Peripheral nervous system. Pars peripherica 14 (systema nervosum periphericum). The peripheral partofthe nervous system which includes all peripheral conducting tracts (nerves). The border between it and the central nervous sys- 15 temliesatthesurfaceofthebrainandspinalcord. CRANIAL NERVES. Nervi craniales (en-cephalici). The 12 pairs of nerves connected with the brain. With the exception of the trochlear (IV), all of them emerge from the base of the brain and exit through the base of the 16 skull (in contrast to the spinal nerves). Area of distribution: head, neck, as well as the thorax and abdomen (via vagus nerve). OLFACTORY NERVE (I). Nn. olfactorii (I). First 17 cranial nerve, which is formed by about 20 small bundles of nonmyelinated axons from the olfactory cells. It passes through the cribriform plate of the ethmoid into the olfactory bulb (synaptic site). A

OPTIC NERVE (II). N. opticus [II]. Second cranial nerve which leaves the eyeball medial to the posterior optic pole and extends up to the optic 18 chiasm. B C

OCULOMOTOR NERVE (III). N. oculomotorius [III]. Third cranial nerve, which exits from the sulcus on the medial side of the cerebral peduncle. This motor nerve (somatic and 19 visceral) passes into the orbit through the superior orbital fissure. B C

Superior ramus (division). Ramus superior. 20 Superior branch for the superior rectus and le-vator palpebrae superioris muscles. B Inferior ramus (division). Ramus inferior. In- 21 ferior branch for the medial and inferior recti and inferior oblique muscles. B Ciliary ganglion. Ganglion ciliare. Located about 2 cm behind the eyeball and lateral to the 22 optic nerve. This parasympathetic ganglion serves as a relay station for fibers innervating the ciliary and sphincter pupillae muscles. B Parasympathetic (motor) root. Radix para-sympathetica (oculomotoria). Branch of the 23 oculomotor nerve with preganglionic, para-sympathetic fibers projecting to the ciliary ganglion. B

Short ciliary nerves. Nn. ciliares breves. Several (up to 20) nerves penetrating the sclera 24 above and below the optic nerve and carrying postganglionic, parasympathetic and sympathetic fibers. B

Sympathetic root. Radix sympathetica. Fine, 25 postganglionic fiber tract from the internal carotid plexus with no synapses in the ciliary 26 ganglion. B

Sensory root. Radix sensoria (nasociliaris). 27 Fine, long connection with afferent fibers to the nasociliary nerve. B

TROCHLEAR NERVE (IV). N. trochlearis [IV]. Fourth cranial nerve. Thin nerve exiting dorsal and caudal to the tectal lamina and supplying the superior oblique muscle. B

Decussation of trochlear nerve. Decussatio nervorum trochlearium. The crossing of trochlear nerve fibers in the superior medullary velum. B

TRIGEMINAL NERVE (V). N. trigeminus [V]. Fifth cranial nerve (nerve of the 1st pharyngeal arch). Nerve that exits laterally from the pons with two groups of fibers, supplies the masticatory muscles and provides sensory innervation to the face. B C

Sensory root of trigeminal nerve. Radix sensoria [portio major]. Sensory part which exits from the pons caudally and enters the trigemi-nal ganglion. C

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