Introduction

Chapter 1. Chapter 26: Digestive System

Interactive Study Guide
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Polaris Trail

Welcome to the Interactive Study Guide for Chapter 26: Digestive System! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Drastic Measures:

For the morbidly obese, stomach-shrinking surgery is a last resort

DRIVING QUESTIONS

  • What is the anatomy of the digestive system?
  • How is food broken down and absorbed as it moves through the digestive tract?
  • What are the risks and benefits of bariatric surgery?

Driving Question 1

What is the anatomy of the digestive system?

Why should you care?

According to the American Society for Metabolic and Bariatric Surgery, 220,000 bariatric surgeries were performed in 2008, an increase of 15,000 from 2007. As of this writing, final numbers from 2009 are expected to be higher still, a pattern predicted to continue into the future. Not surprisingly, this predicted increase is attributed to two factors: an aging population and the obesity epidemic, two major risk factors for diabetes. Bariatric surgery is not, however, a panacea; to understand why not, we need first to understand the basic structure and function of the digestive system.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Draw the organs that are part of the digestive tract and describe their general function.
  2. Draw the accessory organs of the digestive system and describe their general function.
  3. Describe peristalsis and compare and contrast its function in the esophagus and in the stomach.

Infographic Focus

The Infographics most pertinent to the Driving Question are 26.1, 26.2, 26.4, 26.5, and 26.7.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The first portion of the small intestine; the duodenum receives chyme from the stomach and mixes it with digestive secretions from other organs.
Glands that secrete enzymes, including salivary amylase, which digests carbohydrates, into the mouth.
The organ system that breaks down food molecules, absorbs nutrients, and eliminates waste; it is composed of the digestive tract and accessory organs.
To break up large fat globules into smaller fat droplets that can be more efficiently chemically digested by enzymes.
The first and longest portion of the large intestine; the colon plays an important role in water reabsorption.
The expulsion of undigested matter in the form of stool.
An expandable muscular organ that stores, mechanically breaks down, and digests proteins in food.
The central pathway of the digestive system; it is a long muscular tube that pushes food between the mouth and the anus.
The organ in which the bulk of chemical digestion and absorption of food occurs.
An organ that stores bile salts and releases them as needed into the small intestine.
An organ that helps digestion by producing enzymes (such as lipase) that act in the small intestine and by secreting a juice that neutralizes acidic chyme.
The section of the digestive tract between the mouth and the stomach.
A protein-digesting enzyme that is active in the stomach.
The mechanical and chemical breakdown of food into subunits, enabling the absorption of nutrients.
The acidic soup of partially digested food that leaves the stomach and enters the small intestine.
An organ that aids digestion by producing bile salts, which emulsify fats.
The last organ of the digestive tract, in which remaining water is absorbed and solid stool is formed.
Solid waste material eliminated from the digestive tract.
Coordinated muscular contractions that force food down the digestive tract.
The act of taking food into the mouth.
Chemicals produced by the liver and stored by the gallbladder that emulsify fats so that they can be chemically digested by enzymes.
Table
2
Try again.
Correct.
Incorrect.

Draw the digestive organs through which food passes and describe their general function.

1.

In your notebook, draw the path a cheeseburger would take through your digestive tract from first bite to elimination.

Next to each organ you drew, briefly explain its function.

List on your diagram any secretions produced by these organs.

Draw the accessory organs of the digestive system and describe their general function.

2.

In your notebook, add all of the accessory organs of the digestive system to your drawing.

Next to each organ you drew, briefly explain its function.

List any excretions produced by these organs.

Describe peristalsis and compare and contrast its function in the esophagus and in the stomach.

4.

Describe peristalsis.
Peristalsis is a wavelike motion made by involuntary coordinated contraction of muscles.

Review Questions

7.

Which of the following correctly pairs an organ of the digestive tract with its secretion?

A.
B.
C.
D.
E.
2
Try again.
Correct.
Incorrect.

Driving Question 2

How is food broken down and absorbed as it moves through the digestive tract?

Why should you care?

Although the small intestine is approximately 20 feet long, most of the chemical breakdown of our food occurs in the top 10 inches. Within this short space, secretions from several organs are added, and the salad you ate is finally broken down into its smallest components—the amino acids, sugars, fatty acids, and so on that your body needs. Gastric bypass surgery diverts food around this critical region, which helps explain both why the surgery leads to weight loss and why it can lead to nutrient deficiency.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain the two functions of stomach acid.
  2. Explain the function of the liver and gallbladder in digestion.
  3. List the secretions of the pancreas and give the function of each.
  4. Explain how villi make the small intestine capable of absorbing large quantities of nutrients.
  5. Describe the primary roles of the large intestine in digestion by describing what happens to chyme as it passes through this organ.

Infographic Focus

The Infographics most pertinent to the Driving Question are 26.2, 26.4, 26.5, and 26.7.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The first portion of the small intestine; the duodenum receives chyme from the stomach and mixes it with digestive secretions from other organs.
An organ that stores bile salts and releases them as needed into the small intestine.
The acidic soup of partially digested food that leaves the stomach and enters the small intestine.
Fingerlike projections of folds in the lining of the small intestine that are responsible for most nutrient and water absorption.
A fat-digesting enzyme active in the small intestine.
An organ that helps digestion by producing enzymes (such as lipase) that act in the small intestine and by secreting a juice that neutralizes acidic chyme.
A protein-digesting enzyme that is active in the stomach.
An organ that aids digestion by producing bile salts that emulsify fats.
Cells that line organs and body cavities; in the digestive tract they sit in direct contact with food and its breakdown products.
Glands that secrete enzymes, including salivary amylase, which digests carbohydrates, into the mouth.
The organ in which the bulk of chemical digestion and absorption of food occurs.
The uptake of digested food molecules by the epithelial cells lining the small intestine.
To break up large fat globules into smaller fat droplets that can be more efficiently chemically digested by enzymes.
Chemicals produced by the liver and stored by the gallbladder that emulsify fats so that they can be chemically digested by enzymes.
Table
2
Try again.
Correct.
Incorrect.

Explain the two functions of stomach acid.

10.

List and explain the two functions of stomach acid.
Stomach acid has two functions: (1) It kills bacteria and other microorganisms on the food we ingest. (2) It facilitates protein digestion by turning three-dimensional proteins into linear chains of amino acids. This configuration makes it easier for pepsin, an enzyme produced by the stomach, to begin to digest them.

Explain the function of the liver and gallbladder in digestion.

11.

Why must fat droplets be pretreated with special chemicals before they can be broken down by digestive enzymes?
Fat droplets must be pretreated because fat is hydrophobic (meaning it does not interact well with water). Since the secretions in the small intestine are aqueous (and polar), bile salts divide large fat globules into smaller, more accessible droplets, which gives enzymes such as lipase easier access to digest the fats.

List the secretions of the pancreas and give the function of each.

14.

List the major secretions of the pancreas and their functions.
Pancreatic juice: neutralizes acidic chyme so small intestine is not damaged. Pancreatic enzymes: break down carbohydrates, proteins, fats, and nucleic acids into their smallest subunits.

Explain how villi make the small intestine capable of absorbing large quantities of nutrients.

15.

What are villi, and how do they increase the absorptive quality of the small intestine?
Villi are fingerlike projections that are present on epithelial tissue lining the small intestine. They greatly increase the surface area of the small intestine, which allows many more nutrients to be taken in by epithelial cells and deposited in the capillaries in the villi. The capillaries transport the nutrients to the bloodstream, where they are conducted to all of the cells of the body. To put it into perspective, the small intestine is about 22 feet (or 7 meters) long. The surface area is about 2,700 square feet (250 square meters), or the size of a tennis court.

Describe the primary roles of the large intestine in digestion by describing what happens to chyme as it passes through this organ.

16.

List and describe what happens to chyme, beginning with its entry into the large intestine and ending with its elimination.
Chyme enters the first section of large intestine, called the colon. Here, fiber, small amounts of water, vitamins, and other substances mix with mucus and bacteria. Most of the water and some vitamins and minerals are reabsorbed in the colon. Bacteria break down fiber and use some to nourish the epithelial cells that line the colon. Bacteria also produce essential vitamins that are absorbed through the colon.
Next, whatever material is left is pushed into the rectum. Here the waste material, or stool, as it is called at this point, is held until it is ready to be eliminated through the anus (the exit and second opening of the digestive tract).

Review Questions

17.

If you were developing a diet pill that blocked the absorption of a portion of nutrients, where would you likely target this drug to have the greatest effect?

A.
B.
C.
D.
2
Try again.
Correct.
Incorrect.

Driving Question 3

What are the risks and benefits of bariatric surgery?

Why should you care?

Gastric bypass is one of the most common forms of bariatric surgery. Although it can help morbidly obese people lose weight and consequently reduces their risk of developing diabetes and heart disease, it is not to be taken lightly. Knowing exactly how the surgery changes the structure of the digestive system is the first step to understanding why.

Gastric banding, an alternative to gastric bypass surgery, has recently been approved for people who are obese but not severely enough to be appropriate candidates for gastric bypass. It provides several advantages over gastric bypass but may not be as attractive to some patients.

Gastric bypass and gastric banding were developed to help the morbidly obese lose weight and improve their long-term health. Each carries risks, and gastric bypass carries a number of unpleasant side effects. Are the results worth the risk? Do the procedures actually work? We can answer these questions by looking at recent scientific studies.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Illustrate how gastric bypass changes the structure of the stomach and small intestine.
  2. Diagram gastric banding.
  3. Compare and contrast gastric banding with gastric bypass in terms of the structural changes each makes to the digestive system and to the passage of food through the digestive tract.
  4. Compare and contrast the mechanisms by which gastric banding and gastric bypass lead to weight loss.
  5. Discuss the advantages and disadvantages of gastric banding relative to gastric bypass.

Infographic Focus

The Infographics most pertinent to the Driving Question are 26.3, 26.6, and 26.8.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
Cells that line organs and body cavities; in the digestive tract they sit in direct contact with food and its breakdown products.
The acidic soup of partially digested food that leaves the stomach and enters the small intestine.
The uptake of digested food molecules by the epithelial cells lining the small intestine.
The first portion of the small intestine; the duodenum receives chyme from the stomach and mixes it with digestive secretions from other organs.
To break up large fat globules into smaller fat droplets that can be more efficiently chemically digested by enzymes.
Fingerlike projections of folds in the lining of the small intestine that are responsible for most nutrient and water absorption.
An expandable muscular organ that stores, mechanically breaks down and digests proteins in food.
An organ that aids digestion by producing bile salts, which emulsify fats.
An organ that stores bile salts and releases them as needed into the small intestine.
Solid waste material eliminated from the digestive tract.
A fat-digesting enzyme active in the small intestine.
The expulsion of undigested matter in the form of stool.
A protein-digesting enzyme that is active in the stomach.
The organ in which the bulk of chemical digestion and absorption of food occurs.
Chemicals produced by the liver and stored by the gallbladder that emulsify fats so that they can be chemically digested by enzymes.
Table
2
Try again.
Correct.
Incorrect.

Illustrate how gastric bypass surgery changes the structure of the stomach and small intestine.

20.

In your notebook, draw a diagram of the lower esophagus, stomach, and small intestine after gastric bypass surgery.

Diagram the gastric banding procedure.

21.

In your notebook, draw a diagram of the lower esophagus, stomach, and small intestine after gastric bypass surgery.

Compare and contrast gastric banding with gastric bypass surgery in terms of the structural changes each makes to the digestive system and to the passage of food through the digestive tract.

22.

Compare and contrast the effects of gastric banding and gastric bypass to the structure of the digestive system and to the passage of food through the digestive tract by completing the table.

Change(s) to Structure of Upper Stomach (be specific) Change(s) to Small Intestine (be specific) Change(s) to Passage of Food Through Stomach Change(s) to Passage of Food Through Small Intestine
Gastric bypass

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.
Gastric binding

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.
Table

A single mutation in a tumor suppressor gene associated with DNA repair.

Compare and contrast the mechanisms by which gastric banding and gastric bypass lead to weight loss.

23.

List the mechanism or mechanisms by which gastric bypass leads to weight loss. (Review your earlier answers and the table above if necessary.)
smaller stomach; bypass portion of small intestine

Discuss the advantages and disadvantages of gastric banding relative to gastric bypass.

26.

List and briefly describe the advantages of gastric banding over gastric bypass.
The advantages of gastric banding over gastric bypass: Gastric banding can be reversed. The food still travels through the rest of the stomach and the upper intestine (so that there is normal digestion and more nutrients, vitamins, and minerals are absorbed into the bloodstream). The patient can change how much or how little food the stomach can hold. There are also fewer complications because gastric banding is less invasive and adjustable.

Review Questions

28.

Both gastric banding and gastric bypass:

A.
B.
C.
D.
2
Try again.
Correct.
Incorrect.

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