Skip to ContentGo to accessibility page

Key Terms

absorption
the passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals
alimentary canal
the digestive tract from the mouth to the anus
amylase
an enzyme in the saliva and pancreatic juice that catalyzes the breaking down of starch, glycogen, and related polysaccharides into more simple and readily usable forms of sugar
aspiration
the inhalation of fluid or solid objects into the lower airways or lungs
bile
alkaline solution produced by the liver and important for the emulsification of lipids
chyme
the mixture of partly digested food and digestive secretions found in the stomach and small intestine during the digestion of a meal; it is a varicolored, thick, nearly liquid mass
digestion
the process by which food is broken down mechanically and chemically in the gastrointestinal tract and converted to absorbable forms
epiglottis
the uppermost cartilage of the larynx located immediately posterior to the root of the tongue; covers the entrance of the larynx when a person swallows and prevents food or liquids from entering the airway
gastritis
acute or chronic inflammation of the stomach lining
gastroesophageal reflux disease (GERD)
a common condition in which acid from the stomach (gastric and/or duodenal) flows back into the esophagus, causing discomfort and, in some instances, damage to the esophageal lining
hydrochloric (HCl) acid
an inorganic acid normally present in gastric juice; destroys fermenting bacteria that might cause intestinal tract disturbances
ingestion
the process of taking substances (particularly food) into the gastrointestinal tract
lipase
pancreatic enzyme that breaks down triglycerides into free fatty acids and glycerol to be used in the body
lower esophageal sphincter
the sphincter around the opening of the esophagus into the stomach; separates these linked organs from each other and prevents the reflux of stomach acids into the esophagus; also called the cardiac sphincter
mastication
chewing; involves coordination of the large temporal, masseter, and pterygoid muscles as well as other smaller muscles of the mandible and tongue to grind food under the influence of the mandibular division of cranial nerve V
metabolism
sum of all of the body’s chemical reactions
pepsin
the chief enzyme of gastric juice, which converts proteins into proteoses and peptones; formed by the chief cells of gastric glands and producing its maximum activity at a pH of 1.5–2
pepsinogen
the antecedent of pepsin existing in the form of granules in the chief cells of gastric glands
peristalsis
muscular contractions and relaxations that propel food through the GI tract
protease
pancreatic enzyme that breaks down proteins in the diet; also provides protection from organisms that may live in the intestines, such as certain bacteria and yeast
saliva
the fluid secretion of the salivary glands and oral mucous gland that begins the process of food digestion; moistens food for tasting, chewing, and swallowing; initiates digestion of starches; moistens and lubricates the mouth; acts as a solvent for excretion of waste products; also known as spit or spittle
upper esophageal sphincter
a sphincter that keeps the opening between the posterior pharynx and the proximal esophagus closed, except during swallowing; maintained principally by the cricopharyngeal muscle
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution-NonCommercial-ShareAlike License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute OpenStax, and must distribute any derivative works under the same license.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/pharmacology/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/pharmacology/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Apr 23, 2026 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.