Oral Cavity, Teeth & Palate Lecture 2 PDF

Oral cavity, teeth and palate Oral cavity Oral cavity or mouth is the initial part of gastrointestinal tract Receives secretions from salivary glands Parts of oral cavity: 2 parts Vestibule and oral cavity proper Vestibule: Outer narrow space situated inside the lips and cheek and outside the teeth...

Oral cavity, teeth and palate Oral cavity Oral cavity or mouth is the initial part of gastrointestinal tract Receives secretions from salivary glands Parts of oral cavity: 2 parts Vestibule and oral cavity proper Vestibule: Outer narrow space situated inside the lips and cheek and outside the teeth and gums Communicates freely with the oral cavity proper Communicates with the exterior through oral fissure Receives parotid duct from parotid salivary gland Vestibule Oral cavity proper Hard palate Soft palate Oral cavity proper Pharynx Oral fissure Vestibule Sublingual region Oral cavity proper: Continuous anteriorly with vestibule Continuous posteriorly with pharynx Its roof is formed by hard and soft palate Its floor contains tongue The anterior part of floor below the tongue contains sublingual region The sublingual region receives the openings of sublingual and submandibular ducts Teeth: Form the part of the masticatory apparatus and fixed to the jaws Adults have 32 teeth and these are called permanent teeth Each half of the jaw contains 3 molar teeth, 2 premolar teeth, 1 canine tooth and 2 incisor teeth Children have 20 teeth and these are called deciduous or milk teeth Each half of the jaw contains 2 molar teeth, 1 canine tooth and 2 incisor teeth Tooth has vestibular, lingual, mesial, distal and occlusal surfaces Parts of tooth: 3 parts Crown, root and neck Crown Gum Neck Root Crown: part projecting outside the gum (gingiva) Root: fixed in the tooth socket by the periodontal ligament anchor the tooth to the jaw bone and act as shock absorbers for the tooth Neck: situated between root and crown and surrounded by gum Structure of tooth: Enamel The hard outer layer of the crown. Enamel is the hardest substance in the body yet it can decay if teeth are not cared for properly. Dentine Not as hard as enamel, forms the bulk of the tooth and can be sensitive if the protection of the enamel is lost. Cementum The layer of bone-like tissue covering the root. It is not as hard as enamel. Pulp cavity contains connective tissue, blood vessels and nerves. Pulp canal (root canal) transmits the nerves and vessels to and from the pulp cavity through the apical foramen Nerve supply of teeth: Teeth of the upper jaw – anterior, middle and posterior superior alveolar nerves arising from the maxillary nerve Teeth of the lower jaw - inferior alveolar nerves arising from the mandibular nerve Blood supply of teeth: Superior and inferior alveolar arteries from maxillary artery Palate The structure which forms the roof of oral cavity and separates it from the nasal cavity Parts of palate: 2 parts Had palate and soft palate Hard palate: Hard anterior part of palate made up of bones Separates the nasal cavity from the oral cavity Formed by palatine process of maxilla and horizontal plate of palatine bones Has a posterior margin which gives attachment to soft palate Inferior surface presents a depression in the anterior part – incisive fossa Hard palate is supplied by greater palatine arteries and nerves Palate Hard palate Maxilla Hard palate Soft palate Palatine bone Posterior border of hard palate Oral cavity Soft palate: Posterior part of palate Is a movable, muscular fold suspended from the posterior border of hard palate Separates the nasopharynx from the oropharynx Has 2 surfaces: anterior and posterior surfaces Has 2 borders: superior and inferior borders Superior border is attached to hard palate Inferior border is free and contains a projection called uvula Superior border Posterior surface Nasopharynx Anterior surface Oropharynx Inferior border Two folds of mucous membrane each containing a muscle extend down from the soft palate to the tongue and pharynx Palatoglossal fold with palatoglossus muscle Palatopharyngeal fold with palatopharyngeus muscle Muscles of soft palate: Tensor palati Levator palati Palatoglossus Palatopharyngeus Musculus uvulae Nerve supply: Sensory nerve supply: Lesser palatine and glossopharyngeal nerves Motor nerve supply: All muscles are supplied by pharyngeal branch of vagus via pharyngeal plexus except tensor palati which is supplied by the mandibular nerve Blood supply: Lesser palatine arteries and veins Functions of soft palate: Separates oropharynx from nasopharynx during swallowing Isolates oral cavity from oropharynx during chewing so that breathing is not affected Helps to modify the quality of voice by varying the degree of closure of pharyngeal isthmus Protects nasal mucosa during sneezing by appropriately directing the blast of air through nasal and oral cavity Prevents entry of sputum into the nose during coughing Paralysis of muscles of soft palate results in: Nasal regurgitation of liquids Nasal twang in voice Deviation of uvula opposite to the side of lesion Tongue Tongue Muscular organ covered by the mucous membrane Situated in the floor of the oral cavity and oropharynx Functions of tongue include, taste, speech, mastication and swallowing Parts: Tip Tip, root and body Root: Attached to the mandible and Root hyoid bone Geniohyoid Mylohyoid Related to geniohyoid and mylohyoid muscles Body Hyoid bone Body: 2 surfaces – superior and inferior 2 lateral margins Superior (dorsal) surface: Dorsum of tongue Divided into 2 parts by the sulcus terminalis Anterior two-third (oral part) Posterior one-third (pharyngeal part) Inferior surface Oral part Sulcus terminalis Pharyngeal part Superior surface Sulcus terminalis: V shaped sulcus present on the Sulcus dorsum of tongue terminalis Presents a depression – foramen cecum where the 2 limbs of V meet Foramen cecum represents the site of origin of thyroglossal duct Foramen cecum Oral part (anterior two-third): Medline groove divides oral part into right and left parts Mucous membrane is rough because of presence of papillae Papillae are the projections of mucous membrane These increase the surface area of tongue and some contain taste buds These are of 4 types: Vallate (circumvallate) papillae: Largest, rounded, 8-12 in number, arranged in a row, immediately anterior to sulcus terminalis Fungiform papillae: Rounded, situated near the margin and tip Filiform papillae: Conical, pointed, smallest, numerous, scattered throughout the anterior two-third Foliate papillae: 4-5 vertical folds, situated at the margin of the tongue near the sulcus terminalis Pharyngeal part (posterior one-third ): Contains aggregations of lymphoid follicles deep to mucous membrane which are collectively called lingual tonsil Fungiform Inferior surface of tongue: Covered by smooth mucous membrane Presents: Frenulum of tongue – mucosal fold in the median plane connects the tongue and floor of mouth Deep lingual veins – on either side of frenulum Plica fimbriata – mucosal fold, lateral to deep lingual veins Frenulum Deep lingual vein Muscles of tongue: Intrinsic muscles Extrinsic muscles Muscles of 2 sides are separated by the median septum of connective tissue Intrinsic muscles: Superior longitudinal Inferior longitudinal Vertical Transverse Superior longitudinal Vertical & transverse Inferior longitudinal Extrinsic muscles: Genioglossus, hyoglossus Palatoglossus, styloglossus Genioglossus: Origin: superior genial tubercle of mandible Insertion: tip, dorsum of tongue and body of hyoid bone Action: depression and protrusion of tongue Hyoglossus: Origin: body and greater horn of hyoid bone Insertion: side of tongue Action: depression of tongue Palatoglossus Styloglossus Genioglossus Hyoid bone Hyoglossus Palatoglossus: Origin: palatine aponeurosis Insertion: side of tongue Action: elevation of tongue Styloglossus: Origin: styloid process Insertion: side of tongue Action: retraction of tongue Arterial supply of tongue: Lingual artery (from external carotid) Ascending pharyngeal artery (from external carotid) Tonsillar artery (from facial artery) Venous drainage: Lingual vein Palatoglossus Styloid process Styloglossus Nerve supply: Sensory nerve supply: Anterior two-third except vallate papillae: General sensation: lingual nerve (mandibular) Taste sensation: chorda tympani nerve (facial) Posterior one-third and vallate papillae: General and taste sensation: glossopharyngeal Posterior most part: General and taste sensation: internal laryngeal nerve (vagus) Motor nerve supply: Hypoglossal nerve supplies all intrinsic and extrinsic muscles except palatoglossus Palatoglossus supplied by pharyngeal branch of vagus nerve via pharyngeal plexus of nerves Lymphatic drainage: Tip: submental lymph nodes Lateral parts of anterior two-third: submandibular nodes Cental part of anterior two-third: inferior deep lymph cervical nodes Posterior one-third: superior deep cervical lymph nodes Development: Anterior two-third except vallate papillae: Tuberculum impar and 2 lingual swellings Posterior one-third and vallate papillae: Cranial part of hypobranchial eminence (copula) Muscles: Occipital myotomes Applied anatomy: Glossitis: Inflammation or infection of tongue Ankylogossia (tongue tie): Congenital anomaly of tongue due to short and thick frenulum of tongue (frenectomy – cutting frenulum) Injury to hypoglossal nerve: paralysis and atrophy of one side of the tongue. Tongue deviates to the paralyzed side during protrusion because of the unaffected genioglossus muscle on the other side Salivary Glands Parotid salivary gland Three pairs of salivary glands – Parotid, submandibular and sublingual Communicate with the mouth & pour their secretion into its cavity Small accessory salivary glands are scattered over the palate, lips, cheeks, tonsils, and tongue Saliva secreted by these glands – Keeps the mucous membrane of the mouth moist. – Lubricates the food during mastication. – Begins the digestion of starches. Sublingual – Serves as an intrinsic “mouthwash.” salivary gland – Plays significant roles in the prevention of tooth decay and in the ability to taste Submandibular salivary gland Parotid region Anteriorly: Posterior border of ramus of mandible with masseter and medial pterygoid attached to it. Posteriorly: Mastoid process and sternocleidomastoid muscle. Superiorly: External acoustic meatus and posterior part of temporomandibular joint. Medially: Styloid process and muscles attached to it Contents – parotid salivary gland and duct, facial nerve, external carotid artery, retromandibular vein External acoustic meatus Styloid process Parotid gland (cut) Stylohyoid Masseter Posterior belly of digastric Sternocleidomastoid Parotid region Parotid salivary gland Largest of the salivary glands Inverted pyramidal in shape 25 g Situaton: – Below the external acoustic meatus – Between mandible (in front) and mastoid process and sternocleidomastiod (behind) Enclosed within a tough, unyielding fibrous capsule – parotid sheath Derived from investing layer of deep cervical fascia A portion of deep part of capsule extending between styloid process and mandible thickens to form stylomandibular ligament which separates the parotid gland from the submandibular salivary gland Capsule Base External features Presents: Apex Base Superficial surface Anteromedial surface Posteromedial surface Anterior, posterior and medial borders Posterior border Anterior border Apex Relations Base : Temporo mandibular joint External acoustic meatus Temporomandibular joint Auriculotemporal nerve External acoustic meatus Superficial temporal artery and vein pass through the base Auriculotemporal nerve with superficial temporal vessels Apex: – Lies near the angle of mandible – Cervical branch of facial nerve and anterior and posterior divisions of retromandibular vein comes out from the apex Superficial relations: – Skin – Superficial fascia with great auricular nerve, parotid lymph nodes, platysma muscle Deep relations (parotid bed): – Ramus of the mandible and muscles attached to it – Mastoid process and muscles attached to it – Styloid process and muscles attached to it Structures within the gland From within outwards: – External carotid artery – Retromandibular vein – Facial nerve External carotid artery: Enters the gland through its posteromedial surface Divides into maxillary and superficial temporal artery Superficial temporal artery leaves the gland at the base (gives transverse facial artery) Maxillary artery exits from the anteromedial surface Retromandibular vein: Formed in the gland by the union of maxillary and superficial temporal veins Terminates in the lower part of the gland into anterior and posterior divisions These divisions emerge at the apex of gland Facial nerve: Enters the gland by piercing the posteromedial surface Terminates in the gland by dividing into 5 branches – temporal, zygomatic, buccal, marginal mandibular and cervical Most of the terminal branches leave through anterior border Cervical branch exits through the apex of the gland 101 A Parotid duct Stensen’s duct Passes horizontally from anterior border Runs forwards on the masseter Turns medially and pierces – Buccal pad of fat – Buccopharyngeal fascia – Buccinator Opens in the vestibule of mouth opposite crown of the upper second molar tooth Blood supply and lymphatic drainage Arteries: – External carotid artery branches Veins: – Terminate at the retromandibular vein, external jugular vein Lymphatic drainage: – Upper deep cervical lymph nodes via parotid lymph nodes Nerve supply of parotid gland - Parasympathetic (secretomotor) nerve supply Preganglionic (presynaptic) parasympathetic fibres arise from the inferior salivatory nucleus of medulla oblongata These fibres run through the glossopharyngeal nerve, its tympanic branch, tympanic plexus, lesser petrosal nerve Reach the otic ganglion situated in the infratemporal fossa Postganglionic (postsynaptic) fibers arising from the otic ganglion pass through the auriculotemporal nerve and supply the parotid gland Nerve supply of parotid gland Sympathetic nerves: Are vasomotor Run along the external carotid artery Originate from superior cervical sympathetic ganglion Stimulation of these nerves reduce the secretion from the gland Sensory nerve: Auriculotemporal nerve Clinical anatomy Parotidectomy: – Surgical excision of the gland – In case of tumors – Isolation & preservation of facial nerve should be done Infections: – Mumps – viral – Inflammation – parotiditis – Severe pain due to unyielding nature of the parotid fascia Abscess – Due to bacterial infection Sialography – Contrast radiography of parotid gland Blockage of the duct: – May be due to calculus Frey’s Syndrome Penetrating wounds of parotid gland may damage the auriculotemporal and great auricular nerves. During the process of regeneration, secretomotor fibers of auriculotemporal nerve may join the great auricular nerve and supply the sweat glands of the skin covering parotid gland. Therefore, when the person eats food, beads of perspiration appear on the skin over parotid gland because the stimulus intended for salivation produces sweat instead. Submandibular Gland Irregular in form, size of a walnut. Location : situated in the submandibular region Sublingual salivary J shaped has 2 parts – superficial gland and deep Continue with each mylohyoid other around the muscle posterior free margin of mylohyoid muscle Deep part Superficial part Superficial part: Larger part, enclosed by capsule formed by investing layer of deep cervical fascia Located deep to posterior part of body of mandible (forms a depression on the mandible – submandibular fossa) Located superficial to mylohyoid muscle Deep part: Smaller part located deep to mylohyoid muscle and superficial to hyoglossus muscle Duct of the gland exits from the deep part Blood supply: Facial vessels Lymphatic drainage: drain into the deep cervical lymph nodes, particularly the jugulo-omohyod node. Submandibular (Wharton’s) duct: 5 cm long, exits the gland from its deep part Opens on the sublingual papilla by 1 to 3 orifices in the sublingual region of oral cavity lateral to frenulum of tongue Lingual nerve forms a loop around the duct Formation of calculi is more common because submandibular duct ascends to open into the floor of the mouth (against gravity) which affects the drainage. Secondly its secretion is more viscous Sublingual Gland Smallest of the three glands. Situated beneath the mucous membrane of the floor of the mouth Located deep (medial) to anterior part of body of mandible (sublingual fossa) and lies superficial (lateral) to genioglossus muscle Ducts of sublingual salivary gland: Eight to twenty in number Open on the sublingual fold at the sublingual region of oral cavity Vessels: Lingual and facial vessels Nerve supply of submandibular and sublingual salivary glands Parasympathetic: Preganglionic (presynaptic) fibres arise from superior salivatory nucleus of pons Run through the facial nerve, in the chorda tympani branch of facial nerve, in the lingual nerve Reach the submandibular ganglion situated in the submandibular region Postganglionic (postsynaptic) fibers from the ganglion supply the submandibular and sublingual glands Sympathetic fibers: arise from the superior cervical ganglion (vasomotor) Sensory fibers: run through the lingual nerve Temporal fossa The temporal fossa is a shallow depression on the side of the skull Boundaries: Superior: superior temporal line Inferior wall: zygomatic arch Floor: 4 bones – frontal, parietal, temporal and sphenoid, contains area called pterion Roof: skin and temporal fascia Contents: Temporalis muscle Deep temporal nerves and vessels Superficial temporal vessels Auriculotemporal nerve Pterion Frontal bone Greater wing of sphenoid bone Zygomatic arch Temporal lines Parietal bone Temporal fossa Mastoid process of temporal bone Tympanic plate Styloid process Ramus of mandible Pterion Clinically important area located in the anterior part of the temporal fossa, 3-4 cm superior to the midpoint of the zygomatic arch (skull is very thin at this point) Indicated by an H-shaped shaped sutures that unite the frontal, parietal, sphenoid (greater wing), and temporal bones. Anterior branch of middle meningeal artery is located deep to this area Following a blow on the pterion region, the anterior branch of middle meningeal artery is often torn resulting in formation of extradural hematoma which may compress the motor area of cerebrum leading to paralysis of opposite half of the body Infratemporal fossa Area which lies below the skull, medial to ramus of mandible and posterior to maxilla Boundaries: Superior: infratemporal surface of greater wing of sphenoid bone Inferior: Is open Medial: lateral pterygoid plate Anterior: posterior surface of maxilla Posterior: tympanic plate and mastoid and styloid processes of temporal bone Lateral: ramus of mandible Infratemporal surface of greater wing of sphenoid bone Orbit Styloid process of temporal bone Lateral pterygoid plate Posterior surface of maxilla Skull – inferior view (showing roof of infratemporal fossa) Zygomatic arch Infratemporal crest Infratemporal surface of greater wing of sphenoid bone Lateral pterygoid plate Contents of infratemporal fossa Muscles of mastication (temporalis, lateral and medial pterygoid muscles) Maxillary artery and its branches Pterygoid venous plexus Mandibular nerve and its branches Chorda tympani nerve Otic ganglion Contents of temporal and infratemporal fossae Temporalis Auriculotemporal nerve Lateral pterygoid Medial pterygoid External carotid artery Maxillary artery Lingual nerve Inferior alveolar nerve and artery Muscles of mastication 4 muscles which move the mandible during mastication and speech Situated in the infratemporal and temporal fosse Develop from the mesoderm of 1st pharyngeal arch Supplied by the branches of mandibular nerve Masseter Temporalis Lateral pterygoid Medial pterygoid Masseter Zygomatic arch Temporalis fascia Temporalis muscle Masseteric notch Coronoid process Masseter Zygomatic process of maxilla Ramus of madible Masseter Quadrate and most superficial muscle Origin (proximal attachment): Lower border and deep surface of zygomatic arch Adjoining part of zygomatic process of maxilla Insertion (distal attachment): Outer surface of ramus and angle of mandible Nerve supply: Masseteric nerve from mandibular nerve Action: Elevates the mandible (closing jaws) Temporalis muscle Temporal fossa Lateral pterygoid Coronoid process Masseteric nerve Masster muscle (insertion) Anterior margin of ramus Temporalis Fan or triangular shaped muscle, situated in the temporal fossa (origin) and partly in the infratemporal fossa (insertion) Origin: Floor of temporal fossa Deep surface of temporal fascia Insertion: Coronoid process of mandible Anterior border of ramus of mandible Nerve supply: Deep temporal nerves from mandibular nerve Actions: Elevates the mandible (closing jaws) Posterior fibres retract the protruded mandible Lateral pterygoid Triangular shaped muscle, has 2 heads (parts) – upper head and lower head Lower head is the larger part Origin: Upper head – infratemporal surface and infratemproal crest of greater wing of sphenoid bone Lower head – lateral surface of lateral pterygoid plate Insertion: both heads join together and inserted to Pterygoid fovea on the anterior surface of neck of mandible Capsule and articular disc of temporomandibular joint Infratemporal crest Lateral and medial pterygoid muscles Lateral pterygoid (upper head) Articular disc Capsule of temporomandibular joint Neck of mandible Lateral pterygoid (lower head) Medial pterygoid (deep part) Medial pterygoid (superficial part) Lateral pterygoid muscle (continued) Nerve supply: Nerve to lateral pterygoid from mandibular nerve Actions: Depress the mandible Lateral and medial pterygoid muscles of both sides protrude the mandible Lateral and medial pterygoid muscles of same side with similar muscles of opposite side, contract alternatively to produce side to side grinding movements Medial pterygoid Quadrangular shaped muscle Has 2 heads (parts) – superficial head and deep head Deep head is the larger part of the muscle Origin: Superficial head – tuberosity of maxilla Deep head – medial surface of lateral pterygoid plate Insertion: both heads join together and inserted to Medial (inner) surface of ramus and angle of mandible Medial pterygoid (continued) Nerve supply: Nerve to medial pterygoid from mandibular nerve Actions: Elevates the mandible Lateral and medial pterygoid muscles of both sides protrude the mandible Lateral and medial pterygoid muscles of same side with similar muscles of opposite side, contract alternatively to produce side to side grinding movements Pterygoid venous plexus A plexus of veins situated around and within the lateral pterygoid muscle The plexus is drained by the maxillary vein Contraction of the muscle compresses the plexus to pump the blood Plexus is connected to the cavernous sinus by emissary veins and to the facial vein by deep facial vein 152 B 124 103 109