Iliopsoas Anatomy Study: Iliacus, Psoas Major, and Psoas Minor Muscles

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Iliopsoas Muscle Group

Synergist:

• Prime Movers: Pectineus, Tensor fascia latae, Adductor brevis, Sartorius • Accessory Movers: Adductor longus, Adductor magnus (anterior part), Gracilis, Gluteus minimus, Quadratus Lumborum

Antagonist:Gluteus maximus, Adductor magnus (posterior part)

Iliacus

Origin: Superior two-thirds of the internal surface of the iliac fossa, the inner lip of the iliac crest, the ventral surface of the sacroiliac and iliolumbar ligaments, and the upper surface of the lateral part of the sacrum. Insertion: The lesser trochanter of the femur after being joined by the tendon of psoas major. The conjoined tendon passes under the inguinal ligament to enter the thigh Action: Flexion of thigh at hip, assists in extension of the lumbar spine Innervation: Femoral nerve (L2, 3) Blood Supply: Iliolumber artery from internal iliac artery

Primary Actions of the Iliacus:

1. Flexion of thigh at the hip

• Agonists: Psoas Major • Antagonists: Gluteus maximus, Semitendinosus, Semimembranosus, Biceps Femoris (long head), Adductor magnus (posterior part)

2. Flexion of the pelvis at the hip

• Agonists: Psoas Major • Antagonists: Gluteus maximus, Semitendinosus, Semimembranosus, Biceps Femoris (long head), Adductor magnus (posterior)

Psoas Major

Origin: Anterior surfaces of the transverse processes of T12-L5 vertebrae, the upper two thirds of the iliacus Insertion: The lesser trochanter of the femur after being joined by the iliacus Action: Flexion of thigh at hip, assists in extension of the lumbar spine Innervation: Lumbar plexus (L2, 3, 4)

Primary Actions of the Psoas Major:

1. Flexion of thigh at the hip

• Agonists: Iliacus • Antagonists: Gluteus maximus, Semitendinosus, Semimembranosus, Biceps Femoris (long head), Adductor magnus (posterior part)

Secondary Actions of the Psoas Major:

2. Assists with extension of the lumbar spine

• Agonists: Iliocostalis lumborum, Longissimus thoracis • Antagonists: Rectus Abdominis

3. Lateral Flexion of the spine when acting unilaterally

• Agonists: Iliocostalis lumborum, Longissimus thoracis, Quadratus lumborum, External and Internal Oblique • Antagonists: Iliocostalis lumborum, Longissimus thoracis, Quadratus lumborum, External and Internal Oblique on the opposite side.

Psoas Minor

Origin: Bodies of T12 and L1 and intervening intervertebral discs Insertion: Fascia over the psoas major and iliacus Action: Flexion of thigh at hip, assists in extension of the lumbar spine Innervation: Ventral primary rami of L1 Blood Supply: Iliolumbar artery from internal iliac artery

Primary Actions of the Psoas Minor: Because of its position and size the psoas minor is not a prime mover.

Secondary Actions of the Psoas Minor:

1. Assists with flexion of the thigh at the hip

• Agonists: Psoas Major, Iliacus • Antagonists: Gluteus maximus, Semitendinosus, Semimembranosus, Biceps Femoris (long head)

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