Anatomy of the Oral cavity and salivary glands
The oral cavity is bounded anteriorly by the lips, laterally by the cheeks, superiorly by the palate and inferiorly by the floor of the mouth. The oral cavity can be divided into two segments: The oral vestibule which is the space between the dental arches and lips / cheeks. And the oral cavity proper which is the internal segment beyond the dental arches and alveolar processes
The oral cavity is lined with the oral mucous membrane, made up of two layers which are the stratified surface epithelium and the underlying connective tissue. The palate and alveolar process are covered with a toughened layer of keratinized mucosa. The mucosa of the cheeks and floor of the mouth is thin and has no keratin layer.
The upper and lower lips are the borders of the mouth, joining at the left and right commissure. The upper lip is bounded by the cheeks at the nasolabial groove, and by the nose. The lower lip is also bounded laterally by the cheeks, and inferiorly by the labiomental groove.
The nasolabial groove is running diagonally on each side of the nostril toward the corner of the lip. The labiomental groove is a horizontal groove between the lower lip and the chin. The vermilion border is the red transitional zone of the lips, where they merge into labial mucosa. The mucocutaneous margin of the lips is the junction between the vermilion border and the skin of the face.
Tubercle is a small rounded nodule of tissue in the centre of the upper lip. The depression running from the tubercle to the nostrils is named the philtrum.
The vestibular fornix is the depth in mandible or height in maxilla, of the vestibule. The labial frenum is a thin sheet of tissue that attaches the centre of the upper or lower lip to the mucosa between the central incisors. The buccal frenum, in the premolar area, loosely attaches the cheek to the mucosa of the jaw.
The buccal frenum are moved by the facial muscles to various directions in eating, and can dislodge complete dentures. The horizontal line running posteriorly on each side of the cheek mucosa at the level of the commissural area is called the linea alba buccalis — buccal white line.
The parotid papilla (left and right) is a round elevation of tissue in the upper vestibule, next to the first and second molars. These papillae cover the duct opening from the large parotid glands located in front of each ear, they produce 23–33% of our saliva (serous type).
The gingiva is that part of the oral mucous membrane that covers the jaw bone, and surrounds the cervical portions of the teeth.
The Gingival margin (margo gingivalis) is the occlusal (incisal) border at which the gingiva meets the tooth. Usually the gingival margin approximately follows the curvature of the cervical line, it is usually at the same level as the cervical line and the neck of the tooth is tightly embraced by the gingival margin.
The tongue is a broad, flat organ composed of muscle, fibres and glands. It rests in the floor of the mouth within the curvature of the body of the mandible. The posterior one-third on the tongue is the tongue root or tongue base. It has numerous functions as the principal organ of taste, invaluable for speech, mastication and for swallowing.
The dorsal surface (dorsum) of the tongue is covered by two kinds of papillae: filiform papillae — most numerous, hair-like, covering the anterior two-thirds of the dorsum. The fungiform papillae have a round mushroom shape, deep red colour, larger, scattered and located near the tip of the tongue.
Foliate papillae are large, red, leaf-like, found on the lateral surfaces of the tongue in the posterior one-third. The circumvallate papillae are 8 to 12 large, flat papillae that form a V-shaped row on the dorsum near the posterior third of the tongue, containing numerous taste buds.
The ventral surface of the tongue is shiny and blood vessels are visible. The lingual frenum is a thin sheet of tissue that attaches the centre of the tongue to the floor of the mouth.
Sublingual folds, called plica sublingualis, are located on each side of the floor of the mouth, between the first molars and the lingual frenum. Here are the openings of ducts from underlying sublingual salivary glands. They secrete purely mucous saliva, producing 5–8% of our saliva.
In the centre line at the junction between the right and left sublingual folds on either side of the fraenum, is a pair of sublingual caruncles, each with an opening from ducts of salivary glands. They drain the larger, more posteriorly located submandibular glands,which produce about two-thirds of our saliva.
The Mandibular torus is a bulbous protuberance of bone beneath a thin mucous membrane covering on the lingual side of the mandible, usually found in the premolar region. A similar torus may occur in the middle of the palate — torus palatinus.
The hard palate is the firm anterior part of the roof of the mouth, ending opposite the third molars and immediately anterior to fovea palatinae.
The movable part of the roof of the mouth, just posterior to the hard palate, is called the soft palate. The Incisive (nasopalatine) papilla is the small rounded elevation of tissue on the midline just lingual to the central incisors.
The Palatine raphe (raphe palatinum) is the slightly elevated centre line running anteroposteriorly in the hard palate. The mucosa over the raphe is firmly attached to the underlying periosteum. There are numerous salivary glands beneath the mucosa on both sides, in the posterior third of the raphe.
The Palatine rugae (rugae palatinae) are a series of elevations, running from side to side, on the anterior portion of the palate, from the palatine raphe. They function as tactile sensing objects and in production of certain speech sounds.The uvula is a small soft tissue structure hanging from the center of the posterior border of the soft palate. The vibrating line is the place or line where the beginning of the soft palate can be observed and is measured during upper full denture impressions.
The Fovea palatinae (Latin) are a pair of pits in the soft palate, on either side of the centre line, just posterior to the vibrating line. They are openings of ducts of the minor palatine mucous glands.
