Reproductive health and physiological

1. ANATOMY OF FEMALE
PELVIS AND FETAL SKULL
DR IBUA

2. RATIONALE
Anatomy of the pelvis and fetal
skull should be understood in the
context of what happens during
labour

3. TERMINAL OBJECTIVE
 Should be able to describe the structure of
the normal female pelvis
 Should be able to describe the abnormal
female pelvis
 Should be able to describe the fetal skull
and
 The mechanisms of labour

4. ENABLING OBJECTIVES
Student should be able to:
• State the components of the bony pelvis and fetal
skull
• Describe the joints of pelvis and skull
• State dimensions of pelvis and skull
• Differentiate male from female pelvis
• Identify various types of pelvis
• Differentiate various skull malformations

5. COMPONENTS (a)
Innominate Bone-bones formed from fusion of :
a) Ilium. The upper expanded part. Iliopectineal
eminence is where ilium and pubis fuse. 2/5 of
acetabulum
b) Ischium. L shaped and forms the posterior-
inferior part of pelvis
c) Pubis. Has a body and two rami. Upper joins
ilium at iliopectineal eminence, 1/5 of
acetabulum

8. COMPONENTS (b)
 Lower ramus fuses with ramus of ischium
forming anterior boundary of obturator
foramen and subpubic arch
 In gynaecoid pelvis subpubic arch should be
at least 90 degrees

9. COMPONENTS (c)
SACRUM
• Forms the back of the pelvis
• Wedge shaped consisting 5 fused
vertebrae
• First forms the sacral promontory
• Anterior surface smooth and concave
• 4 sets of foramina exit the sacral nerves

10. COMPONENTS (d)
COCCYX
• Small triangular shaped bone
• Consists 4 fused rudimentary vertebrae
• Gives attachment to ligaments, muscle
fibres of anal sphincter, ischiococcygeus
muscle= posterior section of pelvic floor
• During labour it moves backwards to
increase pelvic outlet.

11. PELVIC JOINTS
SACROILIAC JOINTS
• Two slightly movable synovial and fibrous
joints
• Mobility greater in pregnant and puerperal
women
• This mobility enhances diameter of pelvic brim
• N/B Puerperal-period from birth-6wks after
childbearing

12. PELVIC JOINTS
SYMPHYSIS PUBIS
• Slightly movable secondary cartilaginous
joint
• In last two months of pregnancy gap
increases from 4mm to 7mm
• Waste space of Morris smaller in
gynaecoid than in android pelvis

14. DIMENSIONS
• True pelvis bounded by:
• Sacrum at the back, sides by ischia, and
front by pubes. Consists of:
• Brim or inlet= entry point
• A curved cavity, traversed next
• Outlet, emerging point

15. PELVIC BRIM OR INLET
• Bounded by:
• Promontory of the sacrum
• Wings or alae of the sacrum
• Right and left sacroiliac joints
• Right and left iliopectineal lines
• Right and left iliopectineal eminences
• Upper inner borders of the s.p. rami
• Upper inner borders of bodies of pubes
• Upper inner border of symphysis pubis

16. PELVIC CAVITY
Boundaries are:
• Hollow of sacrum
• Sacroiliac joints
• Ischia and the sacrospinous ligaments
• Right and left upper and lower pubic rami
• Bodies of the pubes and the symphysis pubis.
Cavity is circular, anterior is 4.5 cm deep and
posterior is 12cm deep

17. PELVIC OUTLET
Ovoid or diamond shaped and has 2 levels:
Boundaries of upper outlet are
• Lower sacrum
• Sacrospinous ligaments and ischial spines
• Pubic arch
Boundaries of lower outlet are
• Tip of coccyx
• Sacrotuberous ligaments and ischial
tuberosities
• Pubic arch

18. DIAMETERS of BRIM
Anteroposterior diameter
• From sacral promontory to upper inner border
of symphysis pubis=11cm=obstetric conjugate
• True conjugate(anatomical) is from
promontory to centre of upper surface SP
Right and left oblique diameters
• From R sacroiliac to L iliopectineal eminence
and vice versa=12cm
Transverse: Between widest points on
iliopectineal lines=13cm

19. DIAMETERS of BRIM
Sacrocotyloid: From sacral promontory to
iliopectineal eminence on same side=9cm
Diagonal conjugate: From apex of pubic
arch to sacral promontory=1.25cm more
than obstetric conjugate

20. DIAMETERS OF CAVITY
Here cavity is almost circular and measures
about 12 cm

21. DIAMETERS of OUTLET
From sacrococcygeal joint to the lower
border of SP=13cm
Transverse of outlet between ischial spines
measures 10.5-11 cm
Outlet is wider from front to back and
narrower from side to side.
This is why head emerges with its long
diameter anteroposterior

22. SUMMARY OF THE BRIM
DIAMETER
BRIM(INLET) CAVITY OUTLET
ANTERIOR POSTERIOR 11 12 13
OBLIGUE 12 12 12
TRANSERVE 13 12 11

23. COMPARISON OF GENDER
In the female:
• Bones are lighter and smoother
• Brim is rounded
• Cavity shallower and more capacious
• Outlet larger
• Sacrosciatic notch wider
• Acetabula are further apart
• Pubic arch is wider
• Sacrum wider and more curved

24. PELVIC TYPES
1 Gynaecoid=50%. Normal female
• Brim is round in shape
• Pelvis shallow
• Subpubic angle wide
• Sacrosciatic notch is wide
• Transverse diameter of outlet is 10 cm at
least. Mechanism of labour is normal

25. PELVIC TYPES
2 Anthropoid pelvis= 25%
• The brim is oval in shape with an
increase in AP diameter
• Sacrum long and narrow and may have
six vertebrae=high assimilation
• This hinders engagement of fetal head
• POPP common, seen in unusually tall,
well built women

26. PELVIC TYPES
3 Android pelvis= 20%(Caldwell et al 1940)
• Brim triangular, broader at back
• True pelvis deep
• Sacrum straight
• Subpubic angle narrow
• Sacrosciatic notch narrow
• Transverse diameter of outlet < 10 cm
• Funnel shaped. Associated with severe tears coz
head displaced backwards

27. PELVIC TYPES
4 Platypelloid pelvis=5%
• The anteroposterior diameter short
• Sacrosciatic notch narrow
• AP narrowing of pelvis continues in
cavity and outlet.
• Deep transverse arrest common

28. CONTRACTED PELVIS
Definition: One in which one or more diameters
are so reduced as to interfere with normal
mechanism of labour
Types:
• Rachitic flat
• Generally contracted
• Assymetrical, disease of hip or spine or
Naegele’s
• Others: Osteomalacia, spondylolisthesis,
Robert’s pelvis

29. FETAL SKULL
Division of the fetal skull:
• The vault, containing the cerebral hemispheres
• The base
• The face
• The bones of the face and the base are
incompessible
• Vault is from orbital ridges to nape of neck and
is compressible

30. REGIONS OF THE SKULL
VERTEX: Bounded in front by anterior
fontanelle, behind by posterior fontanelle, and
laterally by parietal eminences
BROW: or sinciput, area over frontal bone
OCCIPUT: Area over occipital bone
FACE: Supraorbital ridges to chin
VAULT: Thin sheets of bone separated at sutures,
by membrane.This allows for moulding and
development of the brain

31. VAULT
Made up of:
• Two frontal bones
• Two parietal bones
• Two temporal bones
• One occipital bone all joined together by
sutures. Temporal sutures have no
obstetrical importance

32. DIAMETERS OF FETAL
SKULL
Suboccipitobregmatic, 9.5 cm. Full flexion
Suboccipitofrontal, 10 cm.Almost fully flex
Occipitofrontal, 11.5 cm. Deficient flexion
Mentovertical, 13.5 cm.Brow
Submentovertical, 11 cm Face not fully
extended
Submentobregmatic, 9.5 cm Fully extended
face

33. TRANSVERSE DIAMETERS
Biparietal: 9.5 cm
Bitemporal: 8 cm

34. CIRCUMFERENCE
• Suboccipitobregmatic, 33 cm. Well flexed,
this fits in lower uterine segment
• Occipitofrontal, 35 cm. Deflexed does not
fit well in lower uterine segment
• Mentovertical, 39 cm

35. FEMALE & MALE PELVIC
FEMALE
 Gynecoid pelvis
 Large & broad
 Pelvic inlet in oval shape
 Sciatic notch is wider
 Pelvic outlet wider
 Its to support childbearing &
delivery
 Pubic arch is wider
 Coccyx flexible & straight
MALE
 Android pelvis
 Narrow & compact
 Pelvic inlet is heart shape
 Sciatic notch is narrower
 Pelvic outlet is narrower
 Its to support heavy body &
muscle
 Pubic arch is v-shaped
 Coccyx curved & immovable

36.  THE END