Exam 3 Review:  Chapter 23:  General Terms

digestion - The process by which food is converted into nutrient molecules which can be absorbed and assimilated by the body; it is accomplished in the digestive system by the mechanical and enzymatic breakdown of foods into simpler chemical compounds.

absorption - The process by which the molecules of growth and nutrition are taken in across a membrane and conveyed to cells, tissues and organs; the movement is accomplished by a variety of molecular processes including diffusion, osmosis, passive and active transport.  [Note:  From the perspective of chemistry:  a process in which one substance permeates another; a fluid permeates or is dissolved by a liquid or solid.  This is a part of physiological absorption.]

digestive system - The gastrointestinal tract = alimentary canal (mouth pharynx, esophagus, stomach, small intestine, large intestine) and the accessory digestive structures (lips, cheeks, tongue, teeth) and glands (salivary glands, pancreas, liver) regarded as an integrated system responsible for the ingestion, mechanical and chemical breakdown, and absorption of foods.

gastrointestinal tract = GI tract = alimentary canal - The mucous membrane-and smooth muscle- lined tube of the digestive system through which food passes, in which digestion takes place, and from which wastes are eliminated; it extends from the mouth to the anus and includes the pharynx, esophagus, stomach, and small and large intestines.  aka - digestive tract, gut tube.

accessory structures - The additional connected parts which contribute to the main function of a major organ or system; in the gastrointestinal tract, the mouth (lips, cheeks, salivary glands, tongue, teeth) and the small intestine (pancreas, liver) are associated with such collateral components.

ingestion - The voluntary process of  taking foods or liquids into the body by means of the mouth for digestion or absorption.  aka - eating.

secretion - The physiological process of synthesizing and releasing some functionally specialized substance (especially one which is not a waste) from a gland or cell; at the molecular level, a variety of processes are involved including diffusion, osmosis, passive and active transport mechanisms or exocytosis.

mixing - The mechanical physiological process of combining or blending diverse ingredients or components into one mass or mixture so that constituent parts or elements are diffused among each other and coalesced.

propulsion - The process of driving or propelling something forward or away; in the gastrointestinal tract, food is moved by deglutition (swallowing) and peristalsis.

motility - Having the power to move; in the gastrointestinal tract, propulsive movement is powered by muscular contractions (deglutition = swallowing and peristalsis).

mechanical digestion - The muscular process by which solid food is broken down into smaller particles by the chewing action of the jaws, teeth and tongue in the oral cavity and by the mixing waves created in the stomach; at the same time the food is softened and moistened by the digestive juices (saliva in the mouth, gastric juice in the stomach); reduction in the size of ingested food particles increases the surface area of the particles available to be acted upon by digestive enzymes; it does not alter the molecular structure of the nutrient molecules.

chemical digestion - The physiological process by which food = nutrient molecules have their molecular structure modified by interacting with substances secreted by various digestive glands and tissues; in general, nutrient molecules are broken down into smaller constituent molecules which will be more easily absorbed in the intestines.  [Note:  There is a limited amount of indiscriminant acid hydrolysis of nutrients in the stomach due to the action of gastric HCl; carbohydrates are split into di- and mono-saccharides by salivary amylase in the mouth and pancreatic amylase in the duodenum and disaccharides are split into monosaccharides by disaccharidases (brush border enzymes) in the duodenum; proteins are split into smaller peptides and ultimately into individual amino acids by pepsin in the stomach and pancreatic proteases (trypsin, chymotrypsin, carboxypeptidase) in the duodenum; lipids are split into glycerol and fatty acids by lingual lipase in the mouth and pancreatic lipase and phospholipase in the duodenum; nucleic acids are split into nucleotides by pancreatic nucleases and nucleotides are split into smaller constituents by nucleotidases (brush border enzymes) in the duodenum.]

defecation - The mechanical muscular process of voiding or eliminating feces from the bowels; a complex process involving the smooth muscles of the large intestine, especially those of the sigmoid colon, rectum and anal canal; it is usually initiated consciously but coordinated by the autonomic nervous system.

1. the six processes of Digestion.

        (1)  Ingestion (2)  Propulsion {peristalsis} (3) Mechanical Digestion (4) Chemical Digestion (5) Absorption (6) Elimination {defecation}

                               [Note:  food acquisition processes are important, but outside the parameters of this course.]

2. the organs of the GI tract in the sequence in which they occur starting with the mouth and ending at the anus (include the regions of each organ, ex: oropharynx and laryngopharynx of pharynx).

 4. the hormones, digestive enzymes, and other chemicals related to digestion secreted by the salivary glands, stomach, small intestine, liver/gall bladder, and pancreas.

5. several physical or mechanical processes of digestion.

          mastication (chewing) - bolus formation - deglutition (swallowing) - peristalsis (propulsion) - gastric churning - intestinal segmentation - haustral churning (compaction) - mass peristaslis - defecation

20.  the sphincters of the GI tract in the sequence they occur, starting with the mouth and ending at the anus.

          upper esophageal sphincter → lower esophageal sphincter = cardiac sphincter → pyloric sphincter → ileo-cecal valve → internal anal sphincter →
external anal sphincter

Describe:

3. the process of digestion for carbohydrates (starch), proteins, nucleic acids, and lipids.  (Hint: You may use summary chemical equations to do this).

7.  the secretion and reabsorption of the water involved in digestion.  Indicate the specific gastrointestinal organs involved in the secretion or reabsorption of the water involved in digestion.

8.  the type of movement associated with each organ of the digestive (gut) tube.