20.4: Oral Cavity

Oral Cavity

Above: Anatomy of the oral cavity.

The oral cavity is the entry point into the digestive system. It is equipped with teeth and a tongue to grind up and break apart foodstuffs to begin physical digestion. Chemical digestion also begins in the mouth with enzymes produced and secreted by three pairs (right and left) of salivary glands: sublingual salivary glands, submandibular salivary glands, and parotid salivary glands. Salivary glands secrete fluid saliva containing amylase, an enzyme that breaks down starch, a long-chain carbohydrate found in foods such as pasta and potatoes. Amylase breaks starch into sugars, thereby beginning chemical digestion. Saliva also contains lysozyme, an enzyme that kills some bacteria.

Tonsils are present along in the posterior oral cavity, which collect information about possible infectious agents entering the body and begins preparing the adaptive immune response to those infectious agents. Tonsils include the pharyngeal tonsil at the posterior aspect of the nasal cavity, a pair of palatine tonsils on the right and left of the oropharynx, and a pair of lingual tonsils at the posterior and inferior aspect of the tongue.

Above: Anatomy of the salivary glands, oral cavity, tonsils, and throat.

Adults (that have all of their teeth) have 32 teeth: 4 incisors, 4 canines/cuspids, 8 premolars/bicuspids, and 12 molars. Each tooth is designated with a number 1-32 beginning with 1 on the upper right posterior molar and then numbering each tooth successively from right to left on the top. Tooth 17 is the posterior molar on the lower left and the numbering continues from left to right such that the posterior lower right molar is number 32.

Above: Anatomy of the teeth.

After mastication (chewing) and swallowing food, it passes into the oropharynx, to the laryngopharynx, and the closing of the epiglottis when swallowing diverts the food into the esophagus, posterior to the larynx and trachea. After the food has been chewed and is being swallowed, we now refer to it as a bolus.

Above: Tissues lining the oral cavity. The lining mucosa lines all of the oral cavity except for the gingiva (gums), hard palate and the dorsal surface of the tongue. The masticatory mucosa lines the gingiva and hard palate, areas that undergo abrasive forces during mastication. Specialized mucosa lines the dorsal surface of the tongue. The epithelium of the tongue mucosa is keratinized, but is modified into three types of papillae, only one type is shown. Some papillae serve mechanical functions, while others possess taste buds.

Attributions

• "Anatomy 204L: Laboratory Manual (Second Edition)" by Ethan Snow, University of North Dakota is licensed under CC BY-NC 4.0
• "Digital Histology" by Department of Anatomy and Neurobiology and the Office of Faculty Affairs, Virginia Commonwealth University School of Medicine and the ALT Lab at Virginia Commonwealth University is licensed under CC BY 4.0
• "Illu mouth.jpg" by An officer or employee of the United States Government is in the Public Domain