Al – Rafidain University College General Anatomy Dr. Haydar Munir Salih Lec.9 B.D.S., F.I.B.M.S. (PhD)

NERVOUSE SYSTEM AND - CHAPTER TWO -

TRIGEMINAL NERVE Trigeminal nerve is the fifth cranial nerve. It is called trigeminal because it consists of three divisions, namely: 1. , nerve of orbit 2. , nerve of 3. , nerve of The three nerves arise from a large, semilunar which lies in the trigeminal fossa on the anterior surface of the petrous near its apex.

Course • The trigeminal nerve is attached to the ventral aspect of the pons by two roots, a large sensory and a small motor root. • They pass forward in the posterior cranial fossa towards the apex of the petrous temporal bone. • the sensory root joins the trigeminal ganglion. • The motor root lies deep to the ganglion and does not join it. Instead, it passes out to join the mandibular nerve just at its emergence from the cranial cavity in the foramen ovale.

Trigeminal Ganglion • It is semilunar in shape. It lies in the trigeminal fossa in relation to apex of petrous temporal bone, in . • It is covered by double fold of which forms a trigeminal cave (Meckel’s cave) which is formed by the two layers of dura mater (endosteal and meningeal) which are part of an evagination of the near the apex of the petrous part of the temporal bone. It envelops the trigeminal ganglion.

Distribution of Trigeminal Nerve Three large nerves emerge from the convex anteromedial border of the trigeminal ganglion. These divisions of the trigeminal nerve are:

LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

1. OPHTHALMIC NERVE : It is the smallest of the three divisions of trigeminal nerve. It is purely sensory and It runs forward in the lateral wall of the in the middle cranial fossa and divides into three branches, the lacrimal, frontal, and nasociliary nerves, which enter the orbital cavity through the superior orbital fissure. Branches: The runs forward on the upper border of the lateral rectus muscle. It is joined by the zygomaticotemporal branch of the maxillary nerve, which contains the parasympathetic secretomotor fibers to the lacrimal gland. The lacrimal nerve then enters the lacrimal gland and gives branches to the conjunctiva and the skin of the upper eyelid. The runs forward on the upper surface of the levator palpebrae superioris muscle and divides into the supraorbital and supratrochlear nerves These nerves leave the orbital cavity and supply the frontal air sinus and the skin of the forehead and the scalp. The crosses the optic nerve, runs forward on the upper border of the medial rectus muscle, Its branches include the following: ■■ Sensory fibers to the ■■ that contain sympathetic fibers to the dilator pupillae muscle and sensory fibers to the cornea ■■ that supplies the skin of the eyelid ■■ Posterior ethmoidal nerve that is sensory to the ethmoid and sphenoid sinuses ■■ And continues as the anterior ethmoid nerve through the anterior ethmoidal foramen to enter the cranial cavity. It then descends through a slit at the side of the crista galli to enter the nasal cavity. It gives off two internal nasal branches and it then supplies the skin of the tip of the nose with the .

2. MAXILLARY NERVE Maxillary nerve is the second division of trigeminal nerve. It is also purely sensory. Origin and Course • It arises from the convex anterior border of the trigeminal ganglion and pierces the trigeminal cave of duramater to reach the lower part of the lateral wall of the cavernous sinus. • The nerve leaves the middle cranial fossa through foramen rotundum and reaches the pterygopalatine fossa. • It traverses in a straight line in the upper part of the fossa and enters orbit through the inferior orbital fissure where it is called as the , it appears on the face through the infraorbital foramen.

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

• Therefore, in its course the maxillary nerve traverses in succession, the middle cranial fossa, the pterygopalatine fossa and the orbit

Branches of Maxillary Nerve The maxillary nerve gives off the following branches: In the middle cranial fossa: 1. Meningeal branch: Supplies the duramater of the middle cranial fossa. In the pterygopalatine fossa: 2. Ganglionic (communicating) branches. 3. : Enters the orbit through inferior orbital fissure and divides on the lateral wall of the orbit into two. a. Zygomatico-temporal nerve: This passes through a foramen in the zygomatic bone to supply the skin of the temple. b. Zygomatico-facial nerve: It passes through a foramen in the zygomatic bone to supply the skin of the face on the prominence of cheek. 4. Posterior superior alveolar nerve: Enters the foramen on the posterior surface of the body of maxilla and supplies the mucous membrane of the maxillary air sinus. Then it breaks up to form the which supplies the upper molar teeth and adjoining part of the gum. In the orbit: These are branches from infra-orbital nerve which is a continuation of the maxillary nerve in the infraorbital canal.

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

5. Middle superior alveolar nerve: Passes downwards and forwards along the lateral wall of the maxillary sinus to join the superior dental plexus and supplies the upper premolar teeth. 6. Anterior superior alveolar nerve: Runs in the anterior wall of the maxillary sinus through a bony canal and divides into two branches: a. The dental branches which join the dental plexus and supply the canine and incisor teeth of upper jaw. b. The nasal branches which appear in the lateral wall of the inferior meatus and supply the mucous membrane of the lateral wall and the floor of the nasal cavity. On the face: These are also branches of infra-orbital nerve after it emerges out from infra-orbital foramen. 7. Palpebral branches: These turns upwards and supply the skin of the lower eyelid. 8. Nasal branches: Supply the skin of the side of nose and the mobile part of the nasal septum. 9. Superior labial branches: Supply the skin and mucous membrane of the upper lip.

PTERYGOPALATINE GANGLION (SPHENOPALATINE GANGLION) is the largest peripheral ganglion of the parasympathetic system. It serves as a relay station for the secretomotor fibers of the lacrimal glands and mucous glands of the nose, palate, pharynx and paranasal sinuses. Topographically, it is related to the maxillary nerve, but functionally, it is connected to the facial nerve through greater petrosal nerve. Location: It lies in the deep part of the pterygopalatine fossa Branches ■■ Orbital branches, which enter the orbit through the inferior orbital fissure ■■ Greater and lesser palatine nerves , which supply the palate, the tonsil, and the nasal cavity ■■ Pharyngeal branch, which supplies the roof of the nasopharynx

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

2. MANDIBULAR NERVE This is largest of the three divisions of the trigeminal nerve and is the nerve of the first branchial arch. It consists of both sensory and motor fibres. it is formed by two roots. 1. Larger sensory root: Arises from the convex aspect of the trigeminal ganglion. 2. Small motor root: Arises from the ventral aspect of pons and passes below the trigeminal ganglion. Course Both roots pass through the foramen ovale and join to form the main trunk which lies in the infratemporal fossa. After a short course the main trunk divides into a small anterior and a large posterior division.

Branches of Mandibular Nerve From Main Trunk: 1. Nervous spinosus (meningeal branch): 2. Nerve to medial pterygoid: It supplies three muscles namely: a. Medial pterygoid b. Tensor veli palatini c. Tensor tympani It also forms the motor root of the . From Anterior Division: It gives rise to 3 motor branches and one sensory branch. 1. : They are two in number and supply the temporalis muscle from its deep surface. 2. Nerve to lateral pterygoid, supplies . 3. , supplies masseter muscle. 4. : It is the sensory branch which supplies the skin and mucus membrane of cheek.

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

From Posterior Division: It gives rise to three nerves namely: 1. : It is a sensory nerve. It runs backwards passing behind the insertion of lateral pterygoid muscle and around the neck of to reach behind Branches: a. Auricular branches: Supplies the pinna, external acoustic meatus and adjoining tympanic membrane. b. Articular branches: To temporomandibular joint. c. Superficial temporal branches: These supply the area of skin over the temple. d. Communicating branches: It receives postganglionic secretomotor fibres from otic ganglion to supply the parotid gland.

2. : It is the larger terminal branch of mandibular nerve and it is a mixed nerve. — It emerges below the lateral pterygoid and runs over the ramus of mandible to enter the mandibular foramen along with inferior alveolar vessels. — It traverses the mandibular canal and divides into terminal branches below the level of first and second premolars. a. Nerve to mylohyoid: It is given before the inferior alveolar nerve enters the mandibular foramen. It supplies mylohyoid and anterior belly of digastric. b. : Few nerve fibres in mandibular canal break away to form this plexus which supplies the molar and premolar teeth and the adjoining gum of lower jaw. c. Incisive nerve: Supplies the canine and incisor teeth and adjoining gum of lower jaw. d. : Supplies skin of chin and lower lip. e. Communicating branch to the . 3. Lingual nerve: It is primarily sensory nerve: — It is the smaller terminal branch of mandibular nerve given off in front of the inferior alveolar nerve. It is primarily sensory and also carries secretomotor fibers to submandibular and sublingual salivary glands. — About 2 cm below the base of skull, in the infratemporal fossa, the chorda tympani nerve joins it posteriorly at an acute angle. — It comes in direct contact with the mandible medial to the last molar tooth. Here it is covered by mucus membrane of gum only. — It runs medial to mylohyoid and reaches the tongue. — Finally, it curves under the submandibular duct at the level of genioglossus and turns up medially to the anterior part of tongue and floor of oral cavity.

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

Branches a. Sensory branches to mucus membrane of anterior 2/3rd of tongue, floor of mouth and adjoining area of gum. b. Communicating branches: With chorda tympani: The lingual nerve receives secretomotor fibres for submandibular and sublingual glands. It also conveys fibres for taste sensation from anterior 2/3rd of tongue except vallate papillae to the chorda tympani.

OTIC GANGLION It is a parasympathetic ganglion connected to the mandibular division of trigeminal nerve which provides a relay station to the secretomotor parasympathetic fibres of the parotid gland. Topographically, it is connected to mandibular nerve but functionally, it is associated with glossopharyngeal nerve. It is Pin-head size with Oval shape. Location : Infratemporal fossa, just below foramen ovale

Branches and Distribution 1. Communicating branches to auriculotemporal nerve. These convey postganglionic parasympathetic secretomotor and sympathetic vasomotor fibres to the parotid gland. 2. Communicating branches to chorda tympani which form a part of the alternate taste pathway.

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LEC: 9 GENERAL ANATOMY BY DR. HAYDAR MUNIR SALIH B.D.S. , F.I.B.M.S.

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