Which of the following is incorrect regarding the lumbosacral plexus?
ExplanationC. The iliohypogastric, ilioinguinal, and genitofemoral nerves do not arise from the lumbosacral trunk, but rather from the lumbar plexus. The tensor fasciae latae is a hip abductor; it abducts the thigh when the hip is flexed, not extended. The lumbosacral plexus consists of the lumbar and sacral plexus, connected via the lumbosacral trunk. The lumbar plexus is formed by contributions from T12 to L4 and gives rise to three major and three minor nerves. The three minor nerves are the iliohypogastric, ilioinguinal, and genitofemoral. The first two arise from a common trunk originating from L1 with some contributions from T12. The genitofemoral nerve arises from L1 and L2. The three major nerves are the femoral, obturator, and lateral femoral cutaneous. The lateral femoral cutaneous nerve originates from L2 and L3. The femoral nerve originates from the posterior divisions of L2, L3, and L4 The obturator nerve originates from the anterior divisions of L2, L3, and L4 and divides into an anterior and a posterior division. The anterior division gives innervation to the adductor brevis, adductor longus, and gracilis muscles. The posterior division gives innervation to the obturator externus and a portion of the adductor magnus, which is also innervated by the sciatic nerve. The lumbosacral trunk is a structure that originates from L4 and L5 and joins the sacral plexus to form the sciatic nerve, which is not only the largest nerve of the lumbosacral plexus, but the largest nerve in the body. The sacral plexus originates from the L4, L5, S1, S2, S3, and S4 nerve roots, with L4 and L5 provided by the lumbosacral trunk as already described. The anterior divisions of L4 through S3 The sacral plexus originates from the L4, L5, S1, S2, S3, and S4 nerve roots, with L4 and L5 provided by the lumbosacral trunk as already described. The anterior divisions of L4 through S3 contribute to form the tibial division of the sciatic nerve. The posterior divisions from L4 through S2 contribute to the common peroneal division of the sciatic nerve. The superior gluteal nerve originates from L4, L5, and S1 and innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. These muscles contribute to thigh abduction, with the tensor fasciae latae acting as the main abductor when the hip is flexed, and the gluteus medius and minimus acting as the main abductors when the hip is extended. The inferior gluteal nerve originates from L5, S1, and S2 and innervates the gluteus maximus, which is an extensor of the thigh. The posterior cutaneous nerve of the thigh originates from S1, S2, and S3 and gives sensory cutaneous innervation to the lower buttock and posterior thigh. The pudendal nerve originates from S2, S3, and S4 and provides sensory innervation to the perineal region and perianal region through the inferior rectal nerve, perineal nerve, and dorsal nerve of the penis or clitoris
