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Gastrointestinal
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Constructing Objectives |
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Functions
and Regulation of GI Tract GI
2. For carbohydrates, differentiate the processes of ingestion, digestion,
absorption, secretion, and excretion, including the location in the GI tract
where each process occurs. Repeat the analysis for proteins and fats. GI
3. Identify the approximate normal volumes of fluid entering and leaving the
gastrointestinal tract daily. GI
4. Define the major characteristics and temporally relate the cephalic,
gastric, and intestinal phases of GI tract regulation. GI
5. Describe the four classes of luminal stimuli that trigger GI reflexes. GI
6. Describe the histoanatomical characteristics of the enteric nervous
system. Given either a cross section or a longitudinal section of the
intestine, name and locate the myenteric and submucosal plexus. GI
7. Contrast the
sympathetic and parasympathetic modulation of the enteric nervous system and
the effector organs of the GI tract. GI
8. Classify the following
enteric nervous system neurotransmitters as excitatory or inhibitatory:
norepinephrine, acetylcholine, CCK, VIP, histamine, and somatostatin. GI
9. Describe the terms
“long reflex” and “short reflex” with respect to the GI tract. GI
10. Describe the similarities
and differences in regulating gastrointestinal function by nerves, hormones,
and paracrine regulators. Include
receptors, proximity, and local vs. global specificity. GI
11. Identify the cell type and
anatomical location of the endocrine cells secreting gastrin, secretin, and
cholecystokinin (CCK), GIP, and motilin. GI
12. Identifiy families to which
gastrin, secretin, and CCK and other (non-GI) hormones belong. GI
13. Define the concept of “incretins,”
and state two gastrointestinal hormones believed to function in this manner. GI 14. Describe function of somatostatin and histamine as paracrine regulators of acid secretion in the stomach.
Salivary
Glands GI
16. State the substrates and
digestion products of salivary amylase (ptyalin). GI
17. Identify the stimuli and
cell types involved in GI secretion of mucous, and identify the function of
salivary mucus. GI
18. State three types of
stimuli that increase salivary secretion. GI
19. State the components of the
saliva important in oral hygiene, and identify the role of salivary
secretions in eliminating heavy metals. Esophagus GI
21. Describe the origin and
consequence of the high basal tone found in the upper esophageal sphincter (UES)
and lower esophageal sphincter (LES). GI
22. State the stimulus that
initiates the swallowing sequence. Identify the point at which the swallowing sequence becomes
automatic (independent of voluntary control). GI
23. Contrast the patterns of
external and internal innervations of the upper, middle, and lower
esophagus. GI
24. Describe the pressure
changes that occur in the esophagus as a bolus of food moves from the
pharynx to the stomach, including the pressures immediately oral and aboral
to the bolus, and the pressures in the upper and lower esophageal
sphincters. GI
25. Contrast primary and
secondary peristalsis based on initiating event, voluntary control, reflex
propagation, and regions of the pharynx and esophagus involved. GI 26. Contrast the lower espohageal tone, innervation, and motility defects that lead to heartburn with those leading to achalasia.
Stomach GI
28. Contrast the Na+,
K+, and Cl- concentrations of gastric secretion with
that of plasma at low and at high gastric secretion rates.
Identify the cell types that mediate this change. GI
29. Identify the protein
component of chief cell secretions. GI
30. Describe the generation of
an “alkaline tide” in the hepatic portal venous system following
ingestion of a meal. GI
31. Describe the role, if any,
of HCl in the gastric digestion of carbohydrates, proteins, and fats. GI
32. Describe the pH of the
stomach in the fasted state, and outline the time course and causes of the
pH changes in the two hours after ingestion of a protein meal. GI
33. State the stimuli for
pepsinogen release and the mechanism for activating pepsinogen, and describe
the digestion products of pepsin activity. GI
34. Describe the role of the
stomach in preventing pernicous anemia. GI 35.
Describe the regulation of H+-K+ ATPase, the
stimuli for activation, and process of activation, including vesicular
fusion with the luminal plasma membrane. GI
36. Describe the mechanism of
gastric H+ generation and secretion, including the role of K+,
Cl‑HCO3, carbonic anhydrase, H+-K+
ATPase and Na+-K+ ATPase. GI
37. Describe the modulation of
gastric acid secretion by the enterochromafin-like cell (ECL cell) and the
control of this process (including potentiation) by vagal stimulation,
gastrin, histamine, and somatostatin. GI
38. Describe the pathways, if any, for the gastric absorption of
electrolytes, water, lipids, amino acids, and carbohydrates. GI
39. State the mechanism for
damage to the gastric mucosal barrier by aspirin, bile acids, and GI
40. Identify the stimuli that
a) increase gastrin release and b) inhibit gastrin release. GI
41. State the effects of acid,
fat, and solutions of high osmolarity in the duodenum on gastric secretion,
and describe the mechanisms by which these effects regulate gastric
secretion. GI
42. Define receptive relaxation
of the stomach and state mechanism and consequence. GI
43. Describe origin and form of
electrical activity and the progression of peristaltic waves across the body
and antrum of the stomach. Include
their role in mixing and propulsion of gastric contents and how the
frequency is altered by the volume of gastric contents. GI
44. Predict the effects of a)
meal content (osmolarity, fat content, etc.), b) particle size, and c)
volume on the rate of gastric emptying, including duodenal feedback. GI
45. Describe the causes of peptic ulcer disease.
Pancreas
GI
47. Describe the mechanisms by
which chyme from the stomach is neutralized in the duodenum. GI
48. Describe the mechanism by
which pancreatic zymogens are activated in the small intestine. GI
49. List the stimuli that
release a) secretin and b) CCK and the cellular mechanisms by which these
agents control pancreatic secretion. Include any synergistic effects between CCK and secretin. GI
50. Describes the role of CFTR
in pancreatic ductular secretion, and predict the consequences of cystic
fibrosis on the GI system. GI 51. State the effects of the autonomic nerves to the pancreas and vago-vagal reflexes on pancreatic secretion.
Bile GI
53. Describe the cellular
mechanisms for the hepatic uptake, conjugation, and secretion of bile salts
and bilirubin. GI
54. Describe the role of CCK in
causing release of bile from the gall bladder, including the effects on the
sphincter of Oddi. GI
55. Describe the amphipathic
structure of bile acids, and predict how this property assists the digestion
of fats. GI
56. State the difference
between primary and secondary bile acids. GI
57. Contrast the physical state
of an emulsion with a micellar solution, and explain the conditions for the
formation of emulsifications and miceles in the duodenum. GI
58. Define enterohepatic
circulation. GI
59. Describe the mechanism of
reabsorption of bile acids in the early portion of the small intestine with
the mechanism found in the later part of the small intestine. GI
60. Predict the effects of an
increase in hepatic portal vein bile acid concentration on the rate of bile
secretion, bile acid synthesis, and diseases of the gallbladder.
Small
Intestine GI
62. List the chemical classes
of the carbohydrates entering the duodenum from the stomach, and identify
mechanisms mediating further digestion and absorption across the apical and
basolateral membranes of the intestinal epithelia.
Include pancreatic secretions and brush-border enzymes. GI
63. Predict the small intestine
and colonic consequence of a deficiency in the enzyme lactase, and identify
ethnic groups who commonly exhibit this deficiency. GI
64. List the chemical classes
of the proteins entering the duodenum from the stomach, and identify
mechanisms mediating further digestion and absorption across the apical and
basolateral membranes of the intestinal epithelia.
Include pancreatic secretions and brush-border enzymes. GI
65. Contrast the secondary
active transport of amino acids with that of di- and tri-peptides, including
the ion used as the energy source. GI
66. List the chemical
classes of the lipids entering the duodenum from the stomach, and identify
mechanisms mediating further digestion and absorption across the apical and
basolateral membranes of the intestinal epithelia.
Include the roles of pancreatic lipase, colipase, and micelles. GI
67. Describe the role of the
endoplasmic reticulum in processing lipids absorbed across the apical
membrane of enterocytes. GI
68. Describe the composition
and formation of chylomicrons, their movement across the enterocyte
basolateral membrane, and the route of entry into the cardiovascular system. GI
69. Define steatorrhea, and
predict the effects of steatorrhea on the absorption of fat-soluble
vitamins. GI
70. Describe the absorption of
water-soluble vitamins, including the role of intrinsic factor in the
absorption of vitamin B12. GI
71. Describe the changes in
osmolarity that occur in chyme as it passes from the stomach through the
duodenum and colon, and identify the cause of this change. GI
72. Describe the pathways, if
any, by which sodium ions, water, iron, and calcium are absorbed in the
small intestine and colon.
Large
Intestine GI
74. Define “dietary fiber”
and list sources commonly found in the US diet. GI 75. Identify substrates and products of colonic bacterial metabolism, and predict the impact of metabolites on the rate and composition of intestinal gas formation (flatus). GI
76. Describe the production and
absorption of short chain fatty acids in the colon. Intestinal
Motility GI
78. Describe the role of
“interstitial cells of Cajal” in generation of electrical slow waves,
and predict the consequence of the frequency gradients of electrical slow
waves occurring within the intestinal tract. GI
79. Explain the functional
significance of ongoing activity of enteric inhibitory motor neurons to
intestinal circular muscle. GI
80. Contrast the patterns of
intestinal motility seen during the absorptive phase (segmentation) with
that of the post-absorptive phase between meals [the migrating motility
complex (MMC)]. GI 81. Contrast the effects of parasympathetic and sympathetic nervous activity in modulating small intestinal motility. GI
82. Describe the effects of
distension on small intestinal motility. GI
83. State effects of increased
pressure in the ileum and cecum on the ileocecal sphincter, including
defining the term “gastroileal reflex.” GI
84. Compare colonic motor
activity with the motor activity in the small intestine. GI
85. Contrast the colonic motor
activity during a “mass movement” with that during haustral shuttling
and the consequence of each type of colonic motility. GI
86. Describe the sequence of
events occurring during reflexive defecation, differentiating those
movements under voluntary control and those under intrinsic control.
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Functions
and Regulation of GI Tract