Lumbosacral trunk

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The lumbosacral trunk is nervous tissue that connects the lumbar plexus with the sacral plexus.

Structure
The lumbosacral trunk comprises the whole of the anterior division of the fifth and a part of that of the fourth lumbar nerve; it appears at the medial margin of the psoas major and runs downward over the pelvic brim to join the first sacral nerve.

The anterior division of the third sacral nerve divides into an upper and a lower branch, the former entering the sacral plexus and the latter the pudendal plexus.