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Pelvis and peritoneum
Pelvis and peritoneum
Pelvis
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Body part surrounded by the pelvic girdle, part of appendicular skeleton of
lower limb
Divided into greater and lesser pelvis

Greater pelvis
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Surrounded by superior pelvic girdle
Occupied by inferior abdominal viscera (superior abdominal viscera
protected by inferior thoracic cage)

Lesser pelvis
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Surrounded by the inferior pelvic girdle
Skeletal framework for the pelvic cavity and the peritoneum (separated by
the pelvic diaphragm)

Perineum
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Area of the surface of the truck between the thighs and buttocks
Extends from coccyx to the pubis and compartment deep to this and superior
to pelvic diaphragm
Includes anus and external genitalia (penis and scrotum, vulva)

Pelvic girdle
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Pelvic girdle: ring of bones connecting the vertebral column to the femurs
Functions of the pelvic girdle
o Bear weight of upper body
o Transfer weight from axial to lower appendicular skeleton
o Attachment for muscles of locomotion, posture and abdominal wall
o Contain and protect viscera; pelvic (inferior urinary tract and internal
reproductive organs) and inferior abdominal (intestines), but allow
passage of terminal parts via peritoneum
o Support for abdominopelvic viscera and pregnant uterus
o Attachment for erectile bodies of external genitalia
o Forms pelvic floor, with attachment for muscles and membranes

Bones and features
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Pelvic girdle is formed by three bones
o Right and left hip (pelvic) bones, each formed from fusion of ilium,
ischium and pubis
o Sacrum
In infants and children, the hip bone is three separate bones united by
triadiate cartilage at the acetabulum (depression in lateral surface of hip
bone which articulates with the head of the femur
After puberty, the ilium, ischium and pubis fuse
Two hip bones joined anteriorly by the pubic symphysis (secondary
cartilaginous joint)
Hip bones articulate posteriorly with the sacrum at the sacro-iliac joints

Taken From Moore et al, Clinically Oriented Anatomy, Seventh Edition

Ilium
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Superior, fan shaped part of hip bone
Ala (wing), iliac crest and body
Body participates in the acetabulum on external aspect
Anteromedial concave part of the ala forms the iliac fossa
Sacropelvic surface has auricular surface (synovial articulation with sacrum)
and iliac tuberosity (syndesmotic articulation with sacrum)

Ischium
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Has a body and a ramus
Body forms part of the acetabulum
Ramus forms part of the obturator foramen
Ischial tuberosity is the postero-inferior protuberance
Ischial spine is the small pointed postero-medial projection
Lesser sciatic notch is the concavity between the ischial spine and the ischial
tuberosity
Greater sciatic notch is the formed partly by the ilium, lies superior to the
ischial spine

Pubis
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Superior ramus forms part of the acetabulum
Inferior ramus forms part of the obturator foramen
Pubic crest is a thickening of the anterior part of the body of the pubis, lateral
ending is the pubic tubercle
Pectin pubis is the oblique ridge forming the lateral part of superior pubic
ramus

Features of the pelvic girdle
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Pelvis divided into greater and lesser pelvis by the pelvic inlet (superior pelvic
aperture)
Pelvic brim is the bony rim surrounding the pelvic inlet, formed from
o Sacral promontory and alla
o Right and left linea terminalis (comprising the arcuate line, pectin
pubis, and pubic crest
Pubic arch formed from the two ischiopubic rami
o Rami meet at the pubic symphysis
o Inferior borders define the pubic angle
Pelvic outlet (inferior pelvic aperture) is bounded by
o Pubic arch (superior)
o Ischial tuberosities (latera)
o Sacrotuberous ligament (posterolaterally)

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o Tip of coccyx (posteriorly)
Greater pelvis
o Superior to pelvic inlet
o Bounded by iliac alae and SI
o Occupied by abdominal viscera
Lesser pelvis
o Located between pelvic inlet and outlet
o Bounded by hip bones, sacrum, coccyx
o Includes true pelvic cavity and deep parts of perineum
o Obstetric and gynaecological importance
The musculofascial pelvic diaphragm forms the floor of the true pelvic cavity
o Shallowest centrally, deep peripherally
In the anatomical position, the axis of the pelvis intersects the abdominal axis
at an oblique angle

Taken From Moore et al, Clinically Oriented Anatomy, Seventh Edition

Comparison of male and female bony pelvises


Differences related to heavier build and larger muscles of men, and
adaptations of the pelvis (especially lower pelvis) in women

Feature of bony pelvis
General structure
Greater (false) pelvis
Lesser (true) pelvis
Pelvic inlet (superior aperture)
Pelvic outlet (inferior aperture)
Pubic arch and subpubic
angle
Obturator foramen
Acetabulum
Greater sciatic notch

Male
Thick, heavy
Deep
Narrow, deep, tapering
Heart shaped, narrow
Small
Narrow (<70o)

Female
Thin, light
Shallow
Wide, shallow, cylindrical
Oval/rounded, wide
Large
Wide (>80o)

Round
Large
Narrow (~70o)

Oval
Small
Wide (~90o)

Joints and ligaments of pelvic girdle
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Main joints are the sacro-iliac joints and pubic symphysis

Sacro-iliac joints
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Sacro-iliac joints join the axial skeleton to inferior appendicular skeleton;
transfer weight, limited mobility
o Strong, weight bearing compound joints, with irregular, interlocking
surfaces
Comprises an anterior synovial joint (between auricular surfaces of sacrum
and ilium) and posterior syndesmosis (between the tuberosities)
Sacrum is suspended between the iliac bones, and is firmly attached by the
sacro-iliac ligaments
Anterior sacro-iliac ligaments are the anterior part of fibrous capsule of
synovial part of the joint
Interosseous sacro-iliac ligaments are the primary ligaments involved in
transferring weight from the axial skeleton to the two ilia
Posterior sacro-iliac ligaments are the posterior continuation
The fibres of the interosseous and posterior sacro-iliac ligaments run obliquely
upward and outward from the sacrum, thus the axial weight pushing down on
the sacrum pulls the ilia medially, compressing the sacrum between them
Iliolumbar ligaments are accessory to the above mechanism
Sacrotuberous ligament is the joining of the posterior sacro-iliac ligaments with
fibres from the posterior ilium and coccyx
o Passes from the posterior ilium and lateral sacrum and coccyx to ischial
tuberosity
o Forms a large sciatic foramen along with the sciatic notch of hip bone
Sacrospinous ligament passes from lateral sacrum and coccyx to the ischial
spine, dividing the sciatic foramen into greater and lesser sciatic foramina
Normally the sacroiliac joint is limited to slight gliding and rotation

Taken from Wikipedia
...
wikipedia
...
com/bony-pelvis-anatomy/

Taken from Bone and Spine, Bony Pelvis Anatomy, available at
http://boneandspine
...
com, Pelvic Trauma, available at
http://clinicalgate
...
com, Gray’s Anatomy at Georgetown University School of Medicine,
available at https://www
...
com/notes/note/n/gray-s-anatomy/deck/10272470

Lumbosacral joints
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L5 and S1 articulate at the IV disc joint between their bodies, and at two
posterior zygapophyseal joints between their articular processes
The facet joints are strengthened by iliolumbar ligaments which radiate from
the transverse processes of L5 to the ilia

Sacrococcogeal joint
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Secondary cartilaginous joint with an IV disc
Fibrocartilage and ligaments join sacrum to the coccyx
Anterior and posterior sacrococcogeal ligaments strengthen the joint

Pelvic cavity
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Abdominopelvic cavity is from the thoracic cage to the pelvis
Pelvic cavity is inferior part of abdominopelvic cavity; continuous with
abdominopelvic cavity at pelvic inlet
Pelvic cavity contains terminal ureters, bladder, rectum and genital organs
o Also some abdominal viscera (small and large intestine)
Bounded
o Inferiorly by musculofacial pelvic diaphragm (located at level of pelvic
outlet) – forms bowel-like pelvic floor
o Posteriorly by sacrum and coccyx
o Anteriorly by the pubic bones and pubic symphysis
o Laterally by the iliac bones
Axis of the pelvis is the line in the median plane defined by centre point of the
pelvic cavity; this is curved due to disparity in depth between anterior and
posterior parts

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Walls and floor of pelvic cavity
Anterior-inferior pelvic wall
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Formed by bodies and rami of pubic bones and pubic symphysis
Bears weight of urinary bladder

Lateral pelvic walls
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Formed by right and left hip bones
Obturator foramen covered by an obturator membrane
Obturator internus muscles cover and pad most of the lateral walls; arise from
the lateral pelvis and pass via lesser sciatic foramen to attach to the greater
trochanter of the femur
Medial surfaces of the above muscles covered by obturator fascia

Posterior wall
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Bony wall and roof formed by sacrum and coccyx, plus associated ligaments
Piriformis muscles arise from sacrum and pass through greater sciatic foramen
and attach to greater trochanter of the femur
o Rotates thigh laterally and holds femur head in acetabulum
Obturator internus also form part of the wall; same role as piriformis
Sacral plexus nerves located deep to the piriformis muscles

Pelvic floor
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Formed by the pelvic diaphragm, formed by coccogeus and levator ani
muscles, plus fascia
o Coccogeus forms small part of pelvic diaphragm; flexes coccyx
(redundant in humans)
o Levator ani is major muscle of the pelvic diaphragm, supports pelvic
viscera and resists increases in intra-abdominal pressure
Pelvic diaphragm separates lesser pelvis from the perineum
Diaphragm attaches to obturator fascia, dividing obturator internus muscle
into superior and inferior parts
Anterior gap between the medial borders of the levator ani muscles of each
side is the urogenital hiatus – passage of urethra (plus vagina in females)
Levator ani penetrated centrally by the anal canal
Levator ani has three parts – puborectalis, pubococcogeus, iliococcogeus
Levator ani is tonically contracted most of the time to support the
abdominopelvic viscera, and support urinary and faecal continence
Contracts during forced expiration, coughing sneezing, vomiting, fixation of
the trunk during heavy lifting; relaxes to allow urination and defecation

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
Peritoneum and peritoneal cavity of the pelvis
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Parietal peritoneum lining the abdominal cavity continues inferiorly into the
pelvic cavity, reflecting onto the pelvic viscera
Pelvic viscera are not completely ensheathed in the peritoneum, most lie
inferior
Fascia is loosely connected to the superior bladder, meaning the supravesical
fossa is variable in size
In women
o Pocket in peritoneum formed between the uterus and rectum is the
recto-uterine pouch (Pouch of Douglas) – limited movement here, so
fluid can accumulate which can be a problem in infection
o Pocket also formed between uterus and bladder – vesico-uterine
pouch; this is more mobile, thus less likely to accumulate peritoneal
fluid, so less prone to infection
In men, pocket formed between bladder/seminal glands and rectum – rectovesicular pouch

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Pelvic fascia
Parietal and visceral membranous pelvic fascia
Parietal pelvic fascia is membranous layer of connective tissue lining deep
muscles forming the wall and floor of the pelvis
Visceral pelvic fascia is the membranous layer directly ensheathing pelvic
organs
Parietal and visceral fascia become continuous where the organs penetrate
the pelvic floor – forms tendinous arch, a bilateral band running from pubis to
sacrum

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Endopelvic viscera – loose and condensed
Endopelvic viscera is that located between the parietal and visceral pelvic
viscera
Connective tissue matrix, packing material for the pelvic viscera
Loosely packed fatty tissue in some parts, with a number of potential spaces
o Retropubic – allows bladder expansion
o Retrorectal – allows rectum expansion
Other areas are more fibrous (collagen and elastic fibres plus smooth muscle)
o Forms a thick band called the hypogastric sheath

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Medical application
Injury to pelvic floor
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During childbirth, the peritoneum, levator ani, and ligaments of pelvic
fascia may be injured
Pubococcus and puborectalis, main and most medial parts of levator
ani, are most often torn
Important as they encircle and support the urethra, vagina and anal
canal
Changes can cause urinary stress incontinence, or prolapse of pelvic
organs

Sectional imaging of pelvis and peritoneum

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
Reference
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Clinically Oriented Anatomy
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