Which of the following nerves is associated with the lumbosacral plexus? Select one: a. Median b. Phrenic c. Ulnar d. Obturator e. Musculocutaneous
The correct answer and explanation is:
The correct answer is d. Obturator.
The lumbosacral plexus is a network of nerves formed by the anterior rami of the L1 to L4 spinal nerves (lumbar plexus) and the L4 to S4 spinal nerves (sacral plexus). This plexus supplies the lower limbs and some muscles of the pelvic region. Among the nerves that originate from this complex are several important ones, including the obturator nerve.
The obturator nerve emerges from the lumbar plexus (specifically the L2-L4 spinal nerves) and travels through the pelvis to innervate muscles in the medial compartment of the thigh. These muscles are primarily involved in adducting the thigh at the hip joint. The obturator nerve also provides sensory innervation to the skin of the medial thigh.
In contrast, the median nerve, phrenic nerve, ulnar nerve, and musculocutaneous nerve are not associated with the lumbosacral plexus:
- The median nerve arises from the brachial plexus, which is responsible for the upper limbs.
- The phrenic nerve, which innervates the diaphragm, originates from the cervical plexus.
- The ulnar nerve and musculocutaneous nerve are also branches of the brachial plexus, serving the arm and forearm.
The lumbosacral plexus is crucial for motor and sensory function in the lower limbs, and other key nerves associated with it include the femoral nerve, sciatic nerve, and tibial nerve, all of which also contribute to movement and sensation in the lower extremities.