Which structure or area receives no nerve fibers from the cervical plexus?

Skin over the external occipital protuberance-the skin over the external occipital protuberance is innervated by the greater occipital nerve, which is from the dorsal primary ramus of c2. Since the cervical plexus is made of the ventral primary rami of c1 through c4, the greater occipital nerve has no connection with the cervical plexus. The diaphragm is innervated by the phrenic nerve, which receives contributions from the ventral primary rami of c3, c4, and c5. The skin over the angle of the jaw is innervated by the great auricular nerve, which comes from c2 and c3 branches of the cervical plexus. Finally, the thyrohyoid muscle is innervated by the ansa cervicalis (specifically, c1 and c2 fibers carried by hypoglossal nerve), a motor component of the cervical plexus that innervates the strap muscles.