Oral Cavity and Palate

Oral Cavity and Palate

A. Oral Cavity

• Its roof is formed by the palate , and its floor is formed by the tongue and the mucosa, supported by the geniohyoid and mylohyoid muscles.
• Its lateral and anterior walls are formed by an outer fleshy wall (cheeks and lips) and an inner bony wall (teeth and gums). (The vestibule is between the walls, and the oral cavity proper is the area inside the teeth and gums.)

B. Palate

• Forms the roof of the mouth and the floor of the nasal cavity.

1. Hard palate

• Is the anterior four fifths of the palate and forms a bony framework covered with a mucous membrane between the nasal and oral cavities.
• Consists of the palatine processes of the maxillae and horizontal plates of the palatine bones.
• Contains the incisive foramen in its median plane anteriorly and the greater and lesser palatine
  foramina posteriorly.
• Receives sensory innervation through the greater palatine and nasopalatine nerves and blood from the greater palatine artery.
  

2. Soft palate

• Is a fibromuscular fold extending from the posterior border of the hard palate and makes up one fifth of the palate.
• Moves posteriorly against the pharyngeal wall to close the oropharyngeal (faucial) isthmus when swallowing or speaking.
• Is continuous with the palatoglossal and palatopharyngeal folds .
• Receives blood from the greater and lesser palatine arteries of the descending palatine artery of the maxillary artery, the ascending palatine artery of the facial artery, and the palatine branch of the ascending pharyngeal artery.
• Receives sensory innervation through the lesser palatine nerves and receives skeletal motor innervation from the vagus nerve. A lesion of the vagus nerve deviates the uvula to the opposite side.

C. Tongue

• Is attached by muscles to the hyoid bone, mandible, styloid process, palate, and pharynx.
• Is divided by a V-shaped sulcus terminalis into two parts ”an anterior two thirds and a posterior one third which differ developmentally, structurally, and in innervation.
• The foramen cecum is located at the apex of the â€oeV― and indicates the site of origin of the embryonic thyroglossal duct.
  

Lingual papillae

• Are small, nipple-shaped projections on the anterior two thirds of the dorsum of the tongue.
• Are divided into the vallate, fungiform, filiform, and foliate papillae.

1. Vallate papillae

• Are arranged in the form of a in front of the sulcus terminalis.
• Are studded with numerous taste buds and are innervated by the glossopharyngeal nerve.

2. Fungiform papillae

• Are mushroom-shaped projections with red heads and are scattered on the sides and the apex of the tongue.

3. Filiform papillae

• Are numerous, slender, conical projections that are arranged in rows parallel to the sulcus terminalis.

4. Foliate papillae

• Are found in certain animals but are rudimentary in humans.

Lingual tonsil

• Is the collection of nodular masses of lymphoid follicles on the posterior one third of the dorsum of the tongue.

Lingual innervation

• The extrinsic and intrinsic muscles of the tongue are innervated by the hypoglossal nerve except for the palatoglossus, which is innervated by the vagus nerve. A lesion of the hypoglossal nerve deviates the tongue toward the injured side.
• The anterior two thirds of the tongue receives general sensory innervation from the lingual nerve and taste sensation from the chorda tympani.
• The posterior one third of the tongue and the vallate papillae receive both general and taste innervation from the glossopharyngeal nerve.
• The epiglottic region of the tongue and the epiglottis receive both general and taste innervation from the internal laryngeal branch of the vagus nerve.

Lingual artery

• Arises from the external carotid artery at the level of the tip of the greater horn of the hyoid bone in the carotid triangle.
• Passes deep to the hyoglossus and lies on the middle pharyngeal constrictor muscle.
• Gives rise to the suprahyoid, dorsal lingual, and sublingual arteries and terminates as the deep lingual artery , which ascends between the genioglossus and inferior longitudinal muscles.

D. Muscles of the tongue

Muscle Styloglossus
Origin Styloid process
Insertion Side and inferior aspect of tongue
Nerve Hypoglossal n.
Action Retracts and elevates tongue

Muscle Hyoglossus
Origin Body and greater horn of hyoid bone
Insertion Side and inferior aspect of tongue
Nerve Hypoglossal n.
Action Depresses and retracts tongue

Muscle Genioglossus
Origin Genial tubercle of mandible
Insertion Inferior aspect of tongue; body of hyoid bone
Nerve Hypoglossal n.
Action Protrudes and depresses tongue

Muscle Palatoglossus
Origin Aponeurosis of soft palate
Insertion Dorsolateral side of tongue
Nerve Vagus n. via pharyngeal plexus

Action Elevates tongue

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