Lecture: 8 Head and neck Dr. Omar Riadh
25-10-2017
Mandibular division of trigeminal nerve:-
Trigeminal nerve is the 5th cranial nerve and is the largest cranial nerve, it has the following components:-
General somatic afferent:- cutaneous sensation of head, face, mucous membrane, teeth, part of meninges and proprioception of muscles.
Special visceral efferent:- motor nerve supply to:-
Muscles of mastication.
Mylohyoid.
Anterior belly of digastric.
Tensor villi palatine.
Tensor tympani.
The trigeminal nerve consists of two roots (sensory, motor) the sensory enters the lateral part of the ventral surface of pons, the motor roots emerges medial to the sensory root, both roots pass anteriorly till they reach the trigeminal ganglia which is a flat semilunar ganglia lies in pocket of dura mater located in a shallow depression on the anterior surface of the petrous temporal bone. The motor root passes under the ganglia to joins the mandibular nerve, the trigeminal nerve has three division which are ophthalmic, maxillary and mandibular. The mandibular division leaves the skull through foramen ovale and it takes with it the motor root of trigeminal nerve.
Branches of the trunk of mandibular division:-
Meningeal branch:- which passes through foramen spinosum with middle meningeal artery to supply the middle cranial fossa.
Nerve to medial pterygoid:- which has a connection to the otic ganglia and from it branches pass to tensor villi palatine and tensor tympani muscle.
After that the trunk divided into anterior division (mainly motor) and posterior division (mainly sensory). The anterior division is muscular except buccal nerve which is sensory.
Braches of anterior division:-
Nerve to masseter. (motor).
Deep temporal nerves which are 2 or 3 to temporalis (motor).
Nerve to lateral pterygoid. (motor).
Buccal nerve to the skin and mucous membrane of the cheek and gum (sensory).
Branches of posterior division:-
1-Auriculotemporal nerve:- arises by two roots surrounding the middle meningeal artery, this nerve carries postganglionic parasympathetic from otic ganglia to the parotid gland, it also supplies the auricle and temporomandibular joint and the skin over the temple.
2-Lingual nerve:- concerned with the general sensation of anterior 2/3 of the tongue. In the infratemporal fossa it receives the chorda tympani nerve (which carries preganglionic parasympathetic fibers to the submandibular ganglia and also carries special taste sensation to the anterior 2/3 of the tongue), the lingual nerve descends downward on medial pterygoid muscle deep to the inferior border of mandible, it passes on the lateral surface of styloglossus and hyoglossus muscles crosses the duct of submandibular gland and then turns upward and passes forward to the tongue.
3-Inferior alveolar nerve:- it passes downward to the mandibular foramen, before entering the foramen it gives nerve to mylohyoid which supplies mylohyoid and anterior belly of digastric. The inferior alveolar nerve then enters the mandibular foramen traverse through the mandible then appears again through the mental foramen as mental nerve which is sensory to the lower lip and chin.
Maxillary artery:-
One of the terminal branches of external carotid artery arises behind the neck of mandible, it passes anteriorly to reaches the lateral pterygoid muscle where it runs either superficial or deep to the muscle, then it runs between the two heads of the lateral pterygoid and passes through pterygomaxillary fissure to reaches pterygopalatine fossa. The maxillary artery divided into three portions:-
Mandibular portion:- behind the neck of mandible.
Pterygoid portion:- lies on the lateral pterygoid muscle.
Pterygopalatine portion:- lies in pterygopalatine fossa.
Branches of mandibular portion:-
Deep auricular artery.
Anterior tympanic artery.
Middle meningeal artery:- which runs upward and enters the cranial cavity through foramen spinosum to supplies the middle cranial fossa and the semilunar ganglia, then it divides into anterior and posterior branch.
Accessory meningeal artery:- which not always presents, if presenrs it enters through the foramen ovale and supplies the meninges.
Inferior alveolar artery:- which runs with the inferior alveolar nerve and enters the mandibular foramen, it supplies lower teeth and appears on face through mental foramen as mental artery.
Pterygoid portion:-
This part of maxillary artery runs on the lateral pterygoid muscle and then enters between its two heads to becomes pterygopalatine portion, it gives muscular branches to masseter, pterygoid muscles, deep temporal artery to temporalis and also gives buccal artery which runs with buccal nerve to the cheek.
Branches of pterygopalatine portion:-
Posterior superior alveolar artery:- to the upper teeth.
Infraorbital artery:- passes through the infraorbital canal in the floor of the orbit and it appears in face through infraorbital foramen. In the canal it gives middle and anterior superior alveolar branches to the teeth.
Descending palatine artery:- which gives greater and lesser palatine arteries, they pass through greater and lesser palatine foramen respectively to supply the soft palate.
Pharyngeal branches:- to the roof of pharynx.
Sphenopalatine artery:- which runs with nasopalatine nerve supplies the nose then appears in the roof of mouth through the incisive foramen supplies the hard palate.
Pterygoid branch:- which run in pterygoid canal.
Maxillary vein and pterygoid plexus:-
This plexus presents around the lateral pterygoid muscle, veins corresponding to the branches of maxillary artery open in this plexus, this plexus drains posteriorly with one or two short, wide maxillary veins which pass to the parotid gland and behind the neck of mandible drain to the retromandibular vein. The pterygoid plexus communicates with cavernous sinus through emissary vein which traverses the foramen ovale, with inferior ophthalmic vein through infraorbital fissure and with facial vein by deep facial vein.
Submandibular region:-
It lies between the body of mandible and hyoid bone.
Contents:-
Muscles:- digastric, stylohyoid, mylohyoid, hyoglossus, geniohyoid,genioglossus and styloglossus.
Salivary glands:- submandibular and sublingual salivary gland.
Nerves:- lingual, hypoglossal and glossopharyngeal nerve.
Submandibular parasympathetic ganglia.
Blood vessels:- facial artery and vein, lingual artery and vein.
Lymph nodes:- submandibular groups of lymph nodes.
Submandibular salivary gland:-
It lies below and in front of angle of mandible, it is covered by skin, subcutaneous tissue, platysma muscle and superficial fascia. It consist of two parts, superficial large part and small deep part which lies deep to mylohyoid muscle on hyoglossus and genioglossus muscle.
The submandibular duct arises from the deep part of the gland and passes forward and upward lies on hyoglossus and genioglossus muscle, it opens in the floor of mouth in the summit of sublingual papillae.
The lingual nerve descends into the submandibular triangle passes across the duct and curving forward and upward and passes it again medially. The hypoglossal nerve passes on hyoglossus muscle deep to mylohyoid muscle in the triangle and passes forward and upward to the tongue. The lingual artery passes forward toward the tongue under hyoglossus muscle.
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