Oral Cavity

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oral cavity

[′ȯr·əl ′kav·əd·ē]
(anatomy)
The cavity of the mouth.

Oral Cavity

 

the anterior portion of the digestive tract from the mouth to the pharynx or, in the absence of a pharynx, directly to the esophagus.

In animals the oral cavity develops wholly or partially from an invagination of the ectoderm of the fore gut. In invertebrates special adaptations are often associated with the oral cavity, including the piercing and cutting formations in free-living nematodes, the jaws in gastropod and cephalopod mollusks, and the mouth parts in arthropods. In vertebrates the oral cavity is lined with a multilayered and sometimes horny epithelium. In fish and terrestrial vertebrates the oral cavity is bounded in front and on the sides by the jaws and teeth, and underneath by a muscular floor; the hyoid arch, which in most animals supports the tongue, is contained in the thick of the muscular floor. In fish and amphibians the roof of the oral cavity is reinforced by the bones of the base of the skull, which form the primary palate and the choanae; the latter open immediately into the oral cavity.

In amniotes the oral cavity is divided into a superior (respiratory) section and an inferior section (secondary oral cavity) by the development of a hard palate. In mammals the posterior part of the hard palate is the soft palate, which separates the oral cavity from the pharynx. In birds and more frequently in mammals, there are papillae, transverse ridges, or palatine plates on the palate, which are covered with a horny layer and which facilitate the mastication of food. In baleen whales the horny layer of these ridges is greatly enlarged and forms the baleen, or whalebone. In mammals the development of soft, mobile lips led to the formation of a cavity between the lips and the teeth called the vestibule of the mouth. In some mammals the vestibule forms lateral processes called cheek pouches. In vertebrates and man the oral cavity contains the tongue, teeth, and glands of the mouth.

In man the oral cavity is topographically divided into an anterior section, or the vestibule of the mouth, which is a derivative of the oral inlet, and a posterior section, or the mouth cavity proper. The boundaries of the vestibule are the lips anteriorly, the cheeks laterally, and the teeth and the alveolar processes of the upper and lower jaws posteriorly. The oral cavity proper is delimited superiorly by the vault of the hard and soft palates and inferiorly by the mucous membrane that covers the muscles and root of the tongue and the floor of the oral cavity. Anteriorly and laterally the oral cavity is bounded by the teeth and the interior surface of the alveolar processes of the upper and lower jaws.

Anteriorly the oral cavity communicates with the external environment by means of the oral fissure, and posteriorly it communicates with the pharynx through the fauces. The tonsils—lymphoepithelial organs—are located in the pharynx. Numerous tiny salivary glands are located in the thick of the mucous membrane. The efferent ducts of the major salivary glands—the parotid, sublingual, and submaxillary glands—also open into the oral cavity. The blood supply, lymph drainage, and innervation of the walls of the oral cavity are closely associated with the vascular and nervous systems of the jaws. The taste organs and receptors are located in the mucous membrane. The oral cavity contains permanent microflora, which acts as a biological barrier to microbes, and incidental flora. The oral cavity participates in food digestion, respiration, voice formation, and speech.

Diseases of the oral cavity include gingivitis, stomatitis, leukoplakia, papilloma, and diseases of the teeth, jaws, tongue, lips, and salivary glands.

N. S. LEBEDKINA