Exam 3 Review:  Chapter 23:  Oral Cavity II - Tongue

tongue - The fleshy, movable, contractile organ, attached to the floor of the mouth and connected with the hyoid arch and the mandible, which is the principal organ of taste, an aid in ingestion, chewing and swallowing, and an important organ of speech and some non-verbal communication; it consists primarily of several layers of skeletal muscle arranged in different orientations; its anterior dorsal surface is covered in papillae; its posterior dorsal surface is covered by lingual tonsils; it is lined by a wet stratified squamous epithelium.

lingual frenulum - The thin band or fold of mucosal tissue which attaches the bottom of the tongue to the floor of the mouth and limits the extension of the tongue from the oral cavity.  [Note:  In the photo above to the right, thanks to an unusually flexible lingual frenulum, one of my former students can insert the tip of her tongue into her nasopharynx above her soft palate.  Can you?]

papillae -

  1. A small nipplelike projection, such as a protuberance on the skin, at the root of a hair or feather, or at the base of a developing tooth.
  2. Any of the small, round or cone-shaped protuberances on the top of the tongue that contain taste buds; three types are recognized: filiform, fungiform, and circumvallate; they are lined by a wet stratified squamous epithelium.


filiform papillae - The most common of the small, thin, pointed, cone-shaped protuberances on the anterior dorsal surface of the tongue which contain taste buds; they are lined by a wet stratified squamous epithelium.

fungiform papillae - The second most common of the small, rounded eminences scattered on the anterior dorsal surface of the tongue which contain taste buds; in cross-section they appear to have the outline of a mushroom; they are lined by a wet stratified squamous epithelium.

circumvallate papillae - Eight or ten larger projections from the dorsum of the tongue forming a row anterior to and parallel with the sulcus terminalis, which separates the anterior from the posterior dorsal surface of the tongue; each one is surrounded by a circular trench (fossa) having a slightly raised outer wall ("vallum"); on their sides and the opposed margin of the vallum are numerous taste buds; they are lined by a wet stratified squamous epithelium.

lingual lipase - An enzyme, produced by special cells on the tongue, which catalyses the hydrolysis of fats (monoglycerides, diglycerides and triglycerides) to glycerol and fatty acids, it works in the oral cavity and in the stomach to some degree.

List:

6.  structures which increase the surface area of the tongue.

     The various papillae on the dorsal surface (filiform papillae, fungiform papillae, circumvallate papillae) - the filiform papillae are the most important for increasing the surface area of the tongue because they are the most numerous.

11.  the functions of the tongue.

          assists in:  ingestion, perception of touch and temperature, perception of taste, mastication (chewing), bolus formation, chemical digestion of lipids (lingual lipase), articulation of speech, oral hygiene, deglutition (swallowing), closing the epiglottis during deglutition (swallowing), immune defense of the oral cavity (lingual tonsils)