Cranial Nerves

12 cranial nerves supply the head and the neck, which have a variety of sensory and motor function

I – Olfactory

Foramen:
Cribriform plate

Modality:
Special Sensory

Function:
Smell

II – Optic

Foramen:
Optic canal

Modality:
Special Sensory

Function:
Vision

III – Occulomotor

Foramen:
Superior Orbital Fissure

Modality:
Special Sensory

Function:
Innervation to eye muscles –> Levator palpebrae superioris, superior, Medical & Inferior Oblique
Parasympathetic to ciliary muscles and sphincter pupillae

IV – Trochlear

Foramen:
Superior Orbital Fissure

Modality:
Somatomotor

Function:
Innervation to superior oblique

V – Trigeminal

Foramen:
Superior Orbital Fissure (Va)
Foramen Rotundum (Vb)
Foramen Ovale (Vc)

Modality:
Somatosensory and branchiomotor

Function:
Sensation –> Head and neck, paranasal sinuses, meninges, and external surface of tympanic membrane
Va gives frontal + lacriminal + nasociliary branches
Vb gives zygomatic + ganglionic + infraorbital branches

Motor Innervation to muscles of mastication:
Vc innervates muscles of mastication (pterygoids + masseter + temporalis)
Also gives sensory branches –> buccal, lingual, inferior alveolar + auriculotemporal 

VI – Abducens

Foramen:
Superior Orbital Fissure

Modality:
Somatomotor

Function:
Innervation to lateral rectus

VII – Facial

Foramen:
Internal acoustic meatus

Modality:
Somatosenory
Viscerosensory
Visceromotor
Branchiomotor

Function:
Sensory –> Ear and tympanic membrane

Special sensory –> Taste to anterior two-thirds of tongue (chorda tympani) 

Parasympathetic to sublingual and Submandibular glands

Motor innervation to muscles of facial expression:
– Temporal branch –> Orbicularis oculis and frontalis
– Zygomatic –> muscles of the eyelid
– Buccal –> buccinator, orbicularis oris
– Mandibular –> muscles of lower lip
– Cervical –> Platysma

VIII – Vestibulocochlear

Foramen:
Internal Acoustic Meatus

Modality:
Special Sensory

Function:
Hearing and balance

IX – Glossopharyngeal

Foramen:
Jugular Foramen

Modality:
Somatosensory
Viscerosensory
Branchiomotor
Visceromotor

Function:
Taste –> posterior third of tongue

Viscerosensory –> carotid bodies

Innervation to stylopharyngeus muscle

Parasympathetic to parotid gland

X – Vagus

Foramen:
Jugular Foramen

Modality:
Somatosensory
Viscerosensory
Branchiomotor
Visceromotor

Function:
Innervation to lateral rectus

Sensation –> External ear

Viscerosensory –> pharynx, larynx and viscera

Branchimotor –> taste in epiglottis and valleculae and innervation to the muscles of pharynx and larynx

Parasympathetic to neck, thorax and abdomen

XI – Accessory

Foramen:
Jugular Foramen

Modality:
Somatomotor

Function:
Innervation to trapezius and sternocleidomastoid

XII – Hypoglossal

Foramen:
Hypoglossal Canal

Modality:
Somatomotor

Function:
Innervation to tongue muscles:
– Genioglossus (protracts tongue)
– Styloglossus (retracts tongue)
– Hyoglossus (depresses tongue

Blood Supply

The head receives dual blood supply from internal carotid + vertebral arteries.
– These form an anastomotic connection known as the Circle of Willis.
– Arteries are in the subarachnoid space, and so rupture can give rise to a subarachnoid haemorrhage.
– Venous drainage is via dural sinuses, and then into the internal jugular vein

In addition, the external carotid artery also supplies blood to the face and neck.
– It gives rise to the superior thyroid, lingual and facial branches, before terminating in the superficial temporal and maxillary arteries.
– The maxillary artery gives off the middle meningeal artery, which proceeds to run through the foramen spinosum, deep to the pterion.

External carotid artery
Circle of Willis

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