Human Anatomy - Kotsan I. Ya. 2009

Peripheral Nervous System
Spinal Nerves
Sacral Plexus

The sacral plexus (plexus sacralis) is the largest of all nerve plexuses. It is formed by the anterior rami of the upper four sacral (SI-SIV) nerves, the fifth lumbar (LV) nerve, and a portion of the anterior ramus of the fourth lumbar (LIV) nerve (Figs. 261, 262).

The anterior ramus of the fifth lumbar nerve and part of the anterior ramus of the fourth lumbar nerve unite to form the lumbosacral trunk (truncus lumbosacralis), which descends into the lesser pelvis and joins the anterior rami of the first, second, third, and fourth sacral Spinal Nerves on the anterior surface of the piriformis Muscle. Overall, the sacral plexus is triangular in shape, with its base located near the pelvic sacral foramina and its apex situated near the inferior margin of the greater sciatic foramen, through which the largest Branches of the plexus exit the pelvic cavity. The sacral plexus lies between two Connective Tissue layers: posteriorly, it is covered by the Fascia of the piriformis muscle, and anteriorly, by the pelvic fascia.

The branches of the sacral plexus are divided into short and long groups. The short branches innervate the Muscles and Skin primarily within the lesser pelvis, whereas the long branches supply the muscles and skin of the free lower limb.



Last update: 08/08/2026

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