Final answer:
The nerves that innervate the floor of the pelvic cavity are found in the sacral plexus. The sciatic nerve is a major nerve originating from the sacral plexus.
Step-by-step explanation:
The nerves that innervate the floor of the pelvic cavity and some of the surrounding areas are found in the sacral plexus. The sacral plexus is a nerve plexus that arises from the lower lumbar nerves L4 and L5 and the sacral nerves S1 to S4. The most significant systemic nerve to come from this plexus is the sciatic nerve, which is a combination of the tibial nerve and the fibular nerve.