Lumbar spinal nerves

There are six pairs of Lumbar spinal nerves. The dorsal branches are distributed to the muscles, situated above the transverse processes of the lumbar vertebrae and supplies the skin of the loin. The ventral branches slightly differ in their distribution.

They pass under the psoas minor and psoas major and emerge at the lateral border of the latter. They supply branches to the sublumbar muscles, abdominal muscles and the skin.

The ventral branch of the first lumber is termed ilio-hypogastric nerve, which divides into a superficial cutaneous branch and a deep muscular branch.

The superficial branch passes downward and backward between the internal and external oblique muscles, perforating the latter, supplies skin on the posterior part of the flank and lateral aspect of the thigh.

The deep branch runs under the peritoneum and supplies internal oblique and rectus abdominis muscles.

The ventral branch of the second lumbar supplies psoas major and continues as the ilio-inguinal nerve.

This also divides into a superficial branch supplying skin in front of thigh and lateral face of the stifle.

The deep branch supplies abdominal muscles, unites with a branch from the third lumbar nerve passes through the inguinal canal, supplies external genitalia and skin of inguinal region.

The ventral branch of the third lumbar gives branches to psoas muscles and divides into superficial and deep branches.

The superficial branch continues as the lateral cutaneous nerve of the thigh, passes outward and backward, emerges below the point of hip, between iliacus and obliques abdominis externus, under the cover of tensor fasciae latae and supplies the skin of the stifle region.

The deep branch forms the external spermatic nerve which descends into the inguinal region.

The ventral branches of the fourth, fifth and sixth lumbar spinal nerves enter into the formation of the lumbo-sacral plexus.

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