Pharmacology · chapter 29 · Introduction to the Digestive System
Introduction to the Gastrointestinal System and Oral Cavity
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
What the GI tract provides
Together with the accessory organs, the GI tract provides nutrition and hydration to the body through the processes of ingestion, digestion, absorption, and metabolism.
The mechanical phase
The complex digestive process starts with the mastication process as a person uses their teeth to bite and chew food. This is referred to as the mechanical phase of digestion.
The stomach makes chyme
The stomach further mixes the bolus and blends it with acidic gastric juices and pepsin to digest protein. This process produces chyme.
Bile and bicarbonate protect the intestine
These substances help protect the small intestine from being destroyed by the acidic chyme.
Where nutrients and water are absorbed
Nutrients are absorbed into the blood or lymph in the small intestine. Water, along with some vitamins and minerals, is absorbed in the large intestine.
Small intestine absorbs most food
The small intestine is responsible for the absorption of 90%–95% of food with the aid of the pancreatic enzymes (amylase, trypsin, and lipase) and enzymes secreted in the intestine (maltase, sucrase, lactase, and peptidase).
What the large intestine does
The large intestine receives unabsorbed and undigested food material (waste products), absorbs water and electrolytes, and forms feces.
Bile helps absorb fats
The liver makes and secretes bile (which includes cholesterol, bile acids, and bilirubin). Bile helps emulsify fats into fatty acids, aiding lipid absorption.
Slower transit in older adults
The transit time slows again in older adults due to an aging GI system with decreased GI peristalsis (muscular contractions and relaxations that propel food through the GI tract), motility, and intestinal blood flow.
Constipation and diarrhea
The aging GI system, coupled with medications that may alter absorption of food and fluids, can cause the most common GI complaints: constipation and diarrhea.
Mastication comes first
The teeth are vital for breaking up food (mastication) for digestion and absorption. Mastication is the essential first step in digestion.
What saliva does
Saliva helps protect the teeth from cavity-causing bacteria as well as maintain the pH balance in the mouth, but the most appreciated role of saliva is that of digestive aid.
Painful oral disorders
Common disorders such as “cold sores” from a herpes simplex virus (HSV), canker sores, mucositis, and candida infections may affect the oral cavity. These can be painful conditions.
What the nursing history covers
The nursing health history should include questions about oral health and dental practices, home-based treatments, and the use of both over-the-counter and prescription medications.
Terms to know
- Ingestion
- Ingestion is the process of taking in food, generally by the mouth.
- Digestion
- Digestion is a systematic process that breaks down food into its simplest form to promote absorption and moves this food and fluids through the GI tract.
- Taste buds
- Taste buds are specialized cells that communicate the sense of taste (sweet, salty, sour, bitter, and umami) to the brain.
- alimentary canal
- The GI tract is also known as the alimentary canal.
Practice questions
Stuck on select-all-that-apply? How to take them one option at a time.
The graded version needs JavaScript. Every question is below anyway, with the answer and why.
Every question here, with the answer
An older adult client reports frequent constipation. The client takes several daily medications. Which explanation by the nurse is supported by GI physiology?
- Constipation only occurs in older adults.
- Older adults absorb more water in the stomach.
- Transit time speeds up with age, so stool leaves too fast.
- An aging GI system with slower peristalsis, plus medications, can cause constipation.
Answer: An aging GI system with slower peristalsis, plus medications, can cause constipation.
Transit time slows in older adults because of decreased peristalsis, motility and intestinal blood flow, and together with medications this can cause constipation. Transit does not speed up with age, and constipation can affect people of any age.
A client has painful sores in the mouth and is eating very little. What is the nurse's priority action?
- Switch the client to a liquid diet without assessing.
- Tell the client to rinse with salt water and eat anyway.
- Document that the client refuses meals.
- Take a thorough nursing history and inspect the oral cavity.
Answer: Take a thorough nursing history and inspect the oral cavity.
A thorough nursing history finds the source of the pain so it can be relieved and the client can eat, and inspection of the oral cavity can uncover problems with biting and chewing. The other options skip assessment.
A nurse is taking a health history from a client with an oral cavity disorder. Which topics should the history include? Select all that apply.
- Home-based treatments
- Oral health and dental practices
- Only the client's favourite foods
- Over-the-counter medications
- Prescription medications
Answer: Home-based treatments, Oral health and dental practices, Over-the-counter medications, Prescription medications
The nursing health history includes oral health and dental practices, home-based treatments, and both over-the-counter and prescription medications. Favourite foods alone would miss those areas.
A student asks where most nutrients from food are absorbed. What is the correct answer?
- Esophagus
- Large intestine
- Stomach
- Small intestine
Answer: Small intestine
The small intestine absorbs 90%–95% of food with the help of pancreatic and intestinal enzymes. Minimal absorption of nutrients occurs in the stomach, the large intestine mainly absorbs water and electrolytes, and the esophagus moves food to the stomach.
Which statements about saliva are accurate? Select all that apply.
- It helps maintain the pH balance in the mouth.
- It is produced only when a person is asleep.
- It is made by the gallbladder.
- It helps protect the teeth from cavity-causing bacteria.
- It contains amylase to help break down starches.
Answer: It helps maintain the pH balance in the mouth., It helps protect the teeth from cavity-causing bacteria., It contains amylase to help break down starches.
Saliva protects the teeth, maintains oral pH, and contains amylase that breaks down starches. Food increases saliva secretion, and it is made by the salivary glands, not the gallbladder, which stores bile.
A client asks why chewing food well matters. Which response by the nurse is accurate?
- Chewing only affects taste.
- Food is digested only in the large intestine, so chewing does not matter.
- Chewing is the essential first step in digestion.
- Chewing is needed only for liquids.
Answer: Chewing is the essential first step in digestion.
Mastication breaks up food for digestion and absorption and is the essential first step in digestion. The other options are not supported: digestion begins in the mouth and continues through the stomach and small intestine.
Where every quote comes from
Section 29.1 Introduction to the Gastrointestinal System and Oral Cavity 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.