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MUSCLES of the PELVIS
Pelvic Walls: Obturator internus

Origin:
Most of the internal surface of the
anterolateral wall of the pelvis minor (pelvic
surfaces of the ilium, ischium, and obturator
membrane).

Insertion:
Greater trochanter of femur (medial surface)
via strong tendon which passes through the
lesser sciatic foramen.
Pelvic Walls: Obturator internus

Action:
Lateral thigh rotation (when hip is flexed);
helps to hold femoral head in acetabulum.

Nerve:
Nerve to obturator internus (L5-S1).
Pelvic Walls: Piriformis

Origin:
Anterior aspect of the second through the
fourth lateral masses of the sacrum and the
sacrotuberous ligament.

Insertion:
Greater trochanter of the femur–superior
border.
Pelvic Walls: Piriformis

Action:
Lateral rotation of thigh (when hip is
extended); thigh abduction (when hip is
flexed); helps to hold femoral head in
acetabulum; forms the muscular bed for the
sacral plexus; leaves the pelvis via the
greater sciatic foramen.

Nerve:
Ventral rami of S1-2.
Pelvic Diaphragm: Levator Ani

Composed of three muscles:
Puborectalis.
Pubococcygeus.
Iliococcygeus.

Figure 3.39
Pelvic Diaphragm: Levator Ani

Puborectalis:
Origin:
Insertion:
Action:
Nerve:
Pectin pubis.
Rectum and anal canal.
Maintain anorectal flexure.
Compress abdominal viscera.
Compress pelvic contents.
Perineal nerve.
Pelvic Diaphragm: Levator Ani

Pubococcygeus:
Origin:
Insertion:
Action:
Nerve:
Pectin pubis.
Coccyx.
Raise pelvic floor.
Compress abdominal viscera
Compress pelvic contents.
Perineal nerve.
Pelvic Diaphragm: Levator Ani

Iliococcygeus:
Origin:
Insertion:
Action:
Nerve:
Obturator fascia and ischial
spine.
Coccyx and anococcygeal
ligament.
Same as for pubococcygeus.
Perineal nerve.
Pelvic Diaphragm: Coccygeus
Part of pelvic diaphragm.
 Not part of levator ani.
 Origin:
Ischial spine.
 Insertion:
Inferior sacrum and coccyx.
 Action:
Support pelvic viscera.
Flex coccyx.
 Nerve:
S4, S5
