The iliacus - named from its attachment to the ihum - is a thick, triangula sheet.

Origin

1. The upper surface of the ala of the sacrum;
2. the front of th ilio-lumbar, lumbo-sacral and anterior sacro-iliac ligaments;
3. the upper and oute half of the venter of the ilium;
4. the origin of the upper tendon of the rectu femoris and the ilio-femoral ligament near the anterior inferior spine of the ilium

Insertion

1. The outer surface of the tendon of the psoas, through which it is attached to the back of the lesser trochanter of the femur;
2. the upper an inner part of the shaft of the femur in a line about one inch long leading downward from the lesser trochanter.

Structure

Arising by fleshy fibers, the muscle converges in a fan-shape dowr wards and inwards and its fibres enter the posterior and outer surface of the tendo of the psoas muscle from about two inches above Poupart's ligament to its insertion. The lowest fibers are also continued, still fleshy, into their insertion on the inne part of the shaft of the femur.

Nerve-supply

From the lumbar plexus (through the second and third lumbe nerves) by the anterior crural nerve, which gives branches to its anterior surface about the middle of its inner border.

Action

Similar to that of the psoas, as a flexor of the thigh; and acting froi the femur as a fixed point, it will draw forwards and flex the pelvis upon the thigh.

Relations

The iliac fascia in front separates it from the peritoneum an intestines. The profunda femoris artery and several nerves from the lumbar plexi lie upon it. Behind and to its inner side, lies the psoas. After passing undt Poupart's ligament, it is crossed by the sartorius and behind lie the rectus femor and the capsule of the hip joint.

Variations

A small detached muscle occasionally arises from the anterior inferior spine and is inserted into the lower part of the anterior intertrochanteric line, or the ilio-femoral ligament.

Muscles of the front of the thigh.