Using Figure 23.2, match the following:
8) Absorptive cells that line the intestinal tract.
9) Cell type specialized to secrete mucus into the lumen of the intestinal tract.
10) Structures that increase the absorptive area of the small intestine.
11) Wide lymph capillary located in the villus.
12) Paneth cells are found here.
13) Wavelike smooth muscle contractions that move foodstuffs through the alimentary tube.
14) Chemical or mechanical process of breaking down foodstuffs to substances that can be absorbed.
15) Enzymatic breakdown of any type of food molecule.
16) Process by which the products of digestion pass through the lumen of the gastrointestinal tract into the blood or lymph.
Using Figure 23.3, match the following:
17) Produces enzymes that break down all categories of foodstuffs.
18) Increases surface area for absorption via villi and microvilli.
19) Bacteria process undigested chyme from the small intestine.
20) Only digestive structure with three muscle layers.
21) Receives blood via the hepatic portal system.
22) Contains the brush border enzymes that complete digestion of carbohydrates and proteins.
23) Main function is to filter and process the nutrient-rich blood delivered to it.
24) Produces intrinsic factor.
25) Produces a mucoid barrier.
17. Answer: D (pancreas)
Page Ref: 885; Fig. 23.1
18. Answer: B (s. intestines)
Page Ref: 878; Fig. 23.1
19. Answer: E (l. intestine)
Page Ref: 893; Fig. 23.1
20. Answer: C (stomach)
Page Ref: 869; Fig. 23.1
21.Answer: A (liver)
Page Ref: 881; Fig. 23.1
22. Answer: B (s. intestines)
Page Ref: 878; Fig. 23.1
23. Answer: A (liver)
Page Ref: 881; Fig. 23.1
24. Answer: C (stomach)
Page Ref: 870; Fig. 23.1
25. Answer: C (stomach)
Page Ref: 870; Fig. 23.1
1) Food is contained in the gastrointestinal tract from the time of ingestion until it is completely digested and the waste prepared for elimination.
2) The circular folds of the small intestine enhance absorption by causing the chyme to spiral, rather than to move in a straight line, as it passes through the small intestine.
3) As food passes through the digestive tract, it becomes less complex and the nutrients are more readily available to the body.
4) Some of the microbes that often invade other organs of the body are rarely found in the stomach. The reason for this is the presence of HCl.
5) Kupffer cells are found in the liver and are responsible for removing bacteria and worn-out cells.
6) The pharyngeal-esophageal phase of swallowing is involuntary and is controlled by the swallowing center in the thalamus and lower pons
7) All the chemical and mechanical phases of digestion from the mouth through the small intestine are directed toward changing food into forms that can pass through the epithelial cells lining the mucosa into the underlying blood and lymphatic vessels.
8) Pepsinogen is the precursor to the gastric enzyme for protein digestion and is secreted by the parietal cells.
9) The main chemical activity of the stomach is to begin the digestion of proteins.
10) The major role of absorption in the ileum is to reclaim bile salts to be recycled back to the liver.
12) Peyer's patches are found in the submucosa of the distal end of the small intestine.
13) The myenteric nerve plexus provides the major nerve supply to the GI tract wall and controls GI motility.
19) The intrinsic ability of visceral smooth muscle to exhibit the stress-relaxation response is termed plasticity.
20) The stomach's contractile rhythm is set by pacemaker cells found in the spinal cord.
21) The major stimulus for production of intestinal fluid is distention or irritation of the intestinal mucosa by hypertonic or acidic chyme.
22) Most nutrients are absorbed through the mucosa of the intestinal villi by active transport.
23) Ionic iron is actively transported into the mucosal cells, where it binds to the protein ferritin, a phenomenon called the mucosal iron barrier.
26) The soft palate rises reflexively to open the nasopharynx when we swallow food.
Fill-in-the-Blank/Short Answer Questions
1) The longest portion of the small intestine is the ________.
6) The portal triad contains ________.
7) ________ cells are found in the sinusoids of the liver, and they remove debris from the blood as it flows past.
8) ________ peritoneum covers the external surfaces of most digestive organs.
9) The ________ ligament anchors a tooth in the alveolus of the jaw.
10) The ________ phase of gastric secretions occurs before food enters the stomach.
12) Compare and contrast the structure and function of a premolar and a molar.
13) What are chylomicrons?
14) What is heartburn and what causes it?
Answer: Heartburn is the discomfort felt in the chest area when the acidic gastric juices get regurgitated into the esophagus. This may happen when someone has eaten or drunk too much, or it can be caused by extreme obesity or the discomfort of pregnancy. It is sometimes due to obstructions or structural faults in the esophagus as well.
Page Ref: 864-865
15) Name two regions of the digestive tract where mechanical food breakdown processes are very important. Name two organs that are primarily food conduits. Name the organ where protein digestion is begun. Name the organ where fat digestion begins.
Answer: Mechanical food processes are very important in the mouth (mastication) and stomach (contractions causing mixing of food into chyme). The esophagus and pharynx are primarily food conduits. Protein digestion begins in the stomach. Fat digestion begins in the small intestine.
Page Ref: 853-854
16) Define constipation and diarrhea. Note possible causes of each.
Answer: Watery stools are called diarrhea. Constipation is a condition in which too much water has been absorbed and the stool becomes hard and difficult to pass. Any condition (such as irritation of the colon by bacteria) that rushes food residue through the large intestine before that organ has had sufficient time to absorb the remaining water is known as diarrhea. Constipation may ensue from the lack of fiber in the diet, improper bowel habits, laxative abuse, or anything that decreases motility.
Page Ref: 895
17) Assume you have been chewing a piece of bread for 5 or 6 minutes. How would you expect its taste to change during this time? Why?
18) Name the three pairs of major salivary glands. Describe their relative locations and their microscopic differences.
Answer: The parotid glands lie anterior to the ears between the masseter muscle and the skin. They open into the vestibule next to the second molars of the upper jaw. The submandibular glands lie along the medial aspect of the mandibular body. Their ducts run beneath the mucosa of the oral cavity floor and open at the base of the lingual frenulum. The small sublingual glands lie anterior to the submandibular glands under the tongue. They open via many ducts into the floor of the mouth. Parotid glands contain only serous cells; submandibular glands have equal numbers of serous and mucous cells; and sublingual glands are mostly mucous cells.
Page Ref: 860
19) Why is it necessary for the stomach contents to be so acidic? How does the stomach protect itself from digestion?
Answer: HCl is necessary for the activation and optimal activity of pepsin, and it kills many of the bacteria ingested with food. Mucous cells in the lining of the stomach secrete an alkaline mucus that clings to the stomach wall and helps to shield it from the acid. The epithelial cells of the mucosa are joined together by tight junctions that prevent gastric juice from leaking into underlying tissue layers. Damaged epithelial cells are shed and quickly replaced by cell division.
Page Ref: 870
20) Identify three ways the small intestine is modified to increase the surface area for digestion and absorption.
Answer: The plicae circulares, villi, and microvilli are modifications of the small intestine for digestion and absorption. The plicae circulares are circular folds of the mucosa and submucosa. They force chyme to move spirally through the lumen. The villi are fingerlike projections of the mucosa. They increase the absorptive surface area. Microvilli are projections of the plasma membrane of the absorptive cells of the mucosa that bear intestinal digestive enzymes. They also increase surface area and enhance absorption.
Page Ref: 878
21) How is digestive activity provoked after eating? What activates the secretion of digestive juices into the lumen or hormones into the blood?
Answer: Sensors (mechanoreceptors and chemoreceptors) located in the walls of the gastrointestinal tract respond to stretching by the introduction of food into the lumen. Also, the sensors are able to respond to changes in solute concentration and pH as well as the presence of substrates and end products of digestion.
Page Ref: 854
22) How is salivation controlled?
23) What is bile and where is it produced? What is its digestive function? Where is it stored and concentrated?