CLINICAL ANATOMY OF ORAL CAVITY AND SALIVARY GLANDS Associate Professor Dr. A. Podcheko 2015

CLINICAL ANATOMY OF ORAL CAVITYAND SALIVARY GLANDS

Associate Professor Dr. A. Podcheko

2015

Oral Region•The oral region includes the oral cavity, teeth, gingivae, tongue, palate, and the region of the palatine tonsils.

•The oral cavity is where food is ingested and prepared for digestion in the stomach and small intestine.

•Food is chewed by the teeth, and saliva from the salivary glands facilitates the formation of a manageable food bolus.

•Deglutition (swallowing) is voluntarily initiated in the oral cavity.

•The voluntary phase of the process pushes the bolus from the oral cavity into the pharynx, the expanded part of the alimentary (digestive) system, where the automatic phase of swallowing occurs.

Oral Cavity•The oral cavity consists of two parts: the oral vestibule and the oral cavity proper•It is in the oral cavity that food and drinks are tasted and savored and where mastication and lingual manipulation of food occur. •The oral vestibule is the slit-like space between the teeth and buccal gingiva and the lips and cheeks.

•The vestibule communicates with the exterior through the mouth.

•The size of the oral fissure (rima oris - the oral opening) is controlled by the circumoral muscles, such as the orbicularis oris (the sphincter of the oral fissure), the buccinator, risorius, and depressors and elevators of the lips (dilators of the fissure).

Oral Cavity

•The oral cavity proper is the space between the upper and the lower dental arches (maxillary and mandibular alveolar arches and the teeth they bear). •It is limited laterally and anteriorly by the maxillary and mandibular alveolar arches housing the teeth.

•The roof of the oral cavity is formed by the palate. •Posteriorly, the oral cavity communicates with the oropharynx (oral part of the pharynx).

•When the mouth is closed and at rest, the oral cavity is fully occupied by the tongue.

Oral Cavity

Tongue•The tongue (L. lingua; G. glossa) is a mobile muscular organ that can assume a variety of shapes and positions.

•It is partly in the oral cavity and partly in the oropharynx. •The tongue is involved with mastication, taste, deglutition (swallowing), articulation, and oral cleansing; however, its main functions are forming words during speaking and squeezing food into the oropharynx when swallowing.

Parts and Surfaces of the Tongue•The tongue has a root, a body, an apex, a curved dorsum, and an inferior surface.

•The root of the tongue is the part of the tongue that rests on the floor of the mouth. It is usually defined as the posterior third of the tongue.

•The body of the tongue is the anterior two thirds of the tongue.

•The apex (tip) of the tongue is the anterior end of the body, which rests against the incisor teeth.

•The body and apex of the tongue are extremely mobile.

Parts and Surfaces of the Tongue

•The dorsum (dorsal surface) of the tongue is the posterosuperior surface, which is located partly in the oral cavity and partly in the oropharynx. •It is characterized by a V-shaped groove, the terminal sulcus or groove (sulcus terminalis), the angle of which points posteriorly to the foramen cecum - small pit, frequently absent, is the non-functional remnant of the proximal part of the embryonic thyroglossal duct from which the thyroid gland developed.

Parts and Surfaces of the Tongue, contd.

•The terminal sulcus divides the dorsum of the tongue into the anterior (oral) part in the oral cavity proper and the posterior (pharyngeal) part in the oropharynx. •The margin of the tongue is related on each side to the lingual gingivae and lateral teeth. •The mucous membrane on the anterior part of the tongue is rough because of the presence of numerous small lingual papillae (4 types)

Parts and Surfaces of the Tongue, contd.

Lingual papillae1. Vallate papillae:

•Large and flat topped, they lie directly anterior to the terminal sulcus and are arranged in a V-shaped row. •They are surrounded by deep moat-like trenches, the walls of which are studded with taste buds. •The ducts of the serous glands of the tongue open into the trenches.

2. Foliate papillae:

•Small lateral folds of the lingual mucosa. •They are poorly developed in humans.

3. Filiform papillae: •Long and numerous, they contain afferent nerve endings that are sensitive to touch. •These scaly, conical projections are pinkish gray and are arranged in V-shaped rows that are parallel to the terminal sulcus, except at the apex, where they tend to be arranged transversely.

4. Fungiform papillae: •Mushroom shaped pink or red spots, they are scattered among the filiform papillae but are most numerous at the apex and margins of the tongue.•The vallate, foliate, and most of the fungiform papillae contain taste receptors in the taste buds.

•The mucous membrane over the anterior part of the dorsum of the tongue is thin and closely attached to the underlying muscle. •A shallow midline groove of the tongue divides the tongue into right and left halves. •The groove also indicates the site of fusion of the embryonic distal tongue buds.

Groove of the tongue

•The mucous membrane of the posterior part of the tongue is thick and freely movable. •It has no lingual papillae, but the underlying lymphoid nodules give this part of the tongue an irregular, cobblestone appearance. •The lymphoid nodules are known collectively as the lingual tonsil. •The pharyngeal part of the tongue constitutes the anterior wall of the oropharynx and can be inspected only with a mirror or downward pressure on the tongue with a tongue depressor.

Posterior part of the tongue

•The inferior surface of the tongue is covered with a thin, transparent mucous membrane through which one can see the underlying veins.

•This surface is connected to the floor of the mouth by a midline fold called the frenulum of the tongue.

•The frenulum allows the anterior part of the tongue to move freely.

Inferior surface of the tongue

•On each side of the frenulum, a deep lingual vein is visible through the thin mucous membrane. •A sublingual caruncle (papilla) is present on each side of the base of the lingual frenulum that includes the opening of the submandibular duct from the submandibular salivary gland.

Inferior surface of the tongue

Muscles of the Tongue

•The tongue is essentially a mass of muscles that is mostly covered by mucous membrane.•The muscles of the tongue do not act in isolation and some muscles perform multiple actions; parts of a single muscle are capable of acting independently, producing different, even antagonistic actions. •In general, however, extrinsic muscles alter the position of the tongue while intrinsic muscles alter its shape.

•The four intrinsic and four extrinsic muscles in each half of the tongue are separated by a median fibrous lingual septum, which merges posteriorly with the lingual aponeurosis.

Extrinsic Muscles of the Tongue• palatoglossus• styloglossus• hyoglossus• genioglossus

Tongue

Tongue

21

Muscle Shape and PositionProximal Attachment Distal Attachment Main Action(s)

Extrinsic muscles of the tongue

Genioglossus Fan-shaped muscle; constitutes bulk of tongue

Via a short tendon from superior part of mental spine of mandible

Entire dorsum of tongue; inferior most and posterior most fibers attach to body of hyoid bone

Bilateral activity depresses tongue, especially central part, creating a longitudinal furrow; posterior part pulls tongue anteriorly for protrusion; most anterior part retracts apex of protruded tongue; unilateral contraction deviates (wags) tongue to contralateral side

CNXII

Tongue


Extrinsic muscles of the tongue

Hyoglossus Thin, quadrilateral muscle

Body and greater horn of hyoid bone

Inferior aspects of lateral part of tongue

Depresses tongue, especially pulling its sides inferiorly; helps shorten (retrude) tongue

CNXII

Tongue

23


Extrinsic muscles of the tongueStyloglossus Small, short

triangular muscleAnterior border of distal styloid process; stylohyoid ligament

Sides of tongue posteriorly, interdigitating with hyoglossus

Retrudes tongue and curls (elevates) its sides, working with genioglossus to form a central trough during swallowing

Palatoglossus Narrow crescent-shaped palatine muscle; forms posterior column of isthmus of fauces

Palatine aponeurosis of soft palate

Enters posterolateral tongue transversely, blending with intrinsic transverse muscles

Capable of elevating posterior tongue or depressing soft palate; most commonly acts to constrict isthmus of fauces

CNXII

CNX

TongueIntrinsic Muscles of the Tongue

– The superior and inferior longitudinal– transverse– vertical muscles

• They have their attachments entirely within the tongue and are not attached to bone• The superior and inferior longitudinal muscles act together to make the tongue short

and thick and to retract the protruded tongue • The transverse and vertical muscles act simultaneously to make the tongue long and

narrow, which may push the tongue against the incisor teeth or protrude the tongue from the open mouth (especially when acting with the posterior inferior part of the genioglossus).

• Innervation is CN XII

Innervation of the Tongue•All muscles of the tongue, receive motor innervation from CN XII, the hypoglossal nerve, except the palatoglossus m. (CN X, vagus nerve)

•For general sensation (touch and temperature), the mucosa of the anterior two thirds of the tongue is supplied by the lingual nerve, a branch of CN V3.

Innervation of the Tongue

•For special sensation (taste), anterior 2/3rd part of the tongue, except for the vallate papillae, is supplied through the chorda tympani nerve, a branch of CN VII.•The chorda tympani joins the lingual nerve and runs anteriorly in its sheath.


•chorda tympani nerve - branch of CN VII•The chorda tympani joins the lingual nerve and runs anteriorly in its sheath.


•The mucous membrane of the posterior third of the tongue and the vallate papillae are supplied by the lingual branch of the glossopharyngeal nerve (CN IX) for both general and special sensation.

•Small branches of the internal laryngeal nerve (CN X), supply mostly general but some special sensation to a small area of the tongue just anterior to the epiglottis. •These mostly sensory nerves also carry parasympathetic secretomotor fibers to serous glands in the tongue.


•Parasympathetic fibers from the chorda tympani nerve travel with the lingual nerve to the submandibular and sublingual salivary glands. •These nerve fibers synapse in the submandibular ganglion, which hangs from the lingual nerve.


•There are four basic taste sensations: sweet, salty, sour, and bitter.

•Sweetness is detected at the apex, saltiness at the lateral margins, and sourness and bitterness at the posterior part of the tongue. •All other ‘tastes’ expressed by gourmets are olfactory (smell and aroma).

Taste Anatomy

Vasculature of the Tongue•The arteries of the tongue are derived from the lingual artery, which arises from the external carotid artery.•On entering the tongue, the lingual artery passes deep to the hyoglossus muscle.•The dorsal lingual arteries supply the posterior part (root); the deep lingual arteries supply the anterior part.

•The veins of the tongue are the dorsal lingual veins, which accompany the lingual artery; the deep lingual veins, which begin at the apex of the tongue, run posteriorly beside the lingual frenulum to join the sublingual vein.

•The sublingual veins in elderly people are often varicose (enlarged and tortuous).

•All these lingual veins terminate, directly or indirectly, in the internal jugular vein.

Vasculature of the Tongue

The lymphatic drainage of the tongue is exceptional

•Most of the lymphatic drainage converges toward and follows the venous drainage; however, lymph from the tip of the tongue, frenulum, and central lower lip runs an independent course.

1. Lymph from the posterior third drains into the superior deep cervical lymph nodes.

2. Lymph from the medial part of the anterior two thirds drains directly to the inferior deep cervical lymph nodes.

•Lymph from the tongue takes 4 routes:

3. Lymph from the lateral parts of the anterior two thirds drains to the submandibular lymph nodes.

4. The apex and frenulum drain to the submental lymph nodes.

Gag Reflex

•It is possible to touch the anterior part of the tongue without feeling discomfort; however, when the posterior part is touched, the individual gags.

•Glossopharyngeal (CN IX) and vagus (CN X) are responsible for the muscular contraction of each side of the pharynx.

•Glossopharyngeal branches provide the afferent limb of the gag reflex.

Paralysis of the Genioglossus•When the genioglossus muscle is paralyzed, the tongue has a tendency to fall posteriorly, obstructing the airway and presenting the risk of suffocation.

•Total relaxation of the genioglossus muscles occurs during general anesthesia; therefore, an airway (intubation tube) is inserted in an anesthetized person to prevent the tongue from relapsing.

Injury to the Hypoglossal Nerve•Trauma, such as a fractured mandible, may injure the hypoglossal nerve (CN XII), resulting in paralysis and eventual atrophy of one side of the tongue. •The tongue deviates to the paralyzed side during protrusion because of the action of the unaffected genioglossus muscle on the other side.•Main action of Genioglossus: Bilateral activity depresses tongue, especially central part, creating a longitudinal furrow; posterior part pulls tongue anteriorly for protrusion; most anterior part retracts apex of protruded tongue; unilateral contraction deviates tongue to contralateral side.

Sublingual Absorption of DrugsFor quick absorption of a drug, for instance, when nitroglycerin is used as a vasodilator in angina pectoris, the pill or spray is put under the tongue where it dissolves and enters the deep lingual veins in less than 1 min.

Salivary Glands

40

• The salivary glands are the parotid, submandibular, and sublingual glands.

• The clear, tasteless, odorless viscid fluid, saliva, secreted by these glands and the mucous glands of the oral cavity:– Keeps the mucous membrane of the

mouth moist.– Lubricates the food during mastication.– Begins the digestion of starches.– Serves as an intrinsic mouthwash.– Plays significant roles in the prevention

of tooth decay and in the ability to taste.

• In addition to the main salivary glands, small accessory salivary glands are scattered over the palate, lips, cheeks, tonsils, and tongue.

Parotid Gland

41

• is the largest of three paired salivary glands.

• is enclosed within a tough fascial capsule, the parotid sheath, derived from the investing layer of deep cervical fascia .

• has an irregular shape because the area occupied by the gland, the parotid bed, is anteroinferior to the external acoustic meatus, where it is wedged between the ramus of the mandible and the mastoid process .

• Fatty tissue between the lobes of the gland confers the flexibility the gland must have to accommodate the motion of the mandible.

• The apex of the parotid gland is posterior to the angle of the mandible, and its base is related to the zygomatic arch.

• The subcutaneous lateral surface of the parotid gland is almost flat.

.

Parotid Gland

42

• The parotid duct passes horizontally from the anterior edge of the gland .

The parotid duct

Parotid Gland• At the anterior border of the masseter, the duct turns medially, pierces the buccinator, and

enters the oral cavity through a small orifice opposite the 2nd maxillary molar tooth .

Stensen's duct: also known as the parotid duct, serves as a conduit for saliva between the parotid gland and the oral cavity. Blockage of the duct can lead to inflammation and pain of the parotid gland (parotitis).

Parotid Gland

44

• Embedded within the substance of the parotid gland, from superficial to deep, are the parotid plexus of the facial nerve (CN VII) and its branches ,the retromandibular vein, and the external carotid artery.

facial nerve (CN VII)

retromandibular vein

external carotid artery

Innervation of Parotid Gland and Related Structures

45

• Although the parotid plexus of CN VII is embedded within it, the CN VII does NOT provide innervation to the gland.

• The auriculotemporal nerve, a branch of CN V3, is closely related to the parotid gland and passes superior to it with the superficial temporal vessels provide innervation to the gland – Provides sensory innervation!!!!

•

The auriculotemporal nerve

46

• The great auricular nerve, a branch of the cervical plexus composed of fibers from C2 and C3 spinal nerves, innervates the parotid sheath as well as the overlying skin.

The great auricular nerve


Innervation of Parotid Gland and Related StructuresInnervation of Parotid Gland and Related Structures• The parasympathetic component of the glossopharyngeal nerve (CN IX) supplies

presynpatic secretory fibers to the otic ganglion. • The postsynaptic parasympathetic fibers are conveyed from the ganglion to the

gland by the auriculotemporal nerve .


48

• Sympathetic fibers are derived from the cervical ganglia through the external carotid nerve plexus on the external carotid artery .The vasomotor activity of these fibers may reduce secretion from the gland.

• Sensory nerve fibers pass to the gland through the great auricular and auriculotemporal nerves.

auriculotemporal nerves.

great auricular Nerve

Parotid Gland- Clinical NoteParotidectomy• About 80% of salivary gland tumors

occur in the parotid glands. • Most tumors of the parotid glands are

benign, but most salivary gland cancer begins in the parotid.

• Because the parotid plexus of CN VII is embedded in the parotid gland, the plexus and its branches are in jeopardy during surgery.

• An important step in parotidectomy is the identification, dissection, isolation, and preservation of the facial nerve.

49

Parotid Gland- Clinical NoteInfection of the Parotid Gland• The parotid gland may become infected by infectious

agents that pass through the bloodstream, as occurs in mumps, an acute communicable viral disease. Infection of the gland causes inflammation (parotiditis) and swelling of the gland.

• Severe pain occurs because the parotid sheath limits swelling. Often the pain is worse during chewing because the enlarged gland is wrapped around the posterior border of the ramus of the mandible and is compressed against the mastoid process of the temporal bone when the mouth is opened.

• The mumps virus may also cause inflammation of the parotid duct, producing redness of the parotid papilla, the small projection at the opening of the duct into the superior oral vestibule. Because the pain produced by mumps may be confused with a toothache,

redness of the papilla is often an early sign that the disease involves the gland and not a tooth.50

•Parotid gland disease often causes pain in the auricle, external acoustic meatus, temporal region, and TMJ because the auriculotemporal nerve, from which the parotid gland and sheath receive sensory fibers, also supplies sensory fibers to the skin over the temporal fossa and auricle.

Parotid Gland- Clinical NoteAbscess in the Parotid Gland• A bacterial infection localized in the parotid gland usually produces an abscess. • The infection could result from extremely poor dental hygiene and spread to the gland through

the parotid ducts. Physicians and dentists must determine whether a swelling of the cheek results from infection of the parotid gland or from an abscess of dental origin.

51

Parotid Gland- Clinical NoteSialography of the Parotid Duct• A radiopaque fluid can be injected into the duct system of the parotid gland

through a cannula inserted through the orifice of the parotid duct in the mucous membrane of the cheek. This technique (sialography) is followed by radiography of the gland. Parotid sialograms (G. sialon, saliva + G. grapho, to write) demonstrate parts of the parotid duct system that may be displaced or dilated by disease.

52

Parotid Gland- Clinical NoteBlockage of the Parotid Duct• The parotid duct may be blocked by a calcified deposit, called a sialolith or calculus . The

resulting pain in the parotid gland is made worse by eating. Sucking a lemon slice is painful because of the buildup of saliva in the proximal part of the blocked duct.

Accessory Parotid Gland• Sometimes an accessory parotid gland lies on the masseter muscle between the parotid duct

and the zygomatic arch. Several ducts open from this accessory gland into the parotid duct.

53

Submandibular Glands

54

• Lie along the body of the mandible, and partly superficial and partly deep to the mylohyoid muscle .

• The submandibular duct, approximately 5 cm long– opening by one to three orifices on a small sublingual papilla beside the base of the

lingual frenulum. The orifices of the submandibular ducts are visible, and saliva can often be seen trickling from them (or spraying from them during yawning).

• The arterial supply is from the submental arteries . The veins accompany the arteries.

Submandibular Glands

55

• are supplied by presynaptic parasympathetic secretomotor fibers conveyed from the facial nerve to the lingual nerve by the chorda tympani nerve, which synapse with postsynaptic neurons in the submandibular ganglion .

• The latter fibers accompany arteries to reach the gland, along with vasoconstrictive postsynaptic sympathetic fibers from the superior cervical ganglion.

• The lymphatic vessels of the glands end in the deep cervical lymph nodes, particularly the jugulo-omohyoid node .

Sublingual Glands• the smallest and most deeply situated of

the salivary glands .• Each almond-shaped gland lies in the

floor of the mouth between the mandible and the genioglossus muscle.

• The glands from each side unite to form a horseshoe-shaped mass around the connective tissue core of the lingual frenulum.

• Numerous small sublingual ducts open into the floor of the mouth along the sublingual folds.

• The arterial supply - branches of the lingual and facial arteries

• The nerves: Presynaptic parasympathetic secretomotor fibers are conveyed by the facial, chorda tympani, and lingual nerves to synapse in the submandibular ganglion

Salivary Glands

Frenectomy•An overly large lingual frenulum interferes with tongue movements and may affect speech. •In unusual cases, a frenectomy (cutting the frenulum) in infants may be necessary to free the tongue for normal movement and speech.

Ankyloglossia, also known as tongue-tie

Oral Region

59

Gingivae• The gingivae (gums)

– are composed of fibrous tissue covered with mucous membrane.

– The gingiva proper (attached gingiva) • is firmly attached to the

alveolar processes of the jaws and the necks of the teeth

• The gingiva proper is normally pink, stippled, and keratinizing.

– The alveolar mucosa (unattached gingiva) • is normally shiny red and non-

keratinizing.

Gingivae- Clinical NoteGingivitis• Improper oral hygiene results in food and bacterial deposits in tooth and gingival

crevices that may cause inflammation of the gingivae (gingivitis).

• The gingivae swell and redden as a result.

• If untreated, the disease spreads to other supporting structures, including alveolar bone, producing periodontitis (inflammation and destruction of the bone and the periodontium).

• Dentoalveolar abscesses (collections of pus resulting from death of inflamed tissues) may drain to the oral cavity and lips.

60

Teeth

61

Teeth

• Children have 20 deciduous teeth; • adults normally have 32 permanent teeth .

• The types of teeth are identified by their characteristics: – incisors, thin cutting edges; – canines, single prominent cones; – premolars (bicuspids), two cusps; – molars, three or more cusps.

• The vestibular surface (labial or buccal) of each tooth is directed outwardly, and the lingual surface is directed inwardly.

Teeth, Innervation

62

63

Teeth

Teeth

64

Parts and Structure of the Teeth• A tooth has a crown, neck, and root .• Most of the tooth is composed of dentin ,which

is covered by enamel over the crown and cement (over the root.

• The pulp cavity contains connective tissue, blood vessels, and nerves.

• The root canal (pulp canal) transmits the nerves and vessels to and from the pulp cavity through the apical foramen.

• Adjacent sockets are separated by interalveolar septa;

Teeth

65

Vasculature of the Teeth• The superior and inferior alveolar arteries, branches of the maxillary

artery, supply the maxillary and mandibular teeth, respectively • Alveolar veins with the same names and distribution accompany the

arteries. • Lymphatic vessels from the teeth and gingivae pass mainly to the

submandibular lymph node

Teeth

66

Deciduous Teeth

Central Incisor Lateral Incisor Canine 1st Molar

2nd Molar

Eruption (months)a

6-8 8-10 16-20 12-16 20-24

Shedding (years)

6-7 7-8 10-12 9-11 10-12

Teeth

67

Permanent Teeth

Central Incisor

Lateral Incisor

Canine 1st Premolar 2nd Premolar 1st Molar

2nd Molar 3rd Molar

Eruption (years)

7-8 8-9 10-12 10-11 11-12 6-7 12 13-25

Teeth- Clinical NoteDental Caries, Pulpitis, and Tooth Abscesses• Decay of the hard tissues of a tooth results in the formation of dental caries

(cavities). Treatment involves removal of the decayed tissue and restoration of the anatomy of the tooth with a dental material. Neglected dental caries eventually invade and inflame tissues in the pulp cavity. Invasion of the pulp by a deep carious lesion results in infection and irritation of the tissues (pulpitis). Because the pulp cavity is a rigid space, the swollen tissues cause considerable pain (toothache). If untreated, the small vessels in the root canal may die from the pressure of the swollen tissue, and the infected material may pass through the apical canal and foramen into the periodontal tissues. An infective process develops and spreads through the root canal to the alveolar bone, producing an abscess. Pus from an abscess of a maxillary molar tooth may extend into the nasal cavity or the maxillary sinus. The roots of the maxillary molar teeth are closely related to the floor of this sinus. As a consequence, infection of the pulp cavity may also cause sinusitis or sinusitis may stimulate nerves entering the teeth and simulate a toothache.

Extraction of the Teeth• Sometimes it is not practical to restore a tooth because of extreme tooth

destruction. The only alternative is tooth extraction. A tooth may lose its blood supply as a result of trauma. The blow to the tooth disrupts the blood vessels entering and leaving the apical foramen. It is not always possible to save the tooth. Unerupted 3rd molars are common dental problems; these teeth are the last to erupt, usually when people are in their late teens or early 20s. Often there is not enough room for these molars to erupt, and they become lodged (impacted) under or against the 2nd molars .If impacted 3rd molars become painful, they are usually removed. When doing so, the surgeon takes care not to injure the alveolar nerves.68

Documents

CLINICAL ANATOMY OF ORAL CAVITY AND SALIVARY GLANDS Associate Professor Dr. A. Podcheko 2015