Nerves vary in size from the large pencil-sized sciatic nerve in the back of the thigh muscles to the single, hair-sized ?bres distributed to the skin. A nerve, such as the sciatic, possesses a strong, outer ?brous sheath, called the epineurium, within which lie bundles of nerve-?bres, divided from one another by partitions of ?brous tissue, in which run blood vessels that nourish the nerve. Each of these bundles is surrounded by its own sheath, known as the perineurium, and within the bundle ?ne partitions of ?brous tissue, known as endoneurium, divide up the bundle into groups of ?bres. The ?nest subdivisions of the nerves are the ?bres, and these are of two kinds: medullated and non-medullated ?bres. (See NEURON(E) and NERVOUS SYSTEM for more details on structure and functions of neurons and nerves.)... Medical Dictionary
II. Optic, to the eye (sight).
Trochlear, to eye-muscles.
VI. Trigeminal, to skin of face.
VII. Facial, to muscles of face.
VIII. Vestibulocochlear, to ear (hearing and balancing).
IX. Glossopharyngeal, to tongue (taste).
X. Vagus, to heart, larynx, lungs, and stomach.
XI. Spinal accessory, to muscles in neck.
XII. Hypoglossal, to muscles of tongue.... Medical Dictionary
Symptoms When a sensory nerve is injured or diseased, sensation is immediately more or less impaired in the part supplied by the nerve. Ulceration or death of the tissue supplied by the defective nerve may occur. When the nerve in question is a motor one, the muscles governed through it are instantly paralysed. In the latter case, the portion of nerve beyond the injury degenerates and the muscles gradually waste, losing their power of contraction in response to electrical applications. Finally, deformities result and the joints become ?xed. This is particularly noticeable when the ulnar nerve is injured, the hand and ?ngers taking up a claw-like position. The skin may also be a?ected.
Treatment Damaged or severed (peripheral) nerve ?bres should be sewn together, using microsurgery. Careful realignment of the nerve endings gives the ?bres an excellent chance of regenerating along the right channels. Full recovery is rare but, with regular physiotherapy to keep paralysed muscles in good shape and to prevent their shortening, the patient can expect to obtain a reasonable return of function after a few weeks, with improvement continuing over several months.... Medical Dictionary
– runs up again into the neck, where it enters the larynx and supplies branches to the muscles which control the vocal cords.... Medical Dictionary