ORAL REGION

Oral cavity (mouth)• Is the region inferior to the nasal cavities s

Boundaries

The oral cavity can be thought of as a rectangular box Anteriorly, it communicates with the exterior through the oral fissure Posteriorly, the oral cavity ends at the oropharyngeal isthmus, the opening

the oropharynx roof floor lateral walls

The roof of the oral cavity consists of the hard and soft palates The floor of the oral cavity is formed mainly by 3 structures:

I. A muscular diaphragm, which fills the U-shaped gap between the left and right sides of the body of the mandible and is composed of the paired mylohyoid muscles

II. Two cord-like geniohyoid muscles above the diaphragm, which run from the mandible in front to the hyoid bone behind

III. The tongue, which is superior to the geniohyoid muscles

The lateral walls are the cheeks and merge anteriorly with the lips surrounding the oral fissure (the anterior opening of the oral cavity)

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

Oral cavity• The oral cavity is the start of the alimentary canal • It is where food is ingested and prepared for digestion in the stomach

and small intestine

parts: • has 2 parts oral vestibule oral cavity proper

• in the oral cavity, food and drinks are tasted and savored and where mastication and lingual manipulation of food occur

oral vestibule:• is the slit-like space between the (teeth and buccal gingiva) and

the (lips and cheeks)• it communicates with the exterior through the mouth • The size of the oral fissure is controlled by the circumoral muscles,

such as the orbicularis oris, buccinator, risorius, depressors and elevators of the lips

oral cavity proper: • is the space between the upper and the lower dental arches or

arcades (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

Lips, Cheeks, and Gingivae

Lips • The lips are mobile, musculofibrous folds surrounding the mouth• that are connected to the gums by superior and inferior frenula• they extend from the nares and nasolabial sulci superiorly and laterally

and to the mentolabial sulcus inferiorly• In between the lip (red colored) and the adjacent normal skin is a sharp

demarcation called the vermilion border • The vermilion border of the upper lip is known as the cupid's bow

 {Cupid's bow is a facial feature where the double curve of a human upper lip is said to resemble the bow of Cupid, the Roman god of erotic love}

Cupid’s bow

• The typically reddish area within the borders is called the vermilion zone

• The median part of the upper lip shows a shallow external groove, the philtrum

• The lips are covered externally by skin and internally by mucous membrane

• They contain the orbicularis oris and superior and inferior labial muscles, vessels, and nerves

functions Serves as the valves of the oral fissure, containing the sphincter

(orbicularis oris) that controls entry and exit from the mouth and upper alimentary and respiratory tracts

used for grasping food, sucking liquids, keeping food out of the oral vestibule

forming speech, osculation (kissing)

The transitional zone of the lip, ranging from brown to red, continues into the oral cavity where it is continuous with the mucous membrane

labial frenula • are free-edged folds of mucous membrane in the midline, extending

from the labial gingiva to the mucosa of the upper and lower lips• the one extending to the lower lip is smaller

Arterial supply• The upper lip: superior labial branches of the facial and infraorbital

arteries• The lower lip: inferior labial branches of the facial and mental

arteries

innervation The upper lip : supplied by the superior labial branches of the infraorbital nerves (of CN V2)

and the lower lip is supplied by the inferior labial branches of the mental nerves (of CN V3)

Lymphatic drainage• Lymph from the upper lip and lateral parts of the lower lip passes

primarily to the submandibular lymph nodes • lymph from the medial part of the lower lip passes initially to the

submental lymph nodes

Clinical anatomy

Cleft Lip• Cleft lip (harelip) is a congenital anomaly (usually of the upper lip) that occurs

in 1 of 1000 births • 60-80% of affected infants are males• The clefts vary from a small notch in the transitional zone and vermilion border

to a notch that extends through the lip into the nose • In severe cases, the cleft extends deeper and is continuous with a cleft in the

palate• Cleft lip may be unilateral or bilateral

Large Labial Frenula• Excessively large superior labial frenula in children may cause a space between

the central incisor teeth• Resection of the frenulum and the underlying connective tissue (frenulectomy)

between the incisors allows approximation of the teeth, which may require an orthodontic appliance

• Large lower labial frenula in adults may pull on the labial gingiva and contribute to gingival recession, which results in abnormal exposure of the roots of the teeth

Cheek• They are continuous with the lips• The cheeks form the movable walls of the oral cavity• The prominence of the cheek occurs at the junction of the zygomatic

and buccal regions • The zygomatic bone underlying the prominence and the zygomatic arch

that continues posteriorly are commonly referred to as the cheek bone• Numerous small buccal glands lie between the mucous membrane and

the buccinators • Superficial to the buccinators are encapsulated collections of fat• these buccal fat-pads are proportionately much larger in infants,

presumably to reinforce the cheeks and keep them from collapsing during sucking

Arterial supply• supplied by buccal branches of the maxillary artery

innervation• innervated by buccal branches of the mandibular nerve

Gingivae• The gingivae (gums) are composed of fibrous tissue covered with

mucous membrane

parts

I. 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

11. The alveolar mucosa (unattached gingiva) is normally shiny red and non-keratinizing

Clinical anatomy

Gingivitis• 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)

Teeth• The teeth are set in the tooth sockets and are used in mastication and

in assisting in articulation• A tooth is identified and described on the basis of whether it is deciduous (primary) tooth permanent (secondary) tooth• Children have 20 deciduous teeth• Adults normally have 32 permanent teeth • 20 deciduous teeth (milk teeth or baby teeth) erupt from the ages of 6

to 30 months, beginning with the incisors• Between 6 and 25 years of age, these are replaced by the 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

Parts and Structure of the Teeth A tooth has a: crown Neck root • The crown projects from the gingiva• The neck is between the crown and the root• The root is fixed in the tooth socket by the periodontium• Most of the tooth is composed of dentin • The dentine is covered by enamel over the crown and cement over the

root• The central cavity of a tooth is 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

• The tooth sockets are in the alveolar processes of the maxillae and mandible

• they are the skeletal features that display the greatest change during a lifetime

• Adjacent sockets are separated by interalveolar septa• within the socket, the roots of teeth with more than one root are

separated by interradicular septa

Arterial supply• superior and inferior alveolar arteries, branches of the maxillary

artery, supply the maxillary and mandibular teeth, respectively

Venous drainage• Alveolar veins with the same names and distribution accompany

the arteries

Lyphatic drainage• Lymphatic vessels from the teeth and gingivae pass mainly to the

submandibular lymph nodes

Innervation of the Teeth branches of the maxillary nerve supply the maxillary(upper) teeth and

they are:• Anterior superior alveolar nerve• middle superior alveolar nerve• Posterior superior alveolar nerve The inferior superior alveolar nerve which is a branch of the

mandibular nerve supply the manbibular(lower) teeth

Clinical anatomy

Dental Caries, Pulpitis, and Tooth Abscesses• Decay of the hard tissues of a tooth results in the formation of dental

caries (cavities)• 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

•

Tongue• The tongue 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

parts

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 note: The body and apex of the tongue are extremely mobile.

The dorsum (dorsal surface) of the tongue :• is the posterosuperior surface, which is located partly in the oral

cavity and partly in the oropharynx

• The dorsum is characterized by a V-shaped groove called the terminal sulcus or groove (sulcus terminalis)

• posterior to this groove is foramen cecum.• This small pit, frequently absent, is the non-functional remnant of

the proximal part of the embryonic thyroglossal duct from which the thyroid gland developed

• The terminal sulcus divides the dorsum of the tongue into the: anterior (oral) part in the oral cavity proper 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(small nipple like process):

Vallate papillae: Large and flat topped, they lie directly anterior to the terminal sulcus and are arranged in a V-shaped row

Foliate papillae: Small lateral folds of the lingual mucosa• They are poorly developed in humans Filiform papillae: Long and numerous, they contain afferent nerve

endings that are sensitive to touch 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 called the median sulcus

• 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• 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• On each side of the frenulum, a deep lingual vein is visible through the

thin mucous membrane

Note: There are four basic taste sensations: sweet, salty, sour, and bitter • Sweetness is detected at the apex• saltiness at the anterolateral margins• sourness at the posterolateral margins• bitterness at the posterior part of the

tongue

Muscles of the Tongue• The tongue is essentially a mass of muscles that is mostly covered by

mucous membrane • 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

These include: genioglossus Hyoglossus styloglossus palatoglossus • They originate outside the tongue and attach to it• They mainly move the tongue but they can alter its shape as well

Intrinsic Muscles of the Tongue

They include: superior longitudinal muscle inferior longitudinal muscle transverse muscle vertical muscles • They have their attachments entirely within the tongue and are not

attached to bone

Vasculature of the Tongue

Arterial supply• 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 and give rise to the:

The dorsal lingual arteries supply the posterior part (root);

the deep lingual arteries supply the anterior part.• The deep lingual arteries communicate with each other near the

apex of the tongue.• The dorsal lingual arteries are prevented from communicating by

the lingual septum

Venous drainage• 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 IJV

The lymphatic drainage of the tongue Lymph from the tongue takes four routes • Lymph from the posterior third drains into the superior deep cervical

lymph nodes• Lymph from the medial part of the anterior two thirds drains directly

to the inferior deep cervical lymph nodes• Lymph from the lateral parts of the anterior two thirds drains to the

submandibular lymph nodes• The apex and frenulum drain to the submental lymph nodes• The posterior third and the medial part of the anterior two thirds

drain bilaterally

Innervation of the Tongue

Motor innervation• All muscles of the tongue, except the palatoglossus (actually a

palatine muscle supplied by the vagus nerve(X) of the pharyngeal plexus), receive motor innervation from the hypoglossal nerve (CN XII)

Sensory innervation

The anterior two thirds of the tongue are supplied by:

• the lingual nerve (CN V3) for general sensation

• the chorda tympani, a branch of the facial nerve (CN VII) transferring nerve fibers to the lingual nerve, for taste

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 sensation and taste

• Another contribution is made by the internal laryngeal branch of the vagus (CN X) for general sensation and taste

Hence CN VII, CN IX, and CN X provide nerve fibers for taste; those from CN VII are ultimately conveyed by CN V3

Clinical anatomy

Lingual Carcinoma• A lingual carcinoma in the posterior part of the tongue metastasizes

to the superior deep cervical lymph nodes on both sides, whereas a tumor in the anterior part usually does not metastasize to the inferior deep cervical lymph nodes until late in the disease.

• Because these nodes are closely related to the IJV, metastases from the tongue may be widely distributed through the submental and submandibular regions and along the IJVs in the neck.

Frenectomy• An overly large lingual frenulum (tongue-tie/ ankyloglossa) 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

Thyroglossal Duct Cyst• A cystic remnant of the thyroglossal duct, associated with

development of the thyroid gland, may be found in the root of the tongue and be connected to a sinus that opens at the foramen cecum

• Surgical excision of the cyst may be necessary• Most thyroglossal duct cysts are in the neck, close or just inferior

to the body of the hyoid bone