Cranial Nerves PDF

RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 1 THE CRANIAL NERVES I N. OLFACTORIUS Nn. olfactorii contain sensory fibres and are part of the olfactory pathway. Nn. olfactorii develop...

RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 1 THE CRANIAL NERVES I N. OLFACTORIUS Nn. olfactorii contain sensory fibres and are part of the olfactory pathway. Nn. olfactorii develop in foetus as processes of thelencephalon. The nerves originate by special olfactory cells – cellulae neurosensoriae olfactoriae (the 1st neurons). Dendrites of those cells start with olfactory receptors distributed in the mucous membrane of the nasal cavity – regio olfactoria; axons are collected into 15 – 20 branches – fila olfactoria, which run through lamina cribrosa to bulbus olfactorius. Bulbus olfactorius contains the 2nd neirons of the olfactory pathway; axons of them form tractus olfactorius, which continues into trigonum olfactorium. Bulbus, tractus et trigonum olfactorium lie in sulcus olfactorius (facies inferior thelencephali). From trigonum olfactorium fibres are distributed into bands – striae olfactoriae; they run to subcortical centers of the smell (the 3rd neurons of the pathway): anterior group of thalamic neurons, the mamillary bodies, substantia perforata anterior and the amygdaliod body. The subcortical centers of the smell are connected with the cortical center in uncus. II N. OPTICUS N. opticus is sensory nerve and in foetus it develops as a process of diencephalon. N. opticus participates in formation of the optic (visual) pathway. The optic pathway starts in retina: – the photoreceptors – rods and cones – the 1st neurons, – the bipolar cells – the 2nd neurons, – the ganglionar cells – the 3rd neurons; axons of them leave bulbus oculi and form n. opticus. The nerve passes through canalis opticus together with a. ophthalmica. In fossa cranii media the optic nerve forms chiasma opticum (1), which consists of two sets of fibres – crossed and uncrossed. The crossed fibres start from the medial parts of retina and occupy the central part of chiasma opticum; the uncrossed fibres originate from the lateral parts of retina and occupy the lateral part of chiasma opticum. Chiasma opticum continues into tractus opticus (2), which runs backward and contains fibres from both eyes. Tractus opticus reaches the subcortical visual centers – the 4th neurons of the optic pathway: – nucleus corporis geniculati lateralis, – stratum griseum colliculi superioris. The optic pathway continues from subcortical center nucleus corporis geniculati lateralis. The axons of the 4th neurons form radiatio optica and run through capsula interna to the cortical center in sulcus calcarinus region (cuneus and gyrus occipitotemporalis medialis). There are three reflectoric visual pathways continuing from stratum griseum colliculi superioris. 1. The most part of the axons of the 4th neurons form tractus tectospinalis. At the level of tegmentum mesencephali the tract is crossed – decussatio tegmentalis posterior, then it runs through tegmentum pontis, medulla oblongata, funiculus anterior medullae spinalis to the 5th neurons – nuclei motorii of the spinal cord. Impulses along the axons of the 5th neurons run through the motor root and n. spinalis to supply the skeletal muscles. This reflectoric visual pathway is responsible for reflectory movements according to unexpected visual irritation. 2. Stratum griseum colliculi superioris is connected with fasciculus longitudinalis medialis, which is responsible for coordination of the movements of eyeball, head and neck (fasciculus longitudinalis medialis communicates the motor nuclei of the III, IV, VI and XI cranial nerves with the motor nuclei of the spinal cord). 3. Stratum griseum colliculi superioris is connected with nuclei vegetativi n. oculomotorii. 2 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves Axons of vegetative nuclei are parasympathetic preganglionic fibres and they reach ganglion ciliare. After synapsing in ganglion ciliare parasympathetic postganglionic fibres run to supply smooth muscles of the eyeball – m. sphincter pupillae et m. ciliaris. This reflectoric visual pathway provides light reflex (the narrowing of the pupil) and accomodation. III N. OCULOMOTORIUS N. oculomotorius is mixed nerve. It contains motor and vegetative parasympathetic fibres. It has two nuclei in tegmentum mesencephali at the level of colliculi superiores: – nucleus n. oculomotorii (motor nucleus), – nuclei accessorii n. oculomotorii (parasympathetic vegetative nucleus). The nerve emerges at sulcus oculomotorius mesencephali. Then it extends through the lateral wall of sinus cavernosus, enters the optic cavity via fissura orbitalis superior and divides into two branches: 1. ramus superior contains motor fibres and supplies m. rectus superior, m. levator palpebrae superioris; 2. ramus inferior contains motor and vegetative fibres; motor fibres supply m. rectus inferior, m. rectus medialis, m. obliquus inferior. The vegetative (parasympathetic preganglionic) fibres leave the branch via radix oculomotoria and reach ganglion ciliare; after synapsing the parasympathetic postganglionic fibres run to supply smooth muscles of the eyeball – m. sphincter pupillae et m. ciliaris. IV N. TROCHLEARIS N. trochlearis is motor nerve. It has motor nucleus – nucleus n. trochelaris in tegmentum mesencephali at the level of colliculi inferiores. The nerve emerges on the dorsal side of mesencephalon – on lamina tecti, laterally to frenulum veli medullaris superioris. Then it curves around pedunculi cerebri, passes forward in the lateral wall of sinus cavernosus and enters the orbita through fissura orbitalis superior. N. trochlearis supplies m. obliquus superior. V N. TRIGEMINUS N. trigeminus is mixed nerve – it contains motor and sensory fibres. The nerve has four nuclei in fossa rhomboidea upper part: – nucleus principalis n. trigemini (sensory nucleus), – nucleus mesencephalicus n. trigemini (sensory nucleus), – nucleus spinalis n. trigemini (sensory nucleus), – nucleus motorius n. trigemini (motor nucleus). The nerve appears between pons and pedunculus cerebellaris medius; it has two roots: – radix sensoria, – radix motoria. The sensory root of the nerve forms ganglion trigeminale; the motor root lies inferiorly to the sensory root. The ganglion is surrounded by dura mater cavity – cavum trigeminale in impressio trigeminalis. The nerve splits into three parts: – n. ophthalmicus, – n. maxillaris, – n. mandibularis.  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 3 N. OPHTHALMICUS N. ophthalmicus contains the sensory fibres, passes forward in the lateral wall of sinus cavernosus and gives off ramus meningeus reccurens for tentorium cerebelli. Then n. ophthalmicus enters the optic cavity through fissura orbitalis superior and divides into three nerves: 1. n. lacrimalis – it runs along the lateral wall of the optic cavity together with a. lacrimalis and has a communicating branch with n. zygomaticus. It supplies glandula lacrimalis, conjunctiva and skin at the lateral corner of the eye and the upper eyelid; 2. n. frontalis – it runs along the upper wall of the optic cavity and gives off two branches: a) n. supratrochlearis runs through foramen (incisura) frontalis; it supplies conjunctiva, skin of the forehead, the root of the external nose, the medial corner of the eye and the upper eyelid, b) n. supraorbitalis passes through foramen (incisura) supraorbitalis and supplies skin of the forehead and the upper eyelid; 3. n. nasociliaris passes along the medial wall of the optic cavity and terminates as n. infratrochlearis, which supplies saccus lacrimalis, conjunctiva and skin at the medial corner of the eye. N. nasociliaris along its course gives off side branches: a) n. ethmoidalis posterior – it passes through foramen ethmoidale posterius and supplies the mucous membrane of the nasal cavity, cellulae ethmoidales and sinus sphenoidalis, b) n. ethmoidalis anterior – it passes through foramen ethmoidale anterius to fossa cranii anterior, where it gives off ramus meningeus to supply the meninges. Then n. ethmoidalis anterior descends through foramina cribrosa to the nasal cavity and supplies the mucous membrane of the nasal cavity, cellulae ethmoidales, sinus frontalis. The terminal part of n. ethmoidalis anterior – ramus nasalis externus – pierces the nasal bones and supplies skin of dorsum et apex nasi, c) nn. ciliares longi (2 – 4) – they run between the fibrous and vascular coats of the eye ball and supply sclera and chorioidea, d) sensory root for ganglion ciliare. N. MAXILLARIS N. maxillaris contains the sensory fibres. In fossa cranii media the nerve gives off ramus meningeus for supplying the coverings of this fossa. N. maxillaris leaves the cranial cavity through foramen rotundum and divides into the terminal branches in fossa pterygopalatina: 1. n. infraorbitalis runs through fissura orbitalis inferior to the optic cavity, passes along sulcus et canalis infraorbitalis, then through foramen infraorbitale emerges on the anterior surface of the maxilla. It supplies skin of the face between the eye and mouth openings by small branches: – rr. palpebrales inferiores – skin and conjunctiva of the lower eyelid, – rr. nasales externi – skin of the cheek and lateral surface of the nose, – rr. labiales superiores – skin of the cheek, nasal wing and upper lip. Side branches of n. infraorbitalis: a) nn. alveolares superiores anteriores (1 – 3) – they descend along the anterior wall of sinus maxillaris and supply it; they participate in formation of plexus dentalis superior to supply dentes incisivi et dens caninus, b) nn. alveolares superiores mediae (1 – 2) – they arise from the nerve in sulcus infraorbitalis, take part in formation of plexus dentalis superior and supply dentes premolares, c) nn. alveolares superiores posteriores (1 – 3) – they descend along tuber maxillae, run through foramina alveolaria and canales alveolares to form plexus dentalis superior  4 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves for supplying dentes molares and the mucous of sinus maxillaris. Plexus dentalis superior lies on arcus alveolaris maxillae, supplies the mucous of sinus maxillaris and gives off rr. dentales superiores and rr. gingivales superiores for the upper teeth and gums; 2. n. zygomaticus passes through fissura orbitalis inferior to the optic cavity, runs along its lateral wall and has communicating branch with n. lacrimalis. Then n. zygomaticus leaves the optic cavity through foramen zygomaticoorbitale and divides into two branches: a) ramus zygomaticofacialis – it emerges at the zygomatic region and supplies skin over the cheek, b) ramus zygmaticotemporalis – it supplies skin at the anterior part of the temporal region; 3. sensory root for ganglion pterygopalatinum. N. MANDIBULARIS N. mandibularis is mixed nerve. It leaves the cranial cavity through foramen ovale, enters fossa infratemporalis and divides into the branches. N. mandibularis branches could be divided into three groups – sensory, motor and mixed. Sensory branches of n. mandibularis: 1. ramus meningeus returns into the cranial cavity through foramen spinosum and supplies the meninges of fossa cranii media; 2. n. auriculotemporalis starts by 2 roots surrounding a. meningea media. The nerve runs backward and upward accompaning a. temporalis superficialis. It terminates by rr. temporales superficiales which supply skin of auricula, the posterior part of the temporal region, porus et meatus acusticus externus, membrana tympani, art. temporomandibularis and the parotid gland. N. auriculotemporalis receives vegetative parasympathetic postganglionic fibres from ganglion oticum to supply glandula parotis; 3. n. lingualis passes between m. pterygoideus medialis et lateralis and terminates in the tongue by rr. linguales. The terminal branches supply the mucous membrane of dorsum linguae from apex to sulcus terminalis and papillae filiformes. The beginning part of n. lingualis has communication with chorda tympani (n. intermedius) and receives from it sensory and parasympathetic preganglionic fibres. N. lingualis has side branches: a) n. sublingualis supplies mucous membrane of the mouth cavity and gums, b) sensory root for ganglion submandibulare; 4. n. buccalis runs between m. masseter and m. buccinator; it supplies skin of the cheek and angulus oris and mucous membrane lining the inner surface of the cheek; 5. sensory root for ganglion oticum. Motor branches of n. mandibularis (for muscles – derivates of the 1st visceral arch): 1. n. massetericus – m. masseter; 2. nn. temporales profundi – m. temporalis; 3. n. pterygoideus medialis – m. pterygoideus medialis; 4. n. pterygoideus lateralis – m. pterygoideus lateralis; 5. n. musculi tensoris veli palatini – m. tensor veli palatini; 6. n. musculi tensoris tympani – m. tensor tympani. Mixed branch of n. mandibularis: 1. n. alveolaris inferior descends through foramen mandibulae into canalis mandibulae; it emerges through foramen mentale as n. mentalis to supply skin at the region of the chin and lower lip. In canalis mandibulae the nerve forms plexus dentalis inferior, from which arise rr. dentales inferiores and rr. gingivales inferiores for the lower teeth and gums. N. alveolaris inferior before foramen mandibulae gives off the only muscular branch – n. mylohyoideus – it runs along sulcus mylohyoideus and supplies muscles – derivates of the  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 5 1st visceral arch on the neck – m. mylohyoideus, venter anterior m. digastrici. VI N. ABDUCENS N. abducens is motor nerve. It has nucleus n. abducentis in the upper part of fossa rhomboidea below colliculus facialis. The nerve appears on the ventral surface of medulla oblongata between pons and pyramis. It passes in composition of sinus cavernosus, leaves sinus at processus clinoideus anterior and enters the optic cavity through fissura orbitalis superior. It supplies m. rectus lateralis. VII N. FACIALIS N. facialis contains motor fibres and mixed nerve – n. intermedius. The motor fibres of n. facialis supply mimetic muscles – derivates of the 2nd visceral arch; it has nucleus n. facialis in the upper part of fossa rhomboidea. The nerve emerges between pons and oliva. It runs forward to porus acusticus internus, passes through meatus acusticus internus to canalis nervi facialis and exits from the canal through foramen stylomastoideum. Then the nerve goes to the substance of the parotid gland and forms plexus intraparotideus. From the plexus arise the following branches: 1. rr. temporales supply muscles around auricula (m. auricularis anterior, m. auricularis superior), venter frontalis m. occipitofrontalis, m. orbicularis oculi, m. corrugator supercilii; 2. rr. zygomatici supply m. orbicularis oculi, mm. zygomatici; 3. rr. buccales supply mm. zygomatici, m. levator labii superioris, m. levator anguli oris, m. risorius, m. buccinator, m. orbicularis oris, m. nasalis; 4. r. marginalis mandibulae supplies m. depressor labii inferioris, m. depressor anguli oris, m. mentalis; 5. r. colli supplies platysma. N. facialis side branches: 1. n. stapedius – it arises at the descending part of canalis nervi facialis, runs to the tympanic cavity and supplies m. stapedius; 2. n. auricularis posterior – it starts from n. facialis below foramen stylomastoideum and divides into 2 branches: r. auricularis supplies m. auricularis posterior, r. occipitalis supplies venter occipitalis m. occipitofrontalis; 1. r. digastricus starts from the nerve below foramen stylomastoideum and supplies venter posterior m. digastrici and m. stylohyoideus. N. INTERMEDIUS N. intermedius is part of n. facialis. It has 2 nuclei: – nucleus salivatorius superior (parasympathetic vegetative nucleus) – lies in fossa rhomboidea above striae medullares, – nucleus tractus solitarii (sensory nucleus) – lies in fossa rhomboidea below striae medullares. The nerve appears on the ventral surface of the brain between pons and medulla oblongata laterally from motor fibres of n. facialis. N. intermedius passes through porus et meatus acusticus internus together with n. facialis. At the first curve of canalis nervi facialis the nerve has sensory ganglion – ganglion geniculi. Below it the nerve divides into two branches: 1. n. petrosus major contains parasympathetic preganglionic fibres; it leaves canalis nervi facialis through hiatus canalis n. petrosi majoris, enters fossa cranii media, then it pierces cartilage of foramen lacerum, leaves the cranial cavity and through canalis pterygoideus reaches fossa pterygopalatina. The nerve forms parasympathetic root for ganglion pterygopalatinum;  6 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 2. chorda tympani contains sensory and parasympathetic preganglionic fibres. It leaves canalis nervi facialis through canaliculus chordae tympani, passes through the tympanic cavity, lies between malleus and incus, then through fissura petrotympanica leaves it. Further chorda tympani travels together with n. lingualis; sensory fibres continue to the tongue for supplying papillae fungiformes et papillae foliatae. Parasympathetic preganglionic fibres run to ganglion submandibulare and form the parasympathetic root for it. VIII N. VESTIBULOCOCHLEARIS N. vestibulocochlearis is sensory nerve which consists of two portions: – nervus cochlearis, – nervus vestibularis. N. cochlearis takes part in formation of the auditory pathway. The 1st neurons of the pathway are in ganglion spirale of the internal ear; their dendrits start by the hearing receptors – organon Corti, their axons form n. cochlearis. N. cochlearis passes along meatus et porus acusticus internus to the cranial cavity, joins with n. vestibularis to form n. vestibulocochlearis. The nerve enters the brain between pons and medulla oblongata and runs to nuclei cochleares – the 2nd neurons of the auditory pathway. From nuclei cochleares the most part of the axons go to the opposite side and synapse with nuclei corporis trapezoidei. The other part of axons are not crossed and synapse with nuclei corporis trapezoidei on the same side. The axons of nuclei corporis trapezoidei form lemniscus lateralis, which ascends through tegmentum mesencephali and terminates in subcortical centers of the hearing – colliculus inferior and corpus geniculatum mediale (the 4th neurons of the pathway). The auditory pathway continues from the subcortical centers as radiatio acustica and through capsula interna reaches the cortical center in gyrus temporalis superior. The reflectoric auditory pathway communicates subcortical center in colliculus inferior with stratum griseum colliculi superioris, is crossed in tegmentum mesencephali (decussatio tegmentalis posterior) and descends as tractus tectospinalis. This reflectoric auditory pathway is responsible for reflectory movements according to unexpected hearing irritation. N. vestibularis is part of the balance pathway; it originates by the balance receptors (macula sacculi, macula utriculi, cristae ampullares) in the internal ear. The 1st neurons are in ganglion vestibulare, which lies in meatus acusticus internus; the axons of the 1st neurons form n. vestibularis. It runs along meatus et porus acusticus internus and joins with n. cochlearis to form n. vestibulocochlearis. The nerve enters the brainstem between pons and medulla oblongata and terminates by synapsing with nuclei vestibulares in fossa rhomboidea – the 2nd neurons of the balance pathway. The axons of the 2nd neurons run to nuclei motorii medullae spinalis (tractus vestibulospinalis), to nucleus olivaris (tractus vestibuloolivaris), join with fasciculus longitudinalis medialis, run to cerebellum (tractus vestibulocerebellaris) and to cortex cerebri. Nucleus olivaris is communicated with cerebellum by tractus olivocerebellaris and with nuclei motorii medullae spinalis by tractus olivospinalis. IX N. GLOSSOPHARYNGEUS N. glossopharyngeus is mixed nerve which contains sensory, motor and parasympathetic vegetative fibres. It has three nuclei in fossa rhomboidea: – nucleus ambiguus (motor nucleus), – nucleus tractus solitarii (sensory nucleus), – nucleus salivatorius inferior (parasympathetic vegetative nucleus). The nerve appears at sulcus posterolateralis medullae oblongatae and leaves the cranial cavity  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 7 through foramen jugulare. Above and below the opening there are two sensory ganglions – ganglion superius and ganglion inferius. The nerve descends behind a. carotis interna, then – between the artery and v. jugularis interna. Then it runs to the tongue and distributes into the terminal branches – rr. linguales, which supply the mucous membrane of radix lingue till epiglottis (except vallecula epiglottica) and papillae vallatae. N. glossopharyngeus gives off side branches: 1. n. tympanicus contains sensory and parasympathetic preganglionic fibres; it arises at the level of ganglion inferius, passes into canaliculus tympanicus and forms plexus tympanicus in the tympanic cavity. The plexus is formed also by sympathetic fibres – nn. caroticotympanici from the sympathetic plexus – plexus caroticus internus. Plexus tympanicus supplies cavitas tympani, tuba auditiva, cellulae mastoideae. N. tympanicus terminal part is n. petrosus minor; it contains parasympathetic preganglionic fibres, leaves the tympanic cavity through hiatus canalis n. petrosi minoris, enters fossa cranii media, then goes through foramen lacerum and terminates in ganglion oticum; 2. r. musculi stylopharyngei is motor branch, it supplies m. stylopharyngeus; 3. rr. pharyngei (2 – 3) are sensory branches, they reach the pharynx and together with the branches of n. vagus and sympathetic fibres of truncus sympathicus form plexus pharyngeus. Rr. pharyngei of the IX cranial nerve supply mucous membrane in the upper part of the pharynx; 4. rr. tonsillares (2 – 3) – they are sensory fibres for supplying tonsilla palatina, arcus palatoglossus and arcus palatopharyngeus; 5. r. sinus carotici descends to the hemoreceptors of sinus caroticus and glomus caroticum to participate in regulation of the blood pressure. X N. VAGUS N. vagus is mixed nerve which contains sensory, motor and parasympathetic vegetative fibres. It has three nuclei located in fossa rhomboidea: – nucleus ambiguus (motor nucleus), – nucleus tractus solitarii (sensory nucleus), – nucleus dorsalis n. vagi (parasympathetic vegetative nucleus). N. vagus emerges at sulcus posterolateralis medullae oblongatae. It passes through foramen jugulare and has two sensory ganglions: one is above foramen jugulare – ganglion superius, the other is below foramen jugulare – ganglion inferius. N. vagus descends along the lateral side of the neck. In the upper part of the neck it lies together with a. carotis interna and v. jugularis interna, in the lower part – with a. carotis communis and v. jugularis interna. Then the nerve enters the thoracic cavity through apertura thoracis superior. The course of the nerve differs on the right and left sides of the body. On the righ side n. vagus crosses a. subclavia, descends along the trachea, lies posteriorly to radix pulmonis, approachs the posterior surface of the oesophagus and together with the nerve of opposite side forms plexus oesophageus. On the left side n. vagus passes between a. carotis communis, a. subclavia and v. brachiocephalica. It crosses arcus aortae, then descends behind radix pulmonis, approaches the anterior surface of the oesophagus and together with the nerve of opposite side forms plexus oesophageus. Fibres of plexus oesophageus are arranged into two trunks: – truncus vagalis anterior; – truncus vagalis posterior. The trunks along the anterior and posterior surfaces of the oesophagus pass through the diaphragm (hiatus oesophageus) and distribute to the anterior and posterior walls of the 8 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves stomach – plexus gastricus anterior et posterior, then the fibres of n. vagus run to plexus coeliacus. There are side branches arising from the vagus nerve: 1. ramus meningeus – it contains sensory fibres, starts at the level of ganglion superius, passes through foramen jugulare, returns in the cranial cavity, supplies the meninges of fossa cranii posterior, 2. ramus auricularis – it contains sensory fibres, starts at the level of ganglion superius, supplies skin of the posterior part of auricula and meatus acusticus externus. Between ganglion superius and ganglion inferius to the X cranial nerve joins ramus internus of n. accessorius, which is running to supply muscles of the pharynx, the palatum (except m. tensor veli palatini), the larynx. 3. rr. pharyngei they start at the level of ganglion inferius and contain sensory, motor and parasympathetic vegetative fibres; rr. pharyngei reach the pharynx and together with the branches of n. glossopharyngeus and sympathetic fibres of truncus sympathicus form plexus pharyngeus. Rr. pharyngei of the X nerve supply mucous membrane in the lower part of the pharynx, muscles of the palate (except m. tensor veli palatini), muscles of the pharynx (except m. stylopharyngeus); 4. n. laryngeus superior starts at the level of ganglion inferius and contains sensory, motor and parasympathetic vegetative fibres; it descends along the pharynx and divides into two branches: a) ramus externus – it contains motor fibres and supplies m. cricothyreoideus, b) ramus internus – it contains sensory and parasympathetic fibres; the branch descends along membrana thyreohyoidea, pierces it and supplies the mucous membrane of the larynx from aditus laryngis to plicae vocales, mucous membrane of recessus piriformis and vallecula epiglottica in the tongue. Ramus internus gives small branches to glandula thyroidea and glandula parathyroidea; 5. rr. cardiaci cervicales superiores et inferiores contain sensory and parasympathetic preganglionic fibres; they run along a. carotis communis together with sympathetic fibres of truncus sympathicus to supply the heart; 6. n. laryngeus recurrens contains sensory, motor and parasympathetic fibres; at the right side it originates at the level of a. subclavia, at the left side – below arcus aortae. The nerve ascends between the trachea and the oesophagus and terminates as n. laryngeus inferior, which supplies the mucous membrane of the larynx from plicae vocales to the trachea. It supplies together with n. accessorius muscles of the larynx (except m. cricothyreoideus) and also glandula thyroidea, glandula parathyroidea. It gives off side branches: a) rr. tracheales contain sensory and parasympathetic fibres, they supply mucous membrane, glands and smooth muscular tissue of the trachea, b) rr. oesophagei contain motor, sensory and parasympathetic fibres; they supply the upper third of the esophagus – the mucous membrane, glands and striated muscular tissue. 7. rr. cardiaci thoracici – contain sensory and parasympathetic fibres and supply the heart; 8. rr. bronchiales – they pass along radix pulmonis to the lung and form plexus pulmonalis, which supplies the mucous membrane, glands and smooth muscular tissue of the bronchi and lungs and also pleura visceralis s. pulmonalis; 9. rr. oesophagei start from plexus oesophageus; they supply the mucous membrane, glands and smooth muscular tissue of the oesophagus. In the abdominal cavity the vagus nerve contains sensory and parasympathetic preganglionic fibres and is formed by two trunks – truncus vagalis anterior and truncus vagalis posterior: 1. truncus vagalis anterior passes along anterior surface of the oesophagus and curvatura minor to the anterior surface of the stomach; it gives off two groups of branches: a) rr. gastrici anteriores – they form plexus gastricus anterior to supply the stomach,  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 9 b) rr. hepatici – they supply the liver and omentum minus; 2. truncus vagalis posterior passes along posterior surface of the oesophagus to the posterior wall of the stomach. There are four groups of branches arising from it: a) rr. gastrici posteriores – they form plexus gastricus posterior to supply the stomach, b) rr. renales supply the kidneys, c) rr. hepatici supply the liver and the bile pathway, d) rr. coeliaci pass to plexus coeliacus; via plexus coeliacus the parasymphatic preganglionic fibres of truncus vagalis posterior run to the most part of the organs of abdominal cavity. XI N. ACCESSORIUS N. accessorius is motor nerve. It has two motor nuclei: – nucleus spinalis n. accessorii – it lies in the 6 upper segments of the spinal cord between the anterior and posterior horns of the grey matter, – nucleus ambiguus – in fossa rhomboidea. The nerve consists of two parts: 1. From nucleus ambiguus fibres appear on sulcus posterolateralis medulae oblongatae by radices craniales; 2. From nucleus spinalis n. accessorii fibres appear on sulcus posterolateralis medullae spinalis by radices spinales; they ascend along the spinal cord, enter the cranial cavity via foramen magnum and join with radices craniales to form a single trunk of the nerve – truncus nervi accessorii. The nerve leaves the cranial cavity through foramen jugulare and splits into two branches: 1. ramus externus supplies m. sternocleidomastoideus, m. trapezius, 2. ramus internus travels with n. vagus (rr. pharyngei and n. laryngeus reccurens) to supply muscles of the pharynx, the palate (except m. tensor veli palatini) and the larynx. XII N. HYPOGLOSSUS N. hypoglossus is motor nerve. It has nucleus n. hypoglossi (motor nucleus) in fossa rhomboidea. The nerve emerges at sulcus anterolateralis medullae oblongatae. It leaves the cranial cavity through canalis nervi hypoglossi. Then n. hypoglossus runs between a. carotis interna and v. jugularis interna, turns anteriorly, passes through trigonum submandibulare, reaches the tongue and terminates as rr. linguales to supply the muscles of the tongue. To the XII nerve join motor fibres of the ventral branches of the 1st and 2nd cervical spinal nerves. Some of those fibres leave the XII nerve via radix superior to join with radix inferior and form ansa cervicalis (plexus cervicalis). The other part of those fibres travel via n. hypoglossus to supply m. geniohyoideus. PARASYMPATHETIC GANGLIA OF THE HEAD Parasympathetic ganglia of the head belong to the peripheral part of parasympathetic autonomic nervous system.. They supply smooth muscles and glands of the head. Each ganglion is formed by parasympathetic cells; preganglionic fibres from the centers reach the ganglions and synapse to postganglionic fibres. Through the ganglions pass sympathetic postganglionic fibres and sensory fibres: sympathetic fibres are efferent, sensory fibres – afferent. Sensory fibres transmit irritation of interoreceptors from the organs to the centers, they are 10 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves branches of n. trigeminus and therefore the ganglions lie close to this cranial nerve. Each ganglion has three roots: radix parasympathica, radix sympathica, radix sensoria. Each ganglion gives off branches containing all three groups of fibres to supply smooth muscles and glands. There are four ganglions: ganglion ciliare, ganglion pterygopalatinum, ganglion submandibulare, ganglion oticum. Ganglion ciliare lies in the optic cavity, laterally to n. opticus. It has three roots: 1. radix parasympathica is formed by radix oculomotoria (n. oculomotorius); 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. ophthalmica; 3. radix sensoria is formed by sensory fibres of n. nasociliaris. The ganglion gives off branches – nn. ciliares breves; parasympathetic fibres of the nerves supply m. sphincter pupillae and m. ciliaris, sympathetic fibres – m. dilatator pupillae, sensory fibres – external and middle layers of the eyeball. Ganglion pterygopalatinum lies in fossa pterygopalatina. It has three roots: 1. radix parasympathica is formed by n. petrosus major (n. intermedius); 2. radix sympathica is formed by n. petrosus profundus – sympathetic postganglionic fibres are running from plexus caroticus internus surrounding a. carotis interna; 3. radix sensoria is formed by sensory root of n. maxillaris. N. petrosus major and n. petrosus profundus reach the fossa via canalis pterygoideus and both together form n. canalis pterygoidei. The ganglion gives off three groups of nerves: a) nn. palatini descend through canalis palatinus major to the palate and supply the mucosa of the hard and soft palate and glandulae palatinae; b) rr. nasales posteriores run through foramen sphenopalatinum to the nasal cavity and supply the mucosa of cavitas nasi, sinus sphenoidalis and glandulae nasales. One of the branches is longer – n. nasopalatinus; it runs forward along the nasal sept, descends into the oral cavity through foramen incisivum and supplies mucosa of the hard palate; c) some postganglionic parasympathetic fibres join n. zygomaticus and then via communicating branch with n. lacrimalis reach glandula lacrimalis to supply it. Ganglion submandibulare lies below n. lingualis close to the medial surface of glandula sublingualis. It has three roots: 1. radix parasympathica is formed by parasympathetic preganglionic fibres of chorda tympani, which travels to the ganglion with n. lingualis; 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. facialis; 3. radix sensoria is formed by n. lingualis. The ganglion gives off branches – rr. glandulares to supply glandula submandibularis and glandula sublingualis. Ganglion oticum lies below foramen ovale in fossa infratemporalis. It has three roots: 1. radix parasympathica is formed by n. petrosus minor (n. glossopharyngeus); 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. meningea media; 3. radix sensoria is formed by sensory fibres of n. mandibularis. The ganglion gives off branches – rr. anastomotici; they travel together with n. auriculotemporalis, then leave it and via rr. parotidei reach the parotid gland to supply it.