The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
Mastication is also referred to as chewing. It is the first step in the breakdown of complex blends of nutrients into their energy-producing basic components.
When chunks of food are masticated, they are broken into smaller pieces. This increases the surface area that is available for digestive enzymes to attack. The act of chewing also includes the release of saliva, which softens the food and, because of salivary mucus, makes the food slippery enabling the pieces to be swallowed. Larger pieces of dry food are difficult to swallow and can even become lodged in the esophagus (the digestive tract tube that leads from the back of the throat to the stomach).
Saliva also functions to begin the digestion of food. Saliva contains the enzymes ptyalin and amylase, which digests starches into sugars, and lipase, which digests fats. Furthermore, saliva contains a compound called bicarbonate of soda that can neutralize acidic or alkaline compounds present in the food or drink.
The motions of mastication are stimulated by the presence of food in the mouth. A reflexive action is the relaxation of the muscles of the lower jaw, which causes some muscles that control the mouth to contract. This in turn causes the mouth to close, helping to contain food in the mouth. Mastication then becomes an orchestrated effort involving the tongue, lips, cheeks and the lower jaw to maintain the food between the grinding teeth. For example, the tongue continuously re-positions food by squeezing food against the hard upper palate of the mouth, sweeping the food forward and, by lowering the back portion of the tongue to create negative pressure, causing the food to drop down onto the lower teeth. These motions can be occurring within seconds and occur unconsciously.
The reflexive nature of mastication has been known for a long time. Over 150 years ago the rhythmic jaw movements of chewing were observed in anencephalic human infants. Anencephaly is an always lethal condition (minutes to days after birth) where the top of the skull fails to develop, leaving the brain exposed and sometimes malformed in those infants who survive to birth.