Final answer:
The thoracic plexus. There are four main nerve plexuses in the human body, namely the cervical, brachial, lumbar, and sacral plexuses, while 'thoracic plexus' is not a recognized nerve plexus. The correct answer is c.
Step-by-step explanation:
The question 'Which of the following is not a nerve plexus?' pertains to the nerve plexuses found in the human body. Based on an understanding of human anatomy, the thoracic plexus is not a recognized nerve plexus; therefore, the correct answer to the question is c. the thoracic plexus. Here's an overview of the four main nerve plexuses:
- The cervical plexus is composed of axons from spinal nerves C1 through C5, supplying nerves to the posterior head, neck, and diaphragm.
- The brachial plexus is derived from spinal nerves C4 through T1, providing nerves to the arm.
- The lumbar plexus, arising from all lumbar spinal nerves, supplies nerves to the anterior leg and the pelvic region.
- The sacral plexus, comes from the lower lumbar nerves L4 and L5, as well as the sacral nerves S1 to S4, sending nerves to the posterior leg.
The thoracic plexus does not exist; instead, thoracic spinal nerves directly innervate the body at their respective levels without forming a plexus.