What does the sacral plexus supply to?

The sacral plexus is a network of nerve fibers that emerge from the lumbosacral region of the spinal cord, specifically from the anterior rami of the spinal nerves L4 to S4. Its primary function is to provide motor and sensory innervation to the structures of the lower limb and the pelvic area.

The major nerves that arise from the sacral plexus include the sciatic nerve, which is the largest nerve in the human body and innervates most of the lower limb muscles. Other branches supply the gluteal region, perineum, and parts of the pelvis, contributing to movements and sensory perception in these areas. This extensive innervation explains why the sacral plexus is primarily associated with the lower limb and pelvic area.

In contrast, the other answer choices refer to regions that are innervated by different nerve networks. For instance, upper limb muscles are supplied by the brachial plexus, while the head, neck, and thoracic wall receive innervation from cervical and thoracic plexuses, respectively. Thus, option B correctly identifies the primary area served by the sacral plexus.