Connect: Chapter 46
The movement of food through the digestive system is very controlled. Why is it necessary to control the passage of food through the gastrointestinal tract? Select all of the statements that apply.
--Essential nutrients require specific amounts of time to be drawn from food sources and absorbed by the body. --Chyme must not be released too quickly from the stomach if there is not enough room in the small intestine.
Most animals have evolved to digest food via extracellular digestion in a cavity of some sort. Select the most plausible reason(s) that this method of digestion is superior to intracellular digestion.
--Intracellular digestion cannot support the metabolic demands of an active animal for extended periods. --Intracellular digestion does not provide a mechanism for storing large quantities of food so that an animal can digest it slowly while going about its other activities. --Extracellular digestion protects the interior of the cells from the actions of hydrolytic enzymes and allows animals to consume large prey or large pieces of plants.
You are a research assistant at a pharmaceutical company. Your group has been asked to develop an effective laxative that (1) provides bulk and (2) is nonirritating to the intestinal mucosa. Identify valid reasons why these requests are important. (Check all that apply.)
--The innermost lining of the alimentary canal lumen from our mouth to our anus is made of moist epithelial membranes. If this were to become irritated or destroyed it could cause a GI tract disorder. --Bulk-forming laxatives draw water into the stool to create large soft stools. The larger stools help trigger the bowel to contract and move the stools out. --The mucosa is very important for secreting mucus, digestive enzymes, and hormones, absorbing the end products of digestion into the blood, and protecting against infectious diseases, so it is imperative that the laxative is nonirritating to the intestinal mucosa.
As food travels through our digestive system it passes through a series of regions and organs. Select the correct order of food passage past the mastication stage using the numbering system below 1. Esophagus 2. Large Intestine 3. Oral cavity 4. Small intestine 5. Stomach
1, 5, 4, 2
Analyze the following statement and determine why you agree or disagree with its premise: "Nutrients that are ingested and digested can only by utilized by cells if they are absorbed."
AGREE: Without absorption, we cannot access any of the nutrients we ingest.
How do carnivores and herbivores differ?
Carnivores and herbivores require different enzymes to digest their food.
What events enhance digestion in the stomach?
Central nervous system stimulation, secretion of gastrin, and stomach distention.
When chyme enters the duodenum, gastric secretion increases.
False
One function of HCl secreted in the stomach is to convert pepsinogen into the active enzyme pepsin. Why don't stomach cells simply secrete pepsin instead?
If cells produced active pepsin, they would digest their own cellular proteins.
Which of the following is the correct order for the major parts of the gastrointestinal tract?
Mouth, esophagus, stomach, small intestine, large intestine
If a person has eaten recently and the pH of the duodenum is 3 or higher, what events will occur?
Secretion of hydrochloric acid Secretion of pepsin Stimulation of gastric glands would continue
Oral rehydration solutions that contain both salt and glucose are highly effective in treating severe dehydration caused by diarrhea and vomiting. However, glucose or salt alone are not effective. Why?
Sodium transport and glucose transport are coupled in the small intestine so that glucose accelerates absorption of salt and water.
Why is it efficient for the body to digest foods in the order that it does when one considers the function of the nutrients?
The first requirement is readily-available energy, followed by building blocks for repair and longer-term energy, then protection and longest-term storage of energy.
How is the movement of food through the esophagus most accurately characterized?
The muscular contractions are wave-like.
The liver is not directly responsible for the digestion process, but releases bile that is helpful in the breakdown of fats. What would be a consequence if the liver was not able to release bile?
The small intestine would not be able to absorb fats.
Specific hormones are released from the small intestine and travel through the circulatory system. If these hormones are not released what do you predict would be the initial consequence?
The stomach will continue to release pepsin and hydrochloric acid.
Classify the locations of digestion into voluntary and involuntary stages. 1. Esophagus 2. Large intestine 3. Mouth/oral cavity 4. Pharynx 5. Small intestine 6. Stomach
Voluntary: 3, 4; Involuntary: 1, 2, 5, 6
The large intestine concentrates undigested material by
absorption of salts and water across the epithelial surface of the lumen.
Salivary glands secrete _________blank to start the digestion of _________blank.
amylase; starch
Which type of nutrient can pass across epithelial cells without any expenditure of ATP?
fat
The process of emulsification is crucial to the digestion of
lipids
Involuntary muscle contractions which move a bolus through the gastrointestinal tract are called
peristalsis.
The glandular secretions involved in digestion that would most likely be released as inactive precursors are
protein-digesting enzymes
In the stomach, food processing continues and secretions from stomach glands aid the initial digestion of
proteins.
In the mammalian digestive system, what is the primary site of nutrient absorption?
small intestine
What is peristalsis?
smooth muscle contractions that move food through the alimentary canal
Secretin is released from the duodenum in response to
the presence of chyme in the duodenum.
The surface area of the small intestine is dramatically increased due to the presence of _________blank on the luminal surface.
villi and microvilli