Gyne Anatomy

1. Pelvic Bones and Joints
Themba Hospital FCOG(SA) Part 1 Tutorials
By Dr N.E Manana

2. General description of the Pelvis
• The pelvis and the perineum are interrelated regions associated with
the pelvic bones and parts of the vertebral column
• The pelvis is divided into 2 regions
• False pelvis/Greater pelvis: considered part of the abdomen
• True pelvis/Lesser pelvis: has inlet and outlet
• The pelvic cavity consist of inlet, walls and floor, and contains
elements of the urinary, gastrointestinal and reproductive systems
• The perineum is inferior to the floor of the pelvic cavity, its
boundaries form the pelvic outlet

3. Pelvic bones
• Bones of the pelvis consist of the right and left pelvic bone, the
sacrum and the coccyx
• The sacrum articulates with L5 superiorly at the lumbosacral joint
• The pelvic bones articulates posteriorly with the sacrum at the sacro-
iliac joints
• And with each other anteriorly at the pubic symphysis

4. • Pic 5.4

5. Pelvic bone
• Its irregular in shape, Medial surface has two major parts separated by an
oblique line on its medial surface
• The Linea terminalis is the lower 2/3 of these line and contributes to the
margin of the pelvic inlet
• The lateral surface of the pelvic bone has a large articular socket
(Acetabulum) with together with the head of the femur forms the hip joint
• Inferior to the acetabulum is the large obturator foramen, mostly closed by
the obturator membrane, a small obturator foramen remains
• The posterior part has two notches separated by the ischial spine (Greater
and lesser sciatic notch). Posterior part terminates inferior as the Ischial
tuberosity
• The anterior margin is marked by the ASIP, AIIS and the pubic tubercle

6. • Pic 5.19

7. Components of the Pelvic bone
• Formed by 3 elements:
• The ilium
• The pubis
• The ischium
• These bones are initially (at birth) connected by cartilage
• They fuse at between 16-18 years of age into a single bone

8. • PIC 5.20

9. Ilium
• The most superior of the 3 components, it is separated into upper and
lower parts by the ridge on the medial surface
• Posteriorly the ridge lies immediately superior to the surface of the bone
that articulated with the sacrum
• The sacral surface has an L shaped facet and an expanded posterior
roughened area for ligament attachment
• Anterior the ridge is rounded and termed the arcuate line, which is part of
the linea terminalis

10. • 5.21

11. Ilium
• The upper part of the ilium expands to form a flat-fan shaped “wing” which
provides bony support to the lower abdomen
• It also provides attachment for muscle associated with the lower limb
• The anterior medial surface of the wing is concave and forms the iliac fossa
• The superior part of the wing is thickened forming an iliac crest, terminates
anteriorly as the ASIS and posteriorly as the PSIS, it’s a site of attachment
for muscle and fascia of the abdomen, back and lower limb
• Less prominent AIIS which serves as attachment for rectus fermis muscle
an iliofemoral ligament, the PIIS forms the superior margin of the greater
sciatic notch

12. Pubis
• The anterior and inferior part of the pubic bone is the pubis
• It has a body and two arms (rami), the body is flattened dorsoventrally and
articulates with the body of the pubic bone on the other side at the pubic
symphysis
• The superior surface is rounded and end laterally as the pubic tubercle
• Superior pubic ramus projects posterolateral and joins the ilium and
ischium at its base
• The sharp superior margin is termed the pectineal line (part of the linea
terminalis)
• The inferior rami projects laterally and inferiorly to join with the ramus of
the ischium

13. Ischium
• The posterior and inferior part of the pelvic bone
• Its has a large body that projects superiorly to join the ilium and the
superior ramus of the pubis
• And a ramus that projects anteriorly to join with the inferior ramus of
the pubis
• Posterior margin marked by the ischial spine
• On the posteroinferior aspect is the ischial tuberosity
• This tuberosity is an important site of attachment of lower limb
muscles and supports the body when seating

14. Sacrum
• Has the appearance of an inverted triangle, it is formed by fusion of 5 sacral
vertebrae
• The base of the sacrum articulates with the lumber vertebra and its apex with the
coccyx
• It has an L shaped facet on its lateral side that articulates with the ilium
• Posterior to the facet is a large roughened area for ligament attachment to
support the sacro-iliac joint
• Superiorly its is flat (body of S1) with a flat wing like lateral projection termed the
Ala
• The anterior edge projects forward as the promontory, with an anterior surface
that is concave and convex posterior surface
• Due to the fusion of the transverse processes into posterior and anterior foramen
• The sacral canal terminates at the sacral hiatus

15. • Pic 5.22

16. Coccyx
• It is the small terminal part of the vertebral column, consists of 4
fused vertebrae
• Has the shape of an inverted triangle, with its base directed
superiorly
• It has a facet that articulates with the sacrum and two horns or
cornua, with project upwards to articulate with similar projections
from the sacrum
• Each lateral surface has a rudimentary transverse process
• No bony vertebral canal is present

17. Joints
Lumbosacral joint (LSJ)
• The LS joints are formed between vertebra L5 and the sacrum, it
consist of :
• 2 zygapophysial joints: which occur between adjacent inferior and
superior articular processes and
• An intervertebral disc that joins the bodies of L5 and S1
• The are similar to those of the other vertebrae except that the sacrum
is angled posteriorly, as a result the anterior part of the disc is thicker
than the posterior part
• The LSJ is reinforced by strong iliolumbar and lumbosacral ligaments

18. • 5.23

19. Joints
Sacro-iliac Joints (SIJ) transmit forces from the lower limbs to the vertebral
column
• They are synovial on the lateral surface of the sacrum and on the iliac parts
of the pelvic bones
• The joint surface has irregular contour and interlock to resist movement
• The joint becomes fibrous with age and may ossify
• Each joint is stabilised by three ligaments:
• 1. The Anterior SI ligament (Thinking of the fibrous membrane of the joint
capsule, runs anteriorly and inferiorly)
• 2. Interosseous SI ligament (Largest and strongest, posterosuperior to the
joint, attaches to the roughened areas of the sacrum and ilium)
• 3. Posterior SI ligament (Covers the interosseous SI ligament posteriorly)

20. • 5.24

21. Joints
Pubic symphysis joint (PSJ)
• Lies anterior between the adjacent surfaces of the pubic bone
• Each of the surfaces is covered by hyaline cartilage and is linked
across by fibrocartilage
• The joint is surrounded by interwoven collagen layers, and two major
ligaments:
1. Superior pubic ligament
2. Inferior pubic ligament

22. • 5.25

23. Orientation
• 5.26

24. Gender differences
• 5.27

25. Pelvic wall
• Consists of the sacrum, coccyx, the pelvic bones inferior to the linea
terminalis, 2 Ligaments, 2 Muscles and 3 Apertures
Ligaments (Stabilise the sacrum on the pelvic bone)
1. Sacrospinous ligaments (SSL): Its smaller and triangular in shape, apex
attached to the ischial spine and its base to the sacrum and coccyx
2. Sacrotuberous ligaments (STL): Triangular, superficial to the SSL, it has a
broad base that extends from the PSIS and sacrum into the coccyx surface
• Laterally, the apex of the ligament is attached to the medial margin of the
ischial tuberosity

26. • 5.29

27. Pelvic wall
Muscles
1. Obturator internus (OI): Is a flat, fan-shaped, originates from the deep
surface of the obturator membrane and the pelvic bone assoc with the
obturator foramen
• The muscle fibers converge to form a tendon that leaves the pelvic cavity
via the lesser sciatic foramen, making a 90 degree turn around the ischium
to insert on the greater trochanter of the femur
2. Puriformis (PF): Is triangular, originating in the bridges of bone btn the 4
anterior sacral foramen, crosses the hip posteriorly to insert on the greater
trochanter of the femur, above the OI insertion
• Forms a large part of the posterolateral pelvic cavity wall, separates the
greater sciatic foramen into two regions

28. • 5.30 and Table 5.1

29. Pelvic wall
• 5.31

30. Pelvic outlet
• 5.32

31. Thank you