Oral Cavity & Tongue

8/3/2019 Oral Cavity & Tongue

1/16

Oral cavity [Mouth cavity] [Dr. A. S. D Souza.] 2006

The oral cavity is divided into an outer portion - the vestibule and an inner part the oral cavity proper.

Vestibule

o The vestibule is the cleft between the lips and cheeks externally and the teeth and gums internally.o It communicates with exterior through the oral fissure and when the mouth is open with the oral

cavity proper [Even when the teeth are occluded a small communication remains behind the thirdmolar tooth].

o Parotid duct opens on the inner surface of the cheek opposite the crown of the upper second molartooth.

o Except the teeth, the entire vestibule is lined by mucous membrane, which is reflected from the lipsand cheeks to the gums.

Lips

The lips [upper and lower] are fleshy, mobile and musculo fibrous folds. They bound the openingand meet at the lateral angles of the mouth.

Each lip is composed of skin, superficial fascia, orbicularis oris muscle, submucosa [with glands andblood vessels] and mucous membrane.

Inner surface of each lip is connected to the gums by a median fold of mucous membrane - thefrenulum.

Lymphatics from the central part of the lower lip drain to the sub-mental nodes, from the rest of thelips to the sub-mandibular lymph nodes.

Fig. Coronal section through the oral cavity

Cheeks

The cheeks are part of the face; extend from the angle of mouth to the anterior border of masseter muscle.

The cheeks consist of the following layers from outside inwards (1) Skin (2) Superficial fascia withfacial muscles, parotid duct, molar mucous glands, buccal branches of mandibular and facial nerves

buccal pad of fat [best developed in infants, mostly lies on the buccinator], etc. (3) Buccinator muscle,covered by the buccopharyngeal fascia. (4) Sub-mucosa with mucous secreting glands. (5) Mucous

membrane lined by stratified squamous non-keratinized epithelium.

Lymphatics mainly drain into sub-mandibular and partly to the pre-auricular lymph nodes.

Gums [gingivae]

The gums are composed of dense, fibrous, and vascular tissue, lined by stratified squamous keratinized

[thinly keratinized] epithelium.

asdsouza 1


2/16

asdsouza 2

Each gum has two parts (a) Free part - surrounds the neck of the tooth (b) Attached part firmly fixed

to the alveolar processes of the mandible and / or maxillae.

Nerves for the upper gum are derived from the maxillary nerve [through anterior, middle and posterior

superior alveolar branches and greater palatine and nasopalatine nerves]. For the lower gum are derivedfrom the mandibular nerve [inferior alveolar, lingual and buccal branches]. Lymphatics mainly pass to the

submandibular lymph nodes [except anterior part of the lower gum to the sub mental nodes].

TeethThe teeth form a part of the masticatory apparatus and are fixed to the jaws. In humans [and most of the

mammals] teeth are replaced only once [diphyodont] when compared to non-mammalian vertebrateswhere teeth are replaced throughout life [polyphyodont]. Teeth of the first set [dentition] in human beings

are the milk or deciduous teeth and the second set permanent teeth.

The deciduous teeth are 20 in number. In each half of the jaw there are two incisors, one canine and twomolars [dental formula 2 1 0 2]. Permanent teeth are 32 in number and consist of two incisors, 1 canine, 2

premolars and three molars in each half of the jaw [Formula 2 1 2 3].

Parts of a toothEach tooth has three parts

1. Root embedded in the jaw beneath the gum.2. Crown part projecting above the gum.3. Neck part between the crown and root and surrounded by the gum.

Interior of the tooth contains a pulp cavity, which extends from the crown to the apex of the root. Pulp

cavity reduces in size as age advances.

Structure - Tooth is composed of the following

1. Pulp in the center2. Dentine surrounding the pulp.3. Enamel covering the projecting part of the dentine.4. Cementum surrounding the embedded part of the dentine.5. Periodontal membrane.

Pulp - is a specialized loose connective tissue at the centre containing vessels, nerves and lymphatics. Alayer of tall columnar cells - odontoblasts, which produce dentine throughout life, covers the pulp.

Dentine - is hard, avascular and forms bulk of the tooth. Histologically, dentine consists of numerousspiral tubules, which radiate out from the pulp cavity. The protoplasmic processes from the odontoblasts

occupy each spiral tubule.

Enamel - is considered as the hardest substance in the body, contains dense calcified tissue that covers the

crown of tooth. It consists of crystalline prisms lying roughly at right angles to the surface of the tooth

Cementum - is a calcified tissue that covers the root of tooth, structurally resembles the bone.

Periodontal membrane [ligament] - This membrane acts as periosteum to the cementum and bony socket

and holds the root in its socket.

Eruption of the teeth

No teeth are present at birth. Deciduous teeth begin to erupt at about the sixth month [completed by theend of the second year]. The deciduous lower medial incisors erupt first between the 6 th and 8th months.

Thereafter eruption continues in succession involving the upper medial incisors, lateral incisors, first milk


3/16

molars, canine and second milk molars of both the jaws. Then there is an interval of about four years

during which no teeth are added or replaced. At the 6 th year, the first permanent molar teeth erupt in both

the jaws behind the second milk molar teeth. Between the 6 th and 12th years all the milk teeth are replaced

by the permanent teeth in the following order [Eruption ages are variable] - Medial incisor [6 7 years],lateral incisors [8 years], first premolars [8 9 years], second premolars [10 years] and canine [11 years].

The second permanent molars erupt at about 12th year. Eruption of the third permanent molar teeth

[wisdom] is variable; it may be between 18th

25th

years or even later or may fail to erupt.

Parts of a Tooth

Form & FunctionThe incisors and canines are the anterior teeth and the premolars and molars are the posterior teeth. The

shape of tooth is adapted to its function. The incisors are cutting teeth, with chisel like crowns. The

canines are holding and tearing teeth, with conical crowns. Each premolar has two cusps [bicuspid]. The

molars are grinding teeth with square crowns, bearing 4 - 5 cusps on their crowns. The incisors, caninesand premolars have single roots [with the exception of first upper premolar which may have bifid root].

The lower molars have two roots [anterior and posterior] and the upper molars possess three roots, one

medial and two lateral.

Nerve Supply

1. Upper teeth are supplied by posterior, middle and anterior superior alveolar nerves which arederived from the Maxillary nerve [V2] and its infra orbital branch. [Posterior supply the molars,

middle supply the premolars and the anterior incisors and canines]. The greater palatine and naso

palatine nerves in addition supply lingual surface of the gum.2. Inferior alveolar nerve from the mandibular nerve [V3] supplies the lower teeth. The lingual nerve

supplies lingual surface of the gum; and the buccal nerve and mental nerve supply buccal surface

[all derived from the mandibular nerve].

Development of the teeth

Each tooth is developed from two sources1. Enamel - from the surface ectoderm.2. Dentine, cementum, tooth pulp and periodontal membrane are from the underlying mesoderm.

Applied Anatomy of Teeth and Gums1. Being the hardest and chemically most stable tissue in the body, teeth can be preserved after death and

may be of help in medico-legal practice for identification of otherwise unrecognizable dead bodies.2. Decalcification of enamel and dentine with consequent softening [which may lead to gradual teeth

destruction] is dental caries.

asdsouza 3

3. Infection of the apex of the root may lead to apical abscess.


4/16

asdsouza 4

4. In scurvy [caused by the deficiency of vitamin C], gums get swollen, spongy and bleed on touch.5. Inflammation of the gums - gingivitis [gums are red and bleed easily].6. Improper oral hygiene may cause gingivitis and suppuration, leading to chronic periodontitis

[pyorrhea alveolaris].

PalateThe palate has two parts 1. Hard palate Bony [anterior two thirds]

2. Soft palate Fibro muscular [posterior one third]

Hard Palate It is a partition between the nasal and the oral cavity. Palatine processes of the maxillae [anterior two

thirds] and horizontal plates of the palatine bones [posterior one third] form the hard palate Upper surface of the hard palate forms floor of the nasal cavity and is covered by respiratory

epithelium. Inferior surface forms roof of the oral cavity and is lined by stratified squamous

keratinized epithelium.

Anterolateral margins are continuous with the alveolar arches and gums; posterior margin givesattachment to the soft palate.

Arterial supply - greater palatine artery, a branch of maxillary artery. Venous drainage is into thepterygoid plexus of veins.

Nerve supply - greater palatine and naso palatine branches from the pterygo palatine ganglion.Soft Palate

The soft palate is a movable, mucous covered fibro-muscular-glandular curtain that hangs from theposterior margin of the hard palate. It is a thick fold of mucosa enclosing an aponeurosis, muscular tissue,

vessels, nerves, lymphoid tissue and mucous glands. It extends backwards and downwards between oral

and nasal parts of the pharynx. Movements of the soft palate help in deglutition, speech and blowing airthrough the mouth by closing the pharyngeal isthmus.

Presenting parts - It has two surfaces and four borders.

Anterior surface concave, faces downwards and forwards, presents a median raphe [surface becomesinferior when palate is elevated].

Posterior surface convex, directed backwards and upwards and is continuous with the floor of the nasal

cavity.Upper border attached to the posterior margin of the hard palate.

Two Lateral borders on either side continuous with the wall of the pharynx.

Lower border Free and presents a conical projection in the middle - the uvula. From the base of theuvula two mucous folds palatoglossal and palatopharyngeal, extend downwards on each side. The

palatoglossal fold (arch) passes downwards and forwards to the side of the tongue anterior to the tonsillar

fossa. Palatopharyngeal fold extends downwards and backwards posterior to the tonsillar fossa.

Composition of the soft palateIt consists of a bilaminar fold of mucous membrane within which it contains the following structures.

1. Palatine aponeurosis.2. Palatine muscles 5 pairs.3. Nerves and vessels.4. Palatine glands.

Mucous membrane - is lined by stratified squamous non-keratinized epithelium [except the upper part ofthe posterior surface close to the floor of the nasal cavity where it is lined by respiratory epithelium].


5/16

asdsouza 5

Palatine Muscles

Muscle Origin Insertion Action

Levator velipalatini

[levator palati]

1. Inferior aspect ofthe auditory tube.

2. Adjoining part of

the inferior surface of

the petrous part oftemporal bone.

Muscle passes over the upperconcave margin of the superior

constrictor, runs downward

and medially to spread out in

the soft palate, to be insertedinto upper surface of the

palatine aponeurosis.

1. Closes the pharyngealisthmus by elevating the soft

palate.

2. Opens the auditory tube.

Tensor palati 1. Lateral side of the

auditory tube.2. Scaphoid fossa of

the medial pterygoid

plate.

Muscle descends and

converges to form a roundtendon, which winds round the

pterygoid hamulus and then

flattens out to form the palatineaponeurosis.

1. Stretches and depresses

[tightens] the anterior part ofthe soft palate [closes the

pharyngeal isthmus]

2. Opens the auditory tube[to equalize air pressure

between the naso-pharynx

and middle ear].

Musculus

uvulae

[Longitudinalstrip on either

side of the

median plane].

1. Posterior nasal

spine of the hard

palate.2. Palatine

aponeurosis.

Mucous and sub mucous tissue

of the uvula.

Pulls up the uvula.

Palatoglossus Oral surface of the


Descends in the palatoglossal

arch and is inserted to the sideof the tongue at the junction of

anterior two thirds and

posterior one third.

Elevates the base of the

tongue and approximates thepalatoglossal arches [closes

the oro-pharyngeal isthmus].

Palatopharyn-

geus [consistsof two fasciculi

separated by

the levatorpalatini]

1. Anterior fasciculus

arises from theposterior border of

the hard palate and

palatine aponeurosis.2. Posterior

fasciculus from the


Descends in the palato-

pharyngeal arch and spreadsout to form the longitudinal

muscle coat of the pharynx;

inserted into the posteriorborder of lamina of the thyroid

cartilage and into the posterior

median raphe.

It elevates the larynx and

pharynx during swallowing.

Palatine aponeurosis - is the fibrous framework of the soft palate where all muscles are attached. The

aponeurosis is considered as the expanded tendon of insertion of tensor veli palati muscles. It is attachedin front to the posterior margin of the hard palate extending to the palatine crest and in the middle splits toenclose the musculus uvulae.

Note: Some fibres of the palato-pharyngeus pass circularly deep to the mucous membrane of the pharynx

and form a sphincter internal to the superior constrictor muscle. These fibres constitute Passavants

muscle and raise a ridge - the Passavants ridge, on the posterior wall of the pharynx. The soft palatewhen elevated comes in contact with this ridge.


6/16

Nerves of the soft palate

1. Motor - All muscles of the soft palate are supplied by the cranial part of accessory nerve, throughthe pharyngeal plexus, except tensor veli palatini, which is supplied by the mandibular nerve.

2. Secretomotor - pre-ganglionic fibres arise from the superior salivatory nucleus and passsuccessively through the facial, greater petrosal, nerve of the pterygoid canal and are relayed into

the pterygopalatine ganglion. Postganglionic fibres reach the palatine glands via the greater and

lesser palatine nerves.

3. General sensory - Greater and lesser palatine, long sphenopalatine [all branches of maxillarynerve] and glossopharyngeal nerves

4. Special sensory - glossopharyngeal and lesser palatine nerves convey taste sensation from the oralsurface of the soft palate.

Arterial supply1. Greater palatine branch of maxillary artery.2. Ascending palatine branch of facial artery.3. Palatine branches of ascending pharyngeal artery.

Veins: Drain into the pharyngeal venous plexus.

Lymphatic drainage: to retro-pharyngeal and deep cervical lymph nodes

Movements and functions

Palate regulates two gates, pharyngeal isthmus and oro-pharyngeal isthmus. It can completely close them

or can regulate their size as required. Thus soft palate plays an important role in chewing, swallowing,speech, coughing, sneezing, etc.

Fig. Showing muscles of the soft palateDevelopmentEmbryologically palate consists of two parts primitive and permanent.

Primitive palate includes a wedge shaped area in front of the incisive fossa and carries the four incisorteeth. Primitive palate is developed from the fusion of globular processes [of the medial nasal process]

and the maxillary processes. Permanent palate lies behind the primitive palate and is developed by the

fusion of the palatine processes of both the maxillae across the midline. Fusion between the primitive andpermanent palates takes place in a Y shaped manner, each limb of the Y passes between the lateral

incisor and canine teeth [fusion extends from before backwards and is completed by the 8 th week of intra

asdsouza 6


7/16

uterine life]. Ventral portion of the permanent palate gets ossified to form the hard palate; dorsal un-

ossified portion forms the soft palate.

Applied AnatomyParalysis of the soft palate [lesions of vagus nerve] produces nasal regurgitation of food, nasal twang in

the voice, and flattening of the palatal arch.

TongueTongue is a conical muscular organ situated in the floor of the mouth, has oral and pharyngeal parts,

separated by the sulcus terminalis.

Functions

1. It is an organ of taste.2. Helps in mastication, speech and deglutition.

External features - Tongue has following parts

a. Tip [or apex].b. Rootc. Base.d. 2 surfaces - dorsal and ventral.e. 2 lateral margins.

Fig. Dorsum of the tongue

Tip - forms the anterior free end, which during resting position lies behind the incisor teeth.

Base - directed backwards towards the oropharynx and is formed by the posterior one third of the tongue.Base is connected to the epiglottis by a median and a pair of lateral glosso-epiglottic folds.

Dorsal surface

The dorsal surface is convex in all directions, covered by mucous membrane that is lined by stratifiedsquamous non-keratinized epithelium [patches of keratin are found on filiform papillae]. Dorsal surface is

divided by sulcus terminalis into 2 parts; anterior two thirds - oral or presulcal part and posterior one third

- pharyngeal or post sulcal part. The sulcus is V shaped and passes forwards and laterally from a centraldepression, the foramen caecum. Foramen caecum represents the site from where thyroid diverticulum

asdsouza 7


8/16

grows down in the embryo. Oral and pharyngeal parts of the tongue differ in their development,

topography, structure and function.

Root part of the tongue attached to the floor of the mouth and extends from symphysis menti to thehyoid bone

Oral part

Mucous membrane is adherent to the underlying muscle by the lamina propria and is provided withnumerous papillae of different types. Each papilla is a projection of the lamina propria covered by mucous

membrane and presents the following types.

a. Circumvallate [vallate] papillae large, cylindrical [1 - 2 mm in diameter], 8 -12 in number, usuallyarranged in a single row immediately in front and parallel to the sulcus terminalis. Each papilla istruncated conical with broad base directed to the surface of the tongue and is surrounded by circular

sulcus, walls of the sulcus present taste buds.

b. Fungiform papillae are rounded reddish elevations present near the tip and margins of the tongue.These are smaller than vallate papillae but larger than filiform papillae.

c. Filiform papillae are numerous tiny conical projections covering almost the entire dorsal surface ofanterior two thirds of the tongue. These papillae are devoid of taste buds; and their epithelial tips arekeratinised [this makes the surface rough].

d. Foliate papillae are 3 - 4 vertical mucous folds affecting occasionally the margin of the tongue infront of the sulcus terminalis and contain taste buds [foliate papillae may be absent in human tongue,

but are prominent in animals].

Fig. Undersurface of the tongue seen through the open mouth

Pharyngeal part of the tongue

It lies behind the sulcus terminalis. Mucous membrane is devoid of papillae; but contains numerous

lymphatic follicles [collectively called the lingual tonsil].

Inferior surface

It is covered by mucous membrane, which is devoid of papillae and is reflected on to the floor of themouth. Following points can be noted on the inferior surface.

Frenulum linguae a median fold of mucous membrane connecting tongue to the floor of the mouth.On either side of the frenulum, plica fimbriata passes upwards and medially.

The deep lingual veins intervene between the plica fimbriata and the frenulum. Sublingual papilla - present on either side of the frenulum through which the submandibular duct

opens.

asdsouza 8


9/16

Lateral margins

Palatoglossal arch is attached to the lateral margin at the junction of anterior two thirds and posterior one

third of the tongue.

Taste buds

Taste buds are composed of modified epithelial cells [with terminals of gustatory nerves] arranged as

spherical masses within the epithelium. They are numerous on all types of lingual papillae except filiform.

Taste buds are also present on the inferior surface of the soft palate, palatoglossal arches and posteriorsurface of the epiglottis. Each taste bud is made up of slender, spindle shaped pale cells, some of which

are gustatory sensory cells and others are supporting cells. Each bud opens on the surface of theepithelium by an aperture - gustatory pore. Afferent gustatory nerve fibres penetrate base of the taste bud.

Muscles of the tongueTongue is divided into two symmetrical halves, right and left, by a median fibrous septum. Each half

contains striated muscles, which are arranged in two groups, extrinsic and intrinsic. In general extrinsic

muscles alter the position and intrinsic muscles change the shape of the tongue.

Fig. Coronal section through the anterior part of tongue to show muscles

Intrinsic muscles - Consists of four pairs.

1. Superior longitudinal Lies beneath the mucous membrane of the dorsal surface of the tongue, arisesfrom the posterior part of the median fibrous septum. Fibres pass forwards and laterally and areinserted into the side of the tongue. It shortens the tongue and makes the dorsum concave from side to

side.

2. Inferior longitudinal lies beneath the mucous membrane of the under surface of the tongue, arisesfrom the posterior part of the side of the tongue and passes forwards for its insertion into the median

fibrous septum. Muscle shortens the tongue and makes it dorsum convex.

3. Transverse linguae Fibres arise from the median fibrous septum and pass laterally for insertion intothe side of the tongue. It reduces width and increases length of the tongue.

4. Verticalis linguae arises from the lamina propria of the dorsum of the tongue, passes downwards andlaterally for insertion into the side of the tongue. It increases width of the tongue and makes dorsal

surface concave from side to side.

Extrinsic Muscles [five pairs]

1. Genoiglossus Fan shaped forms bulk of the tongue.2. Hyoglossus Quadrilateral in shape.3. Chondroglossus Considered as a part of hyoglossus.4. Styloglossus.5. Palatoglossus Described with the palate.

asdsouza 9


10/16

asdsouza 10

Muscle Origin Insertion Action

Genioglossus From the Superior

genial tubercle of the

mandible

Upper fibres inserted in to the

tongue extending from the root

to its apex.Intermediate fibres continuous

with the fibres of middle

constrictor of the pharynx

Lowest fibres- attached to thebody of hyoid bone.

Upper fibres retract tip

of the tongue.

Middle fibres depress thetongue.

Lower fibres pull the

posterior part of the

tongue forwards.

Hyoglossus Upper surface of

greater cornu and body

of the hyoid bone

Inserted into side of the tongue

between styloglossus and

inferior longitudinal muscle.

Depresses the side of the

tongue and makes the

dorsum convex.

Chondroglossus Lesser cornu and part

of the body of hyoid

bone

Side of the tongue Depresses side of the

tongue.

Styloglossus From the tip of styloid

process andstylomandibular

ligament

Into the side of the tongue Retracts the tongue

[backwards and up wardsopposite to that of

genioglossus].

Arterial supply of the tongue

1. Main artery is the lingual artery, a branch of external carotid artery.2. Ascending palatine and tonsillar branches of facial artery.3. Ascending pharyngeal artery branch of external carotid artery.

Venous drainageVeins of the tongue are arranged in two sets, superficial and deep. Superficial drains tip and under surface

of the tongue and pass along with hypoglossal nerve [superficial to hyoglossus] and drains into the

internal jugular vein. Deep veins drain the dorsum of tongue and run along with the lingual artery [deep to

hyoglossus] and terminate either into the internal jugular vein or common facial vein.

Nerve supply

Motor

a. Somato-motor All muscles of the tongue are supplied by the hypoglossal nerve, exceptpalatoglossus, which is supplied by the cranial part of accessory nerve through pharyngeal plexus.

b. Secreto-motor [to lingual glands] fibres reach through the lingual nerve - fibres arise from thesuperior salivatory nucleus and pass successively through facial, chorda tympani and lingual nerve.

Fibres are relayed to the submandibular ganglion, post-ganglionic fibres leave through lingual nerve.

Sensory1. Anterior two thirds General sensory by lingual nerve and Special sensory [taste] except vallate

papillae by chorda tympani.2. Posterior one-third General and special sensory [including vallate papillae] by the

glossopharyngeal nerve.

3. Posterior most part adjoining the vallecula general and special sensory by internal laryngealbranch of the vagus nerve.

Lymphatic drainage

Lymphatics of the tongue consist of intra-muscular and sub mucous plexuses and are arranged in four sets

Apical, marginal, central and dorsal.


11/16

asdsouza 11

Apical - It drains the tip and frenulum linguae. Some vessels drain into sub-mental nodes and to a smaller

extent into submandibular and jugulo-omohyoid nodes.

Marginal drain the sides of the tongue anterior to sulcus terminalis and terminate into submandibular

nodes. Some pass into jugulo-omohyoid and jugulo-digastric nodes.Central set Drain the dorsal surface of anterior two thirds of the tongue, most of which terminate into

jugulo-omohyoid nodes and some into submandibular and jugulo-digastric nodes.

Dorsal set Drains the posterior one- third into jugulo-omohyoid and jugulo-digastric nodes.

Peculiarities of the lymphatics

Lymphatics do not accompany the blood vessels. Pass bilaterally. Tip of the tongue has rich lymphatic drainage. Group of nodes at the bifurcation of CCA are the principal lymph nodes of the tongue.

Applied Anatomy

1. Injury to the hypoglossal nerve leads to paralysis of muscles of the tongue [leading to gradualatrophy of muscles]. In unilateral injury to the nerve, tip of the tongue when protruded deviates tothe affected [paralyzed] side.

2. Inflammation with or without infection is referred to as glossitis.3. Carcinoma of tongue spreads rapidly and bilaterally through the cervical lymph nodes.

Development

1. Epithelium Anterior two thirds [ectodermal] - from two lingual swellings and one tuberculum impar [from

the first branchial arch], so supplied by the lingual nerve [post-trematic] and chorda tympani

[pre-trematic].

Posterior one third [endodermal] from the cranial part of the hypobranchial eminence [thirdarch], therefore supplied by the glossopharyngeal nerve.

Posterior most part [endodermal] from the fourth arch and is supplied by the vagus nerve.2. Muscles develop from occipital myotomes and are supplied by the hypoglossal nerve.3. Connective tissue stroma from the local mesoderm.

SALIVARY GLANDS [Dr. A. S. D Souza]

Parotid gland

It is the largest of the three- paired salivary glands. The gland is shaped like an inverted pyramid and

weighs around 25gms. It is situated below the external acoustic meatus, between the ramus of mandibleand sternocliedomastoid. Anteriorly it overlaps a part of the masseter muscle.

Coverings

An inner true and an outer false capsule invest the gland. The true capsule is formed by the peripheralcondensation of the fibrous stroma of the gland.

False capsule is formed by the splitting of the general investing layer of deep cervical fascia. In between

the angle of the mandible and the mastoid process fascia splits to enclose the gland. The superficiallamella passes superficial to the masseter muscle and is attached to the lower border of the zygomatic arch

[parotido-masseteric fascia]. The deep lamella is attached to the styloid process, mandible and the

tympanic plate. Part of this fascia between the angle of mandible and the styloid process is thickened toform stylomandibular ligament, which intervenes between the parotid and submandibular salivary glands.


12/16

External features

The gland presents an apex, base, three surfaces and three borders.

Fig. Structures emerging at the periphery of the parotid gland

Apex directed downwards, overlaps the posterior belly of digastric and the adjoining carotid triangle.

Cervical branch of facial nerve and two divisions of the retromandibular vein emerge at the apex.

Base concave and directed upwards and is related to the external auditory meatus and temporo-

mandibular joint. Structures passing through the base are temporal branch of facial nerve, superficialtemporal vessels and auriculotemporal nerve.

Superficial surface covered with skin, superficial fascia [with branches of great auricular nerve and pre-auricular lymph nodes] and parotidomasseteric fascia.

Anteromedial surface grooved by the posterior border of the ramus of mandible and is related to

masseter, lateral surface of the TMJ and emerging branches of the facial nerve.

Posteromedial surface related to the mastoid and styloid processes with the structures attached to them

[sternocleidomastoid, posterior belly of digastric, styloid apparatus etc.] The ECA and facial nerve enterthe gland through this surface. Internal carotid artery lies deep to the styloid process.

Anterior border separates superficial from the anteromedial surface. Following structures emerge at theanterior border [from above downwards]

1. Zygomatic branch of facial nerve

2. Transverse facial vessels [Branch of superficial temporal artery]3. Upper buccal branch of facial nerve4. Parotid duct

5. Lower buccal branch of facial nerve

6. Mandibular branch of facial.

Medial border separates anteromedial from the posteromedial surface and is related to the lateral wall of

the pharynx.

asdsouza 12


13/16

Posterior border separates superficial surface from the posteromedial surface. It overlaps the

sternocleidomastoid

Fig. Arteries & veins within the parotid gland

Structures within the parotid gland

Three major structures within the substance of the parotid gland are [superficial to deep] facial nerve,

retromandibular vein and ECA [In addition deep parotid group of lymph nodes and auriculotemporalnerve are within.]

Fig. Facial nerve & its branchesFacial nerve emerges from the stylomastoid foramen, passes downward and forward to enter the

substance of the gland through its posteromedial surface. Within the gland facial nerve runs for a short

course and then divides into temporo-facial and cervico-facial trunks. Temporo-facial passes upwards tosubdivide into temporal and zygomatic branches and the cervico-facial passes downwards and divides

into buccal, mandibular and cervical branches [Note: gland is roughly divided into superficial and deep

parts or lobes by the facial nerve and its branches.]

The retromandibular vein occupies the intermediate zone and is formed by the union of superficialtemporal and maxillary veins. It ends below by dividing into anterior and posterior divisions [Anterior

division joins with facial vein to form the common facial vein and posterior division joins with posterior

auricular vein to form the external jugular vein]. The ECA occupies the deep zone and as it ascendsdivides into terminal branches maxillary and superficial temporal arteries.

Blood supply - Arteries supplying the gland are derived from branches of ECA and the veins drain intoexternal jugular vein.

asdsouza 13


14/16

asdsouza 14

Parotid duct

It is about 5cm long, emerges through the anterior border. It runs forwards and slightly downwards on the

masseter muscle. At the anterior border of masseter it turns medially and pierces the buccal pad of fat,

buccopharyngeal fascia, buccinator and oral mucous membrane to open into the vestibule of mouth on apapilla opposite the crown of the upper second molar tooth [oblique course of the duct acts as a valve and

prevents inflation during blowing].

Nerve supplySecreto-motor supply of the gland is derived from sympathetic and parasympathetic nerves. [Para-

sympathetic stimulation produces watery secretion and sympathetic produces mucous secretion]. Inaddition sympathetic is vasomotor.The sympathetic fibres are derived from superior cervical ganglion and

pass through the plexus around ECA. Sensory fibres to the gland are from the auriculotemporal nerve.

Parasympathetic fibres are derived from the inferior salivatory nucleus [medulla oblongata]. Fibres passthrough the glossopharyngeal nerve tympanic branch tympanic plexus lesser petrosal nerve

Otic ganglion. Postganglionic fibres from the ganglion pass through auriculotemporal nerve to the gland.

Lymphatic drainage

The lymph drains into superficial and deep group of parotid lymph nodes, efferent vessels from these

nodes terminate into jugulo-digastric group of deep cervical nodes.

Applied Anatomy

1. Inflammatory swellings of the parotid gland are extremely painful due to unyielding nature of theparotido-masseteric fascia.

2. Parotid abscess may be caused by retrograde spread of bacterial infection from the oral cavity.Surgical incisions around the gland should be horizontal to avoid damage to the branches of facial

nerve. During parotidectomy facial nerve is preserved by removing the gland in two parts[superficial and deep].

Submandibular salivary gland

This is one of the three major pairs of salivary glands situated in the anterior part of the digastric triangleand weighs around 10 to 15 gms. The gland consists of a large superficial part and a small deep part,

which are continuous around the posterior border of mylohyoid muscle.

Superficial part

It presents two ends - anterior and posterior and three surfaces medial, lateral and inferior. Superficialpart of the gland is enclosed within two layers of the deep cervical fascia, which forms its false capsule.

Anterior end extends up to the anterior belly of digastric and posterior end extends up to thestylomandibular ligament.

Inferior surface - is covered by skin, platysma and deep fascia and is crossed by the facial vein andcervical branch of facial nerve.

Lateral surface is related to the submandibular fossa of the mandible, facial artery and the medialpterygoid muscle.

Medial surface related to mylohyoid muscle, hyoglossus, lingual nerve, submandibular ganglion,hypoglossal nerve and styloglossus muscle.

Deep part

This part of the gland extends forward in between mylohyoid and hyoglossus muscles. Posteriorly it iscontinuous with the superficial part of the gland round the posterior border of mylohyoid, anteriorly it

extends close to the posterior end of the sublingual gland.


15/16

Fascial covering of the superficial part Horizontal section through the submandibular region

Relations

Lateral mylohyoid

Medial Hyoglossus

Superior Lingual nerve and submandibular ganglionInferior - Hypoglossal nerve

Fig. Relationship of facial artery & vein to the submandibular gland

Submandibular duct

It is about 5cm long, emerges at the anterior end of the deep part of the gland. The duct runs on thehyoglossus muscle [with lingual nerve above and hypoglossal nerve below]. At the anterior border of

hyoglossus lingual nerve crosses the duct. It opens on the floor of the mouth, on the summit of sublingual

papilla, at the side of the frenulum of the tongue.

Nerve supply [The nerves pass to the gland through submandibular ganglion]Parasympathetic Pre-ganglionic fibres arise from the superior salivatory nucleus in the pons Facial

nerve- Chorda tympani Lingual nerve relay in the submandibular ganglion. Postganglionic fibresfrom the ganglion supply the gland directly [postganglionic fibres reach the sublingual gland via the

lingual nerve]. Sympathetic fibres to the gland are derived from superior cervical ganglion and pass

through the plexus around the facial artery. Sensory fibres are from the lingual nerve.

Blood supply

Branches from the facial and lingual arteries supply the gland. The veins correspond to arteries and drain

into the internal jugular vein.

asdsouza 15


16/16

Lymphatic drainage to submandibular lymph nodes [and then to the jugulodigastric nodes]

Sublingual salivary gland

It is the smallest of the three major salivary glands, each gland weighs about 3 - 4gms. It is located in thefloor of the mouth cavity and is lodged in the sublingual fossa of the mandible.

Relations

Anterior related to the opposite side glandPosterior deep part of the submandibular gland

Superior covered by mucous membrane, which is raised to form the sublingual foldInferior Mylohyoid muscle

Lateral sublingual fossa of the mandible

Medial submandibular duct, lingual nerve and genioglossusDucts The gland possesses about 10-20 ducts, most of them open separately in the floor of the mouth on

the summit of the sublingual fold [some of them may open into the submandibular duct].

Blood supply Lingual and submental arteries

Nerve supply refer submandibular gland.

Fig. Relations of the hyoglossus, submandibular ganlgion

Submandibular ganglion

It is a parasympathetic ganglion, topographically connected to lingual nerve, but functionally connected

to the facial nerve. The ganglion lies on the hyoglossus muscle suspended by lingual nerve by two roots.

Parasympathetic root derived from the fibres of chorda tympani and pass into the ganglion via theposterior root where the fibres are relayed [preganglionic parasympathetic fibres arise in the superior

salivatory nucleus to pass into the facial nerve]. The postganglionic fibres arising from the ganglion

supply the submandibular gland directly. Some fibres join the lingual nerve through the anterior root to

supply the sublingual and scattered lingual glands.

Sympathetic root from the plexus around the facial artery, this conveys postganglionic sympatheticfibres from the superior cervical ganglion. Fibres pass through the submandibular ganglion without

interruption to the salivary glands [similar to the parasympathetic fibres].

Sensory fibres are from the lingual nerve.

asdsouza 16

Oral Cavity & Tongue

Documents

Transcript of Oral Cavity & Tongue