H&N 3 NERVES PDF

 Human Anatomy Lecture 3 Trigeminal nerve ,Facial nerve& Autonomic Nerves of the Head By Assistant professor Dr. Hatem A Hatem 2023-2024  Trigeminal nerve Learning objectives: Trigeminal n...

 Human Anatomy Lecture 3 Trigeminal nerve ,Facial nerve& Autonomic Nerves of the Head By Assistant professor Dr. Hatem A Hatem 2023-2024  Trigeminal nerve Learning objectives: Trigeminal nerve: 1. Anatomical Course. 2. Divisions. 3. Functions.  Trigeminal nerve Fifth paired ,mixed & Largest cranial nerve. ✓ Sensory: 3 terminal branches innervate skin, mucous membranes and sinuses of face. ✓ Motor: Only mandibular branch has motor fibres. It innervates muscles of mastication, anterior belly of digastric, tensor veli palatini and tensor tympani. ✓ Parasympathetic Supply: Post- ganglionic neurones of parasympathetic ganglia travel with branches of trigeminal nerve. ❖ Anatomical Course: Trigeminal nerve originates from three sensory nuclei (Mesencephalic, Principal sensory, Spinal nuclei of trigeminal nerve) and one motor nucleus extending from midbrain to medulla.. Supratrigeminal nucleus embedded in upper pole of motor nucleus acts as a pattern generator for masticatory rhythm. At level of pons, sensory nuclei merge to form a sensory root. The motor nucleus continues to form a motor root. 1975 mixed nerves 1973 autonomic nerves  In middle cranial fossa; sensory root expands into trigeminal ganglion. Tri. ganglion located lateral to cavernous sinus, in a depression of temporal bone known as trigeminal cave. Trigeminal ganglion gives rise to 3 divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3).  Motor root passes inferiorly to sensory root, along floor of trigeminal cave. Its fibres only distributed to mandibular division. Ophthalmic nerve and maxillary nerve travel lateral to cavernous sinus exiting cranium via superior orbital fissure and foramen rotundum respectively. Mandibular nerve exits via foramen ovale entering infra-temporal fossa. Ophthalmic Nerve: After arising from trigeminal ganglion, It travels laterally to cavernous sinus and gives rise to recurrent tentorial branch (which supplies tentorium cerebelli). Nerve then then exits cranium via superior orbital fissure, where it divides into 3 branches: Frontal nerve Lacrimal nerve Nasociliary nerve Nerve Branches Innervation Frontal (largest of three Supraorbital Upper eyelid and conjunctiva terminal branches of Scalp CNV1) Supratrochlear Upper eyelid and conjunctiva Forehead Lacrimal (smallest of Receives branch from zygomatic nerve of Sensory innervation of lacrimal gland, three terminal CNV2 containing parasympathetic fibers upper eyelid and conjunctiva branches of CNV1) Contains parasympathetic fibers to lacrimal gland. Nasociliary Anterior ethmoid nerve Sensory innervation of mucous membranes of frontal, ethmoid and sphenoid sinuses. Nasal cavity Posterior ethmoid nerve Absent in approximately 30% of people Sensory innervation to mucous membranes of sphenoid sinus Infratrochlear nerve Bridge of nose Upper eyelid and conjunctiva Long ciliary nerves Sensory innervation to eye (cornea, ciliary bodies, iris) Contains sympathetic fibers to dilator pupillae muscle. Note: Short ciliary nerves Are part ofparasympathetic and sympathetic nervous systems, arising from ciliary ganglion. Located between the optic nerve and the lateral rectus muscle in the orbit. There are usually 6 to 10 short ciliary nerves. They travel from ciliary ganglion and pass through sclera of eye near optic nerve, then move towards ciliary body and iris. Components: ❑ Parasympathetic fibers: These come from oculomotor nerve (CN III) via ciliary ganglion. They control the sphincter pupillae, responsible for constricting the pupil (pupillary light reflex). ❑ Sympathetic fibers: These come from the superior cervical ganglion and are responsible for controlling the dilator pupillae, which dilates the pupil. ❑ Sensory fibers: These originate from the nasociliary branch of the ophthalmic nerve (CN V1), providing sensory innervation to the cornea, ciliary body, and iris. Short ciliary nerves are not a branches of ophthalmic nerve  Mapping Cutaneous Innervation cutaneous innervation of CNV1 can seen in image below: Sensory Function Ophthalmic nerve provides sensory innervation to the following structures: 1. Forehead and scalp. 2. Frontal, ethmoid and sphenoid sinuses. 3. Upper eyelid and its conjunctiva. 4. Cornea. 5. Dorsum of the nose. 6. Lacrimal gland. 7. Parts of meninges and tentorium cerebelli (recurrent tentorial branch). Autonomic Functions ❑ Ophthalmic nerve itself does not contain any autonomic fibers. ❑ Nerves from sympathetic and parasympathetic system ‘hitchhike’ on CNV1: Sympathetic fibers (from superior cervical ganglion) hitchhike ‘on branches of nasociliary nerve (long ciliary nerves) to reach dilator pupillae in eye. Parasympathetic fibers (from pterygopalatine ganglion) hitchhike along zygomatic branch of maxillary nerve (CNV2) and then lacrimal branch of ophthalmic nerve (CNV1) to reach lacrimal gland. Lacrimal branch itself provides sensory innervation to lacrimal gland. Maxillary nerve Second branch of trigeminal nerve. Sensory supply to mid third of face. Anatomical Course: After arising from trigeminal ganglion, maxillary nerve passes through lateral wall of cavernous sinus, before leaving skull through foramen rotundum. It gives rise to sensory branches: 1. Superior alveolar nerve (anterior, posterior and middle) 2. Middle meningeal nerve 3. Infraorbital nerve 4. Zygomatic nerve(Zygomaticofacial & Zygomatictemporal) 5. Inferior palpebral nerve, Superior labial nerve & nasal nerve. 6. Pharyngeal nerve 7. Greater and lesser palatine nerves 8. Nasopalatine nerve  Sensory Function Maxillary nerve’s terminal branches innervate : 1. Lower eyelid and its conjunctiva. 2. Inferior posterior portion of nasal cavity (superior anterior is CNV1). 3. Cheeks and maxillary sinus. 4. Lateral nose. 5. Upper lip, teeth and gingiva. 6. Superior palate. Parasympathetic Function Post ganglionic fibers from pterygopalatine ganglion (derived from facial nerve) travel with maxillary nerve to: Lacrimal gland. Nasal glands.  Mandibular nerve Has a sensory role, parasympathetic fibers of other cranial nerves. unlike other branches, has a motor function. Anatomical Course Mandibular nerve contains both sensory and motor axons. Motor root runs along floor of trigeminal cave, beneath ganglion, joining sensory root before leaving cranium through foramen ovale. Anatomical Course Once mandibular has emerged from cranium, it courses through infratemporal fossa, branching into 4 tributaries Auriculotemporal Nerve. Buccal Nerve. Inferior Alveolar Nerve. Lingual Nerve. Auriculotemporal Nerve Arises as 2 roots: Superior root –sensory fibers. Inferior root –parasympathetic fibers, originating from CN IX, to parotid gland. 2 roots converge in close proximity to middle meningeal artery. After converging, secretory-motor fibers run to synapse in otic ganglion, while sensory fibers pass through ganglion without synapsing to eventually innervate: 1. Anterior part of auricle 2. Lateral part of temple. 3. Anterior external meatus.  Buccal Nerve Contains sensory fibers. As it emerges from mandibular nerve, it passes between two heads of lateral pterygoid muscle before heading to its target sites. Nerve provides general sensory innervation to buccal membranes of mouth (i.e. cheek), second and third molar teeth, which is important when performing dental work on those structures. Inferior Alveolar Nerve Carries both sensory and motor. After branching, it gives rise to mylohyoid nerve, a motor nerve to mylohyoid and anterior digastric muscles. Remaining sensory enter mandibular canal. Within this canal, nerve provides branches to mandibular teeth. Nerve emerges through mental foramen as mental nerve. This provides sensory innervation to lower lip and chin. Lingual Nerve Carries general sensory &special sensory and autonomic fibers belonging to chorda tympani. General sensory fibers innervate anterior two-thirds of tongue. Special sensory fibers carry on with lingual nerve to provide taste to anterior two-thirds of tongue. Autonomic fibers branch to synapse in submandibular ganglion, eventually innervating submandibular and sublingual glands. Sensory Functions The sensory fibers associated with mandibular branch of CN V provide innervation to: 1. Facial skin in lower third of face, including chin and lower lip 2. Inferior row of teeth and gingiva. 3. Anterior two thirds of tongue. Motor Functions The motor root supply muscles of mastication : 1. Masseter 2. Medial and lateral pterygoids 3. Temporalis In addition to : 1. Tensor tympani. 2. Tensor veli palatini. 3. Anterior belly of digastric. 4. Mylohyoid.  Autonomic Functions Trigeminal nerve does not have an autonomic nucleus and, as such, does not give rise to any autonomic axons directly. However, all three branches of CN V take on autonomic fibers of other cranial nerves. Mandibular nerve is associated with parasympathetic secretory-motor fibers from two other cranial nerves.7,9 Parasympathetic Supply: Lacrimal gland: Post ganglionic fibres from pterygopalatine ganglion (derived from facial nerve), travel with zygomatic branch of V2 and then join lacrimal branch of V1. B. Parasympathetic Supply: Nasal glands: Parasympathetic fibres are carried to mucous glands of nasal mucosa. Post- ganglionic fibres travel with nasopalatine and greater palatine nerves (branches of V2). C. Parasympathetic Supply: Submandibular and Sublingual glands: Post-ganglionic fibres from submandibular ganglion (derived from facial nerve), travel with lingual nerve to innervate these glands. Parotid gland: Post- ganglionic fibres from otic ganglion ganglion (derived from glossopharyngeal nerve, CN IX), travel with auriculotemporal branch of V3 to innervate parotid gland.  Facial nerve Learning objectives: Facial nerve : 1. Anatomical Course. 2. Branches. 3. Functions. Facial nerve (CN VII) is the seventh paired mixed cranial nerve. Overview Motor – muscles of facial expression, posterior belly of digastric, stylohyoid and stapedius muscles. Sensory – a small area around concha of external ear. Special Sensory – provides special taste sensation to anterior 2/3 of tongue via chorda tympani Parasympathetic – supplies many of glands of head and neck, including: Submandibular and sublingual salivary glands. Nasal, palatine and pharyngeal mucous glands. Lacrimal glands. Anatomical Course Course of facial nerve is very complex. There are many branches, which transmit a combination of sensory, motor and parasympathetic fibers. Anatomically, course of facial nerve can be divided into two parts: Intracranial – the course of nerve through cranial cavity, and cranium itself. Extracranial –course of nerve outside cranium, through face and neck. Intracranial Facial nerve arises in pons, an area of brainstem. It begins as two roots; a large motor root, and a small sensory root (part of facial nerve that arises from sensory root is known as intermediate nerve). https://teachmeanatomy.info/wp-content/uploads/Schematic Two roots travel through internal acoustic meatus, a 1cm long opening in petrous part of temporal bone. Here, they are in very close proximity to inner ear. Intracranial Still within temporal bone, roots leave internal acoustic meatus, and enter into facial canal. Facial canal is a ‘Z’ shaped structure. Within facial canal, three important events occur: Firstly two roots fuse to form t facial nerve. Next, nerve forms geniculate ganglion. Intracranial Lastly, nerve gives rise to: Greater petrosal nerve – parasympathetic fibers to mucous glands and lacrimal gland. Nerve to stapedius – motor fibers to stapedius muscle of middle ear. Chorda tympani – special sensory fibers to anterior 2/3 tongue and parasympathetic fibers to submandibular and sublingual glands. Intracranial Facial nerve then exits facial canal (and cranium) via stylomastoid foramen(located just posterior to styloid process of temporal bone). Extracranial After exiting skull, facial nerve turns superiorly to run just anterior to outer ear. The first extracranial branch to arise is posterior auricular nerve. It provides motor innervation to some of muscles around ear. Immediately distal to this, motor branches are sent to posterior belly of digastric muscle and to stylohyoid muscle. Extracranial The main trunk of nerve, now termed motor root of facial nerve, continues anteriorly and inferiorly into parotid gland (note –facial nerve does not contribute towards innervation of parotid gland, which is innervated by glossopharyngeal nerve ). Extracranial Within parotid gland, nerve terminates by splitting into five branches: 1. Temporal branch. 2. Zygomatic branch. 3. Buccal branch. 4. Marginal mandibular branch. 5. Cervical branch. These branches are responsible for innervating muscles of facial expression. Motor Functions The first motor branch arises within facial canal; nerve to stapedius. nerve passes through pyramidal eminence to supply stapedius muscle in middle ear. Between stylomastoid foramen, and parotid gland, three more motor branches are given off: Posterior auricular nerve – Ascends in front of mastoid process, and innervates intrinsic and extrinsic muscles of outer ear. It also supplies occipital part of occipitofrontalis muscle. Motor Functions Nerve to posterior belly of digastric muscle – Innervates posterior belly of digastric muscle (a suprahyoid muscle of neck). It is responsible for raising hyoid bone. Nerve to stylohyoid muscle – Innervates stylohyoid muscle (a suprahyoid muscle of neck). It is responsible for raising hyoid bone. Motor Functions Within parotid gland, facial nerve terminates by bifurcating into five motor branches. These innervate muscles of facial expression: Temporal – Innervates frontalis, orbicularis oculi and corrugator supercilii. Zygomatic – Innervates orbicularis oculi. Buccal – Innervates orbicularis oris, buccinator and zygomaticus. Marginal mandibular – Innervates depressor labiiinferioris, depressor angulioris and mentalis. Cervical – Innervates platysma. Special Sensory Functions The chorda tympani branch of facial nerve is responsible for innervating anterior 2/3 of tongue with special sense of taste. Nerve arises in facial canal, and travels across bones of middle ear, exiting via petrotympanic fissure, and entering infratemporal fossa. Here, chorda tympani ‘hitchhikes’ with lingual nerve. Parasympathetic fibers of chorda tympani stay with lingual nerve, but main body of nerve leaves to innervate anterior 2/3 of tongue. Parasympathetic Functions Parasympathetic fibers of facial nerve are carried by greater petrosal and chorda tympani branches. Greater Petrosal Nerve Arises immediately distal to geniculate ganglion within facial canal. It then moves in anteromedial direction, exiting temporal bone into middle cranial fossa. From here, its travels across (but not through) foramen lacerum, combining with deep petrosal nerve to form nerve of pterygoid canal. Parasympathetic Functions The nerve of pterygoid canal then passes through pterygoid canal (Vidian canal) to enter pterygopalatine fossa, and synapses with pterygopalatine ganglion. Branches from this ganglion then go on to provide parasympathetic innervations to mucous glands of oral cavity, nose and pharynx, and lacrimal gland. Parasympathetic Functions Parasympathetic fibers of facial nerve are carried by greater petrosal and chorda tympani branches. Chorda Tympani Chorda tympani also carries some parasympathetic fibers. https://teachmeanatomy.info/wp-content/uploads/The-Submandibular-Ganglio These combine with lingual nerve (a branch of trigeminal nerve) in infratemporal fossa and form submandibular ganglion. Branches from this ganglion travel to submandibular and sublingual salivary glands. Clinical Relevance: Damage to Facial Nerve Damage to facial nerve, depending on site of lesion. Intracranial Lesions Intracranial lesions occur during intracranial course of facial nerve (proximal to stylomastoid foramen). Muscles of facial expression will be paralyzed or severely weakened.Other symptoms produced depend on location of lesion, and branches that are affected: Chorda tympani – reduced salivation and loss of taste on ipsilateral 2/3 of tongue. Nerve to stapedius – ipsilateral hyperacusis (hypersensitive to sound). Greater petrosal nerve – ipsilateral reduced lacrimal fluid production. The most common cause of an intracranial lesion of facial nerve is infection related to external or middle ear. If no definitive cause can be found, the disease is termed Bell’s palsy. Fig 1.4 - Right sided weakness of the muscles of facial expression, due to facial nerve paralysis. Extracranial Lesions: Extracranial lesions occur during extracranial course of facial nerve (distal to stylomastoid foramen). Only motor function of facial nerve is affected, therefore resulting in paralysis or severe weakness of muscles of facial expression. There are various causes of extracranial lesions of facial nerve: Parotid gland pathology – e.g a tumour, parotitis, surgery. Infection of the nerve – particularly by herpes virus. Compression during forceps delivery – the neonatal mastoid process is not fully developed and does not provide complete protection of nerve. Idiopathic – If no definitive cause can be found then disease is termed Bell’s palsy. Objectives of this lecture: Parasympathetic nervous system 1. Anatomical Course and Structure 1.1 Ciliary Ganglion 1.2 Pterygopalatine Ganglion 1.3 Submandibular Ganglion 1.4 Otic Ganglion. Sympathetic nervous system Contents 1. Anatomical Structure and Course 1.1 Superior Cervical Ganglion 1.2 Middle Cervical Ganglion 1.3 Inferior Cervical Ganglion Parasympathetic nervous system(PNS) Is a division of autonomic nervous system. It is involuntary acts with sympathetic system to maintain body homeostasis. Actions of PNS are associated with ‘rest and digest’ response. Anatomical Course and Structure parasympathetic fibers(PF) begin in CNS. Nerves supplying H&N situated within 4 nuclei, located within brainstem. Each nucleus is associated with a cranial nerve (3, 7, 9 and 10) These nerves carry PF out of brain. After leaving brain, PF from each nuclei synapse in a peripheral ganglion. These ganglia are located near to target viscera. From ganglia, post-ganglionic PF continue to organs in H&N, providing parasympathetic innervation. Anatomical Course and Structure There are four parasympathetic ganglia located within head &N (ciliary, otic, pterygopalatine and submandibular. They receive fibers from oculomotor, facial and glossopharyngeal nerves (vagus nerve only innervates structures in thorax and abdomen). Ciliary Ganglion Located within bony orbit, situated anteriorly to superior orbital fissure, between lateral rectus muscle and optic nerve. Pre-ganglionic fibers: fibers from Edinger-Westphal nucleus (associated with oculomotor nerve) supply ciliary ganglion. Post-ganglionic fibers: PF leave ganglion via short ciliary nerves. Target Organs: pupillae (contracts pupil) and ciliary muscles (accommodates for near vision).  In addition, two sets of nerve fibers pass through ciliary ganglion without synapsing: Sympathetic nerves from internal carotid plexus – innervate dilator pupillae muscle Sensory fibers from nasociliary nerve (a branch of ophthalmic division of trigeminal nerve) – innervate cornea, ciliary body and iris. Pterygopalatine Ganglion (sphenopalatine) Largest of four parasympathetic ganglia located within pterygopalatine fossa. Pre-ganglionic fibers: fibers from superior salivatory nucleus (associated with facial nerve). fibers travel within greater petrosal nerve and nerve of pterygoid canal to reach ganglion. Post-ganglionic fibers: PF leave ganglion by hitchhiking on branches of maxillary nerve ( from trigeminal nerve). Target organs: lacrimal gland, mucous glands of posterosuperior nasal cavity, nasopharynx, and palate. Sympathetic fibers from internal carotid plexus and sensory branches from maxillary nerve pass through pterygopalatine ganglion without synapsing. Submandibular ganglion Located inferiorly to lingual nerve, from which it is suspended. Pre-ganglionic fibers: from superior salivatory nucleus (associated with facial nerve). carried within chorda tympani. This nerve hitchhikes along lingual branch of mandibular nerve to reach ganglion. Submandibular ganglion Post-ganglionic fibers: travel directly to submandibular and sublingual glands. Target Organs: submandibular and sublingual glands. Sympathetic fibers from facial artery plexus pass through submandibular ganglion. They thought to innervate glands in base of oral cavity. Otic Ganglion: Located inferiorly to foramen ovale, within infratemporal fossa. It is medial to mandibular branch of trigeminal nerve. Pre-ganglionic fibers: fibers from inferior salivatory nucleus (associated with glossopharyngeal nerve) supply ganglion. Parasympathetic fibers travel within a branch of glossopharyngeal nerve, lesser petrosal nerve, to reach otic ganglion. Otic Ganglion Post-ganglionic fibers: PF hitchhike along auriculotemporal nerve (branch of mandibular division of trigeminal nerve) to parotid gland. Target Organs: parotid gland. Sympathetic fibers from superior cervical chain pass through otic ganglion. They travel with middle meningeal artery to innervate parotid gland. Sympathetic nervous system(SNS) Division of autonomic nervous system. It is involuntary, acts with parasympathetic system to maintain body homeostasis. Actions of SNS are associated with ‘fight or flight’ response. Anatomical Structure and Course Sympathetic fibers begin in spinal cord. Originate from thoracic region (T1- 6), need to ascend to reach structures in head and neck. After leaving spinal cord, fibers enter sympathetic chain. Sympathetic chain spans from base of skull to coccyx, and formed by nerve fibers and ganglia. Superior, middle and inferior cervical ganglia. Sympathetic fibers synapse with these 3 ganglia, postganglionic branches continuing into H&N. Each of 3 ganglia related to specific arteries in H&N. Post-ganglionic fibers hitchhike along arteries in order to reach target organs. Superior cervical ganglion Located posteriorly to carotid artery, and anterior to C1-4 vertebrae. Post-ganglionic nerves originate from : 1. Internal carotid nerve – hitch-hikes along internal carotid artery. Branches from internal carotid plexus innervate structures in eye, pterygopalatine artery and internal carotid artery itself. 2. External carotid nerve – hitch-hikes along common and external carotid arteries. It innervates smooth muscle of arteries. Superior cervical ganglion 3. Nerve to pharyngeal plexus – combines with branches from CN 9&10 to form pharyngeal plexus. 4. Superior cardiac branch – contributes to cardiac plexus in thorax. 5. Nerves to cranial nerves II, III, IV, VI and IX. 6. Gray rami communicants to anterior rami of C1-C4.  Middle Cervical Ganglion Absent in some individuals. When present, located anteriorly to inferior thyroid artery and C6 vertebra. Middle Cervical Ganglion Its postganglionic fibers are: 1. Gray rami communicants to anterior rami of C5 and C6. 2. Thyroid branches – travel along inferior thyroid artery, distributing fibers to larynx, trachea, pharynx and upper oesophagus. 3. Middle cardiac branch – contributes to cardiac plexus in thorax.  Inferior Cervical Ganglion Situated anteriorly to C7 vertebra. It sometimes fused with T1 vertebrae, forming cervicothoracic ganglion. Inferior Cervical Ganglion 3 post-ganglionic fibers arise from : 1. Gray rami communicants to anterior rami of C7, C8 and T1. 2. Branches to subclavian and vertebral arteries. 3. Inferior cardiac nerve – contributes to cardiac plexus in thorax.