Pharmacology · chapter 29 · Introduction to the Digestive System
Introduction to the Esophagus and Stomach
The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.
Key points
Upper sphincter prevents aspiration
The upper esophageal sphincter, also known as the oropharyngeal sphincter, is located between the pharynx and the mouth. A properly functioning upper esophageal sphincter is vital to prevent aspiration of food and liquids into the airways.
The epiglottis
The epiglottis is a sheetlike flap that closes over the trachea to prevent food and fluids from entering the lungs (aspiration).
The lower esophageal sphincter
The lower esophageal sphincter is located where the esophagus meets the stomach. It is commonly referred to as the gastroesophageal sphincter because of its location between the esophagus and the stomach.
When a sphincter fails
If either of the esophageal sphincters is not functioning properly, ingested food, fluids, and acidic stomach contents may move backward into the esophagus, causing irritation or damage to the tissues.
Common esophageal problems
Common problems with the esophagus include GI inflammation, esophagitis, gastroesophageal reflux disease (GERD), esophageal varices, and hiatal hernia.
Pyloric sphincter problems
A malfunctioning pyloric sphincter may lead to delayed gastric emptying, known as gastroparesis. In another type of dysfunction, the pyloric sphincter empties the gastric contents too quickly into the small intestine, causing bloating and discomfort.
What makes the stomach release acid
Histamine, gastrin (released from G cells), and acetylcholine are substances necessary for the parietal cells to produce and release hydrochloric (HCl) acid.
Acid and vitamin B12
The stomach produces 1500–2000 mL of HCl acid daily, and an adequate amount of it is necessary for vitamin B 12 to be extracted from food sources. In addition, intrinsic factor, which is crucial for vitamin B 12 absorption, is produced and released by the parietal cells.
The proton pump
Within the parietal cells, hydrogen–potassium (H + -K +) ATPase enzymes comprise the proton pump that generates and secretes HCl acid in response to acetylcholine, histamine, or gastrin binding to receptors on the parietal cells.
Acid also controls microorganisms
The acidic environment further aids digestion by controlling harmful microorganisms such as bacteria or viruses in the stomach.
Mucus protects the stomach
One of the main ways the stomach keeps itself from becoming irritated by the HCl acid is by producing mucus via the goblet cells.
Dangers of gastritis
Gastritis can be painful and impair digestion and may cause life-threatening complications, such as bleeding or perforation.
Prostaglandin E2 protects the lining
Gastric mucosal cells counteract the HCl acid by secreting prostaglandin E 2, a strong, lipid-rich molecule that stimulates gastric mucus and pancreatic bicarbonate. Prostaglandins ensure adequate submucosal perfusion.
Too much ibuprofen
Nurses should instruct clients that taking too much ibuprofen can be harmful to the stomach and kidneys and can lead to bleeding due to altered platelet aggregation.
Terms to know
- gastroparesis
- A malfunctioning pyloric sphincter may lead to delayed gastric emptying, known as gastroparesis.
- epiglottis
- The epiglottis is a sheetlike flap that closes over the trachea to prevent food and fluids from entering the lungs (aspiration).
- gastritis
- This condition is commonly referred to as gastritis and may lead to serious problems as the stomach lining becomes irritated and inflamed.
- pyloric sphincter
- The pyloric sphincter separates the stomach from the first part of the small intestine, the duodenum.
Practice questions
Stuck on select-all-that-apply? How to take them one option at a time.
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Every question here, with the answer
A client takes large amounts of over-the-counter ibuprofen for back pain. Which teaching should the nurse give?
- Ibuprofen protects the stomach lining.
- Ibuprofen only affects the liver.
- Too much ibuprofen can harm the stomach and kidneys and lead to bleeding.
- Ibuprofen is safe in any amount because it is sold over the counter.
Answer: Too much ibuprofen can harm the stomach and kidneys and lead to bleeding.
Ibuprofen inhibits prostaglandin synthesis, and prostaglandins protect the stomach, so too much can injure the stomach and kidneys and cause bleeding through altered platelet aggregation. Being sold over the counter does not make any amount safe.
A client with gastritis asks why it is taken seriously. Which complication should the nurse mention?
- Improved absorption of vitamin B12
- Faster healing of the esophagus
- Bleeding or perforation
- Increased appetite
Answer: Bleeding or perforation
Gastritis can be painful, impair digestion, and cause life-threatening complications such as bleeding or perforation. The other options are not complications of an inflamed stomach lining.
Which substances stimulate the parietal cells to produce hydrochloric acid? Select all that apply.
- Gastrin
- Histamine
- Acetylcholine
- Prostaglandin E2
- Mucus
Answer: Gastrin, Histamine, Acetylcholine
Histamine, gastrin and acetylcholine are needed for parietal cells to produce and release HCl acid. Prostaglandin E2 and mucus protect the stomach against acid rather than stimulating it.
A client reports a burning sensation and sour taste after meals. The nurse suspects the lower esophageal sphincter is not closing properly. What is happening?
- Food is entering the trachea.
- Food is moving too slowly out of the stomach.
- Bile is not being produced.
- Acidic stomach contents are moving backward into the esophagus.
Answer: Acidic stomach contents are moving backward into the esophagus.
If an esophageal sphincter does not function properly, food, fluids and acidic stomach contents can move backward into the esophagus and irritate or damage it. Food entering the airway is aspiration, which the upper sphincter and epiglottis prevent.
Which statements about protection of the stomach lining are accurate? Select all that apply.
- Prostaglandin E2 stimulates gastric mucus and pancreatic bicarbonate.
- Drugs that inhibit prostaglandin synthesis can injure the stomach.
- Excess HCl acid strengthens the mucosal membrane.
- Pepsin protects the stomach lining from acid.
- Goblet cells produce mucus that protects the stomach from acid.
Answer: Prostaglandin E2 stimulates gastric mucus and pancreatic bicarbonate., Drugs that inhibit prostaglandin synthesis can injure the stomach., Goblet cells produce mucus that protects the stomach from acid.
Mucus from goblet cells and prostaglandin E2 protect the lining, so drugs that block prostaglandins can injure the stomach. Excess acid and pepsin can erode the mucosal membrane rather than protect or strengthen it.
A client has delayed gastric emptying. Which structure is most likely malfunctioning?
- Salivary glands
- Epiglottis
- Pyloric sphincter
- Upper esophageal sphincter
Answer: Pyloric sphincter
A malfunctioning pyloric sphincter may lead to delayed gastric emptying, called gastroparesis. The upper esophageal sphincter and epiglottis protect the airway, and the salivary glands do not control stomach emptying.
Where every quote comes from
Section 29.2 Introduction to the Esophagus and Stomach of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.
The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.