1. Introduction
• Name origin: “Trigeminal” = tri (three) + gemini (twins) → three major branches.
• Cranial Nerve V – largest cranial nerve.
• Type: Mixed nerve
• Sensory: Face, scalp, mucosa of oral & nasal cavities, cornea, teeth, anterior 2/3 tongue (general sensation).
• Motor: Muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini.
2:Component
Fiber Type
Function
GSA (General Somatic Afferent)
Sensory
Touch, pain, temperature from face, scalp, eye, mucosa
SVE (Special Visceral Efferent)
⸻
3. Nuclei of the Trigeminal Nerve
Located in the brainstem from midbrain to medulla.
1. Sensory Nuclei (Three parts):
• Mesencephalic nucleus (midbrain)
• Proprioception from muscles of mastication, TMJ, periodontal ligaments.
• Principal (chief) sensory nucleus (pons)
• Touch, pressure.
• Spinal trigeminal nucleus (pons → medulla → cervical cord)
• Pain, temperature.
2. Motor Nucleus:
• Located in mid-pons, medial to principal sensory nucleus.
• Sends SVE fibers to muscles of mastication.
4. Brainstem Connections
• Sensory root → larger root, enters pons at mid-lateral aspect.
• Motor root → smaller, medial to sensory root.
• Both pass forward toward Meckel’s cave.
5. Trigeminal (Gasserian) Ganglion
• Location: Meckel’s cave, over petrous apex of temporal bone.
• Shape: Crescent-shaped.
• Contains sensory neuron cell bodies.
• Divides into three major divisions.
6. Divisions and Branches
V1 – Ophthalmic Nerve (Sensory)
• Path: Through cavernous sinus → superior orbital fissure.
• Main branches:
1. Frontal nerve → supratrochlear, supraorbital.
2. Lacrimal nerve.
3. Nasociliary nerve → long ciliary, anterior/posterior ethmoidal, infratrochlear.
• Supplies:
• Forehead, scalp, upper eyelid, cornea, conjunctiva, dorsum of nose.
• Clinical: Corneal reflex afferent limb.
V2 – Maxillary Nerve (Sensory)
• Path: Cavernous sinus → foramen rotundum → pterygopalatine fossa.
• Branches:
1. Zygomatic (zygomaticofacial, zygomaticotemporal).
2. Infraorbital.
3. Superior alveolar (ant/middle/post).
4. Greater and lesser palatine.
5. Nasopalatine.
• Supplies:
• Lower eyelid, cheek, upper lip, upper teeth & gums, nasal mucosa, palate.
V3 – Mandibular Nerve (Mixed)
• Path: Foramen ovale → infratemporal fossa.
• Motor branches (muscles of mastication: temporalis, masseter, medial & lateral pterygoids) + mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini.
• Sensory branches:
• Auriculotemporal.
• Buccal.
• Lingual (general sensation anterior 2/3 tongue).
• Inferior alveolar (→ mental nerve).
• Also carries chorda tympani fibers (taste, submandibular/ sublingual gland parasympathetics).
7. Sensory Pathways
• First-order neuron: In trigeminal ganglion → central processes enter brainstem.
• Second-order neuron: In sensory nuclei → cross midline → ascend as trigeminothalamic tract.
• Third-order neuron: In ventral posteromedial (VPM) nucleus of thalamus → projects to primary somatosensory cortex.
8. Reflexes Involving CN V
Corneal
V1 (nasociliary)
VII (orbicularis oculi)
Jaw jerk
V3 (mesencephalic)
V3 (motor)
Blink (touch eyelash)
V1
VII
Sneezing
V2
9. Blood Supply
• Mainly from branches of middle meningeal artery and nearby meningeal branches.
• Venous drainage → cavernous sinus, pterygoid venous plexus.
10. Clinical Correlations
1. Trigeminal neuralgia – paroxysmal lancinating facial pain (usually V2/V3); treated with carbamazepine or microvascular decompression.
2. Herpes zoster ophthalmicus – V1 involvement; risk of corneal ulcer.
3. Loss of corneal reflex – lesion of V1 or VII.
4. Cavernous sinus thrombosis – affects V1 & V2.
5. Jaw deviation – towards side of lesion (V3 motor root).
6. Perineural tumor spread – from head & neck cancers via V2 or V3.
11. Imaging
• MRI: Evaluate ganglion, cisternal segment, Meckel’s cave.
• High-resolution CT: For skull base foramina (superior orbital fissure, foramen rotundum, foramen ovale).
#anatomy #biology #ear #ent #nose #nosebleed #otolaryngology #science #throathealth #tonsils
Информация по комментариям в разработке