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The lumbosacral trunk is formed by the union of the entire anterior ramus of lumbar nerve L5 and a part of L4 [clarification needed]. [1] [2] [3] L4 first issues its branches to the lumbar plexus, then emerges from the medial border of the psoas muscle [3] to unite with the anterior ramus of L5 just superior to the pelvic brim to form the thick, cord-like trunk which [4] crosses the pelvic ...
the lumbosacral trunk; the anterior division of the first sacral nerve; portions of the anterior divisions of the second and third sacral nerves; The nerves forming the sacral plexus converge toward the lower part of the greater sciatic foramen, and unite to form a flattened band, from the anterior and posterior surfaces of which several ...
It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve. Additionally, the ventral rami of the fourth lumbar nerve pass communicating branches, the lumbosacral trunk, to the sacral plexus. The nerves of the lumbar plexus pass in front of the hip ...
The anterior divisions of the lumbar nerves, sacral nerves, and coccygeal nerve form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. For descriptive purposes this plexus is usually divided into three parts: lumbar plexus; sacral plexus; pudendal plexus
The plexus extends toward the armpit. The ventral rami of C5 and C6 form upper trunk, the ventral ramus of C7 forms the middle trunk, and the ventral rami of C8 and T1 join to form the lower trunk of the brachial plexus. Under the clavicle, the trunks reorganize to form cords (fasciculi) around the axillary artery (arteria axillaris).
The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and ala, and the S1 to S3 roots emerge from the ventral sacral foramina. These nerve roots unite to form a single nerve in front of the piriformis muscle. The nerve passes beneath the piriformis and through the greater sciatic foramen, exiting the pelvis.
The anterior divisions communicate with the sympathetic trunk. Near the origin of the divisions, they are joined by gray rami communicantes from the lumbar ganglia of the sympathetic trunk. These rami consist of long, slender branches which accompany the lumbar arteries around the sides of the vertebral bodies, beneath the Psoas major.
The lumbosacral trunk is a communicating branch passing between the sacral and lumbar plexuses containing ventral fibers from L4. The coccygeal nerve , the last spinal nerve, emerges from the sacral hiatus , unites with the ventral rami of the two last sacral nerves, and forms the coccygeal plexus .