Musculoskeletal Anatomy of the Lower Limb
Musculoskeletal Anatomy of the Lower Limb COMPARISON OF UPPER AND LOWER LIMBS
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Upper and lower limbs develop from same primordial tissue type •
Bud grows to become limb
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Difference is in rotation of limb
Tetrapods have common pattern of limb bone structure •
Stylo/propodial – single proximal element
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Zygo/epipodials – two middle bone segments that articulate, some species have lost one
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Autopodium – two or three carpal or tarsal rows, pentadactyl
Understanding homology helps understand shared limb structure and function •
Not all homologies are linear due to ontogenic limb rotation
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Some fundamental differences between limbs due to biomechanics and functional differences – being bipedal has caused changes
PELVIS
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Pelvic girdle composed of three elements: •
Two os coxae – left and right
! !
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Sacrum – unites os coxae, series of fused sacral vertebrae
Os coxa begins as three units in utero that fuse to form one bone and acetabulum: •
Ilium – homologue for scapula, although no defined spine
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Ischium – homologue for coracoid process, gradually fuses onto ilium
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Pubis – no direct homologue
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Acetabulum is socket for head of femur, point where all three bones join
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When born, os coxa is cartilage •
Doesn’t begin to fuse until 8 or 9 years old
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Entirely fused and ossified by 25
Subdivisions of pelvis: •
Pelvic inlet – inner ring of pelvis, defined by bony pelvic brim
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False pelvis – superior to pelvic inlet, occupied by abdominal viscera
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True pelvis – inferior to pelvic inlet, occupied by pelvic viscera !
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Pelvic outlet (inferior pelvic aperture) – bounded by pubic arch anteriorly, ischial tuberosities laterally, inferior margin of sacrotuberous ligament posterolaterally and tip of coccyx posteriorly
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Differences between male and female anatomy of pelvis:
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Biological continuum – gynecoid and android are extremes of each, but can be anywhere along scale
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Android pelvic inlet heart-shaped and narrow, gynecoid oval and rounded, and wide !
!
•
•
Upper and lower limbs develop from same primordial tissue type •
Bud grows to become limb
•
Difference is in rotation of limb
Tetrapods have common pattern of limb bone structure •
Stylo/propodial – single proximal element
•
Zygo/epipodials – two middle bone segments that articulate, some species have lost one
•
•
Autopodium – two or three carpal or tarsal rows, pentadactyl
Understanding homology helps understand shared limb structure and function •
Not all homologies are linear due to ontogenic limb rotation
•
Some fundamental differences between limbs due to biomechanics and functional differences – being bipedal has caused changes
PELVIS
•
Pelvic girdle composed of three elements: •
Two os coxae – left and right
! !
•
•
Sacrum – unites os coxae, series of fused sacral vertebrae
Os coxa begins as three units in utero that fuse to form one bone and acetabulum: •
Ilium – homologue for scapula, although no defined spine
•
Ischium – homologue for coracoid process, gradually fuses onto ilium
•
Pubis – no direct homologue
•
Acetabulum is socket for head of femur, point where all three bones join
•
•
When born, os coxa is cartilage •
Doesn’t begin to fuse until 8 or 9 years old
•
Entirely fused and ossified by 25
Subdivisions of pelvis: •
Pelvic inlet – inner ring of pelvis, defined by bony pelvic brim
•
False pelvis – superior to pelvic inlet, occupied by abdominal viscera
•
True pelvis – inferior to pelvic inlet, occupied by pelvic viscera !
!
•
Pelvic outlet (inferior pelvic aperture) – bounded by pubic arch anteriorly, ischial tuberosities laterally, inferior margin of sacrotuberous ligament posterolaterally and tip of coccyx posteriorly
•
Differences between male and female anatomy of pelvis:
•
Biological continuum – gynecoid and android are extremes of each, but can be anywhere along scale
•
Android pelvic inlet heart-shaped and narrow, gynecoid oval and rounded, and wide !
!
