The lumbosacral trunk is nervous tissue that connects the

lumbar plexus The lumbar plexus is a web of nerves (a nervous plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the su ...

with the

sacral plexus In human anatomy, the sacral plexus is a nerve plexus which provides motor and sensory nerves for the posterior thigh, most of the lower leg and foot, and part of the pelvis. It is part of the lumbosacral plexus and emerges from the lumbar verteb ...

Structure

The lumbosacral trunk comprises the whole of the

ventral rami The ventral ramus (pl. ''rami'') (Latin for ''branch'') is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk and the limbs. They are mainly larger than the dorsal rami. Shortly after a spinal n ...

of L5 and a part of L4. It appears at the medial margin of the

psoas major The psoas major ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the il ...

and runs downward over the

pelvic brim The pelvic brim is the edge of the pelvic inlet. It is an approximately Mickey Mouse head-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis. Structure The pel ...

to join the first

sacral nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

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

and the latter the pudendal plexus. This connects the

and the

Clinical significance

The lumbosacral trunk may be compressed by the

fetal head The fetal head, from an obstetrical viewpoint, and in particular its size, is important because an essential feature of labor is the adaptation between the fetal head and the maternal bony pelvis. Only a comparatively small part of the head at ter ...

during the second stage of labour. This causes some muscle weakness in the

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element c ...

. A full recovery is usually expected.

Additional images

File:Slide9w.JPG, Lumbosacral trunk File:Slide2ROGER.JPG, Ramus communicans.Sacral symphatetic with S1.

Reference

External links

* - "The Female Pelvis: The Posterolateral Pelvic Wall" * * {{Authority control Spinal nerves