Cranial Nerves Sanjaya Adikari Department of Anatomy

12 pairs of cranial nerves III to XII attached to brain stem Their cell bodies form nuclei in the brain stem First cell body of sensory nerves lie out side CNS (form ganglia)

Summary of cranial nerves Aspects to study Position of nucleus Emerging point from brain stem Intracranial course Point of exit from the cranial cavity Extracranial course Distribution

Few terms: Somatic, branchial and visceral

Branchial (Pharyngeal) Arches ectoderm endoderm Core of mesodermal tissue covered by ectoderm and endoderm Each of the arch will have its own bone/cartilage, muscles, nerve and artery

Mandibular branch of trigeminal nerve (V) Facial nerve (VII) Premaxilla, maxilla, zygomatic bone, part of temporal bone and mandible Glossopharyngeal nerve (IX) Superior laryngeal branch of vagus nerve (X) Recurrent laryngeal branch of vagus nerve (X)

Visceral In relation to internal organs Heart Lung Intestines ……………… ……………..

Few hints Nerve A Nerve B

Posterior Somatic sensory Visceral sensory Motor Sensory Visceral motor Somatic motor Spinal cord (thoracic or lumbar) Posterior horn Lateral horn Anterior horn Motor Sensory

Brain stem SpS GSS SS VS VM BM SM

Types of sensations General Visceral sensory Visceral sensory pain, temperature, touch, viration position sense Visceral sensory Special Visceral sensory taste General Somatic sensory pain, temperature, touch, vibration position sense Somatic sensory Special Somatic sensory hearing

SpS SS VS BM SM VM SpS SS VS BM SM VM

III IV V VI VII XII IX X XI III VII IX VII X IX X V VII IX X VIII SS GSS VS VIII SM BM VM VII IX X V VII IX X XI

Functional components of cranial nerves III IV Somatic Motor Muscles of the orbit (III, IV, VI) Muscles of tongue (XII) VI XII

Branchial Motor Muscles of mastication (V) Facial muscles (VII) Pharyngeal and laryngeal muscles (Nucleus ambiguus via IX, X, XI nerves)

Visceral Motor Edinger Westphal nucleus (accessory oculomotor) Salivary nuclei (NI part of VII, IX) Dorsal motor nucleus of vagus (for cardiac muscles, smooth muscles of alimentary tract)

Sensory Visceral sensory with taste Consists of single nuclei for visceral and somatic sensory Visceral sensory with taste Nucleus of tractus solitarious which receives taste fibres from the tongue through VII, IX and sensory from heart, lungs and other viscera through X

General somatic sensory Sensory nucleus of trigeminal nerve extending from the midbrain to the cervical spinal cord

Special somatic sensory Hearing via VIII (vestibulocochlear nerve)

III IV III VI VII XII IX X V VII IX VII X IX XI X V VII IX X VIII SS GSS SS VS VIII BM SM VM VII IX X V VII IX X XI

Intracranial course and exit Sanjaya Adikari Department of Anatomy

Optic canal (II) Superior orbital fissure (III, IV, V1, VI) Foramen rotundum (V2) Foramen ovale (V3) Foramen spinosum Foramen lacerum Internal acoustic meatus (VII, VIII) Jugular foramen (IX, X, XI) Hypoglossal canal (XII)

Olfactory Nerve (I) Anterior perforated substance Olfactory tract Uncus Olfactory bulb Nerve filaments Cribriform plate of ethmoid bone Bypass thalamus and goes directly into the taste area

Optic Nerve (II) T N

Optic Nerve (II) Optic nerve Optic chiasma Optic tract Optic radiation Superior colliculus (body reflexes) Pretectal nucleus (pupillary reflexes) Internal capsule Lateral geniculate body of thalamus

Oculomotor Nerve (III) Somatic motor nucleus Visceral motor nucleus (Edinger westphal nucleus) Nerve emerges from ventral aspect of midbrain travel’s in the lateral wall of the cavernous sinus

Oculomotor Nerve… cont. Levator palpabrae superioris Dilator pupillae Sympathetic from Internal carotid plexus Superior division Superior rectus Medial rectus, inferior rectus, inferior oblique Inferior division Parasympathetic from EW nucleus Ciliary muscle Sphincter pupillae Ciliary ganglion

Trochlear Nerve (IV) Somatic motor nucleus Emerges from the dorsal aspect of midbrain Travels in the lateral wall of the cavernous sinus Supplies the superior oblique muscle

Abducens Nerve (VI) Somatic motor nucleus Nucleus lies in lower pons near midline Emerge between pons and pyramid of medulla Travels through the cavernous sinus Supply the lateral rectus muscle

Oculomotor N (III) Trochlear N (IV) Abducent N (VI) Ventral midbrain Lateral wall Cavernous S Divide Sup. & Inf. divisions Sup/infraorbital fissure Trochlear N (IV) Dorsal midbrain Lateral wall Cavernous S Superior orbital fissure Abducent N (VI) Between Pons & pyramid of medulla within Cavernous S Superior orbital fissure

Cavernous sinus 1- Oculomotor N 2- Trochlear N 3- Abducent N 4- Ophthalmic branch of TN 5- Maxillary branch of TN 6- Sympathetic plexus of N 7- Internal carotid A 8- Pituitary gland

LR6(SO4)3

Trigeminal nerve (V) Branchial motor nucleus Somatic sensory nucleus Emerge from the ventral aspect of pons Sensory and motor roots emerge separately

Trigeminal nerve… cont. Somatic sensory nucleus Trigeminal ganglion Cell bodies of 1st order SA fibres Ophthalmic division Lat. Wall of cavernous sinous Maxillary division Mandibulardivision Mandibularnerve (mixed) Branchial motor nucleus Foramen ovale

Facial Nerve (VII) Visceral motor nucleus (Superior salivary nucleus) Branchial motor nucleus Visceral motor nucleus (Superior salivary nucleus) Taste sensory nucleus (Tractus solitarius) Main facial nerve and the nervous intermedius parts emerge from the cerebellopontine angle

Facial Nerve…cont. Internal acoustic meatus Geniculate ganglion (taste 1st order cell bodies) Nucleus of Tractus solitarious Chorda tympani nerve Taste from anterior tongue Nervous intermedius Branchial motor nucleus VE to submandibular gland and glands on the mouth floor Greater petrosal nerve Sup. salivary nucleus Nerve to stapedius Ear drum Stylomastoid foramen Pure branchial motor facial nerve Supply muscles of facial expression

Vestibulocochlear Nerve (VIII) Internal acoustic meatus Spiral ganglion of cochlea Cochlear nuclei in pons Cochlear nerve Hair cells of spiral organ Vestibular ganglion Vestibular nuclei in medulla Cerebellopontine angle Vestibular nerve Hair cells of utricle, saccule and semilunar canals

Glossopharyngeal Nerve (IX) Branchial motor nucleus (Nucleus ambiguus) supplies stylopharyngeus muscle Parasympathetic nucleus (Inferior salivary nucleus) supplies parotid gland Sensory nuclei GSS from posterior tongue goes to sensory nucleus of trigeminal nerve Taste from the posterior tongue goes to the tractus solitarius VS from baroreceptors go to nucleus of tractus solitarius

Vagus Nerve (X) Branchial motor nucleus (Nucleus ambiguus) supplies pharyngeal constrictors Visceral motor nucleus (Dorsal motor nucleus of vagus) supplies muscles of heart, bronchi, oesophagus, stomach and intestines Visceral sensory nucleus VS from larynx, heart, lung… goes to nucleus of tractus solitarius GSS goes to sensory nucleus of trigeminal nerve

Accessory Nerve (XI) Branchial motor nerve Somatic motor nerve Cranial root From nucleus ambiguus Fibres in the cranial root join the vagus nerve Somatic motor nerve Spinal root Anterior horn cells of upper 5-6 cervical spinal segments Fibres in the spinal root supply sternocleidomastoid and trapezius muscles

Hypoglossal Nerve (XII) Somatic motor nerve Leaves cranial cavity through the hypoglossal canal Supplies all muscles (intrinsic and extrinsic) of tongue except palatoglossus

GSA VE BE BA

GSA BE BA VE