Nerves of head

• There are 12 pairs of cranial nerves (CN's)
• CN’s are part of the peripheral nervous system (PNS)
• Cranial nerves exit the cranial cavity through foramina or fissures
• All cranial nerves innervate structures in the head and neck
• The vagus nerve (X) descends into the thorax and abdomen
• The Accessory nerve innervates trapezius and sternocleidomastoid muscles

Olfactory Nerve (CN I)

• This is a special sensory nerve
• CN I carries fibers for the special sense of smell (olfaction)
• It passes through the cribriform plate of the ethmoid bone

Special Senses

• Olfaction is the sense of smell
• Vision is sight
• Gustation is taste
• Equilibrium is balance
• Auditory is hearing

Optic Nerve (CN II)

• This is a special sensory nerve
• CN II carries fibers for vision
• It passes through the optic canal of the sphenoid bone

Oculomotor Nerve (CN III)

• This is a motor nerve
• CN III carries motor fibers for extra-ocular muscles (eye movements) and the levator palpebrae superioris
• It passes through the superior orbital fissure of the sphenoid bone
• The Oculomotor Nerve has parasympathetic fibers for the muscles of pupil and lens

Trochlear Nerve (CN IV)

• This is a motor nerve
• CN IV carries motor fibers for an extra-ocular muscle
• CN IV passes through the superior orbital fissure of the sphenoid bone

Abducens Nerve (CN VI)

• This is a motor nerve
• CN VI carries motor fibers for an extra-ocular muscle
• It passes through the superior orbital fissure of the sphenoid bone

Trigeminal Nerve (CN V)

• This is both a sensory and motor nerve
• CN V is the major general sensory nerve of the head
• CN V transmits pain, temperature, touch, pressure, vibration, and proprioception
• The Trigeminal Nerve innervates muscles that move the lower jaw, which are the muscles of mastication
• It innervates the mylohyoid, anterior belly of the digastric, tensor veli palatini, and tensor tympani muscles
• The trigeminal nerve exits from the anterolateral surface of the pons
• It has a large sensory root and a small motor root
• In the middle cranial fossa, the sensory root expands into the trigeminal ganglion (TG)
• The trigeminal ganglion (TG) contains cell bodies for the sensory neurons
• Arising from the anterior border of the trigeminal ganglion (TG) are the three terminal divisions of the trigeminal nerve (CN V), that are the ophthalmic nerve (V1), maxillary nerve (V2), and mandibular nerve (V3)

Ophthalmic Nerve (CN V1)

• This is a sensory nerve (branch of trigeminal nerve)
• CN V1 carries sensory branches from the anterior part of the scalp, the eyes, upper eyelids, conjunctiva, orbital contents (with lacrimal gland), dorsum of nose, nasal cavity, frontal sinus, ethmoidal cells, falx cerebri, and dura in the anterior cranial fossa
• The ophthalmic nerve leaves the cranial cavity and enters the orbit through the superior orbital fissure
• Before it enters the orbit, CN V1 divides into 3 branches: lacrimal, frontal, and nasociliary nerves

Frontal Nerve

• The frontal nerve divides into two:
  • The supratrochlear nerve
  • The supra-orbital nerve

Nasociliary Nerve

• The nasociliary nerve gives off several branches:
  • The long ciliary nerves
  • The posterior ethmoidal nerve
  • The infratrochlear nerve
  • The anterior ethmoidal nerve which terminates as external nasal nerve(s)
• The ophthalmic nerve (CN V1) gives branches that innervate the skin of the face

Supra-orbital Nerve

• The supraorbital nerve innervates the upper eyelid, forehead, and scalp. -The supraorbital nerve passes through the supraorbital foramen / notch.

Supratrochlear Nerve

• The supratrochlear nerve innervates the upper eyelid, forehead, and scalp

Infratrochlear Nerve

• The infratrochlear nerve innervates the medial half of the upper eyelid, medial angle and the side of the nose

Lacrimal Nerve

• This innervates the lateral half of the upper eyelid

External Nasal Nerve

• This innervates the anterior part of the nose

Maxillary Nerve (CN V2)

• Innervates the dura in the middle cranial fossa, nasopharynx, palate, nasal cavity, teeth of the upper jaw, and maxillary sinus
• Innervates the skin covering the side of the nose, lower eyelid, cheek, and the upper lip
• Leaves the cranial cavity through the foramen rotundum
• Enters the pterygopalatine fossa
• CN V2 gives branches that innervate the skin of the face:
  • Zygomaticotemporal nerve supplies a small area at the anterior temporal fossa
  • Zygomaticofacial nerve supplies the skin over the zygomatic bone
  • Infra-orbital nerve supplies the lower eyelid, cheek, side of the nose, and upper lip

Mandibular Nerve (CN V3)

• Receives sensory information from the skin of the lower face, cheek, lower lip, anterior part of the external ear, part of external acoustic meatus and temporal region
• Receives information from the anterior 2/3 of the tongue, teeth of the lower jaw, mastoid air cells, mucous membranes of the cheek, mandible, and dura in the middle cranial fossa
• Leaves the middle cranial cavity through the foramen ovale
• The motor root of the trigeminal nerve also passes through the foramen ovale and unites with the mandibular nerve
• The motor root of the mandibular nerve innervates:
  • 4 muscles of mastication(temporalis, masseter, medial and lateral pterygoid muscles)
  • Anterior belly of the digastric, mylohyoid, tensor tympani, and tensor veli palatini
• The auriculotemporal nerve passes through the parotid gland, external acoustic meatus, outer surface of tympanic membrane, and skin over the temporal region (temple)
• The buccal nerve supplies the cheek
• The mental nerve the lower lip and skin of the chin _ The inferior alveolar nerve gives origin to the nerve to the mylohyoid (mylohyoid nerve)
• The nerve to the mylohyoid innervates the mylohyoid and anterior belly of the digastric muscles

Facial Nerve (CN VII)

• CN VII is both sensory and motor
• It provides sensory input from part of the external acoustic meatus and deeper parts of the auricle
• CN VII carries fibers for the special sense of taste from the anterior 2/3 of the tongue
• CN VII has parasympathetic innervation of lacrimal, submandibular, and sublingual glands
• This also innervates the nasal cavities, hard and soft palates
• This innervates facial expression muscles (stapedius, posterior belly of the digastric, and stylohyoid mm.)
• The facial nerve arises from the lateral surface of the brainstem between the pons and medulla oblongata
• CN VII has a large motor root and a smaller sensory root (intermediate nerve)
• CN VII crosses the posterior cranial fossa
• The facial nerve leaves the cranial cavity through the internal acoustic meatus and enters the facial canal in the petrous part of the temporal bone
• In the facial canal sensory root (intermediate nerve) enlarges as the geniculate ganglion
• Geniculate ganglion contains cell bodies for the sensory neurons
• It exits the skull through the stylomastoid foramen
• CN VII gives off the posterior auricular nerve, which supplies the occipital belly of occipitofrontalis and posterior auricular muscles
• Supplies the posterior belly of digastric and stylohyoid muscles
• The facial nerve passes into the parotid gland
  • The trunk then dives into the lower and upper (temporofacial and cervicofacial) divisions in the parotid gland

Terminal Group of Branches Emerging from Parotid Gland

• Temporal

• Zygomatic

• Buccal

• Marginal mandibular

• Cervical branches for platysma

• Branches of the Facial Nerve take part in anastomotic network in the parotid gland (parotid plexus)

Vestibulocochlear Nerve (CN VIII)

• This is a special sensory nerve
• The Vestibular division (for balance) and cochlear division (for hearing) emerge from the internal acoustic meatus
• Two divisions combine into single vestibulocochlear nerve that carries special senses of balance and hearing

Glossopharyngeal Nerve (CN IX)

• This is a sensory and motor nerve

• CN IX carries the sensory fibers to the sinuses and artery in the carotid

• Sensory input from the posterior 1/3 of the tongue, palatine tonsils, oropharynx, mucosa of the middle ear, pharyngotympanic tube and mastoid air cell

• CN IX allows sensation of taste from the posterior 1/3 of the tongue

• Parasympathetic fibers for the parotid gland

• CN IX innervates the muscle derived from 3rd pharyngeal arch (only stylopharyngeus muscle)

• The Glossopharyngeal Nerve leaves the posterior cranial cavity through the jugular foramen

Vagus Nerve (CN X)

• This is a sensory and motor nerve
• This Carries sensory fibers from the larynx, laryngopharynx, deeper parts of the auricle, part of the external acoustic meatus, and dura in the posterior cranial fossa
• The vagus nerve Allows Sensory input from the aortic body chemoreceptors and aortic arch baroreceptors, esophagus, bronchi, lungs, heart, and abdominal organs
• It Allows us to experience Taste (special) sensation around the epiglottis and pharynx
• Provides Parasympathetic fibers for: pharynx, larynx, thoracic and abdominal organs
• Innervates the palatoglossus, muscles of the soft palate, pharynx, and larynx The Vagus nerve Leaves the posterior cranial cavity through the jugular foramen

Vagus Nerve in the Neck

• The vagus nerve is in the neck, and sits lateral to the trachea; the common carotid artery, internal jugular vein and vagus nerve are surrounded with a fascia carotid sheath

Accessory Nerve (CN XI)

• This is a motor nerve
• Fibers from the C1-C6 form the spinal part of the accessory nerve
  • Spinal part ascends through the foramen magnum The spinal part joins the cranial part to form the accessory nerve in the posterior cranial fossa
• Most of the cranial part joins the vagus nerve Spinal part leaves Through the jugular foramen as accessorynerve (spinal accessory nerve)
• The nerve descends and innervates the SCM in neck and Trapezius Muscles The Anterior jugular vein intersects with internal and passes over jugular

Hypoglossal Nerve (CN XII)

• This is a motor nerve
• The nerve Carries motor fibers to Innervate all of muscles Intrinsic All muscles of the tongue and extrinsic (EXCEPT the palatoglossus)
• it Exists the brain and travels Though Hypoglossal canal
• There are Nerve fibers originating from which also contribute C1,These Fibers Form which Form superior root ansa (Anulus)cervicalis
  • The Ansa is connected To Thyrohyoid Muscle and Geniohyoid