The Pelvic Girdle
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The many names for this region
◦ Pelvis: composed of 2 innominate bones and the
sacrum
◦ Innominate (or Os Coxae): each half of the “pelvic
bowl” formed by the fusion of
 Ilium
 Ischium
 Pubis
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ILIUM – most superior of the 3
the blade
ISCHIUM - most inferior of the 3
the ‘sit bone’
PUBIS – most anterior of the 3
forms the symphysis
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FUNCTIONS:
◦ Support internal organs
◦ Changes in the human pelvis allow for bipedal
locomotion
Each innominate articulates with
*sacrum (at the auricular surface)
*one femur (at the acetabulum)
*the other innominate (at pubic symph)
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The ilium: medially ◦
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Iliac crest – superior rim
Iliac fossa – superior depression under rim
ASIS and AIIS
Arcuate line – midline inferior ridge
Iliac tuberosity – posterior rugosity
Auricular surface - posterior (art.w/ sacrum)
Preauricular sulcus
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The ilium: laterally –
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Iliac crest
Iliac pillar – ridge on midline of blade
PSIS and PIIS
Greater sciatic notch
Acetabulum (actually the point where all three
bones fuse together, art. w/femur)
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The ischium and pubis – medially
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Pubic ramus: anterior/superior, twists
Pubic symphysis: most anterior point
Ischiopubic ramus: flat
Obturator foramen: big hole
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Ischial spine: most inferior/posterior
Lesser sciatic notch: inferior
Ischial tuberosity: very thick
Pubic tubercle: anterior, above symph
The ischium and pubis – laterally
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Orient ilium (crest and blade) superior
Orient the pubic symphysis anteriorly and
medially, ischium posterior and inferior
The acetabulum is on the side of origin (lateral)
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Ischiopubic ramus; 5-8 years
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Acetabululm; 11-17 years
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Ischial tuberosity; 16-20 years
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Iliac crest; 17-23 years
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The pelvis is best for sex – due to changes in
the pelvis for childbirth, there are numerous,
easy to distinguish features that help
differentiate males from females in both the
PUBIS and the ILIUM
ALSO, well developed methods for aging
adults based on changes in the PUBIC
SYMPHYSIS
TO RECAP:
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SEX: PUBIS AND ILIUM
AGE: FUSIONS, AURICULAR SURFACES, PUBIC
SYMPHYSIS
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Large, wedge-shaped
Composed of 5 sacral vertebrae – fused
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Articulates with L5, both innominates
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Characteristics
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◦ Large bodies
◦ Reduced spinous processes
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19464.jpg
http://www.back.com/images/sacrum-4-19.jpg
http://www.botany.uwc.ac.za/sci_Ed/grade10/manphys/images/man/sacrum.gif
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Superiorly
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◦ Sacral promontory
(sup/ant): central,
superior border of S1
◦ Superior articular
facets: articulation of
L5-S1
◦ Spinal canal
◦ Ala (wings)
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Laterally
◦ Auricular surface
◦ Spinous processes
Posteriorly –
◦ Posterior sacral
foramina
Anteriorly
◦ Anterior sacral
foramina
◦ Transverse line of
fusion
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Male vs female
◦ Males sacrum curved
◦ Females sacrum straight (WHY?)
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Age
◦ Transverse line between S1 – S2 closes mid
twenties
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Coccyx – group of fused bones vs coccygeal
vertebra (individual bone)
Usually 4 segments fused – variation 3-5
CV1 had transverse processes and horns
(cornua)
CV2+ are variable, small, frequently lost
Typically all fuse together and frequently to
sacrum
http://content.answers.com/main/content/wp/
en/thumb/6/62/200px-Gray100.png