Trigeminal And Facial Nerve

TRIGEMINAL AND FACIAL NERVE (a) TRIGEMINAL NERVE : COURSE : The trigeminal nerve contains both sensory and motor fibres and is the largest cranial nerve. It emerges from the anterior surface of the pons by a large sensory root and a small motor root.. the nerve passes forward out of the posterior cranial fossa and reaches the apex of the petrous part of temporal lobe in the middle cranial fossa ---- the sensory root expands to form the TRIGEMINAL GANGLION. The motor root lies below the sensory ganglion and lies completely saperate from it. The ophthalmic, maxillary and mandibular nerves arise from the anterior border of the ganglion. THE OPTHALMIC DIVISION is PURELY SENSORY AND IS THE SMALLEST DIVISION OF THE TRIGEMINAL NERVE. It pierces the duramater and runs in the lateral wall of cavernous sinus . it divides into 3 branches ---- lacrimal, frontal and nasocialiary nerves which enter the orbital cavity through the superior orbital fissure.. LACRIMAL NERVE : passes forward along the upper border of lateral rectus muscle and SUPPLIES THE SKIN OF THE LATERAL PART OF THE UPPER LID. FRONTAL NERVE : passes forward on the superior surface of the levator palpebrae superioris, between the muscle and the roof of the orbit. Just befor it reaches the orbital margin it divudes into SUPRATROCHLEAR AND SUPRAORBITAL BRANCH. The supratrochlear branch supplies the skin and conjunctiva of the medial side of upper eyelid and the skin of the lower part of forehead near the medial side. The supraorbital branch supplies the skin and conjunctiva of the lateral side of upper eyelid and the remaining skin of forehead. IT ALSO SUPPLIES THE MUCOUS MEMBRANE OF THE FRONTAL AIR SINUS. NASOCILIARY NERVE: It runs forward along the upper margin of the medial rectus muscle and ends by dividing into anterior ethmoidal( supplies the skin of the medial part of the upper eyelid and the adjacent nose) and infratrochlear nerves ( supplies skin of the nose upto the tip). The other branches include posterior ethmoidal nerve to the ethmoidal and sphenoidal air sinus. And ciliary nerves that contain sympathetic fibres for dilator pupillae. THE MAXILLARY NERVE is PURELY SENSORY : It passes along the lateral wall of the cavernous sinus and leaves the skull through the foramen rotundum to enter the pterygopalatine fossa it supplies the skin over the maxilla and the upper lip, teeth of the upper jaw, mucous membrane of the nose, maxillary air sinus and the palate. THE MANDIBULAR DIVISION: it has motor and sensory part and is the largest division of the trigeminal nerve. The motor part supplies the muscles of mastication , mylohyoid, anterior belly of the digastric, tensor veli palatine and tensor tympani. The sensory nerve supplies the skin of the cheek, over the mandible, lower lip, side of the head, teeth of the lower jaw, mucous membrane of the mouth and anterior twothird of the tongue.