This document provides an overview of the pelvic wall and related structures. It describes the bones that make up the pelvic girdle (hip bones, sacrum, coccyx), their features, and how they come together. It also details the pelvic cavity and its boundaries (inlet, outlet), as well as the peritoneum and pelvic floor. Key anatomical structures are defined such as the ilium, ischium, pubis, sacrum, and coccyx. Their landmarks and articulations are outlined.

1. Pelvic Wall
Dr: Abdulrahman Muhammed ( MD )
1

2. Outline
1.Introduction
2.Pelvic girdle
3.Peritoneum and
peritoneal cavity of
pelvis
4.Walls of pelvic cavity
5.Pelvic floor 2

3. Introduction
• Pelvis
– Part of the trunk infero-posterior to the
abdomen
– Area of transition between the trunk and
the lower limbs
– Space or compartment surrounded by the
pelvic girdle ( bony pelvis )
• Bony pelvis is subdivided into greater and lesser
pelves
– Greater pelvis is the inferior part of
abdominal cavity between the alae of the
ilium
– Lesser pelvis provides the skeletal framework
for the pelvic cavity and the perineum
3

4. • Pelvic cavity
– Basin-shaped inferior part of abdomino-pelvic
cavity inferior to the plane of pelvic brim
–Pelvic brim: extends from superior border
of pubic symphysis to promontory of sacrum
– Enclosed by true pelvis and consists of pelvic
inlet, outlet, walls, and floor
– Continuous superiorly with the abdominal cavity
– Contains organs of the urinary,
gastrointestinal, and reproductive systems
• Urinary bladder, terminal parts of
ureters, pelvic genital organs, rectum,
blood vessels, lymphatics, and nerves
4

5. • Perineum
– Area of the trunk between thighs and
buttocks
– Extend from pubis to coccyx and to the
shallow compartment lying deep to this
area and inferior to the pelvic diaphragm
( floor of the pelvic cavity )
– Its boundaries form the pelvic outlet
– Contains the external genitalia and
external openings of the genitourinary
and gastrointestinal systems
• Anus, penis and scrotum of male and
vulva of female
5

6. 6

7. Pelvic Girdle
• Basin-shaped ring of bones that connects the
vertebral column to the femurs in the thighs
• The bony pelvis is formed by 4 bones united by 4
joints
– Bones: 2 hip bones, sacrum and coccyx
– Joints: 2 sacroiliac joints, pubic symphysis and
sacrococcygeal joint
• Functions
1. Bear the weight of the upper body
2. Transfer the weight of the upper body from the
axial to the lower appendicular skeleton
3. Provide attachment for muscles of locomotion and
posture, as well as those of the abdominal wall
4. Contain and protect the pelvic viscera and the
inferior abdominal viscera
5. Provide attachment for the erectile bodies of the
external genitalia
7

8. 8

9. Hip bones
• The two hip bones are joined at the pubic
symphysis anteriorly and to the sacrum
posteriorly at the sacroiliac joints to form a
bony ring, the pelvic girdle
• Each hip bone (os coxae) is formed by 3
bones fusing at the acetabulum ( a cup-like
articular depression on lateral aspect for the
head of the femur) by a y-shaped cartilage
• Begin to fuse at 15-17 years and complete at
20-25 years of age
• The 3 bones are:
1. Ilium
2. Ischium
3. Pubis
9

10. 10

11. Ilium
• The superior, flattened, fan-shaped
part of the hip bone
• Located superior to the acetabulum
• Body
– Forms the superior part of the acetabulum
– Joins ischium and pubis at acetabulum
• Ala (wing)
– Bordered superiorly by iliac crest
– Dorsum feature anterior, posterior and
inferior gluteal lines ( origins of gluteus
minimus, medius and maximus muscles )
11

12. • Iliac crest
– The rim of the ilium
– Has a curve that follows the contour of the
ala between the anterior and the posterior
superior iliac spines
– A line joining the most superior point of the
bilateral iliac crests will cross the 4th lumbar
spine (L4)
– The anterior concave part of the ala forms
the iliac fossa
• Landmarks:
1. Anterior superior iliac spine
2. Anterior inferior iliac spine
3. Posterior superior iliac spine
4. Posterior inferior iliac spine
5. Greater sciatic notch
12

13. Ischium
• Postero-inferior part of hip bone
• Has a body and a ramus
• Body
– Forms the posterior part of the acetabulum
– Joins ilium and superior ramus of pubis to
form acetabulum
• Ramus
– Fuses with the inferior ramus of pubis
– Forms part of the inferior boundary of the
obturator foramen
– Ramus of Ischium + Inferior ramus of Pubis
== Obturator Foramen
13

14. • Landmarks
–Ischial tuberosity
• Large postero-inferior protuberance
of the ischium
• Supports body during sitting
–Ischial spine
• Small pointed posterior projection
near the junction of the ramus and
body
–Lesser sciatic notch
• Ischial Spine Divides the Greater
sciatic notch and Lesser sciatic notch
14

15. Pubis
• Anteromedial part of hip bone
• Forms anterior part of the acetabulum
• Angulated bone; has two rami ( inferior &
superior ) and body
• Body
– Has a symphyseal surface for articulation
with the contralateral pubis
• Rami
– Superior pubic ramus: forms anterior part
of acetabulum
– Inferior pubic ramus: forms part of the
inferior boundary of the obturator foramen
15

16. • Landmarks
–Pecten pubis or pectineal line
•Oblique ridge on superior pubic
ramus on its superior aspect
–Pubic crest
•Thickening on the anterior part
of the body of the pubis
•Ends laterally as a swelling -
pubic tubercle
16

17. • Pubic arch ( sub-pubic angle )
–Formed by the ischio-pubic rami
(conjoined inferior rami of the pubis
and ischium) of the two sides
–These rami meet at the pubic
symphysis
–Their inferior borders define the sub-
pubic angle
• The distance between right and left
ischial tuberosities
• Measured with the fingers in the
vagina during a pelvic examination
17

18. 18

19. 19

20. 20

21. 21

22. 22
In anatomical position the anterior superior iliac spine and
the anterior aspect of the pubis lie in the same vertical
plane

23. Sacrum
1. Large, triangular, wedge-shaped
2. Composed of five fused sacral vertebrae
in adults
3. Located between the hip bones and forms
the roof and postero-superior wall of the
pelvic cavity
4. Supports the vertebral column and forms
the posterior part of the bony pelvis
5. Provides strength and stability to the
pelvis
6. Transmits the weight of the body to the
pelvic girdle 23

24. • Base
– Formed by the superior surface of the S1 vertebra
– Its superior articular processes articulate with the
inferior articular processes of the L5 vertebra
– The anterior projecting edge of the body of the
S1 vertebra is the sacral promontory
• Apex
– Tapering inferior end
– Has an oval facet for articulation with the coccyx
• The sacrum is tilted so that it articulates with the L5
vertebra at the lumbosacral angle, which varies from
130° to 160°
• The sacrum is often wider in proportion to length in
the female than in the male, but the body of the S1
vertebra is usually larger in males
24

25. • Pelvic surface of the sacrum
– Smooth and concave
– Four transverse lines in adults indicate where
fusion of the sacral vertebrae occurred
– Fusion of the sacral vertebrae starts after age
20; however, most of the IV discs remain
unossified up to or beyond middle life
• Dorsal surface of the sacrum
– Rough, convex
– Marked by five prominent longitudinal ridges
1. Central ridge (median sacral crest):
represents the fused rudimentary spinous
processes of the superior three or four
sacral vertebra; S5 has no spinous process
2. Intermediate sacral crests: represent the
fused articular processes
3. Lateral sacral crests: the tips of the
transverse processes of the fused sacral
vertebrae 25

26. • Sacral hiatus
– Inverted U-shaped opening
– Results from the absence of the laminae and
spinous process of S5 and sometimes S4
– Leads into the sacral canal
• Sacral cornua
– Representing the inferior articular processes of
S5 vertebra
– Project inferiorly on each side of the sacral
hiatus
• Auricular surface
– Superior part of the lateral surface of the
sacrum
– Site of the synovial part of the sacroiliac joint
between the sacrum and ilium
– During life, the auricular surface is covered with
hyaline cartilage
26

27. • Sacral foramina
–Four pairs
–On the pelvic ( anterior ) and
posterior surfaces of the sacrum
between its vertebral components
–For the exit of the posterior and
anterior rami of the spinal nerves
–The anterior ( pelvic ) sacral
foramina are larger than the
posterior ( dorsal ) ones
27

28. • Sacral canal
– Continuation of the vertebral canal in the sacrum
– Contents
• Roots of sacral and coccygeal nerves called
cauda equina
– Roots pierce dura and arachnoid to unite and
form trunks in the canal
– Divide into ventral and dorsal rami
 Upper four pairs of sacral nerves leave
through the corresponding sacral anterior
and posterior foramina
 5th pairs of sacral nerves and coccygeal
nerves leave through sacral hiatus
28

29. Contents of Sacral Canal
1. Sacrococcygeal Nerves (
Cauda Equina )
2. Filum Terminale
3. Lateral and Medial Sacral
Arteries
4. Fat

30. 30

31. 31

32. Coccyx (tail bone)
• Small triangular bone
• Formed by fusion of the four rudimentary
coccygeal vertebrae
• The coccygeal vertebra 1 (Co1) may be
separate
• The coccyx is the remnant of the skeleton of
the embryonic tail-like caudal eminence,
which is present in human embryos from the
end of the 4th week until the beginning of
the 8th week
• The pelvic surface of the coccyx is concave
and relatively smooth, and the posterior
surface has rudimentary articular processes
32

33. • Co1
– The largest and broadest
– Its short transverse processes are
connected to the sacrum, and its
rudimentary articular processes form
coccygeal cornua, which articulate with
the sacral cornua
• The last three coccygeal vertebrae often
fuse during middle life, forming a beak-like
coccyx
• With increasing age, Co1 often fuses with
the sacrum, and the remaining coccygeal
vertebrae usually fuse to form a single bone
33

34. Pelvic inlet and pelvic outlet
• Pelvic inlet
– Superior boundary of the pelvic cavity
– Superior pelvic aperture
– Bounded by the linea terminalis of the
pelvis, which is formed by:
1. Superior margin of the pubic symphysis
anteriorly
2. Posterior border of the pubic crest
3. Pecten pubis, the continuation of the superior
ramus of the pubis, which forms a sharp ridge
4. Arcuate line of the ilium
5. Anterior border of the ala of the sacrum
6. Sacral promontory 35

35. • Pelvic outlet
– The pelvis is limited inferiorly by the
pelvic outlet, the inferior pelvic
aperture
– Bounded by:
1. Inferior margin of the pubic
symphysis anteriorly
2. Inferior rami of the pubis and
ischial tuberosities anterolaterally
3. Sacrotuberous ligaments
posterolaterally
4. Tip of the coccyx posteriorly
35

36. Greater and lesser pelves
• The bony pelvis is divided into
greater (false) and lesser
(true) pelves by the oblique
plane of the pelvic inlet
(superior pelvic aperture)
• The bony edge (rim)
surrounding the pelvic inlet is
the pelvic brim
36

37. • Greater or false pelvis (pelvis major)
– Superior to the pelvic inlet
– Lies between iliac fossa
– Bounded by the abdominal wall anteriorly, the iliac
alae laterally, and the L5 and S1 vertebrae
posteriorly
– Part of abdominal cavity
• Lesser or true pelvis (pelvis minor)
– Actual pelvis
– Between the pelvic inlet and the pelvic outlet
– The location of the pelvic viscera
– Bounded by the pelvic surfaces of the hip bones,
sacrum, and coccyx
– Limited inferiorly by the musculofascial pelvic
diaphragm (levator ani)
37

38. 38

39. 39

40. Joints and ligaments of pelvic girdle
• The primary joints of the pelvis are
the sacroiliac joints and the pubic
symphysis, which link the skeleton of
the trunk and the lower limb
• The lumbosacral and sacrococcygeal
joints are directly related to the
pelvic girdle
• Strong ligaments support and
strengthen these joints
40

41. Sacroiliac Joints
• Strong weight bearing compound joints
• In the line of weight transmission from the
spine to the hip bone and then to the femur
• Compound joints
– Anterior synovial joint ( between the ear-shaped
auricular surfaces of the sacrum and ilium covered
with articular cartilage )
– Posterior syndesmosis ( between the tuberosities
of the same bones )
• The articular surfaces of the synovial joint
have irregular but congruent elevations and
depressions that interlock
• Differ from most synovial joints in that
limited mobility is allowed
– Slight gliding and rotary movements
41

42. 42

43. • Ligaments are arranged to allow a small
amount of movement and to resist major
displacement of the sacrum
–Posterior or dorsal interosseous
sacroiliac ligaments: posterior sacrum to
posterior ilium
–Anterior or ventral sacroiliac
ligament is weaker
–Sacrospinous ligament: from ischial
spine to side of sacrum. Converts greater
sciatic notch into a foramen
–Sacrotuberous ligament: from ischial
tuberosity to side of sacrum. Converts
lesser sciatic notch into a foramen
–Iliolumbar ligament: from the
transverse process of L5 to posterior part
of iliac crest
43

44. 44

45. 45

46. Pubic Symphysis
• Secondary cartilaginous joint
• Formed by the union of the bodies of the
pubic bones in the median plane
• The fibrocartilaginous interpubic disc is
generally wider in women than in men
• The ligaments joining the pubic bones are
thickened superiorly and inferiorly to form the
superior pubic ligament and the inferior
(arcuate) pubic ligament, respectively
• The decussating fibers of tendinous
attachments of the rectus abdominis and
external oblique muscles also strengthen the
pubic symphysis anteriorly 46

47. 47

48. Lumbosacral Joints
• The L5 and S1 vertebrae articulate at the
anterior intervertebral joint
• Formed by the intervertebral (IV) disc
between their bodies and at two posterior
zygapophysial joints (facet joints) between the
articular processes of these vertebrae
• The facets on the S1 vertebra face
posteromedially, interlocking with the
anterolaterally facing inferior articular facets
of the L5 vertebra, preventing L5 from sliding
anteriorly
• Iliolumbar ligaments unite the transverse
processes of L5 to the ilia
48

49. Sacrococcygeal Joint
• Secondary cartilaginous joint with an IV
disc
• Fibrocartilage and ligaments join the
apex of the sacrum to the base of the
coccyx
• The anterior and posterior
sacrococcygeal ligaments are long
strands that reinforce the joint, much
like the anterior and posterior
longitudinal ligaments do for superior
vertebrae
49

50. Greater and lesser sciatic foramina
• The parts of bony pelvis are bounded
by gluteal ligaments
• Sacrotuberous and sacrospinous
ligaments convert sciatic notches into
greater and lesser sciatic foramina
• Greater sciatic foramina is passageway
for structures entering or leaving the
pelvis
• Lesser sciatic foramina is passageway
for structures entering or leaving
perineum
50

51. 51

52. 52

53. 53

54. Sexual differences in bony pelves
• The male and female bony pelves differ in several
respects
• These sexual differences are related mainly to the
heavier build and larger muscles of men and to the
adaptation of the pelvis, particularly the lesser
pelvis, in women for childbearing
• The female pelvic modifications accommodate the
growing fetus as well as providing a birth canal wide
enough to allow the infants head to exit at birth
• The male pelvis is heavier and thicker than the
female pelvis and usually has more prominent bone
markings
• The female pelvis is wider, shallower, lighter, and
rounder than the male and has a larger pelvic inlet
and outlet
54

55. 55

56. 56

57. 57

58. Variations in the male and female pelvis
• The pelvis of any person may have some
features of the opposite sex
• Gynecoid pelvis
– Normal female type
– Its pelvic inlet has a rounded or oval shape
and a wide transverse diameter
• Android pelvis
– Masculine
– Funnel-shaped
– In a woman may present hazards to
successful vaginal delivery of a fetus
58

59. 59
A and C are most common in males
B and A in white females
B and C in black females
D is uncommon in both sexes

60. Pelvic diameters (Conjugates)
• The shape and size of the pelvic inlet ( and
the pelvic brim ) are significant because it is
through this opening that the fetal head
enters the lesser pelvis during labor
• The ischial spines face each other and the
interspinous distance between them is the
narrowest part of the pelvic canal ( the
passageway traversing the pelvic inlet, lesser
pelvis, and pelvic outlet through which a
baby's head must pass at birth )
• To determine the capacity of the female
pelvis for childbearing, the diameters of the
lesser pelvis are noted radiographically or
manually during a pelvic examination
60

61. • Antero-posterior (AP) diameter
– True ( obstetrical ) conjugate
– From the middle of the sacral promontory
to the posterosuperior margin of the pubic
symphysis
– The narrowest fixed distance through
which the baby's head must pass in a
vaginal delivery
– This distance, however, cannot be
measured directly during a pelvic
examination because of the presence of
the bladder
61

62. • Diagonal conjugate
–Measured by palpating the sacral
promontory with the tip of the middle
finger, using the other hand to mark
the level of the inferior margin of the
pubic symphysis on the examining hand
–The distance between the tip of the
index finger and the marked level of
the pubic symphysis is measured to
estimate the true conjugate, which
should be 11.0 cm or greater
62

63. • Interspinous distance
– The ischial spines extend toward each other
– The distance between them is normally the
narrowest part of the pelvic canal
– But it is not a fixed distance due to
relaxation of pelvic ligaments and increased
joint mobility during pregnancy
– During a pelvic examination, if the ischial
tuberosities are far enough apart to permit
three fingers to enter the vagina side by
side, the sub-pubic angle is considered
sufficiently wide to permit passage of an
average fetal head at full term
63

64. 64

65. Pelvic fractures
• Pelvic fractures can result from
– Direct trauma to the pelvic bones
– Foces transmitted to these bones from the
lower limbs during falls on the feet
• Weak areas of the pelvis
1. Pubic rami
2. Acetabula
3. Region of the sacroiliac joints
4. Alae of the ilium
• Pelvic fractures may cause injury to
pelvic soft tissues, blood vessels,
nerves, and organs
65

66. • Fractures in the pubo-obturator area are
relatively common and are often complicated
because of their relationship to the urinary
bladder and urethra, which may be ruptured
or torn
• Falls on the feet or buttocks from a high
ladder may drive the head of the femur
through the acetabulum into the pelvic
cavity, injuring pelvic viscera, nerves, and
vessels
• In individuals < 17 years of age, the
acetabulum may fracture through the
triradiate cartilage into its three
developmental parts
66

67. Peritoneum and peritoneal cavity of
pelvis
• The peritoneum lining the abdominal cavity
continues into the pelvic cavity, reflecting onto
the superior aspects of most pelvic viscera
• Only the uterine tubes except for their ostia,
are intraperitoneal and suspended by a
mesentery
• The ovaries, although suspended in the
peritoneal cavity by a mesentery, are not
covered with peritoneum
• The peritoneum is not firmly bound to the
suprapubic crest, allowing the bladder to expand
between the peritoneum and the anterior
abdominal wall as it fills
67

68. • The undulating course of the
peritoneum around and over the various
pelvic structures produces blind ended
peritoneal pouches
• In male
– Rectovesical pouch: between the bladder
and rectum
• In female
– Vesicouterine pouch: between bladder
and uterus
– Rectouterine pouch: between rectum and
uterus
68

69. Walls of pelvic cavity
• The pelvic cavity has an anteroinferior
wall, two lateral walls, and a posterior
wall
• Formed by framework of bones, joints,
ligaments and muscles lined by
membrane
1. Anteroinferior pelvic wall
– Formed primarily by the bodies and rami of
the pubic bones and the pubic symphysis
– Participates in bearing the weight of the
urinary bladder
69

70. 2. Lateral pelvic walls
– Have a bony framework formed by the hip bones,
including the obturator foramen
– Are covered and padded by the obturator internus
muscles
– Each obturator internus passes posteriorly from its
origin within the lesser pelvis, exits through the
lesser sciatic foramen, and turns sharply laterally
to attach to the femur
– The medial surfaces of these muscles are covered
by obturator fascia, thickened centrally as a
tendinous arch that provides attachment for the
pelvic diaphragm
– Obturator nerves and vessels and other branches of
the internal iliac vessels located on their medial
aspects 70

71. Obturator Internus
• Origin : Pelvic surfaces of ilium and
ischium; obturator membrane, runs
through the lesser sciatic foramen
• Insertion : greater tochanteric of
the femur
• Action : rotates thigh laterally;
assissts in holding head of the femur
in acetabulum
• Nerve supply : nerve to obturator
internus ( L5, S1, S2 )

72. Cont…
• Obturator fascia
–Covers medial surface of
obturator internus
–Partly is origin of levator ani
–Splits in the lateral wall of
ischiorectal fossa to form
pudendal canal ( External
Genitalia )

73. 73

74. 74

75. 3. Posterior pelvic wall
– Consists
• Bony wall and roof: midline; formed by
sacrum and coccyx
• Musculoligamentous posterolateral walls:
formed by sacroiliac joints and their
associated ligaments and piriformis
muscles
– Each piriformis muscle leaves the lesser
pelvis through the greater sciatic foramen
to attach to the femur
– Site of the nerves forming the sacral
plexus
75

76. Piriformis
• Origin
– Pelvic surface of S2 - S4 segments
– Superior margin of greater sciatic notch
and sacrotuberous ligament
– Passes through greater sciatic foramen
• Insertion - greater trochanter of femur
• Nerve supply – nerve to piriformis from sacral
plexus ( S1 and S2 )
• Action – Rotates thigh laterally; abducts
thigh; assists in holding head of femur in
acetabulum
• Levator ani, coccygeus and piriformis are
covered by a layer of fascia
76

77. 77

78. Pelvic floor
• Formed by the funnel-shaped pelvic
diaphragm, which consists of the levator ani
and coccygeus muscles and the fascias
covering the superior and inferior aspects of
these muscles
• The coccygeus muscles extend from the
ischial spines to the inferior sacrum and
coccyx
• The levator ani is attached to the pubic
bones anteriorly, to the ischial spines
posteriorly, and to a thickening in the
obturator fascia ( tendinous arch of levator
ani ) on each side 78

79. 79

80. Pelvic diaphragm
• Levator ani and coccygeus form the pelvic
diaphragm, separating the pelvis from the
ischiorectal fossa
–Urethra, vagina and rectum pass
through the pelvic diaphragm
and vessels go around it
–Pudendal Nerve arises from 2,3 and 4th
sacral nerves and supplies the genitalia,
Perineum, and the Anal sphincters
80

81. Levator ani
• Broad muscular sheet ( THIN )
• Attached to the bodies of the pubic bones
anteriorly, to the ischial spines posteriorly, and
to a thickening in the obturator fascia ( tendinous
arch of the levator ani ) between the two bony
sites on each side
• The pelvic diaphragm thus stretches between the
anterior, the lateral, and the posterior walls of
the lesser pelvis, giving it the appearance of a
hammock suspended from these attachments,
closing much of the ring of the pelvic girdle
• An anterior gap between the medial borders of
the levator ani muscles of each side ( the
urogenital hiatus ) gives passage to the urethra
and, in females, the vagina
81

82. 82

83. •Origin
–Back of body of pubis, lateral
to the symphysis
–Ischial spine
–Tendinous arch of obturator
fascia
• The muscle sweeps inferiorly,
medially and posteriorly
83

84. • Insertion
– Perineal body; coccyx; anococcygeal ligament;
walls of prostate or vagina, rectum, and anal
canal
– Muscles of the two sides unite to form hammock
like sheet
– Most anterior fibers from the back of the pubis
run:
• In the male, posteriorly and inferiorly just
below the prostate gland, to be inserted into
the perineal body
• In the female, the muscle surrounds the vagina
and forms the sphincter vaginae
– Other fibers pass around the recto-anal junction
and blends in with fibers of the anal sphincter:
this is the puborectalis or recto-anal sling
– Posterior fibers meet their opposite and form the
anococcygeal raphe
– Most posterior fibers insert into the coccyx
84

85. • Consists of three parts, each named
according to the attachment of its
fibers
1. Puborectalis
– Consisting of the thicker, narrower,
medial part of the levator ani, which is
continuous between the posterior aspects
of the right and left pubic bones
– It forms a U-shaped muscular sling
(puborectal sling) that passes posterior to
the anorectal junction
– This part plays a major role in maintaining
fecal continence
85

86. 86

87. 2. Pubococcygeus
– Wider but thinner intermediate part of the levator
ani
– Arises from the posterior aspect of the body of
the pubis and the anterior part of the tendinous
arch and passes posteriorly in a nearly horizontal
plane
– The lateral fibers attach posteriorly to the
coccyx, and the medial fibers merge with those of
the contralateral side to form part of the
anococcygeal body or ligament
3. Iliococcygeus
– The posterolateral part of the levator ani
– Arising from the posterior part of the tendinous
arch and ischial spine
– Thin and often poorly developed and blends with
the anococcygeal body posteriorly
87

88. 88

89. • Nerve supply
– Nerve to levator ani ( branches of S4 )
– Inferior anal (rectal) nerve
– Coccygeal plexus
• Action
1. Support pelvic viscera
• Forms a dynamic floor for supporting the
abdominopelvic viscera
• Acting together, raise the pelvic floor,
following its descent when relaxed to
allow defecation and urination, restoring
its normal position
89

90. 2. Resist the increased intra-abdominal
pressure that would otherwise force the
abdominopelvic contents through the pelvic
outlet
• This action occurs reflexively during
forced expiration, coughing, sneezing,
vomiting, and fixation of the trunk
during strong movements of the upper
limbs
3. Has role in the voluntary control of
urination, fecal continence, and support of
the uterus
90

91. Coccygeus ( ischio-coccygeus )
• Origin: Ischial spine
• Insertion: Inferior end of sacrum
• Nerve supply: branches of S4 &
S5
• Action: Forms posterior part of
pelvic floor that supports pelvic
viscera; flexes coccyx
91

92. 92

93. 93

94. Injury to pelvic floor
• During childbirth, the pelvic floor supports
the fetal head while the cervix of the uterus
is dilating to permit delivery of the fetus
• The perineum, levator ani, and pelvic fascia
may be injured during childbirth
• It is the pubococcygeus, the main and most
medial part of the levator ani, that is usually
torn
– This part of the muscle is important
because it encircles and supports the
urethra, vagina, and anal canal
• Weakening of the levator ani and pelvic fascia
resulting from stretching or tearing during
childbirth may alter the position of the neck
of the bladder and urethra
–Cause urinary stress incontinence
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