213: HUMAN FUNCTIONAL ANATOMY: PRACTICAL CLASS 10 Mouth and mastication OSTEOLOGY Study a skull and identify bony features associated with the mouth and mastication: Mandible Ramus Angle Body Head Notch Coronoid process Genial tubercles Digastric fossae Mylohyoid line Locate the areas of attachment of: temporalis, masseter, medial pterygoid, lateral pterygoid, mylohyoid, genioglossus, geniohyoid and digastric. Maxilla Alveolar margin Maxillary tuberosity Palate Incisive foramen. Palatine bone Palate Palatine foraminae Temporal bone Mandibular fossa Articular eminence Post-glenoid tubercle Styloid process Stylomastoid foramen Mastoid process Sphenoid bone Foramen ovale Spine of the sphenoid Lateral pterygoid plate Medial pterygoid plate Pterygoid hamulus. MUSCLES OF MASTICATION AND THE TEMPOROMANDIBULAR JOINT Surface Anatomy With your mouth closed, feel the head of the mandible, just in front of the tragus of your auricle. Open and close your mouth, and feel the head of mandible slip forwards, out from under your finger. Feel your temporalis and masseter muscles while; clenching and unclenching your teeth; and protracting and retracting your jaw. Use the wet specimens to examine the TMJ (temporomandibular joint) and the muscles of mastication. There is also a bottle which shows each muscle of mastication, but be sure to identify them on a specimen as well. On superficial dissections of the side of the face identify the temporalis and masseter muscles and the TMJ. On deeper dissections in the infratemporal fossa identify the medial and lateral pterygoid muscles. Identify the intra-articular disc of the TMJ, and the insertion of the lateral pterygoid muscle to this disc and the neck of the mandible. All these muscles are supplied by the mandibular division of the trigeminal nerve. Two other muscles associated with movements of the mandible are supplied by the mandibular nerve (nerve to mylohyoid). Find mylohyoid muscle and the anterior belly of digastric under the chin. Make sure you understand the movements of the TMJ, and the muscles involved in each case: Elevation Protraction Retraction Depression What is the function of bilateral protraction of both TMJs? What is the function of unilateral protraction and retraction? Also in the infratemporal fossa, find the mandibular division of the trigeminal nerve emerging from the foramen ovale, and the maxillary artery. Identify the lingual and inferior alveolar nerves, and the nerve to mylohyoid. You may also be able to see the chorda tympani; this branch of the facial nerve (carrying taste and parasympathetic fibres) emerges from the petrotympanic fissure just medial to the TMJ, and joins the lingual nerve. ORAL CAVITY Look into a partner's mouth and, with the tongue depressed and protracted, identify and draw: 1. Teeth - Incisors (2), canines (1), premolars (2) and molars (3); (determine which teeth are missing from the adult complement). 2. Dorsum of the tongue with small papillae all over, you may be able to see a row of large (vallate papillae) at the back of the anterior two thirds of the tongue. 3. Palate, soft palate and uvula 4. palatoglossal and palatopharyngeal folds 5. Tonsils may be visible between those two folds 6. Posterior pharyngeal wall With the tongue elevated, identify and draw 1. Frenulum of the tongue with papillae of the submandibular ducts 2. Sublingual glands in the floor of the mouth Find these structures on a hemisected head. THE SALIVARY GLANDS AND PARASYMPATHETIC NERVE SUPPLIES There are three main salivary glands (parotid, sublingual and submandibular), However the whole lining of the mouth, nose and pharynx is a mucus membrane, with many tiny glands in the mucosa. On a superficial prosection of the face identify the parotid gland, with its duct passing forwards across the masseter muscle. The parotid duct enters the mouth by piercing buccinator adjacent to the 2nd upper molar. Study a superficial prosection of the submandibular region; the submandibular gland is obvious below the body of the mandible. The facial artery hooks over the submandibular gland before coming onto the face. The submandibular gland is folded over the posterior edge of the mylohyoid muscle, so that its duct passes over the muscle into the floor of the mouth. The submandibular duct is accompanied by the lingual nerve, and as it passes the gland, you should be able to see the submandibular ganglion hanging off the nerve. Also in this region identify the hypoglossal nerve. The parasympathetic nerves to the glands of the head: Parasympathetic Origin Ganglion Distributed with Glands nerve Chorda tympani Facial (CNVII) Submandibular Lingual (V1) Submandibular Sublingual Greater petrosal Facial (CNVII) Pterygopalatine Maxillary(V2) Nasal, palatine nerve and lachrymal Lesser petrosal Glossopharyngea Otic Auriculotemporal Parotid nerve l (CNIX) (V3) Use colour to trace the Taste and Parasympathetic branches of the Facial and Glossopharyngeal nerves on the diagram below. Also identify the parasympathetic ganglia and the branches of the trigeminal nerve that carry some of these fibres MUSCLES OF THE TONGUE On the lateral view of the tongue, indicate all the extrinsic muscles (and nerve supplies): Styloglossus (XII) Palatoglossus (X) Genioglossus (XII) Hyoglossus (XII) Add the accessory muscles of the tongue; Digastric (VII+V) Geniohyoid (XII) Mylohyoid (V). Consider what extrinsic muscles would be involved in the movements of the tongue: Protraction Retraction Elevation Depression What muscles would perform movements like rolling the tongue? THE DENTIST AND THE TRIGEMINAL NERVE Consider which branches of the trigeminal nerve, the dentist needs to anaesthetise in order to work on: Lower teeth Upper front teeth Upper back teeth Palate and internal aspect of the gums Cheeks and outer aspect of the gums Practical anatomy checklist Osteology The skull and mandible You should know all the features of the skull (from week 8) and especially the mandible and features associated with mastication. Temporomandibular joint Muscles of mastication The Mouth The Oral cavity Salivary glands Muscles and movements of the tongue .