THE SACRAL PLEXUS -Gross anatomy - Dr G Bhanu Prakash

Video Description

Sacral plexus
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The sacral plexus is a network of nerve fibres that supplies the skin and muscles of the pelvis and lower limb. It is located on the surface of the posterior pelvic wall, anterior to the piriformis muscle.

The plexus is formed by the anterior rami (divisions) of the sacral spinal nerves S1, S2, S3 and S4. It also receives contributions from the lumbar spinal nerves L4 and L5.

In this article, we shall look at the anatomy of the sacral plexus – its formation and major branches.

The sacral plexus is formed by anterior rami of L4 to S5 and its branches innervate the pelvis, perineum and lower limb.

Gross anatomy
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The sacral plexus forms on the anterior belly of the piriformis muscle and is formed by the lumbosacral trunk (L4-5) of the lumbar plexus, which enters the pelvis coursing medially to psoas major and unites with the ventral rami of the S1 to S4 nerve roots, which emerge from the anterior foramen of the sacrum. It forms a triangular shape with an inferiorly pointing apex.

The anterior sacral rami give off six branches and then divide into the anterior and posterior division, each giving off further branches (see below).

Branches
Anterior rami
nerve to piriformis (S1-S2)
perforating cutaneous nerve (S2-S3)
posterior femoral cutaneous nerve (S1-S3)
parasympathetic pelvic splanchnic nerves (S2-S4)
pudendal nerve (S2-S4)
perineal branch (S4)


Anterior division of anterior rami
nerve to quadratus femoris and inferior gemellus muscles (L4-S1)
nerve to internal obturator and superior gemellus muscles (L5-S2)
tibial portion (L4-S3) of the sciatic nerve (L4-S3)


Posterior division of anterior rami
superior gluteal nerve (L4-S1)
inferior gluteal nerve (L5-S2)
common peroneal portion (L4-S2) of the sciatic nerve (L4-S3)