Iliacus muscle
Encyclopedia
The iliacus is a flat, triangular muscle which fills the iliac fossa
Iliac fossa
The iliac fossa is a large, smooth, concave surface located on the internal surface of the ilium...

.

Course

The iliacus arises from the iliac fossa
Iliac fossa
The iliac fossa is a large, smooth, concave surface located on the internal surface of the ilium...

 on the interior side of the hip bone
Hip bone
The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

, and also from the region of the anterior inferior iliac spine (AIIS). It joins the psoas major
Psoas major muscle
-External links: - "Posterior Abdominal Wall: Muscles of the Posterior Abdominal Wall"* *...

 to form the Iliopsoas
Iliopsoas
-External links:*...

 as which it proceeds across the iliopubic eminence through the muscular lacuna
Muscular lacuna
The Muscular lacuna is the lateral compartment beneath the inguinal ligament, for the passage of the iliopsoas muscle and femoral nerve; it is separated by the iliopectineal arch from the vascular lacuna....

 to its insertion on the lesser trochanter
Lesser trochanter
The lesser trochanter of the femur is a conical eminence, which varies in size in different subjects-Anatomy:It projects from the lower and back part of the base of the femur neck.From its apex three well-marked borders extend:...

 of the femur. Its fibers are often inserted in front of those of the psoas major and extends distally over the lesser trochanter
Lesser trochanter
The lesser trochanter of the femur is a conical eminence, which varies in size in different subjects-Anatomy:It projects from the lower and back part of the base of the femur neck.From its apex three well-marked borders extend:...

.

Action

In open-chain movements, as part of the iliopsoas
Iliopsoas
-External links:*...

, the iliacus is important for lifting (flexing) the leg forward. In closed-chain movements, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture (i.e. sit-ups) because the psoas major crosses several vertebral joints and the sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...

. From its origin in the lesser pelvis the iliacus acts exclusively on the hip joint.

Innervation

The iliopsoas is innervated by the femoral nerve
Femoral nerve
The femoral nerve, the largest branch of the lumbar plexus, arises from the dorsal divisions of the ventral rami of the second, third, and fourth lumbar nerves...

 and direct branches from the lumbar plexus.

External links

  • PTCentral - "Muscles and nerves of the posterior abdominal wall."
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