GASTROINTESTINAL- Physiology Flashcards
1
Q
Which cells produce cholecystokinin?
A
I cells
2
Q
Where are I cells located?
A
Duodenum, Jejunum
3
Q
What is the effect of cholecystokinin?
A
↑ Pancreatic secretion
↑ Gallbladder contraction
↓ gastric emptying
↑ sphincter of Oddi relaxation
4
Q
Who regulates cholecystokinin?
A
↑ fatty acids, amino acids
5
Q
Where does cholecystokinin acts? what is its effect?
A
Acts on neural muscarinic pathways to cause pancreatic secretion
6
Q
Which cells secrete gastrin?
A
G cells
7
Q
Where are G cells located?
A
Antrum of stomach
8
Q
Actions of Gastrin
A
↑ gastric H+ secretion
↑ growth of gastric mucosa
↑ gastric motility
9
Q
What stimulates Gastrin secretion?
A
↑ by stomach distention/ alkalinization, amino acids, peptides, vagal stimulation
10
Q
Who decreases Gastrin secretion?
A
Decreased by stomach pH
11
Q
In which situations do we find Gastrin secretion increased?
A
↑↑ in Zollinger Ellison syndrome
↑ by chronic PPI use
12
Q
Who are potent stimulators of Gastrin?
A
Phenylalanine and tryptophan
13
Q
What do K cells produce?
A
Glucose dependet insulinotropic peptide
14
Q
Where are Glucose dependent insulinotropic peptide cells producers?
A
Duodenum
Jejunum
15
Q
K cells type of secretions
A
Exocrine
Endocrine
16
Q
Action of K cells exocrine secretion
A
↓ gastric H+ secretion
17
Q
Action of K cells endocrine secretion
A
↑ insulin release
18
Q
What regulates Glucose dependent insulinotropic peptide secretion?
A
↑ by fatty acids, amino acids, oral glucose
19
Q
Alternative name for Glucose dependent insulinotropic peptide?
A
Gastric inhibitory peptide (GIP)
20
Q
Why oral glucose is used more rapidly than equivalent given by IV?
A
Due to GIP
21
Q
Where is Motilin produced?
A
Small intestine
22
Q
What is the action of Motilin?
A
Produces migrating motor complexes (MMCs)
23
Q
When is Motilin increased?
A
In fasting state
24
Q
Which drugs are Motilin receptor agonists?
A
Erytromycin
Used to stimulate intestinal peristalsis
25
What do S cells secrete?
Secretin
26
Where are S cells found?
Duodenum
27
Action of Secretin
↑ pancreatic HCO3- secretion
↓ gastric acid secretion
↑ Bile secretions
28
What stimulates the Secretin production?
↑ by acid, fatty acids in lumen of duodenum
29
Which factor neutralizes gastric acid in duodenum? and What for?
↑ HCO3-, allowing pancreatic enzymes to function
30
Which cells produce Somatostatin?
D cells
31
Where do we find D cells?
Pancreatic islets, GI mucosa
32
What is the effect of Somatostatin?
↓ gastric acid and pepsinogen secretion
↓ pancreatic and small intestine fluid secretion
↓ gallbladder contraction
↓ insulin and glucagon release
33
What increases the production of Somatostatin?
↑ by acid
34
What decreases Somatostatin secretion?
↓ by vagal stimulation
35
How is Somatostatin consider?
Inhibitory hormone
36
Antigrowth hormone effects
Somatostatin
37
Explain somatostatin antigrowth hormone effects
Inhibits digestion and absorption of substances needed for growth hormone
38
Action of Nitric oxide
↑ smooth muscle relaxation, including lower esophageal sphincter (LES)
39
In which disease is nitric oxide implicated to be lost?
In ↑ Lower esophageal sphincter tone of Achalasia
40
What is VIP?
Vasoactive intestinal polypeptide
41
Source of VIP
Parasympathetic ganglia in sphincters, gallbladder, small intestine
42
What is the effect of VIP?
↑ intestinal water and electrolyte secretion
| ↑ relaxation of intestinal smooth muscle and sphincter
43
What factors regulate VIP?
↑ by distention and vagal stimulation
| ↓ by adrenergic input
44
What is a VIPoma?
non-α, non β islet cell pancreatic tumor that secretes VIP
45
Findings of VIPoma
Copious Watery Diarrhea
Hypokalemia
Achlorhydia (WDHA syndrome)
46
Findings of VIPoma
Copious Watery Diarrhea
Hypokalemia
Achlorhydia (WDHA syndrome)
47
GI secretory products
Intrinsic factor
Gastric acid
Pepsin
HCO3-
48
Secretion of Parietal cells
Intrinsic factor
| Gastric acid
49
Vitamin B12 binding protein
Intrinsic factor
50
Where is B12 uptake?
Terminal ileum
51
What is the result of autoimmune destruction of parietal cells?
Chronic gastritis
| Pernicious anemia
52
Who secretes gastric acid?
Parietal cells
53
What is the function of gastric acid?
↓ stomach pH
54
What factors increase Gastric acid secretion?
↑ by histamine, ACh, gastrin
55
Factors that decrease Gastric acid secretion
↓ by somatostatin, GIP, prostaglandin, secretin
56
What is a gastrinoma? What does it cause?
Gastrin sectreting tumor that Causes high levels of acid secretion and ulcers refractory to medical therapy
57
Which cells are the source of pepsin?
Chief cells
58
Action of pepsin
Protein digestion
59
Who regulates pepsinogen secretion?
↑ by vagal stimulation, local acid
60
Process of pepsin activation
Inactive pepsinogen → pepsin by H+
61
Which cells produce HCO3-?
Mucosal cells
| Brunner glands
62
Where are mucosal cells producers of HCO3- producers located?
Stomach, duodenum, salivary glands and pancreas
63
Where do we find Brunner cells?
Duodenum
64
Neutralizes acid secretion in GI tract
HCO3-
65
What regulates HCO3- secretion?
↑ by pancreatic and biliary secretion with secretin
66
Normally where is HCO3- located?
Is trapped in mucus that cover the gatric epithelium
67
Who stimulates G cells to relase Gastrin?
Gastrin Release Peptide (GRP)
68
Who liberates ACH and GRP ?
Vagus nerve
69
What is the effect of Atropine in parietal cells?
Blocks vagal stimulation of parietal cells inhibiting ACh
70
Although Atropine blocks vagal nerve stimulation, why doesn't affect G cells?
Because it only blocks ACh, not GRP which is the peptide that stimualtes G cells Gatrin production
71
Once Gastrin is secreted by G cells what is next?
Secreted to circulation, then positively stimualtes Enterochromaffin-like cells (ECL cells) who produce histamine, then it stimulates Parietal cells to produce HCl
72
Which special cells are located in Body of stomach?
Parietal cells and Chief cells
73
Special cells located at Antrum
D cells
Mucous cells
G cells
74
Which special cells are located at duodenum?
I cells
S cells
K cells
75
Which is the way Gastin increases acid secretion?
Primary through its effects on enterochromaffin like cells (leading to histamine release) rather than through its direct effect on parietal cells
76
In parietal cells, which are the ACh receptors?
M3 receptor
77
In parietal cell, For Gastrin which are the receptors?
CCKb receptor
78
Who stimualte Gastric Parietal cells?
```
ACh
Gastrin
Histamine
Prostaglandins/ misoprostol
Somatostatin
```
79
In parietal cells, which are Histamine receptors?
H2 receptors
80
Negative signals for Parietal cells
Prostaglandins/ misoprostol
| Somatostatin
81
In parietal cells once M3 and CCKb receptors are stimulated, who is next positively stimulated?
Gq → IP3/ Ca2+ → stimulating H+/K+ ATPase of parietal cells → H+ liberation
82
In parietal cells once Prostaglandins/ misoprostol and Somatostatin reach the receptor, who is next negatively inhibited?
Gi→ cAMP→ inhibitng H+/K+ ATPase of parietal cells
83
In parietal cells once H2 receptors are stimulated, who is next positively stimulated?
Gs → cAMP→ stimulating H+/K+ ATPase of parietal cells
84
What does Proton pump inhibitors inhibibit?
H+/K+ ATPase of parietal cells
85
Where are Brunner cells located?
In duodenal submucosa
86
What do Brunner cells secrete?
Alkaline mucus
87
When do we see Brunner cell hypertrophy?
Seen in peptic ulcer disease
88
In which kind of fluid do pancreatic secretions are liberated?
Isotonic fluid, low flow
89
When high Cl-, high flow is produced, what happens with pancreatic secretions?
Lead to high HO3- secretion
90
When high Cl-, high flow is produced, what happens with pancreatic secretions?
Lead to high HO3- secretion
91
Main enzymes produced by pancreas?
α amylase
Lipase, phospholipase A, colipase
Proteases
Trypsinogen
92
Which is the role of α amylase?
Starch digestion
93
Which pancreatic products make fat digestion?
Lipase, phospholipase A, colipase
94
Which pancreatic products make fat digestion?
Lipase, phospholipase A, colipase
95
Pancreatic enzyme that causes protein digestion
Protease
96
Which pancreatic enzymes are protease?
Trypsin, chymotripsin, elastase, carboxypeptidase
97
How are protease secreted from pancreas?
Proenzymes also known as zymogen
98
Role of Trypsinogen
Converted to active enzyme trypsin → activation of other proenzymes and cleaving of additional trypsinogen molecules into active trypsin (positive feedback loop)
99
Who converts Trypsinogen to trypsin? and how?
Converted to trypsin by enterokynase/ enteropeptidase,
100
Where are enterokynase/ enteropeptidase?
A brush border enzyme on the duodenal and jejunal mucosa
101
Which cells of GI tract manage carbohydrate absoption?
Enterocytes
102
Which carbohydrates are absorbed by enterocytes?
Only monosaccharides
103
Who are monosaccharides?
Glucose, galactose, fructose
104
Who take Glucose and galactose on the GI tract?
SGLT1
105
Which channels does SGLT1 has?
Na+
106
How is Fructose taken up in the GI tract?
By facilitated diffusion by GLUT- 5
107
Which GLUT transports all monosacharides?
GLUT-2`
108
What is D- xylose absorption test?
Distinguishes GI mucosal damage from other causes of malabsorption
109
How is iron absorbed in GI tract?
Absorbed as Fe2+ in duodenum
110
Where is Folate absorbed?
Absorbed in jejunum and ileum
111
Where is B12 absorbed?
In Terminal ileum
112
What does vitamin B12 needs to be absorbed?
Requires intrinsic factor
113
Vitamin B12 is absorbed in terminal ileum along with...
Bile acids
114
What are Peyer patches?
Unencapsulated lymphoid tissue
115
Where are Peyer patches found?
In lamina propria and submucosa of ileum
116
What is the function of Peyer patches?
Contain specialized M cells that sample and present antigens to immune cells
117
Which relationship do Peyer patches have with B cells?
B cells stimulated in germinal centers of Peyer patches differentiate into IgA secreting plasma cells
118
Where does IgA produced by B cells of Peyer patches reside?
Reside in lamina propia
119
Which is the function of IgA produced by B cells of Peyer patches?
IgA Receives protective secretory component and is then transported across the epithelium to the gut to deal with intraluminal antigen
120
Components of Bile
```
Bile salts
Phospholipids
Cholesterol
Bilirubin
Water
Ions
```
121
What makes Bile salts water soluble?
Bile acids conjugated to glycine or taurine
122
Catalyzes rate limiting step of bile synthesis
Cholesterol 7α hydroxylase
123
Bile functions
Digestion and absorption of lipids and fat soluble vitamins
Cholesterol excretion
Antimicrobial activity
124
How does Bile has antimicrobial activity?
Via membrane disruption
125
Body's only means of eliminating cholesterol
By bile
126
What is Bilirubin?
Product of heme metabolism
127
Resume, how is the process of Bilirubin?
Bilirubin is removed from blood by liver, conjugated with glucoronate, and excreted in bile
128
Characterisitcs of Direct Bilirubin
Conjugated with glucoronic acid; water soluble
129
Characteristics of Indirect bilirubin
Unconjugated; water insoluble
130
From RBCs which is the way to get to Urobilinogen?
RBCs → Heme → Unconjugated bilirubin → Unconjugated bilirubin-albumin complex → Conjugated bilirubin → Urobilinogen
131
From RBCs to Unconjugated Bilirubin which cells carry that function?
Macrophages
132
Where is formed the unconjugated bilirubin-albumin complex?
Bloodstream
133
Enzyme that manages conversion from Unconjugated bilirubin albumin complex to Conjugated bilirubin
UDP glucoronosyl transferase
134
Where is conjugated bilirubin formed?
Liver
135
In order to form Urobilinogen from Conjugated bilirubin, what is needed?
Gut bacteria
136
Where is Urobilinogen formed?
Gut
137
How is Urobilinogen secreted?
80% excreted in feces
| 20%- 10% to kidney and 90% enterohepatic circulation return to liver
138
How is Urobilinogen secreted in feces?
Stercobilin
139
What gives brown color of stool?
Stercobilin
140
How is urobilinogenexcreted in urine?
Urobilin
141
What gives yelow color of urine?
Urobilin
