Chapter 23

By clicking on this link (http://openstaxcollege.org/ I/fooddigestion) , you can watch a short video of what happens to the food you eat as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?

Visit this site (http://openstaxcollege.org/I/ fooddigestion2) for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.

Watch this animation (http://openstaxcollege.org/I/ stomach1) that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?

By watching this animation (http://openstaxcollege.org/I/foodgroups), you will see that for the various food groups-proteins, fats, and carbohydrates- digestion begins in different parts of the digestion system, though all end in the same place. Of the three major food classes (carbohydrates, fats, and proteins), which is digested in the mouth, the stomach, and the small intestine?

Watch this video (http://openstaxcollege.org///liver) to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and wastes. At rest, about \(1500 \mathrm{~mL}\) of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?

Which of these organs is not considered an accessory digestive structure? a. mouth b. salivary glands c. pancreas d. liver

Which of the following organs is supported by a layer of adventitia rather than serosa? a. esophagus b. stomach C. small intestine d. large intestine

Which of the following membranes covers the stomach? a. falciform ligament b. mesocolon C. parietal peritoneum d. visceral peritoneum

Which of these processes occurs in the mouth? a. ingestion b. mechanical digestion c. chemical digestion d. all of the above

Which of these processes occurs throughout most of the alimentary canal? a. ingestion b. propulsion c. segmentation d. absorption

Which of the following stimuli activates sensors in the walls of digestive organs? a. breakdown products of digestion b. distension c. \(\mathrm{pH}\) of chyme d. all of the above

Which of these statements about reflexes in the GI tract is false? a. Short reflexes are provoked by nerves near the GI tract. b. Short reflexes are mediated by the enteric nervous system. c. Food that distends the stomach initiates long reflexes. d. Long reflexes can be provoked by stimuli originating outside the GI tract.

Which of these ingredients in saliva is responsible for activating salivary amylase? a. mucus b. phosphate ions c. chloride ions d. urea

Which of these statements about the pharynx is true? a. It extends from the nasal and oral cavities superiorly to the esophagus anteriorly. b. The oropharynx is continuous superiorly with the nasopharynx. C. The nasopharynx is involved in digestion. d. The laryngopharynx is composed partially of cartilage.

Which structure is located where the esophagus penetrates the diaphragm? a. esophageal hiatus b. cardiac orifice C. upper esophageal sphincter d. lower esophageal sphincter

Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis? a. voluntary phase b. buccal phase c. pharyngeal phase d. esophageal phase

Which of these cells secrete hormones? a. parietal cells b. mucous neck cells c. enteroendocrine cells d. chief cells

Where does the majority of chemical digestion in the stomach occur? a. fundus and body b. cardia and fundus c. body and pylorus d. body

During gastric emptying, chyme is released into the duodenum through the ________. a. esophageal hiatus b. pyloric antrum c. pyloric canal d. pyloric sphincter

Parietal cells secrete ________. a. gastrin b. hydrochloric acid c. pepsin d. pepsinogen

In which part of the alimentary canal does most digestion occur? a. stomach b. proximal small intestine C. distal small intestine d. ascending colon

Which of these is most associated with villi? a. haustra b. lacteals C. bacterial flora d. intestinal glands

What is the role of the small intestine's MALT? a. secreting mucus b. buffering acidic chyme c. activating pepsin d. preventing bacteria from entering the bloodstream

Which part of the large intestine attaches to the appendix? a. cecum b. ascending colon c. transverse colon d. descending colon

Which of these statements about bile is true? a. About \(500 \mathrm{~mL}\) is secreted daily. b. Its main function is the denaturation of proteins. c. It is synthesized in the gallbladder. d. Bile salts are recycled.

Pancreatic juice ________. a. deactivates bile. b. is secreted by pancreatic islet cells. c. buffers chyme. d. is released into the cystic duct.

Where does the chemical digestion of starch begin? a. mouth b. esophagus c. stomach d. small intestine

Which of these is involved in the chemical digestion of protein? a. pancreatic amylase b. trypsin c. sucrase d. pancreatic nuclease

Where are most fat-digesting enzymes produced? a. small intestine b. gallbladder C. liver d. pancreas

Which of these nutrients is absorbed mainly in the duodenum? a. glucose b. iron C. sodium d. water

Explain how the enteric nervous system supports the digestive system. What might occur that could result in the autonomic nervous system having a negative impact on digestion?

Offer a theory to explain why segmentation occurs and peristalsis slows in the small intestine.

What prevents swallowed food from entering the airways?

Explain the mechanism responsible for gastroesophageal reflux.

Describe the three processes involved in the esophageal phase of deglutition.

Explain how the stomach is protected from selfdigestion and why this is necessary.

Describe unique anatomical features that enable the stomach to perform digestive functions.

Explain how nutrients absorbed in the small intestine pass into the general circulation.

Why is it important that chyme from the stomach is delivered to the small intestine slowly and in small amounts?

Describe three of the differences between the walls of the large and small intestines.

Why does the pancreas secrete some enzymes in their inactive forms, and where are these enzymes activated?

Describe the location of hepatocytes in the liver and how this arrangement enhances their function.

Explain the role of bile salts and lecithin in the emulsification of lipids (fats).