ANHB2212 Lecture Notes - Lecture 20: Xiphoid Process, Coccyx, Ischium
28 May 2018
School
Course
Professor
L20 Pelvis + Reproductive Perspective
Outcomes
Sexual dimorphism in the pelvis
• Inlet
• Cavity
• Outlet
Pelvic dimensions
Practical considerations
Changes in Uterine anatomy during pregnancy
Sexual dimorphism in the pelvis
Females
Males
Inlet
Body of the
sacrum
Smaller
Larger
(pubis,
ilium,
ischium)
but we
talk
about
the
“area”
of inlet
Promontory
of the sacrum
Projects less
Projects
more
the inlet of
female = more
circle
the inlet
of males =
more heart
shaped
Cavity
Pubic bone in
general (the
whole pubic
bone)
Wider
Narrow
Greater
sciatic notch
Wider
Narrow
Curve of the
sacrum
The curve of the
sacrum curves
backwards and
the tip curves
Uniform
Ischial spines
Straight
Inverted
Outlet
Ischial
tuberosities
(left to right)
Wider
Narrow
Arch of
ischiopubic
rami
Roman
ischiopubic arch
Gothic
ischiopubic
arch
Pelvic dimensions
• 3 main planes
o inlet
o mid-cavity
o outlet
• Inlet
o Anteroposterior: Midpoint of
promontory to anterior end of symphysis
o Transverse: Greater diameter at right
angles to anteroposterior
• Outlet
o Anteroposterior: Tip of coccyx to
posterior end of symphysis
o Transverse: Between ischial tuberosities
Practical considerations
Changes in uterine anatomy pregnancy
• Uterus rises to abdomen
• Smooth muscles cells increase in amount during
pregnancy
• First 12 weeks = uterus is in pelvic
• 24 = fundus at umbilicus
• 36 = fundus close to xiphisternum
• 36-40 = slightly descent
• pressure effects = on IVC, on GIT
• return to the 24th week position after childbirth but
never the same place (fundus at umbilicus)
• before childbirth: cervical opening is tiny, and
circular
• after childbirth: cervical opening is transverse
slit
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