Sacroiliac joints. (Synovial Sacrococcygeal joint (cartilaginous)
Joints joint) joins)
The pelvis is divided into two parts by the pelvic brim. Above the brim is the False or greater pelvis, which is part of the abdominal
cavity. Below the brim is the True or lesser pelvis
The False pelvis is bounded by: The True pelvis has:
Posteriorly: Lumbar vertebrae. An Inlet \ An Outlet \ A Cavity
Laterally: Iliac fossae and the iliacus muscle. The cavity is a short, curved canal, with a shallow anterior wall
Anteriorly: Lower part of the anterior abdominal wall. and a deeper posterior wall.
It supports the abdominal contents. It lies between the inlet and the outlet.
Pelvic inlet Pelvic outlet
Anteriorly: Symphysis pubis. Anteriorly: Symphysis pubis.
Posteriorly: Promontory of sacrum, ala of sacrum. Posteriorly : Coccyx,
Laterally: Ileopectineal (arcuate) lines. Anterolaterally: ischiopubic ramus
Posterolaterally: Sacrotuberous ligament,
In female the Sacrum is usually wider and shorter. Also, the Angle of the pubic arch is wider. The promontory and the ischial
spines are less projecting. Information of the shape and dimensions of the female pelvis is of great importance for obstetrics,
because it is the bony canal through which the child passes during birth.
Typical bony pelvis in female : gynecoid
The pelvis has 4 walls:
Anterior, Posterior, Lateral, Inferior or floor.
Pelvic walls The walls are formed by bones and ligaments that are lined with
muscles covered with fascia and parietal peritoneum.
ANTERIOR PELVIC
WALL
It is the shallowest wall and is formed by the posterior surfaces of the bodies
of the pubic bones, the pubic rami, and the symphysis pubis.
POSTERIOR PELVIC
WALL It is large and formed by sacrum, coccyx , piriformis muscles and
their covering of parietal pelvic fascia.
LATERAL PELVIC It is formed by:
WALL 1- Part of the hip bone below the pelvic inlet,
2- Obturator internus and its covering fascia & the obturator fascia.
3- Sacrotuberous ligament.
4- Sacrospinous ligament.
INFERIOR PELVIC WALL, Basin-like structure which supports the pelvic viscera and is formed by the pelvic
OR PELVIC FLOOR diaphragm.
It stretches across the true pelvis and divides it into:
It is formed by the
Main (true) pelvic cavity above, which contains the pelvic viscera, &
levator ani and the
Perineum below which carries the external genital organs .
coccygeus muscles
and their covering It is incomplete anteriorly to allow passage of the urethra in males and urethra and vagina in
fasciae. females.
Muscles
Piriformis Obturator Internus Coccygeus muscle
small triangular muscle.
Origin Pelvic surface of the middle 3 sacral Inner surface of the
vertebrae. obturator membrane and Ischial spine.
It leaves the pelvis through the greater the hip bone.
sciatic foramen.
Insertion It leaves the pelvis
through the lesser sciatic
foramen to be inserted Lower end of sacrum
Greater trochanter of the femur. into the greater and coccyx
trochanter of the femur.
Action Lateral rotator of the femur at the hip Lateral rotator of the Assist the levator ani in
joint. femur at the hip joint supporting the pelvic
viscera
Nerve Sacral plexus . Nerve to obturator branches of the 4th and
supply internus. 5th sacral nerves
LEVATORES ANI MUSCLES
It is a wide thin sheet-like muscle .
*Back of the body of the pubis
Origin *Tendinous arch of the obturator fascia
*Spine of the ischium.
the levator ani is divided into three parts:
Iliococcygeus muscle , Pubococcygeus muscle , Puborectalis muscle
The pubococcygus muscle is then divided into three parts on its own.
*The true pubococcygeus , *puborectalis , *pubovaginalis (female) or puboprostaticus (male) .
originates from the posterior surface of the body of the pubis
descend upon the side of the prostate to unite beneath it with the muscle of the opposite side, joining with the
fibers of the external anal sphincter and transversus perinei, at the central tendinous point of the perineum.
Anterior fibers : inserted into the perineal body (and coccyx).
1.Pubococcygeus. -The anterior portion is occasionally separated from the rest of the muscle by connective tissue.
From this circumstance, as well as from its peculiar relation with the prostate, which it supports as in a sling, it
has been described as a distinct muscle, under the name of levator prostatæ.
In the female the anterior fibers of the levator ani descend upon the side of the vagina (sphincter vagina)
forms a sling around the recto-anal Junction.
The puborectalis They are inserted into the side of the rectum, blending with the fibers of the Sphincter muscles
(middle fibers) It has a very important role in maintaining fecal continence.
Posterior Part
Iliococcygeus inserted into the side of the last two segments of the coccyx; those placed more anteriorly unite with the
(ischiococcygeus) muscle of the opposite side, in a median fibrous ridge called the anococcygeal body or raphe, which extends
between the coccyx and the margin of the anus.
LEVATORES ANI MUSCLES “ continue “
Nerve supply to
levator ani: 1. perineal branch of the fourth sacral nerve “pelvic surface”
2. perineal branch of the pudendal nerve. “perineal surface”
1. The muscles of the two sides form an efficient muscular sling that supports
and maintains the pelvic viscera in position (posterior part).
Actions of levator 2. They resist the rise in intra pelvic pressure during the straining and expulsive
ani: efforts of the abdominal muscles (as in coughing).
3. They have a very important role in maintaining fecal continence.(middle part)
4. They serve as a vaginal sphincter in the female (anterior part).
Arteries of the Pelvis
1. Internal iliac artery(IIA):
One of the 2 terminal branch of the Common iliac artery.
Arises in front of the sacroiliac joint
It descends downward & backwards over the pelvic inlet.
It divides at the upper border of the greater sciatic foramen into: Anterior & Posterior divisions.
Posterior division Supplies:
1. Posterior abdominal wall. 2. Posterior pelvic wall. 3. Gluteal region.
Anterior division supplies:
1. Gluteal region 2. Perineum.3. Pelvic viscera. 4. Medial (adductor) region of thigh
5.The fetus (through the umbilical arteries).
2. Ovarian
Visceral Branches
(all from anterior division) artery:
Umbilical artery : Arises from the
Parietal Branches Gives the superior vesical artery: The distal part of this abdominal
From posterior division: artery fibrosed and forms the Medial Umbilical aorta.
1. Iliolumbar artery. Ligament.
2. Lateral sacral arteries (2 branches.) Inferior Vesical artery in male or vaginal artery in
3. Superior gluteal artery. femail:
From anterior division: In the male it supplies, the Prostate and the Seminal
1. Obturator artery. Vesicles.
2. Inferior Gluteal artery. It also gives the artery of the Vas Deferens.
Middle rectal artery
Internal pudendal artery
It is the main arterial supply to the perineum.
Visceral Branches (in Female) : Vaginal artery: Replaces the inferior vesical artery.
Uterine artery:. Crosses the Ureter superiorly and supplies the uterus & uterine tubes.
Venous Drainage LYMPHATICS OF THE Nerve Supply
PELVIS
INTERNAL ILIAC VEINS The lymph nodes and vessels Somatic:
It collect tributaries are arranged in a chain along Sacral plexus
corresponding to the branches the main blood vessels. Autonomic:
of the internal iliac artery. Thus, there are external iliac Sympathetic:
joins the external iliac vein in nodes, internal iliac nodes, Pelvic part of sympathetic trunk
front of the sacroiliac joint to and common iliac nodes. :The 2 sympathetic trunks unite
form the common iliac vein inferiorly in front of the coccyx
lymph from Common iliac and form a single ganglion
Ovarian vein: nodes & the (Ovaries, uterine (Ganglion Impar).
Right vein drains into IVC tubes & fundus of uterus)
Left vein drains into left renal passes to Lateral aortic II- Superior & Inferior
Vein. (paraortic) nodes. Hypogastric plexuses
Parasympathetic:
Pelvic splanchnic nerves
(From S 2 , 3 & 4)
MCQs
1-which one of the following joints lies in the posterior 6-Which one of the following Not formed the lateral
of pelvic bone : pelvic wall :
a) Symphysis Pubis
a) sacrospinous ligament
b) Sacrococcygeal joint
b) obturator internus and its covering fascia
C) Two Sacroiliac joints
C) pubic rami
2- the posterior boundary of false pelvis is :
a) iliac fossae and iliacus muscle 7- which one of these is false origin of leveator ani
b) lumbar vertebrae muscle :
C)coccyx a) tendinous arch of the obturator fascia
3-regarding the female pelvis which one is false : b) ischial spine
C) middle 3 sacral vertebrae
a) wider and shorter sacrum 8- which fiber from levatores ani muscles has
b) angle of the pubic arch is wider important role in maintaining fecal continence :
C) promontory and the ischial spines are more a) pubococcygeus
projecting b) puborectalis
4- the most female bony pelvis is: C) iliococcygeus
a) android 9- the drainage of right ovarian vein is :
b) anthropoud a) common iliac vein
C) gynecoid b) inferior venia cave(IVC)
C) left renal vein
5- what are the action and the nerve supply of piriformis
10- the parasympathetic nerve fiber is :
muscle
A) lateral rotator of the femur + sacral plexus a) pelvic splanchnic nerves (S2,S3,S4)
b) medial rotator of the femur + sacral plexus b) pelvic splanchnic nerves (S1,S2,S3)
C )lateral rotator of the femur +4th ,5th sacral nerves C) Sacral plexus
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Key Answers
B -1
B -2
C -3
C -4
A -5
C- 6
C- 7
B- 8
B -9
A-10
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