obturator nerve, accessory

nerve (nerv) a cordlike structure comprising a collection of nerve fibers that convey impulses between a part of the central nervous system and some other body region.

abducent nerve sixth cranial nerve; origin, a nucleus in the pons, beneath the floor of the fourth ventricle, emerging from the brain stem anteriorly between the pons and medulla oblongata; distribution, lateral rectus muscle of eye; modality, motor.

accelerator nerves the cardiac sympathetic nerves, which, when stimulated, accelerate action of the heart.

accessory nerve eleventh cranial nerve; origin, by cranial roots from the side of the medulla oblongata, and by spinal roots from the side of the spinal cord (from the upper three or more cervical segments); the roots unite to form the trunk of the accessory nerve, which divides into an internal branch (cranial portion) and an external branch (spinal portion); distribution, the internal branch to the vagus and thereby to the palate, pharynx, larynx, and thoracic viscera; the external branch branches to the sternocleidomastoid and trapezius muscles; modality, parasympathetic and motor.

acoustic nerve vestibulocochlear n.

afferent nerve any nerve that transmits impulses from the periphery toward the central nervous system; see sensory n.

alveolar nerve, inferior origin, mandibular nerve; branches, mylohyoid, inferior dental, mental, and inferior gingival nerves; distribution —teeth and gums of lower jaw, skin of chin and lower lip, mylohyoid muscle and anterior belly of digastric muscle; modality, motor and general sensory.

alveolar nerves, superior the superior alveolar branches (anterior, middle, and posterior) that arise from the maxillary and infraorbital nerves, innervating the teeth of the upper jaw and the maxillary sinus, and forming the superior dental plexus.

ampullar nerve, anterior the branch of the vestibular nerve that innervates the ampulla of the anterior semicircular duct, ending around the hair cells of the ampullary crest.

ampullar nerve, inferior posterior ampullar n.

ampullar nerve, lateral the branch of the vestibular nerve that innervates the ampulla of the lateral semicircular duct, ending around the hair cells of the ampullary crest.

ampullar nerve, posterior the branch of the vestibular nerve that innervates the ampulla of the posterior semicircular duct, ending around the hair cells of the ampullary crest.

ampullar nerve, superior anterior ampullar n.

anal nerves, inferior origin, pudendal nerve, or independently from sacral plexus; distribution, external anal sphincter muscle, skin around anus, and lining of anal canal up to pectinate line; modality, general sensory and motor.

anococcygeal nerve origin, coccygeal plexus; distribution, sacrococcygeal joint, coccyx, skin over coccyx; modality, general sensory.

auditory nerve vestibulocochlear n.

auricular nerves, anterior origin, auriculotemporal nerve; distribution, skin of anterosuperior part of external ear; modality, general sensory.

auricular nerve, great origin, cervical plexus—C2–C3; branches, anterior and posterior branches; distribution, skin over parotid gland and mastoid process, and both surfaces of auricle.

auricular nerve, posterior origin, facial nerve; branches, occipital branch; distribution, posterior auricular and occipitofrontal muscles and skin of external acoustic meatus; modality, motor and general sensory.

auriculotemporal nerve origin, by two roots from the mandibular nerve; branches, anterior auricular nerve, nerve of external acoustic meatus, parotid branches, branch to tympanic membrane, and branches communicating with facial nerve; its terminal branches are superficial temporal to the scalp; distribution, parotid gland, scalp in temporal region, tympanic membrane; modality, general sensory.

autonomic nerve any of the parasympathetic or sympathetic nerves of the autonomic nervous system.

axillary nerve origin, posterior cord of brachial plexus (C5–C6); branches, lateral superior brachial cutaneous nerve and muscular branches; distribution, deltoid and teres minor muscles, skin on back of arm; modality, motor and general sensory.

buccal nerve origin, mandibular nerve; distribution, skin and mucous membrane of cheeks, gums, and perhaps the first two molars and the premolars; modality, general sensory.

cardiac nerve, inferior inferior cervical cardiac n.

cardiac nerve, middle middle cervical cardiac n.

cardiac nerve, superior superior cervical cardiac n.

cardiac nerves, thoracic branches of the second through fourth or fifth thoracic ganglia of the sympathetic trunk, supplying the heart and having a sympathetic (accelerator) modality as well as a visceral afferent one (chiefly for pain).

caroticotympanic nerves origin, internal carotid plexus; inferior and superior nerves can be distinguished; together with tympanic nerve, they form the tympanic plexus; distribution, tympanic region and parotid gland; modality, sympathetic.

carotid nerves, external origin, superior cervical ganglion; distribution, cranial blood vessels and glands via the external carotid plexus; modality, sympathetic.

carotid nerve, internal origin, superior cervical ganglion; distribution, cranial blood vessels and glands via internal carotid plexus; modality, sympathetic.

cavernous nerves of clitoris origin, uterovaginal plexus; distribution, erectile tissue of clitoris; modality, parasympathetic, sympathetic, and visceral afferent.

cavernous nerves of penis origin, prostatic plexus; distribution, erectile tissue of penis; modality, sympathetic, parasympathetic, and visceral afferent.

centrifugal nerve efferent n.

centripetal nerve afferent n.

cerebral nerves cranial n's.

cervical nerves the eight pairs of nerves (C1–C8) that arise from the cervical segments of the spinal cord and, except for the last pair, leave the vertebral column above the correspondingly numbered vertebra. The ventral branches of the upper four, on either side, unite to form the cervical plexus, and those of the lower four, together with the ventral branch of the first thoracic nerve, form most of the brachial plexus.

cervical nerve, transverse origin, cervical plexus (C2–C3); branches, superior and inferior branches; distribution, skin on side and front of neck; modality, general sensory.

cervical cardiac nerve, inferior origin, cervicothoracic ganglion; distribution, heart via cardiac plexus; modality, sympathetic (accelerator) and visceral afferent (chiefly pain).

cervical cardiac nerve, middle origin, middle cervical ganglion; distribution, heart; modality, sympathetic (accelerator) and visceral afferent (chiefly pain).

cervical cardiac nerve, superior origin, superior cervical ganglion; distribution, heart; modality, sympathetic (accelerator).

ciliary nerves, long origin, nasociliary nerve, from ophthalmic nerve; distribution, dilator muscle of pupil, uvea, cornea; modality, sympathetic and general sensory.

ciliary nerves, short origin, ciliary ganglion; distribution, smooth muscle and tunics of eye; modality, parasympathetic, sympathetic, and general sensory.

cluneal nerves, inferior general sensory nerve branches of the posterior femoral cutaneous nerve, innervating the skin of the lower part of the buttocks.

cluneal nerves, middle general sensory nerve branches of the plexus formed by the lateral branches of dorsal branches of the first four sacral nerves, innervating ligaments of the sacrum and the skin over the posterior buttocks.

cluneal nerves, superior general sensory nerve branches of the dorsal branches of the upper lumbar nerves, innervating the skin of the upper part of the buttocks.

coccygeal nerve either of the thirty-first pair of spinal nerves (Co), arising from the coccygeal segment of the spinal cord.

cochlear nerve the part of the vestibulocochlear nerve concerned with hearing, consisting of fibers that arise from the bipolar cells in the spiral ganglion and have their receptors in the spiral organ of the cochlea.

cranial nerves the twelve pairs of nerves that are connected with the brain, including the olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII) nerves.

cubital nerve ulnar n.

cutaneous nerve, perforating one of the inferior cluneal nerves which pierces the sacrotuberous ligament and supplies the skin over the inferomedial gluteus maximus; it is absent in one third of the population.

cutaneous nerve of arm, inferior lateral origin, radial nerve; distribution, skin of lateral surface of lower part of arm; modality, general sensory.

cutaneous nerve of arm, medial origin, medial cord of brachial plexus (T1); distribution, skin on medial and posterior aspects of arm; modality, general sensory.

cutaneous nerve of arm, posterior origin, radial nerve in the axilla; distribution, skin on back of arm; modality, general sensory.

cutaneous nerve of arm, superior lateral origin, axillary nerve; distribution, skin of back of arm; modality, general sensory.

cutaneous nerve of calf, lateral origin, common fibular nerve; distribution, skin of lateral side of back of leg, rarely may continue as the sural nerve; modality, general sensory.

cutaneous nerve of calf, medial origin, tibial nerve; usually joins fibular communicating branch of common fibular nerve to form the sural nerve; distribution, may continue as the sural nerve; modality, general sensory.

cutaneous nerve of foot, intermediate dorsal origin, superficial fibular nerve; branches, dorsal digital nerves of foot; distribution, skin of front of lower third of leg and dorsum of foot, and skin and joints of adjacent sides of third and fourth, and of fourth and fifth toes; modality, general sensory.

cutaneous nerve of foot, lateral dorsal origin, continuation of sural nerve; distribution, skin and joints of lateral side of foot and fifth toe; modality, general sensory.

cutaneous nerve of foot, medial dorsal origin, superficial fibular nerve; distribution, skin and joints of medial side of foot and big toe, and adjacent sides of second and third toes; modality, general sensory.

cutaneous nerve of forearm, lateral origin, continuation of musculocutaneous nerve; distribution, skin over radial side of forearm and sometimes an area of skin of dorsum of hand; modality, general sensory.

cutaneous nerve of forearm, medial origin, medial cord of brachial plexus (C8, T1); branches, anterior and ulnar; distribution, skin of front, medial, and posteromedial aspects of forearm; modality, general sensory.

cutaneous nerve of forearm, posterior origin, radial nerve; distribution, skin of dorsal aspect of forearm; modality, general sensory.

cutaneous nerve of neck, anterior , cutaneous nerve of neck, transverse

1. nervus transversus colli.

2. transverse cervical n.

cutaneous nerve of thigh, lateral origin, lumbar plexus—L2–L3; distribution, skin of lateral and frontal aspects of thigh; modality, general sensory.

cutaneous nerve of thigh, posterior origin, sacral plexus—S1–S3; branches, inferior cluneal nerves and perineal branches; distribution, skin of buttock, external genitalia, and back of thigh and calf; modality, general sensory.

depressor nerve

1. a nerve that lessens the activity of an organ.

2. an afferent nerve whose stimulation causes a fall in blood pressure.

digital nerves, radial dorsal dorsal digital n's of radial nerve.

digital nerves, ulnar dorsal dorsal digital n's of ulnar nerve.

digital nerves of foot, dorsal

1. nerves supplying the third, fourth, and fifth toes; origin, intermediate dorsal cutaneous nerve; distribution, skin and joints of adjacent sides of third and fourth, and of fourth and fifth toes; modality, general sensory.

2. nerves supplying the first and second toes; origin, medial terminal division of deep fibular nerve; distribution, skin and joints of adjacent sides of great and second toes; modality, general sensory.

digital nerves of lateral plantar nerve, common plantar number, two; origin, superficial branch of lateral plantar nerve; branches, the medial nerve gives rise to two proper plantar digital nerves; distribution, the lateral one to the short flexor muscle of little toe and to skin and joints of lateral side of sole and little toe; the medial one to adjacent sides of fourth and fifth toes; modality, motor and general sensory.

digital nerves of lateral plantar nerve, proper plantar origin, common plantar digital nerves; distribution, short flexor muscle of little toe, skin and joints of lateral side of sole and little toe, and adjacent sides of fourth and fifth toes; modality, motor and general sensory.

digital nerves of medial plantar nerve, common plantar number, four; origin, medial plantar nerve; branches, muscular and proper plantar digital nerves; distribution, flexor hallucis brevis muscle and first lumbrical muscles, skin and joints of medial side of foot and big toe, and adjacent sides of first and second, second and third, and third and fourth toes; modality, motor and general sensory.

digital nerves of medial plantar nerve, proper plantar origin, common plantar digital nerves; distribution, skin and joints of medial side of first toe, and adjacent sides of first and second, second and third, and third and fourth toes; the nerves extend to the dorsum to supply nail beds and tips of toes; modality, general sensory.

digital nerves of median nerve, common palmar number, four; origin, lateral and medial divisions of median nerve; branches, proper palmar digital nerves; distribution, thumb, index, middle, and ring fingers, and first two lumbrical muscles; modality, motor and general sensory.

digital nerves of median nerve, proper palmar origin, common palmar digital nerves; distribution, first two lumbrical muscles, skin and joints of both sides and palmar aspect of thumb, index, and middle fingers, radial side of ring finger, and back of distal aspect of these digits; modality, general sensory and motor.

digital nerves of radial nerve, dorsal origin, superficial branch of radial nerve; distribution, skin and joints of back of thumb, index finger, and part of middle finger, as far distally as the distal phalanx; modality, general sensory.

digital nerves of ulnar nerve, common palmar number, two; origin, superficial branch of ulnar nerve; branches, proper palmar digital nerves; distribution, little and ring fingers; modality, general sensory.

digital nerves of ulnar nerve, dorsal origin, dorsal branch of ulnar nerve; distribution, skin and joints of medial side of little finger, dorsal aspects of adjacent sides of little and ring fingers and of ring and middle fingers; modality, general sensory.

digital nerves of ulnar nerve, proper palmar proper palmar digital nerves of ulnar nerve: origin, the lateral of the two common palmar digital nerves from the superficial branch of the ulnar nerve; distribution, skin and joints of adjacent sides of fourth and fifth fingers; modality, general sensory.

dorsal nerve of clitoris origin, pudendal nerve; distribution, deep transverse muscle of perineum, sphincter muscle of urethra, corpus cavernosum of clitoris, and skin, prepuce, and glans of clitoris; modality, general sensory and motor.

dorsal nerve of penis origin, pudendal nerve; distribution, deep transverse muscle of perineum, sphincter muscle of urethra, corpus cavernosum of penis, and skin, prepuce, and glans of penis; modality, general sensory and motor.

dorsal scapular nerve origin, brachial plexus—ventral branch of C5; distribution, rhomboid muscles and occasionally the levator muscle of scapula; modality, motor.

efferent nerve any that carries impulses from the central nervous system to the periphery, e.g., a motor nerve.

ethmoidal nerve, anterior origin, continuation of nasociliary nerve, from ophthalmic nerve; branches, internal, external, lateral, and medial branches; distribution, mucosa of upper and anterior nasal septum, lateral wall of nasal cavity, skin of lower bridge and tip of nose; modality, general sensory.

ethmoidal nerve, posterior origin, nasociliary nerve, from ophthalmic nerve; distribution, mucosa of posterior ethmoid cells and of sphenoidal sinus; modality, general sensory.

exciter nerve , excitor nerve one that transmits impulses resulting in an increase in functional activity.

excitoreflex nerve a visceral nerve that produces reflex action.

nerve of external acoustic meatus origin, auriculotemporal nerve; distribution, skin lining external acoustic meatus, and tympanic membrane; modality, general sensory.

facial nerve seventh cranial nerve, consisting of two roots: a large motor root, which supplies the muscles of facial expression, and a smaller root, the intermediate nerve (q.v.). Origin, inferior border of pons, between olive and inferior cerebellar peduncle; branches (of motor root), stapedius and posterior auricular nerves, parotid plexus, digastric, temporal, zygomatic, buccal, lingual, marginal mandibular, and cervical branches, and a communicating branch with the tympanic plexus; distribution, various structures of face, head, and neck; modality, motor, parasympathetic, general sensory, special sensory.

femoral nerve origin, lumbar plexus (L2–L4); descending behind the inguinal ligament to the femoral triangle; branches, saphenous nerve, muscular and anterior cutaneous branches; distribution, skin of thigh and leg, muscles of front of thigh, and hip and knee joints; modality, general sensory and motor.

fibular nerve, common origin, sciatic nerve in lower part of thigh; branches and distribution, supplies short head of biceps femoris muscle (while still incorporated in sciatic nerve), gives off lateral sural cutaneous nerve and fibular communicating branch as it descends in popliteal fossa, supplies knee and superior tibiofibular joints and tibialis anterior muscle, and divides into superficial and deep fibular nerves; modality, general sensory and motor.

fibular nerve, deep origin, a terminal branch of common fibular nerve; branches and distribution, winds around the neck of the fibula and descends on the interosseous membrane to the front of the ankle; gives off muscular branches to anterior tibial, extensor of great toe, long extensor of toes, and third fibular muscles, and a twig to ankle joint; a lateral terminal division supplies the short extensor muscle of toes and tarsal joints; medial terminal division, or digital branch, divides into dorsal digital nerves for skin and joints of adjacent sides of first and second toes; modality, general sensory and motor.

fibular nerve, superficial origin, a terminal branch of common fibular nerve; branches and distribution, descends in front of the fibula, supplies long and short fibular muscles and, in the lower part of the leg, divides into the muscular branches, medial and intermediate dorsal cutaneous nerves; modality, general sensory and motor.

frontal nerve origin, ophthalmic division of trigeminal nerve; enters the orbit through the superior orbital fissure; branches, supraorbital and supratrochlear nerves; distribution, chiefly to the forehead and scalp; modality, general sensory.

furcal nerve the fourth lumbar nerve.

fusimotor nerves those with nerve endings that innervate intrafusal fibers of the muscle spindle.

gangliated nerve any nerve of the sympathetic nervous system.

genitofemoral nerve origin, lumbar plexus (L1–L2); branches, genital and femoral branches; distribution, cremaster muscle, skin of scrotum or labium majus and of adjacent area of thigh and femoral triangle; modality, general sensory and motor.

glossopharyngeal nerve ninth cranial nerve; origin, several rootlets from lateral side of upper part of medulla oblongata, between the olive and the inferior cerebellar peduncle; branches, tympanic nerve, pharyngeal, stylopharyngeal, tonsillar, and lingual branches, branch to the carotid sinus, and a branch communicating with the auricular branch of the vagus nerve; distribution, it has two enlargements (superior and inferior ganglia) and supplies the tongue, pharynx, and parotid gland; modality, motor, parasympathetic, and general, special, and visceral sensory.

gluteal nerves

1. the superior and inferior gluteal nerves (qq.v.).

2. the cluneal nerves in the lumbar and sacral regions; see inferior cluneal n's, middle cluneal n's, and superior cluneal n's.

gluteal nerve, inferior

1. origin, sacral plexus (L5–S2); distribution, gluteus maximus muscle; modality, motor.

2. (in plural) inferior cluneal n's.

gluteal nerves, middle middle cluneal n's.

gluteal nerve, superior

1. origin, sacral plexus (L4–S1); distribution, gluteus medius and minimus muscles, tensor fasciae latae, and hip joint; modality, motor and general sensory.

2. (in plural) superior cluneal n's.

gustatory nerves sensory nerve fibers innervating the taste buds and associated with taste, including branches from the lingual and glossopharyngeal nerves.

hemorrhoidal nerves, inferior

1. nervi anales inferiores.

2. inferior anal n's.

hypoglossal nerve twelfth cranial nerve; origin, several rootlets in the anterolateral sulcus between the olive and the pyramid of the medulla oblongata; it passes through the hypoglossal canal to the tongue; branches, lingual branches; distribution, styloglossus, hyoglossus, and genioglossus muscles and intrinsic muscles of the tongue; modality, motor.

iliohypogastric nerve origin, lumbar plexus—L1 (sometimes T12); branches, lateral and anterior cutaneous branches; distribution, the skin above the pubis and over the lateral side of the buttock, and occasionally the pyramidal muscle; modality, motor and general sensory.

ilioinguinal nerve origin, lumbar plexus—L1 (sometimes T12); accompanies the spermatic cord through the inguinal canal; branches, anterior scrotal or labial branches; distribution, skin of scrotum or labia majora, and adjacent part of thigh; modality, general sensory.

infraoccipital nerve suboccipital n.

infraorbital nerve origin, continuation of the maxillary nerve, entering the orbit through the inferior orbital fissure, and occupying in succession the infraorbital groove, canal, and foramen; branches, middle and anterior superior alveolar, inferior palpebral, internal and external nasal, and superior labial branches; distribution, incisor, cuspid, and premolar teeth of upper jaw, skin and conjunctiva of lower eyelid, mobile septum and skin of side of nose, mucous membrane of mouth, skin of upper lip; modality, general sensory.

infratrochlear nerve origin, nasociliary nerve from ophthalmic nerve; branches, palpebral branches; distribution, skin of root and upper bridge of nose and lower eyelid, conjunctiva, lacrimal duct; modality, general sensory.

inhibitory nerve one that transmits impulses resulting in a decrease in functional activity.

intercostobrachial nerves two nerves arising from the intercostal nerves and supplying the skin of the upper limb. The first is constant: origin, second intercostal nerve; distribution, skin on back and medial aspect of arm; modality, general sensory. A second intercostobrachial nerve is often present;origin, third intercostal nerve; distribution, skin of axilla and medial aspect of arm; modality, general sensory.

intermediate nerve the smaller root of the facial nerve, lying between the main root and the vestibulocochlear nerve; it joins the main root at, or merges with, the geniculate ganglion at the geniculum of the facial nerve; branches, chorda tympani and greater petrosal nerve; distribution, lacrimal, nasal, palatine, submandibular, and sublingual glands, and anterior two-thirds of tongue; modality, parasympathetic and special sensory.

interosseous nerve of forearm, anterior origin, median nerve; distribution, long flexor of thumb, deep flexor of fingers, and pronator quadratus muscles, wrist and intercarpal joints; modality, motor and general sensory.

interosseous nerve of forearm, posterior origin, continuation of deep branch of radial nerve; distribution, long abductor muscle of thumb, extensor muscles of the thumb and second finger, and wrist and intercarpal joints; modality, motor and general sensory.

interosseous nerve of leg origin, tibial nerve; distribution, interosseous membrane and tibiofibular syndesmosis; modality, general sensory.

ischiadic nerve sciatic n.

jugular nerve a branch of the superior cervical ganglion which communicates with the vagus and glossopharyngeal nerves.

labial nerves, anterior origin, ilioinguinal nerve; distribution, skin of anterior labial region of labia majora, and adjacent part of thigh; modality, general sensory.

labial nerves, posterior origin, pudendal nerve; distribution, labium majus; modality, general sensory.

lacrimal nerve origin, ophthalmic division of trigeminal nerve, entering the orbit through the superior orbital fissure; distribution, lacrimal gland, conjunctiva, lateral commissure of eye, and skin of upper eyelid; modality, general sensory.

laryngeal nerve, external the smaller of the two branches into which the superior laryngeal nerve divides, descending under cover of the sternothyroid muscle and innervating the cricothyroid and the inferior constrictor of the pharynx; modality, motor.

laryngeal nerve, inferior origin, recurrent laryngeal nerve, especially the terminal portion of this nerve; distribution, intrinsic muscles of larynx, except cricothyroid; communicates with the internal laryngeal nerve; modality, motor.

laryngeal nerve, internal the larger of the two branches of the superior laryngeal nerve, which innervates the mucosa of the epiglottis, base of the tongue, and larynx; modality, general sensory.

laryngeal nerve, recurrent origin, vagus nerve (chiefly the cranial part of the accessory nerve): branches, inferior laryngeal nerve and tracheal, esophageal, and inferior cardiac branches; distribution, tracheal mucosa, esophagus, cardiac plexus; modality, parasympathetic, visceral afferent, and motor.

laryngeal nerve, superior origin, inferior ganglion of vagus nerve; branches, external, internal, and communicating branches; distribution, inferior constrictor of the pharynx, cricothyroid muscle, and mucous membrane of back of tongue and larynx; modality, motor, general sensory, visceral afferent, and parasympathetic.

lingual nerve origin, mandibular nerve, descending to the tongue, first medial to the mandible and then under cover of the mucous membrane of the mouth; branches, sublingual nerve, lingual branch, branch to the isthmus of the fauces, and branches communicating with the hypoglossal nerve and chorda tympani; distribution, anterior two-thirds of tongue, adjacent areas of mouth, gums, isthmus of fauces; modality, general sensory.

lumbar nerves the five pairs of nerves (L1–L5) that arise from the lumbar segments of the spinal cord, each pair leaving the vertebral column below the correspondingly numbered vertebra. The ventral branches of these nerves participate in the formation of the lumbosacral plexus.

mandibular nerve one of three terminal divisions of the trigeminal nerve, passing through the foramen ovale to the infratemporal fossa. Origin, trigeminal ganglion; branches, meningeal branch, masseteric, deep temporal, lateral and medial pterygoid, buccal, auriculotemporal, lingual, and inferior alveolar nerves; distribution, extensive distribution to muscles of mastication, skin of face, mucous membrane of mouth, and teeth; modality, general sensory and motor.

masseteric nerve origin, mandibular division of trigeminal nerve; distribution, masseter muscle and temporomandibular joint; modality, motor and general sensory.

maxillary nerve one of the three terminal divisions of the trigeminal nerve, passing through the foramen rotundum, and entering the pterygopalatine fossa. Origin, trigeminal ganglion; branches, meningeal branch, zygomatic nerve, posterior superior alveolar branches, infraorbital nerve, pterygopalatine nerves, and, indirectly, the branches of the pterygopalatine ganglion; distribution, extensive distribution to skin of face and scalp, mucous membrane of maxillary sinus and nasal cavity, and teeth; modality, general sensory.

median nerve origin, lateral and medial cords of brachial plexus—C6–T1; branches, anterior interosseous nerve of forearm, common palmar digital nerves, and muscular and palmar branches, and a communicating branch with the ulnar nerve; distribution, ultimately, skin on front of lateral part of hand, most of flexor muscles of front of forearm, most of short muscles of thumb and elbow joint, and many joints of hand; modality, general sensory.

mental nerve origin, inferior alveolar nerve; branches, mental, gingival, and inferior labial branches; distribution, skin of chin, and lower lip; modality, general sensory.

mixed nerve , nerve of mixed fibers one composed of both sensory and motor fibers.

motor nerve an efferent nerve that stimulates muscle contraction.

musculocutaneous nerve origin, lateral cord of brachial plexus—C5–C7; branches, lateral cutaneous nerve of forearm, and muscular branches; distribution, coracobrachial and biceps brachial muscles, the elbow joint, and skin of radial side of forearm; modality, general sensory and motor.

musculocutaneous nerve of foot superficial fibular n.

musculocutaneous nerve of leg deep fibular n.

myelinated nerve one whose axons are encased in a myelin sheath.

mylohyoid nerve origin, inferior alveolar nerve; distribution, mylohyoid muscle, anterior belly of digastric muscle; modality, motor.

nasociliary nerve origin, ophthalmic division of trigeminal nerve; branches, long ciliary, posterior ethmoidal, anterior ethmoidal, and infratrochlear nerves, and a communicating branch to the ciliary ganglion; distribution —see individual nerve branches; modality, general sensory.

nasopalatine nerve origin, pterygopalatine ganglion; distribution, mucosa and glands of most of nasal septum and anterior part of hard palate; modality, parasympathetic and general sensory.

obturator nerve origin, lumbar plexus—L3–L4; branches, anterior, posterior, and muscular branches; distribution, adductor muscles and gracilis muscle, skin of medial part of thigh, and hip and knee joints; modality, general sensory and motor.

obturator nerve, accessory origin, ventral branches of ventral branches of L3–L4; distribution, pectineus muscle, hip joint, obturator nerve; modality, general sensory and motor.

obturator nerve, internal origin, ventral branches of ventral branches of L5, S1–S2; distribution, posterior gemellus superior muscle and obturator internus muscle; modality, general sensory and motor.

occipital nerve, greater origin, medial branch of dorsal branch of C2; distribution, semispinal muscle of head and skin of scalp as far forward as the vertex; modality, general sensory and motor.

occipital nerve, lesser origin, superficial cervical plexus (C2–C3); distribution, ascends behind the auricle and supplies some of the skin on the side of the head and on the cranial surface of the auricle; modality, general sensory.

occipital nerve, third origin, medial branch of dorsal branch of C3; distribution, skin of upper part of back of neck and head; modality, general sensory.

oculomotor nerve third cranial nerve; origin, brain stem, emerging medial to cerebral peduncles and running forward in the cavernous sinus; branches, superior and inferior branches; distribution, entering the orbit through the superior orbital fissure, the branches supply the levator muscle of upper eyelid, all extrinsic eye muscles except the lateral rectus and superior oblique, and carry parasympathetic fibers for the ciliary muscle and sphincter pupillae; modality, motor and parasympathetic.

olfactory nerves the nerves of smell, consisting of about 20 bundles which arise in the olfactory epithelium and pass through the cribriform plate of the ethmoid bone to the olfactory bulb.

ophthalmic nerve one of the three terminal divisions of the trigeminal nerve. Origin, trigeminal ganglion; branches, tentorial branches, frontal, lacrimal, and nasociliary nerves; distribution, eyeball and conjunctiva, lacrimal gland and sac, nasal mucosa and frontal sinus, external nose, upper eyelid, forehead, and scalp; modality, general sensory.

optic nerve second cranial nerve, the so-called nerve of sight, actually part of the central nervous system throughout its course; it consists chiefly of axons and central processes of cells of the ganglionic layer of the retina, which leave the orbit through the optic canal, and joins with its opposite number to form the optic chiasm (the medial fibers of each nerve crossing over to the opposite side), then continues as the optic tract to end in the lateral geniculate body.

palatine nerve, anterior , palatine nerve, greater origin, pterygopalatine ganglion; branches, posterior inferior (lateral) nasal branches; distribution, emerges through the greater palatine foramen and supplies the palate; modality, parasympathetic, sympathetic, and general sensory.

palatine nerves, lesser origin, pterygopalatine ganglion; distribution, emerge through the lesser palatine foramen and supply the soft palate and tonsil; modality, parasympathetic, sympathetic, and general sensory.

perineal nerves origin, pudendal nerve in the pudendal canal; branches, muscular branches and posterior scrotal or labial nerves; distribution, muscular branches supply the bulbocavernous, ischiocavernous, and superficial transverse perineal muscles and bulb of the penis and, in part, the external anal sphincter and levator ani muscles; the scrotal (labial) nerves supply the scrotum or labium majus; modality, general sensory and motor.

peripheral nerve any nerve outside the central nervous system.

peroneal nerve, common common fibular n.

peroneal nerve, deep

1. nervus fibularis profundus.

2. deep fibular n.

peroneal nerve, superficial superficial fibular n.

petrosal nerve, deep origin, internal carotid plexus; distribution, joins greater petrosal nerve to form nerve of pterygoid canal, and supplies lacrimal, nasal, and palatine glands via pterygopalatine ganglion and its branches; modality, sympathetic.

petrosal nerve, greater origin, intermediate nerve via geniculate ganglion; distribution, running forward from the geniculate ganglion, it joins the deep petrosal nerve of the pterygoid canal, and reaches lacrimal, nasal, and palatine glands and nasopharynx, via pterygopalatine ganglion and its branches; modality, parasympathetic and general sensory.

petrosal nerve, lesser origin, tympanic plexus; distribution, parotid gland via otic ganglion and auriculotemporal nerve; modality, parasympathetic.

pharyngeal nerve a nerve running from the posterior part of the pterygopalatine ganglion, through the pharyngeal canal with the pharyngeal branch of the maxillary artery, to the mucous membrane of the nasal part of the pharynx posterior to the auditory tube.

phrenic nerve origin, cervical plexus (C4–C5); branches, pericardiac and phrenicoabdominal branches; distribution, pleura, pericardium, diaphragm, peritoneum, and sympathetic plexuses; modality, general sensory and motor.

phrenic nerves, accessory an inconstant contribution of the fifth cervical nerve to the phrenic nerve; when present, they run a separate course to the root of the neck or into the thorax before joining the phrenic nerve.

piriform nerve origin, dorsal branches of ventral branches of S1–S2; distribution, anterior piriform muscle; modality, general sensory and motor.

plantar nerve, lateral origin, the smaller of terminal branches of tibial nerve; branches, muscular, superficial, and deep branches; distribution, lying between first and second layers of muscles of sole, it supplies the quadratus of sole, abductor of little toe, short flexor of little toe, adductor of great toe, interosseous, and second, third, and fourth lumbrical muscles, and gives off cutaneous and articular twigs to lateral side of sole and fourth and fifth toes; modality, general sensory and motor.

plantar nerve, medial origin, the larger of the terminal branches of tibial nerve; branches, common plantar digital nerves and muscular branches; distribution, abductor of great toe, short flexor of toes, short flexor of great toe, and first lumbrical muscles, and cutaneous and articular twigs to the medial side of the sole, and to the first to fourth toes; modality, general sensory and motor.

pneumogastric nerve vagus n.

popliteal nerve, external , popliteal nerve, lateral common fibular n.

pressor nerve an afferent nerve, irritation of which stimulates a vasomotor center and increases intravascular tension.

pterygoid nerve, lateral origin, mandibular nerve; distribution, lateral pterygoid muscle; modality, motor.

pterygoid nerve, medial origin, mandibular nerve; distribution, medial pterygoid, tensor tympani, and tensor veli palatini muscles; modality, motor.

nerve of pterygoid canal origin, union of deep and greater petrosal nerves; distribution, pterygopalatine ganglion and branches; modality, parasympathetic and sympathetic.

pterygopalatine nerves the two nerves which connect the maxillary nerve to the pterygopalatine ganglion; they are the sensory roots of the ganglion.

pudendal nerve origin, sacral plexus (S2–S4); branches, enters the pudendal canal, gives off the inferior anal nerve, and then divides into the perineal nerve and dorsal nerve of the penis (clitoris); distribution, muscles, skin, and erectile tissue of perineum; modality, general sensory, motor, and parasympathetic.

nerve of quadrate muscle of thigh origin, ventral branches of ventral branches of L4–L5; distribution, inferior gemellus muscle, anterior quadratus muscle of thigh, hip joint; modality, general sensory and motor.

radial nerve origin, posterior cord of brachial plexus (C6–C8, and sometimes C5 and T1); branches, posterior cutaneous and inferior lateral cutaneous nerves of arm, posterior cutaneous nerve of forearm, muscular, deep, and superficial branches; distribution, descending in the back of arm and forearm, it is ultimately distributed to skin on back of arm, forearm, and hand, extensor muscles on back of arm and forearm, and elbow joint and many joints of hand; modality, general sensory and motor.

rectal nerves, inferior inferior anal n's.

recurrent nerve

1. nervus laryngeus recurrens.

2. recurrent laryngeal n.

saccular nerve the branch of the vestibular nerve that innervates the macula of the saccule.

sacral nerves (S1–S5) that arise from the sacral segments of the spinal cord; the ventral branches of the first four pairs participate in the formation of the sacral plexus.

saphenous nerve origin, termination of femoral nerve, descending first with femoral vessels and then on medial side of leg and foot; branches, infrapatellar and medial crural cutaneous branches; distribution, knee joint, subsartorial and patellar plexuses, skin on medial side of leg and foot; modality, general sensory.

sciatic nerve the largest nerve of the body: origin, sacral plexus (L4–S3); it leaves the pelvis through the greater sciatic foramen; branches, divides into the tibial and common fibular nerves, usually in lower third of thigh; distribution, see individual nerve branches; modality, general sensory and motor.

scrotal nerves, anterior origin, ilioinguinal nerve; distribution, skin of anterior scrotal region; modality, general sensory.

scrotal nerves, posterior origin, perineal nerves; distribution, skin of scrotum; modality, general sensory.

secretory nerve any efferent nerve whose stimulation increases glandular activity.

sensory nerve a peripheral nerve that conducts impulses from a sense organ to the spinal cord or brain.

somatic nerves the motor and sensory nerves supplying skeletal muscle and somatic tissues.

sphenopalatine nerves pterygopalatine n's.

spinal nerves the thirty-one pairs of nerves that arise from the spinal cord and pass out between the vertebrae, including the eight pairs of cervical, twelve of thoracic, five of lumbar, five of sacral, and one pair of coccygeal nerves.

splanchnic nerves those of the blood vessels and viscera, especially the visceral branches of the thoracic, lumbar, and pelvic parts of the sympathetic trunks.

splanchnic nerve, greater origin, thoracic sympathetic trunk and fifth through tenth thoracic ganglia; distribution, descending through the diaphragm or its aortic openings, ends in celiac ganglia and plexuses, with a splanchnic ganglion commonly occurring near the diaphragm; modality, preganglionic sympathetic and visceral afferent.

splanchnic nerve, lesser origin, ninth and tenth thoracic ganglia of sympathetic trunk; branches, renal branch; distribution, pierces the diaphragm, joins the aorticorenal ganglion and celiac plexus, and communicates with the renal and superior mesenteric plexuses; modality, preganglionic sympathetic and visceral afferent.

splanchnic nerve, lowest origin, last ganglion of sympathetic trunk or lesser splanchnic nerve; distribution, aorticorenal ganglion and adjacent plexus; modality, sympathetic and visceral afferent.

splanchnic nerves, lumbar origin, lumbar ganglia or sympathetic trunk; distribution, upper nerves join celiac and adjacent plexuses, middle ones go to intermesenteric and adjacent plexuses, and lower ones descend to superior hypogastric plexus; modality, preganglionic sympathetic and visceral afferent.

splanchnic nerves, pelvic origin, sacral plexus—S3–S4; distribution, leaving the sacral plexus, they enter the inferior hypogastric plexus and supply the pelvic organs; modality, preganglionic parasympathetic and visceral afferent.

splanchnic nerves, sacral origin, sacral part of sympathetic trunk; distribution, pelvic organs and blood vessels via inferior hypogastric plexus; modality, preganglionic sympathetic and visceral afferent.

stapedius nerve origin, facial nerve; distribution, stapedius muscle; modality, motor.

subclavian nerve origin, upper trunk of brachial plexus (C5); distribution, subclavius muscle and sternoclavicular joint; modality, motor and general sensory.

subcostal nerve origin, anterior branch of twelfth thoracic nerve; distribution, skin of lower abdomen and lateral side of gluteal region, parts of abdominal transverse, oblique, and rectus muscles, and usually the pyramidal muscle, and adjacent peritoneum; modality, general sensory and motor.

sublingual nerve origin, lingual nerve; distribution, sublingual gland and overlying mucous membrane; modality, parasympathetic and general sensory.

suboccipital nerve origin, dorsal branch of first cervical nerve; distribution, emerges above posterior arch of atlas and supplies muscles of suboccipital triangle and semispinal muscle of head; modality, motor.

subscapular nerves origin, posterior cord of brachial plexus (C5); distribution, usually two or more nerves, upper and lower, supplying subscapular and teres major muscles; modality, motor.

supraclavicular nerves a term denoting collectively the common trunk, which is a branch of the cervical plexus (C3–C4) and which emerges under cover of the posterior border of the sternocleidomastoid muscle and divides into the intermediate, lateral, and medial supraclavicular nerves.

supraclavicular nerves, anterior medial supraclavicular n's.

supraclavicular nerves, intermediate origin, cervical plexus (C3–C4); distribution, descend in the posterior triangle, cross the clavicle, and supply the skin over pectoral and deltoid region; modality, general sensory.

supraclavicular nerves, lateral origin, cervical plexus (C3–C4); distribution, descend in the posterior triangle, cross the clavicle, and supply the skin of superior and posterior parts of shoulder; modality, general sensory.

supraclavicular nerves, medial origin, cervical plexus (C3–C4); distribution, descend in posterior triangle, cross the clavicle, and supply the skin of medial infraclavicular region; modality, general sensory.

supraclavicular nerves, middle intermediate supraclavicular n's.

supraclavicular nerves, posterior lateral supraclavicular n's.

supraorbital nerve origin, continuation of frontal nerve, from ophthalmic nerve; branches, lateral and medial branches; distribution, leaves orbit through supraorbital notch or foramen, and supplies the skin of upper eyelid, forehead, anterior scalp (to vertex), mucosa of frontal sinus; modality, general sensory.

suprascapular nerve origin, brachial plexus (C5–C6); distribution, descends through suprascapular and spinoglenoid notches and supplies acromioclavicular and shoulder joints, and supraspinous and infraspinous muscles; modality, motor and general sensory.

supratrochlear nerve origin, frontal nerve, from ophthalmic nerve; distribution, leaves orbit at medial end of supraorbital margin and supplies the forehead and upper eyelid; modality, general sensory.

sural nerve origin, medial sural cutaneous nerve and fibular communicating branch of common fibular nerve; branches, lateral dorsal cutaneous nerve and lateral calcaneal branches; distribution, skin on back of leg, and skin and joints on lateral side of heel and foot; modality, general sensory.

sympathetic nerve

1. see under trunk.

2. any nerve of the sympathetic nervous system.

temporal nerves, deep usually two in number, anterior and posterior, with a third middle one often seen: origin, mandibular nerve; distribution, temporal muscles; modality, motor.

nerve to tensor tympani origin, mandibular nerve via nerve to medial pterygoid muscle and otic ganglion; distribution, tensor tympani muscle; modality, motor.

nerve to tensor veli palatini origin, mandibular nerve via nerve to medial pterygoid muscle and otic ganglion; distribution, tensor veli palatini muscle; modality, motor.

tentorial nerve a branch that arises from the ophthalmic nerve close to its origin from the trigeminal ganglion, turning back to innervate the dura mater of the tentorium cerebelli and falx cerebri; modality, general sensory.

thoracic nerves the twelve pairs of spinal nerves (T1–T12) that arise from the thoracic segments of the spinal cord, each pair leaving the vertebral column below the correspondingly numbered vertebra. They innervate the body wall of the thorax and upper abdomen.

thoracic nerve, long origin, brachial plexus (ventral branches of C5–C7); distribution, descends behind brachial plexus to serratus anterior muscle; modality, motor.

thoracic splanchnic nerve, greater greater splanchnic n.

thoracic splanchnic nerve, lesser lesser splanchnic n.

thoracic splanchnic nerve, lowest lowest splanchnic n.

thoracodorsal nerve origin, posterior cord of brachial plexus (C7–C8); distribution, latissimus dorsi muscle; modality, motor.

tibial nerve tibial nerve: origin, sciatic nerve in lower part of thigh; branches, interosseous nerve of leg, medial cutaneous nerve of calf, sural nerve, and medial and lateral plantar nerves, and muscular and medial calcaneal branches; distribution, while still incorporated in the sciatic nerve, it supplies the semimembranous and semitendinous muscles, long head of biceps, and great adductor muscle; it supplies the knee joint as it descends in the popliteal fossa and, continuing into the leg, supplies the muscles and skin of the calf and sole of the foot, and the toes; modality, general sensory and motor.

trigeminal nerve fifth cranial nerve, which emerges from the lateral surface of the pons as a motor and a sensory root, together with some intermediate fibers. The sensory root expands into the trigeminal ganglion, which contains the cells of origin of most of the sensory fibers, and from which the three divisions of the nerve arise. See mandibular n., maxillary n., and ophthalmic n. The trigeminal nerve is sensory in supplying the face, teeth, mouth, and nasal cavity, and motor in supplying the muscles of mastication.

trochlear nerve fourth cranial nerve; origin, the fibers of each trochlear nerve (one on either side) decussate across the median plane and emerge from the back of the brain stem below the corresponding inferior colliculus; distribution, runs forward in lateral wall of cavernous sinus, traverses the superior orbital fissure, and supplies superior oblique muscle of eyeball; modality, motor.

tympanic nerve origin, inferior ganglion of glossopharyngeal nerve; branches, helps form tympanic plexus; distribution, mucous membrane of tympanic cavity, mastoid air cells, auditory tube, and, via lesser petrosal nerve and otic ganglion, the parotid gland; modality, general sensory and parasympathetic.

ulnar nerve origin, medial and lateral cords of brachial plexus (C7–T1); branches, muscular, dorsal, palmar, superficial, and deep branches; distribution, ultimately to skin on front and back of medial part of hand, some flexor muscles on front of forearm, many short muscles of hand, elbow joint, many joints of hand; modality, general sensory and motor.

unmyelinated nerve one whose axons are not encased in a myelin sheath.

utricular nerve the branch of the vestibular nerve that innervates the macula of the utricle.

utriculoampullary nerve a nerve that arises by peripheral division of the vestibular nerve, and supplies the utricle and ampullae of the semicircular ducts.

vaginal nerves origin, uterovaginal plexus; distribution, vagina; modality, sympathetic and parasympathetic.

vagus nerve vagus nerve: tenth cranial nerve; origin, by numerous rootlets from lateral side of medulla oblongata in the groove between the olive and the inferior cerebellar peduncle; branches, superior and recurrent laryngeal nerves, meningeal, auricular, pharyngeal, cardiac, bronchial, gastric, hepatic, celiac, and renal branches, pharyngeal, pulmonary, and esophageal plexuses, and anterior and posterior trunks; distribution, descending through the jugular foramen, it presents as a superior and an inferior ganglion, and continues through the neck and thorax into the abdomen. It supplies sensory fibers to the ear, tongue, pharynx, and larynx, motor fibers to the pharynx, larynx, and esophagus, and parasympathetic and visceral afferent fibers to thoracic and abdominal viscera; modality, parasympathetic, visceral afferent, motor, general sensory.

vasoconstrictor nerve one whose stimulation contracts blood vessels.

vasodilator nerve one whose stimulation dilates blood vessels.

vasomotor nerve one concerned in controlling the caliber of vessels, whether as a vasoconstrictor or vasodilator.

vertebral nerve origin, cervicothoracic and vertebral ganglia; distribution, ascends with vertebral artery and gives fibers to spinal meninges, cervical nerves, and posterior cranial fossa; modality, sympathetic.

vestibular nerve the posterior part of the vestibulocochlear nerve, which is concerned with the sense of equilibrium. It consists of fibers arising from bipolar cells in the vestibular ganglion, and divides peripherally into a rostral and a caudal part, with receptors in the ampullae of the semicircular canals, the utricle, and the saccule.

vestibulocochlear nerve eighth cranial nerve; it emerges from the brain between the pons and the medulla oblongata, at the cerebellopontine angle and behind the facial nerve. It divides near the lateral end of the internal acoustic meatus into two functionally distinct and incompletely united components, the vestibular nerve and the cochlear nerve, and is connected with the brain by corresponding roots, the vestibular and the cochlear roots.

vidian nerve n. of pterygoid canal.

vidian nerve, deep deep petrosal n.

zygomatic nerve origin, maxillary nerve, entering the orbit through the inferior orbital fissure; branches, zygomaticofacial and zygomaticotemporal branches; distribution, communicates with the lacrimal nerve and supplies the skin of the temple and adjacent part of the face; modality, general sensory.

nerve (nûrv)

1. Any of the cordlike bundles of nervous tissue made up of myelinated or unmyelinated nerve fibers and held together by a connective tissue sheath through which sensory stimuli and motor impulses pass between the brain or other parts of the central nervous system and the eyes, glands, muscles, and other parts of the body.

2. The sensitive tissue in the pulp of a tooth.

3. nerves Nervous agitation caused by fear, anxiety, or stress.

Nerve

Fibers that carry sensory information, movement stimuli, or both from the brain and spinal cord to other parts of the body and back again. Some nerves, including the vagus nerve, innervate distantly separated parts of the body.

Mentioned in: Hiccups

nerve

[nurv]

Etymology: L, nervus

one or more bundles of impulse-carrying fibers, myelinated or unmyelinated or both, that connect the brain and the spinal cord with other parts of the body. Nerves transmit afferent impulses from receptor organs toward the brain and spinal cord and efferent impulses peripherally to the effector organs. Each nerve consists of an epineurium enclosing fasciculi of nerve fibers. Each fasciculus is surrounded by its own sheath of connective tissue, or epineurium. Individual nerve fibers, which are microscopic, consist of formed elements within a matrix of protoplasm enclosed in endoneurium that are enclosed in a neurilemmal sheath. Inside the neurilemma are nerve fibers, also enclosed in a myelin sheath. See also axon, dendrite, neuroglia, neuron, Schwann cell.

nerve [nerv]

a macroscopic cordlike structure of the body, comprising a collection of nerve fibers that convey impulses between a part of the central nervous system and some other body region. See Appendix 2-6 and see color plates.

Depending on their function, nerves are known as sensory, motor, or mixed. Sensory nerves, sometimes called afferent nerves, carry information from the outside world, such as sensations of heat, cold, and pain, to the brain and spinal cord. Motor nerves, or efferent nerves, transmit impulses from the brain and spinal cord to the muscles. Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions at once.

Together, the nerves make up the peripheral nervous system, as distinguished from the central nervous system (brain and spinal cord). There are 12 pairs of cranial nerves, which carry messages to and from the brain. Spinal nerves arise from the spinal cord and pass out between the vertebrae; there are 31 pairs, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The various nerve fibers and cells that make up the autonomic nervous system innervate the glands, heart, blood vessels, and involuntary muscles of the internal organs.

Details of structure of components of nerve tissue.

A whitish cord made up of myelinated or unmyelinated nerve fibres held together by connective tissue sheath in bundles and through which stimuli are transmitted from the central nervous system to the periphery or vice versa.
abducens nerve Sixth cranial nerve. It has its origin from the abducens nucleus at the lower border of the pons and at the lateral part of the pyramid of the medulla. It passes through the cavernous sinus and enters the orbit through the superior orbital fissure. It supplies motor innervation to the ipsilateral lateral rectus muscle. Additionally, interneurons leave the abducens nucleus and project to the contralateral medial rectus sub nucleus to allow conjugate gaze. A lesion in the nuclear region will cause gaze palsy, whereas an abducens nerve lesion will produce only an abduction deficit. See abducens nucleus; paralysis of the sixth nerve.
cranial nerve's Twelve pairs of nerves, one set on each side of the brain, that emerge, or enter the cranium. They carry sensory information from the sense organs, the muscles of the head, neck, shoulders, heart, viscera and vocal tract. The motor neurons with axons in the cranial nerves control pupil diameter, accommodation, movements of the eyes and eyelids, mastication, facial expression, head movements, as well as cardiorespiratory and digestive functions.
nerve fibre layer See retina.
fifth cranial nerve See trigeminal nerve.
fourth cranial nerve See trochlear nerve.
frontal nerve See ophthalmic nerve.
nerve impulse See action potential.
infratrochlear nerve See ophthalmic nerve.
lacrimal nerve See ophthalmic nerve.
long ciliary nerve One of a pair of nerves that comes off the nasociliary nerve and runs with the short ciliaries, pierces the sclera, travels in the suprachoroidal space and supplies sensory fibres to the iris, cornea, and ciliary muscle and sympathetic motor fibres to the dilator pupillae muscle (Fig. N2). See ophthalmic nerve; pupil light reflex.
nasociliary nerve See ophthalmic nerve.
oculomotor nerve Third cranial nerve. It is classified as a motor nerve. Its origin lies in the tegmentum of the midbrain. It passes through the cavernous sinus and just before it enters the orbit it divides into a small superior and a larger inferior division. Both divisions penetrate into the orbit through the superior orbital fissure. In the orbit the superior division passes inward above the optic nerve to supply the superior rectus and the levator palpebrae superioris muscles. The inferior division sends branches to the medial rectus, the inferior rectus and inferior oblique muscles, as well as providing parasympathetic fibres to the sphincter pupillae and ciliary muscles via a branch to the ciliary ganglion. See oculomotor nucleus; paralysis of the third nerve.
ophthalmic nerve This is the smallest of the three divisions of the trigeminal nerve, the other two being the maxillary and mandibular branches. It comes off the medial and upper part of the convex anterior border of the gasserian ganglion (trigeminal ganglion), passes through the cavernous sinus and just behind the superior orbital fissure it divides into three branches, the lacrimal, frontal and nasociliary, which pass through the fissure to enter the orbit. (1) The smallest of the three, the lacrimal nerve, supplies sensory fibres to the lacrimal gland, the skin of the upper eyelid and the conjunctiva. Just before reaching the gland the nerve communicates with the zygomaticotemporal nerve (itself a branch of the zygomatic nerve). This branch contains parasympathetic fibres from the facial nerve that pass to the lacrimal gland. (2) The frontal nerve, which is the largest of the three divisions, divides into the supratrochlear and supraorbital nerves. The supratrochlear further anastomoses with the infratrochlear nerve and supplies the lower part of the forehead, the upper eyelid and the conjunctiva. The infratrochlear supplies sensory fibres to the skin and conjunctiva round the inner angle of the eye, the root of the nose, the lacrimal sac and canaliculi and caruncle. The supraorbital nerve sends sensory fibres to the forehead, the upper eyelid and conjunctiva. (3) The nasociliary nerve gives origin to several nerves: the long ciliary nerves, the long or sensory root (ramus communicans) to the ciliary ganglion, the posterior ethmoidal nerve and the infratrochlear nerve (Fig. N2).
optic nerve Second cranial nerve. It forms a link in the visual pathway. It takes its origin at the retina and is made up of nearly 1.2 million fibres from the ganglion cells and some efferent fibres that end in the retina. The nerve runs backward from the eyeball and emerges from the orbit through the optic canal and then forms the optic chiasma. The total length of the optic nerve is 5 cm; the portion before the chiasma called intracranial being about 1 cm, the intracanalicular 6 mm, the intraorbital 3 cm and the intraocular 0.7 mm. The optic nerve is more often divided into only two portions: the intraocular (bulbar) portion and the orbital (retrobulbar) portion (Fig. N2). See optic atrophy; pupillary fibres; optic neuritis; anterior ischaemic optic neuropathy; papilloedema.
short ciliary nerve One of six to ten branches from the ciliary ganglion that enters the eye around the optic nerve, travels in the suprachoroidal space and innervates the ciliary muscle, the sphincter pupillae muscle and the cornea. See pupil light reflex.
sixth cranial nerve See abducens nerve.
supraorbital nerve; supratrochlear nerve See ophthalmic nerve.
third cranial nerve See oculomotor nerve.
trigeminal nerve Fifth cranial nerve. It is the largest of the cranial nerves. It originates above the middle of the lateral surface of the pons as two divisions, a larger sensory root and a motor root. The sensory root passes to the gasserian ganglion (trigeminal ganglion) and from that ganglion the three divisions of the fifth nerve are given off: the ophthalmic, maxillary and mandibular nerves. The fifth nerve is sensory to the face, the eyeball, the conjunctiva, the eyebrow, the teeth, the mucous membranes in the mouth and nose. The motor root of the nerve has no connection with the ganglion. It joins the mandibular nerve and is motor to the muscles of mastication.
trochlear nerve Fourth cranial nerve. It is the most slender of the cranial nerves but with the longest intracranial course (75 mm). It is the only motor nerve that originates from the dorsal surface of the brain between the midbrain and the cerebellum. It passes through the cavernous sinus and then enters the orbit through the superior orbital fissure and supplies motor fibres to the superior oblique muscle. See trochlear nucleus; paralysis of the fourth nerve.
zygomatic nerve A branch of the maxillary division of the trigeminal nerve, it enters the orbit by the inferior orbital fissure and soon divides into the zygomaticotemporal and zygomaticofacial branches. The former gives a twig to the lacrimal nerve and is thought to conduct autonomic fibres to the lacrimal gland and the latter supplies the skin over the zygomatic bone.

Fig. N2 Diagram of the ophthalmic division of the trigeminal nerve (fifth). This is a view of the right eye from above (c.b.z, communicating branch to the zygomatic nerve)

Table N1 Cranial nerves
nerve		type	function (sensory is in italic, the rest is motor)
I	olfactory	sensory	smell
II	optic	sensory	vision
III	oculomotor	mixed, primarily motor	movement of eye and eyelids, regulation of pupil size, accommodation, proprioception
IV	trochlear	mixed, primarily motor	eye movements, proprioception
V	trigeminal	mixed	chewing movements, sensations from head and face, proprioception
VI	abducens	mixed, primarily motor	abduction, proprioception
VII	facial	mixed	facial expression, secretion of saliva and tears, taste, proprioception
VIII	vestibulo-cochlear1. auditory (or cochlear) branch2. vestibular branch	sensory	hearingsense of balance
IX	glossopharyngeal	mixed	secretion of saliva, taste, control of blood pressure and respiration, proprioception
X	vagus	mixed	smooth muscle contraction and relaxation (e.g. heart) sensations from organs supplied, proprioception
XI	accessory	mixed, primarily motor	movements of head, swallowing movements and voice production, proprioception
XII	hypoglossal	mixed, primarily motor	tongue movements, proprioception

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abducent nerve accessory nerve acoustic nerve afferent nerve anococcygeal nerve deep temporal nerve depressor nerve lacrimal nerve			obstructive sleep apnea obstructive small airways disease obstructive thrombus obstructive uropathy obstruent obtund obtundation obtunded obtundent obturate obturating obturating embolism obturation obturator obturator artery obturator canal obturator crest obturator dislocation obturator externus obturator foramen obturator hernia obturator internus obturator membrane obturator muscles obturator nerve obturator nerve, accessory obturator sign obturator vein obtuse obtusion obv Obviousness OC oc- OCA occ Occam's Razor occasion occipit- occipita occipital occipital anchorage occipital artery occipital bone occipital condyle syndrome occipital condyles occipital cortex occipital horn occipital lobe Occipital neuralgia occipital pole			obturator foramen obturator foramen obturator foramen obturator foramen obturator foramens obturator foramens obturator foramens obturator hernia obturator hernia obturator hernia Obturator internus Obturator internus muscle Obturator membrane Obturator membrane obturator muscle, external obturator muscle, external obturator muscle, external obturator muscle, internal obturator muscle, internal obturator muscle, internal Obturator muscles Obturator muscles Obturator muscles obturator nerve obturator nerve obturator nerve obturator nerve obturator nerve degeneration obturator nerve degeneration obturator nerve degeneration obturator nerve, accessory obturator nerve, internal obturator nerve, internal obturator nerve, internal obturator nerve, internal obturator pad obturator paralysis obturator paralysis obturator paralysis Obturator sign Obturator sign Obturator sign obturator spindle obturator vein obturator vein Obturator veins Obturator veins Obturator veins Obturator vessels Obturator vessels obturators obturators obturators Obturatory membrane Obturatory membrane Obtusangular obtuse obtuse obtuse obtuse obtuse angle

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