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M1 GI > GI Physiology/Histology > Flashcards

GI Physiology/Histology Flashcards

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1
Q

How does parasympathetic stimulation cause vasodilation?

A

Parasympathetic stimulation increases metabolic activity, which casues indirect vasodilation

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2
Q

The gastrointestinal peptide that inhibits gastrin-stimulated growth of the gastric mucosa is:

A

Secretin

In most ways, gastrin and secretin have antagonistic effects.

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3
Q

The major stimulus for release of glucose-dependent insulinotropic hormone (GIP) is:

A

Intraduodenal carbohydrates.

Although digested proteins and fats can stimulate GIP secretion, the strongest stimulus is carbohydrate (sugars and starches) entering the duodenum.

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4
Q

Is slow wave frequency influenced by GI hormones?

A

No

Slow wave frequency is an inherent property of GI smooth muscle cells. While the amplitude can be influenced by hormones and neurotransmitters, the frequency is unaltered by nerves or hormones.

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5
Q

A congenital lack of enteric ganglia in the distal colon, as in Hirschprung’s disease, results in:

A

Tonic contraction of the distal colon causing blockage of fecal material.

Large intestine smooth muscle has high tone, it likes to stay contracted. Enteric nerves are required to stimulate relaxation. Loss of these nerves, as in Hirshsprung’s results in the muscle remaining contracted and blocking passage of chyme or feces to more distal segments.

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6
Q

Inhibitors of gastrointestinal smooth muscle contraction, such as vasoactive intestinal peptide (VIP) and nitric oxide (NO), act by:

A

increasing smooth muscle cell cAMP or cGMP levels.

Elevated cyclic nucleotides (cAMP and cGMP) antagonize calcium by enhancing dephosphorylation of myosin light chains.

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7
Q

Two vagus nerve dependent activities of esophagus and stomach

A

esophageal peristalsis and receptive relaxation of the proximal stomach

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8
Q

achalasia

A

Intrinsic nerves of the lower esophageal sphincter are not causing relaxation of the lower esophageal sphincter

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9
Q

Cutting vagal branches that innervate the small intestine usually results in?

A

little change in contractile activity.

The enteric nervous system, without additional inputs from the CNS, is capable of normal small bowel motility. The CNS has little control of small bowl motility.

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10
Q

The rectosphincteric reflex is initiated by?

A

Distention of the rectum

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11
Q

The migrating motor complex (MMC) ceases upon?

A

Consuming a meal

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12
Q

A patient receiving chemotherapy for a osteosarcoma (bone cancer) and develops severe nausea, abdominal pain and diarrhea. Several days after completing treatment, his gastrointestinal symptoms begin to subside. The resolution of his symptoms most likely reflects repair of which of the following cell types?

A

Gastric and intestinal mucosal epithelial cells

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13
Q

Of the major gastrointestinal hormones, the release of which one is stimulated by consumption of each class of macronutrient (carbohydrates, fats, and proteins)?

A

Glucose-dependent insulinotropic peptide (GIP)

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14
Q

Actions of secretin

A

-Inhibition of gastric acid secretion
-Stimulation of pepsinogen secretion (“everything stimulates pepsinogen secretion”)
-Inhibition of gastric emptying
-Inhibition of gastric mucosal growth

Does not stimulate gastric motility - secretin is inhibitory

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15
Q
A

Reabsorption of Na+ from the primary secretion

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16
Q

What feature(s) of cells comprising striated ducts within salivary glands play(s) a role in the ability to modify glandular secretions?

A

Numerous basal membrane infoldings and mitochondria

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17
Q

The most common mutation responsible for cystic fibrosis produces a defect in Cl- transport across epithelial cells, which also reduces the transmembrane movement of cations such as Na+. This results in the production of saliva containing higher than normal concentrations of NaCl. Which of the following cells in salivary glands is most likely affected in individuals who have this mutation?

A

Striated duct cell

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18
Q

A pathologist notes structures near the edges of secretory acini in a biopsy specimen from the submaxillary gland that appear as serous cells capping mucous acini. What is the most accurate explanation for these structures?

A

They are fixation artifacts termed serous demilunes

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19
Q

Which mechanism of secretion is commonly seen in major salivary glands?

A

Merocrine

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20
Q
A

Parotid gland

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21
Q
A

Secretory acinus

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22
Q
A

Blood vessel

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23
Q

What excitatory agents increase release of AcH and substance P

A

-CCK
-Gastin releasing peptide (bombesin)

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24
Q
A

B. Submucosal plexus nerves

Mostly involved with secretions (regulating mucosa and submucosa as opposed to regulating smooth muscle)

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25
Which of the following regions of the GI tract are the most dependent on extrinsic nerves for regulation? A. Lower esophagus and distal stomach B. Lower esophagus and proximal stomach C. Small intestine and large intestine D. Upper esophagus and distal stomach E. Upper esophagus and external anal sphincter
E. Upper espohagus and external anal sphincter | Upper esophagus and external anal sphincter are skeleta muscle
26
D. Decreased amounts of skeletal muscle along the upper third of esophagus
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28
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Treatments for achalasia
30
D. The enteric nerves of the lower esophageal sphincter
31
C. Narrowing of the pyloric opening (pyloric stenosis) ## Footnote In infants, pyloric stenosis leads to **projectile vomiting**
32
What does the manometry illustrate?
Esophageal spasms
33
Movement that grinds and mixes foods
Antral systole
34
Half-time for material in the small intestines
3-4 hours
35
Half-time for material in the colon
12-48 hours ## Footnote Lots of individual variation
36
Half-time for liquids in the stomach vs. solids
Liquids - ~20 min. Solids - ~ 120 min.
37
C. Dysfunciton of gastric enteric neurons ## Footnote Diabetic gastroparesis, or delayed gastric emptying, is a complication of diabetes where the stomach doesn't empty food properly, often due to nerve damage from high blood sugar
38
B. Reduced rate of gastric emptying ## Footnote Secretin increase - inhibits peristalsis
39
Effect of increased acidity in stomach vs. duodenum
Secretin - long term response (several minutes) Enteric NS response - immediate
40
B. A period of fasting | Eating inhibits migrating motor complex (MMC)
41
Where is the orad of the stomach
42
B. This condition is caused by congenital absence of intramural ganglia in the rectum
43
What helps keep the bacterial content of the duodenum and small intestines low?
The migratory motor complex (MMC) ## Footnote Diabetes can cause a disruption due to neuropathy of the enteric NS
44
D. High fat meal ## Footnote Liquids>isotonic>hypertonic>carbs>protein>fats
45
How does botulinum toxin effect the synapse?
46
A. Decreased colonic smooth muscle activity ## Footnote Progesterone decreases smooth muscle contractions during pregnancy (estrogen has the opposite effect)
47
Section of the lip is prepared after biopsy with H&E staining. ID structure indicated by arrows
B. Minor salivary glands
48
A. Circumvallate papilla
49
Taste buds
50
Surface for food movement
51
A. Lingual tonsil
52
B. Intercalated duct
53
B. Mixed acinus | Serous demilunes around periphery of acinus
54
A or E ## Footnote Striated/intercalated ducts are intralobular ducts
55
List the histological tissue layers of the alimentary canal from the luminal surface toward the periphery
Mucosa -> submucosa -> muscularis externa -> serosa/adventitia | Adventitia when retroperitoneal
56
D. Small intestine (duodenum) | Duodenum ID'd by Brunners glands (submucosal glands that secrete bicarb)
57
D. Muscularis mucosae
58
E. Metaplasia
59
Lymph nodule
60
Muscularis externa
61
Esophagus - stratified squamous Stomach - simple columnar
62
C. Gastric pits
63
What are the cells that line the gastric pits?
Surface mucous cells - secrete mucous
64
C. Fundus of the stomach | Shallow pits - deep glands
65
Parietal cells - HCl/IF
66
Chief cells - pepsinogen/lipase
67
C. Chemoreception ## Footnote Open enteroendocrine cells signal the closed enteroendocrine cells to secrete gastrin and secretin
68
Secrete into the interstitial space/blood stream
69
D. Infection | *H. pylori* is most common cause of peptic ulcers
70
E. Urease
71
E. Brush border (microvilli)
72
Lymphocytes
73
Goblet cells
74
Simple columnar
75
Lamina propria
76
B. Goblet cells | Secrete substances in the glycocalyx ## Footnote PAS stains glycogen, glycoprotein, proteoglycans
77
Lacteals
78
D. Paneth cells | Secrete zymogens/defensins
79
C. Ileum
80
M cells - antigen processing/presenting
81
Crypts of Lieberkuhn
82
Submucosa | Larger vessels are characteristically in the submucosa
83
What tissue layer are macrophages found in the alimentary canal?
The lamina propia
84
D. Colon
85
E. Appendix
86
What histological layer of the mucosa are parietal cells found?
The lamina propria
87
Stimuli for acid secretion in the stomach:
## Footnote ECL = enterochromaffin like cells
88
What acts on parietal cells to inhibit acid secretion?
Somatostatin and prostaglandins inhibits the proton-potassium ATPase
89
Secondary messengers of parietal cells
90
Cells that secrete pepsin
Chief cells | Stimulated to secrete pepsin by vagus innervation
91
Where are G-cells found and what do they secrete?
G-cells are found in the mucosa of the **antrum** and secrete **gastrin**
92
Effects of gastrin
-Stimulates proton secretion by parietal cells -Stimulates growth of gastric mucosa (hypertrophy and hyperplasia) -Increases gastric motility
93
Stimuli for gastrin secretion
-Stomach distension -Alkinlization -AA's (phenylalanine and tryptophan) -Vagal stimulation (mediated by GRP)
94
Actions of cck
95
What cells release CCK?
I-cells in the duodenum and jejunem
96
Do triglycerides stimulate CCK release?
No ## Footnote Only fatty acids and monoglycerides (as well as AA's and small proteins)
97
Where is secretin released? | And what cells
98
Action of secretin on pancreatic duct cells
Secretin causes pancreatic duct cells to **increase bicarbonate secretion**
99
What cells produce and secrete somatostatin?
D-cells found throughout GI tract and nerves
100
What cells release glucose-dependent insulinotropic peptide (GIP)?
K cells of duodenum and jejunum
101
Action of GIP
Stimulates insulin release from pancreas Blunts proton secretion
102
Why is oral glucose metabolized faster than IV glucose?
IV glucose does not stimulate K cells to release glucose-dependent insulinotropic peptide (GIP)
103
Actions of vasoactive intestinal pepetide
-Relaxation of smooth muscule (Important for LES) -Raises pH (similar to secretin - stimulates pancreatic bicarb secretion) -Inhibits gastric proton secretion
104
WDHA syndrome
105
Why is erythromycin used to Tx gastroporesis?
Eryhtromycin binds motilin receptors to improve gastric motility
106
What hormones can be found to some degree along the entire length of the GI tract (from antrum to ileum)
-Motilin -VIP -Somatostatin
107
Salive is always (hyper/hypotonic) to plasma?
Saliva is always hypotonic to plasma
108
What stimulates sodium reabsorption in the salivary duct cells?
Aldosterone
109
What type of stimulation produces saliva with a greater mucus content?
Sympathetic stimulation
110
Oxyntic glands contain:
1. Parietal (oxyntic cells) 2. Chief (peptic) cells 3. Mucous neck cells (proliferative - migrate up to beocome surface epithelia or down to become oxyntic or chief cells)
111
Pyloric glands contain:
1. Mucous cells 2. G cells 3. Stem cells in neck region
112
What g-coupled protein do gastrin and ACh stimulate in the parietal cell?
Gq proteins
113
What g-coupled protein does histamine stimulate in the parietal cell?
Gs
114
What g-coupled protein do somatostatin and prostaglandins stimulate?
Gi to decrease cAMP and subsequently decrease H+ secretion by parietal cells
115
In the corpus of the stomach, the vagus stimulates:
-parietal cells -ECL cells (enhances gastric-acid secretion by increasing histamine release) -D cells (promotes gastric-acid secretion by inhibiting release of somatostatin)
116
Gastric phase of acid secretion
117
Intestinal phase of gastric acid secretion
118
Stimuli that inhibit acid secretion but increase pepsinogen secretion
1. Secretin in response to duodenal acid 2. CCK in response to duodenal fatty acids
119
Stimuli that increase parietal acid secretion and increase pepsinogen release by chief cells
1. Cholinergic fibers - Vagal stimulation during cephalic and gastric phases. 2. Gastrin 3. Acid in contact with gastric mucosa (Local cholinergic reflex)
120
What syndrome causes duodenal ulcer, increased gastric emptying, steatorrhea, and GERD
Zollinger-Ellision syndrome
121
What channels are responsible for chloride reabsorption in salivary gland's luminal membrane?
Cl is absorbed by a Cl/HCO3 exchanger and CFTR Cl channel in the lumen membrane.
122
Parasympathetic activation of secretion
1. Activation of ion transport pathways. 2. Contraction of myoepithelial cells in acini and intercalated ducts. (ejects fluid) 3. Vasodilation brings more blood to the glands. 4. Increased oxygen and glucose utilization causes additional metabolic vasodilation. 5. Release of kallikrein leads to vasodilation via bradykinin production.
123
Which of the following does not stimulate pepsinogen secretion by gastric Chief cells?
Elevated release of paracrine somatostatin
124
Which of the following is not a function of gastric acid secretion:
Stimulating the absorption of nutrients in the small intestine
125
Low intragastric pH (less than 3.0):
Stimulates release of somatostatin from gastric mucosal D cells ## Footnote Somatostatin release from gastric mucosal D cells is stimulated by falling pH. Somatostatin inhibits gastrin release from G cells.
126
A. Bicarbonate ## Footnote Argument for mucus here
127
What is gastric accomodation
Reflex where the stomach relaxes and expands in response to food intake, allowing it to hold a larger volume without a significant rise in pressure
128
C. Plasma secretin ## Footnote E. Gastric accomodation regulated by the vagovagal reflex
129
Enzymes that metabolize PPIs
CYP3A4 and CYP2C19. ## Footnote PPIs inhibit CYP2C19, which may reduce activation of clopidogrel (a prodrug), decreasing its antiplatelet effect.
130
Bile salts are absorbed by a sodium coupled transport mechanism in which region of the GI tract?
Ileum
131
A. The gastric antrum
132
Receptor for gastrin in the pancrease
CCK-a receptor - stimulates pancreatic fluid secretion
133
C. ACh D. Gastrin
134
D. Acids and fats (secretin and CCK have highest degree of potentiation) ## Footnote Stimulus for secretin - acid Stimulus for CCK - fats
135
B. Secretin stimulated fluid secretion
136
C. High enzyme content and low volume (gastric phase of digestion)
137
A. Chloride decreases and bicarbonate increases
138
All digestive secretions are isotonic to plasma except for?
Saliva = hypotonic
139
A. Steatorrhea
140
D. Highly elevated plasma amylase and lipase
141
B. CCK
142
E. Chloride
143
D. Urinary bilinogen ## Footnote Decreased urinary bilinogen can indicate inability of the liver to synthesize/release bile
144
A. The pH of hepatic bile increases | Not bile in the gallbladder ## Footnote **Secretin** increases bicarbonate secretion in hepatic bile ducts (same mechanism as in pancreatic ducts) Not D becuase the duodenocolic reflex increases colonic motility
145
E. Conjugated bile acids
146
B. Reduced gall gladder emptying ## Footnote Cholestasis increases likelihood of gallstone formation
147
What protects against gall stones?
Phosphatidyl choline and bile acid
148
C. Bile acids
149
B. The rate of hepatocyte extraction of bile acids from portal blood
150
Secretory granules
151
Pancreas
152
Gallbladder
153
Which of the following cells found in the liver are normally associated with storage of lipids and vitamin A? These same cells play a role in liver injury due to excessive alcohol consumption.
Ito cell | Aka stellate cells
154
A 68-year-old man with congestive heart failure developed liver cirrhosis. Hepatocytes in which region of his liver would you expect to show the earliest necrotic changes with normal tissue being replaced by fibrous connective tissue?
Zone 3
155
Sinusoidal capillary
156
Pancreatic acinar cells are stimulated to release zymogen granules by what hormone?
Cholecystikinin
157
What cells in the liver are part of the innate immune system and as such, function as antigen-presenting cells as well as phagocytic cells?
Kupffer cells | Macrophages
158
What tissue layer is absent in the gallbladder?
Muscularis mucosae
159
What ducts are absent in the pancreas but can be found in the parotid glands?
Striated ducts
160
What are the first cells that make up the intercalated ducts of the pancreas?
Centroacinar cells
161
The muscularis mucosae is divided into:
An inner circular layer and outer longitudinal layer
162
What is the underlying mechanism of Dubin-Johnson syndrome?
Deficiency in a canalicular ABC transporter | Canalicular ABC transporter = bile acid secretion ## Footnote Sinusoidal ABC transporter = bile acid reabsorption
163
An 11-year-old boy presents with balance problems and difficulty with night vision. His mother says he had foul-smelling stools and failure to thrive as an infant. Physical examination reveals poor muscle coordination, ataxia, decreased proprioception, and vibratory sensation. Blood smears showed the presence of dysmorphic erythrocytes and blood labs showed abnormal values for total cholesterol of 55mg/dl (reference range ~200mg/dl), Vitamin E, 0.5µg/mL (reference range 5-17 µg/mL) and Vitamin A 6µg/dL (reference range 30-95 µg/dL). The patient most likely has an inherited inactivating mutation in ?
Microsomal Triglyceride Transfer Protein (MTP)
164
A 15-year-old girl limits her diet to carrots, tomatoes, green vegetables, bread, pasta, rice, and skim milk. She has an increased risk for vitamin A deficiency because its absorption requires the presence of?
Triglycerides
165
An individual has developed pancreatitis, and with it, steatorrhea. The patient also reports problems with his night vision, although visual acuity appears normal. Another expected finding in this patient would be which of the following? A. Nystagmus B. Easy bruising C. Loss of teeth D. Orange tonsils
B. Easy bruising
166
What is the most likely mechanism by which cirrhosis and other diseases of the liver can produce steatorrhea?
Reduced production and excretion of bile acids
167
What is the main function carried out by bile acids/bile salts in adults?
To serve as emulsifiers of dietary lipids
168
What enzyme is required to be present to prevent inacation of pancreatic lipase by bile salts/acids?
Pancreatic co-lipase
169
Differentiating between different types of gall stones
170
B. Lactase ## Footnote Lactose intolerance presents after cessation of breastfeeding - usually earliest onset 4-5 years old
171
C. SGLT1
172
In a meal containing glucose, glucose absorption would be most significantly increased by:
drinking an isotonic saline solution
173
How is fructose absorbed in the intestinal lumen? | What channel
GLUT5
174
C. Jejunum
175
Where is the primary site of active absorption for iron, folate, and calcium?
The duodenum
176
D. Sucrase (aka sucrase-isomaltase) | Liniked to **CLL**
177
B. SGLT1
178
D. Pancreatic amylase and isomaltase (alpha-dextrinase)
179
E. Zinc
180
Celiac disease and sucrase deficiency
181
Which of the following mechanisms contributes least colonic fluid absorption? A. Electrogenic Na channel activity B. Na-couple solute transport C. Coupled Na/H and Cl/HCO3 exchangers D. Electronetural Na/Cl absorption
B. Na-coupled solute transport
182
Removal of the ileum due to inflammatory bowel disease/Crohn's disease will result in:
increased stool volume ## Footnote Diarrhea due to bile acids not being absorbed and acting as osmolytes
183
In addition to the distal nephron, which GI cell is an aldosterone sensitive tissue?
Colonic enterocytes | Also occurs somewhat in the rectum
184
Short chained fatty acids (SCFA) are a product of bacterial metabolism in the colon. Active secretion of which ion helps to neutralize the pH effects of SCFAs?
Bicarbonate
185
D. Nutrient malabsorption
186
E. Gastrinoma ## Footnote A low stool osmotic gap indicates secretory diarrhea (vs. osmotic diarrhea which would have a high osmotic gap).
187
Dumping syndrome
188
Postprandial hypotension
189

M1 GI (4 decks)

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