Trigeminal (v) nerve

INTRODUCTION:

• Largest cranial nerve, passes through Meckel’s cave.
• Derived from 1st pharyngeal arch.
• Mixed nerve (sensory component is more prominent).
• Large sensory root: carries sensation from the skin and mucosa of most of the head.
• Smaller motor root: innervates most of the masticatory muscles (masseter, temporalis, pterygoids, mylohyoid), and the tensor tympani muscle of the middle ear.
• The efferent fibers originate in the motor nucleus of V in the pons and controls the muscles involved in mastication
• The sensory root (the main portion of the nerve) arises from cells in the semilunar ganglion (also known as the Gasserian, or trigeminal, ganglion) in a pocket of dura (Meckel’s cavity) lateral to the cavernous sinus.

NUCLEI OF TRIGEMINAL NERVE:

1. General somatic afferent:

• These sensory fibers arise from ‘pseudounipolar neurons’ of trigeminal ganglion.
• These fibers terminate in three sensory nuclei of trigeminal: 

a.  Main (principal) sensory nuclei (superior sensory nucleus):

• Recieves sensory fibres of fine touch & pressure from face.

b. Spinal nuclei (sensory in upper pons to C2 segment of spinal cord):

• Recieves sensory fibers of pain & temperature from face.
• Also recieves sensory inputs (general somatic afferents) from facial nerve (skin of ear), Glossopharyngeal (middle ear), & auricular branch of Vagus (skin of ear).

c. Mesencephalic nuclei (sensory in midbrain):

• Recieves proprioceptive fibers from muscle of mastication & TMJ.
• Also recieves proprioceptive inputs by inputs III, IV, VI cranial nerves (from extraocular muscles) IX nerve (from Stylopharangeus); VII nerve (from facial muscles); & from XII nerve (from muscles of tongue). 

2. Special visceral efferent (branchial efferent):

• for muscles of mastication, tensor veli palatini, tensor tympani & anterior belly of digastric, through motor nucleus of trigeminal.

Thus, trigeminal nerve has four nuclei: 3 sensory & 1 motor.

THE TRIGEMINAL GANGLION (GASSERION GANGLION or SEMILUNAR GANGLION):

• Lies in a dural pouch, the Cavum trigeminale (MECKEL’S CAVE) lodged in trigeminal impression close to petrous apex.
• Peripheral process of pseudounipolar neurons of ganglion form the three division of nerves & central process of these neurons form the sensory root of trigeminal.
• Blood supply of ganglion is from: Internal carotid artery, middle meningeal artery, accessory meningeal artery & meningeal branch of ascending pharyngeal artery.

ASSOCIATED ROOTS AND BRANCHES:

• The central processes  of the ganglion cells form the large sensory root of the trigeminal nerve ,which is attached to pons at its junction with the middle cerebellar peduncle.
• The small motor root of the trigeminal nerve is attached to the pons superomedialy to the sensory root.
• It passes under the ganglion from its medial to the lateral side and joins the mandibular nerve at the foramen ovale.
  

RELATIONS:

• MEDIALLY- Internal carotid artery & posterior part of cavernous sinus
• LATERALLY-Middle meningeal artery
• SUPERIORLY- Parahippocampal Gyrus
• INFERIORLY-Motor root of trigeminal nerve, greater petrosal nerve, apex of the petrous temporal bone & foramen lacerum

BRANCHES:

 

Branches	Functional Components	Cells of Origin / Termination	Cranial     Exit	Distribution and                       Functions
Ophthalmic    division   (CN V1)	General sensory	Trigeminal ganglion/spinal, principal and mesencephalic nucleus of CN V	Superior   orbital     Fissure	Sensation from cornea,      skin of forehead, scalp,          eyelids, nose, and mucosa      of nasal cavity and                paranasal sinuses
Maxillary      division     (CN V2)			Foramen   rotundum	Sensation from skin of         face over maxilla including     upper lip, maxillary teeth,       mucosa of nose, maxillary     sinuses, and palate
Mandibular    division        (CN V3)			FORAMEN    OVALE
	Branchial motor	Trigeminal motor nucleus		Motor to muscles of               mastication,                         mylohyoid, anterior belly     of digastric, tensor veli         palatini, andtensor               tympani

Exam Question

Don’t Forget to Solve all the previous Year Question asked on TRIGEMINAL (V) NERVE