These are deeply situated in the sublumbar region at the ventral face of the lumbar vertebra and the anterior face of the ilium. These muscles occupy not only the sublumbar region but also extend both forwards and backwards beyond this region, and enter into the formation of the roof of the abdominal cavity. They are in contact with the abdominal viscera.
Fascia
- The ventral face of the iliacus and psoas major is covered by a strong fibrous expansion the iliac fascia, which is attached to the tendon of the psoas minor internally and the lateral angle and the border of the ilium laterally.
- It is thin where it covers the anterior part of the psoas major. It also becomes thin posteriorly where it covers the terminal portion of the psoas major and iliacus. Its inferior part furnishes one of the origin of the sartorius.
- The sublumbar muscles are-
- Psoas minor
- Psoas major
- Iliacus
- Quadratus lumborum
- Intertransversales lumborum
- Psoas minor
- This is an elongated muscle, which lies along the ventro-lateral aspect of the bodies of the last dorsal and lumbar vertebrae.
- Origin: The intervertebral fibro-cartilage between the 12 th and 13 th and all lumbar vertebrae.
- Insertion: Psoas tubercle on the shaft of the ilium.
- Action: To flex the pelvis on the loin and incline the lumbar region laterally.
- Blood supply: Lumbar arteries.
- Nerve supply: Lumbar nerves.
- Psoas major
- This muscle is larger than the preceding and is situated ventral to the lumbar transverse processes and ilium.
- Origin: Upper posterior borders of the last two ribs and the transverse processes of the lumbar vertebrae.
- Insertion: In common with the iliacus to the trochanter minor of the femur.
- Action: T o flex the hip and rotate the thigh outwards.
- Blood supply: Lumbar and circumflex iliac arteries.
- Nerve supply: Ilio- psoas nerve.
- Iliacus
- This muscle is situated on the anterior part of the pelvic surface of the ilium lateral to the ilio-pectineal line. It appears to have two parts forming a groove to receive the preceding muscles with which it forms iliopsoas.
- Origin: Iliac surface, shaft of ilium between the psoas tubercle and origin of rectus femoris and tendon of psoas minor and wing of the sacrum. The muscle begins under the body of the sixth lumbar vertebra.
- Insertion: In common with the preceding to the trochanter minor of the femur.
- Action: Same as preceding.
- Blood supply: Lumbar and deep femoral arteries.
- Nerve supply: Ilio- psoas nerve.
- Quadratus lumborum
- This muscle is partly covered by the psoas minor.
- Origin: Ventral surface of the upper part of the last two or three ribs and transverse processes of the lumbar vertebrae.
- Insertion: The anterior border of the first five lumbar transverse processes and wing of sacrum.
- Action: Acting singly, to flex the loin laterally, acting together to fix the lumbar vertebrae and last two ribs .
- Blood supply: Lumbar arteries.
- Nerve supply: Lumbar nerves.
- Intertransversales lumborum
- These are small, flat muscles fill the inter-transverse spaces of the lumbar vertebrae.
- Origin: The anterior border of the transverse process of the preceding lumbar vertebra.
- Insertion: The posterior border of the transverse process of the lumbar vertebra in front.
- Action: To aid in lateral flexion of loin.
- Blood supply: Lumbar arteries.
- Nerve supply: Lumbar nerves.
Horse
- The psoas minor extends from the last three dorsal vertebrae.
- The psoas major completely covers quadratus lumborum.
- The quadratus lumborum is narrower.
- The iliacus does not arise from the sixth lumbar vertebra and not so closely blended with the psoas major as in the ox.
Dog
- The psoas minor is relatively larger than the psoas minor. Its anterior part blends with the quadratus lumborum but does not extend into the thoracic cavity.
- The psoas major is short as it begins from third or fourth lumbar vertebra.
- The quadratus lumborum is larger and stronger and better developed than any other animals. Its arises from last three or four thoracic vertebra in common with psoas minor to teminate in the upper part of the pelvic surface of the ilium.
- The intertransversales lumborum is same as that of ox.
