Gastrointestinal Physiology Flashcards
1
Q
Muscle layer responsible for decreasing the diameter of the lumen
A
Inner circular muscle layer
2
Q
Muscle layer responsible for shortening the segment of the GI tract
A
Outer longitudinal layer
3
Q
Found between submucosal and inner circular muscle layer; for secretion, absorption, and contraction of muscularis mucosae
A
Meissner’s plexus (submucosal plexus)
4
Q
Found between the inner circular and outer longitudinal muscle layers; for motility
A
Auerbach’s plexus (myenteric plexus)
5
Q
What innervates the muscularis mucosa?
A
Meissner’s plexus
6
Q
Which layer is NOT seen in the esophagus?
A
Serosa
7
Q
Strongest layer of the esophagus
A
Submucosa
8
Q
3 muscle layers found in the stomach
A
Inner oblique, middle circular, outer longitudinal
9
Q
What is the significance of the inner oblique layer?
A
causes retropulsion for more mixing of chyme
10
Q
The myenteric/Auerbach plexus is mainly excitatory except for which regions?
A
Pyloric sphincter and Ileocecal valve
11
Q
VIP is responsible for the relaxation of these 4 structures:
A
lower esophageal sphincter, orad stomach, pyloric sphincter, ileocecal valve
12
Q
Peyer’s patches contain secretory IgA and is found where:
A
lamina propria of mucosa layer of ileum
13
Q
Brunner’s glands contain HCO3-rich fluid and is found where:
A
submucosa of the duodenum
14
Q
Extrinsic parasympathetic innervation from the esophagus to the upper large intestine is from what nerve?
A
Vagus nerve
15
Q
Extrinsic parasympathetic innervation from the lower large intestines to anus is from what nerve?
A
Pelvic nerves
16
Q
The intrinsic innervation of the GI tract coordinates and relays information from ANS to GI tract is made up of:
A
Meissner’s and Auerbach plexus
17
Q
This hormone increases gastric H+ secretion by the parietal cells. It is secreted by: _____
A
Gastrin, secreted by G cells in the stomach antrum
18
Q
This hormone increases pancreatic and biliary HCO3 secretion; counterregulatory hormone of Gastrin; it is secreted by: _____
A
Secretin, secreted by S cells in the duodenum
19
Q
This hormone stimulates gallbladder contraction for bile secretion, inhibits gastric emptying, sphincter of Oddi relaxation. It is secreted by:______
A
Cholecystokinin, secreted by I cells in the duodenum and jejunum
20
Q
This hormone increases insulin secretion, stimulated by oral glucose, inhibits gastric emptying. It is secreted by: ______
A
Glucose-dependent Insulinotropic Peptide (formerly Gastric Inhibitory Peptide), secreted by K cells in the duodenum
21
Q
This hormone stimulates the interdigestive myoelectric complex (contractions every 90 minutes) which is responsible for removing remnant food in the GIT in preparation for the next meal. It is secreted by: _____
A
Motilin, secreted by M cells in the duodenum and jejunum
22
Q
Most potent stimuli for gastrin secretion
A
Phenylalanine, tryptophan, methionine
23
Q
Neurocrine from vagus nerve to G cells which increases gastrin secretion
A
GRP/Bombesin
24
Q
GI hormone classified as an incretin
A
Glucose-dependent Insulinotropic Peptide
25
A candidate GI hormone secreted by the pancreas in response to CHO, CHON, lipids that inhibits pancreatic HCO3 and enzymes.
Pancreatic polypeptide
26
A candidate GI hormone secreted by the intestinal cells in response to hypoglycemia which stimulates glycogenolysis and gluconeogenesis.
Enteroglucagon
27
A candidate GI hormone secreted by L-cells of small intestines which stimulates insulin secretion
Glucagon-like peptide (GLP-1)
28
A GI paracrine secreted by cells throughout the GI tract in response to H+ which inhibits release of all GI hormones and inhibits gastric H+ secretion
Somatostatin
29
A GI paracrine secreted by mast cells of gastric mucosa which increases H+ secretion, and potentiates gastrin and Ach action
Histamine
30
Inhibits appetite; found at the ventromedial hypothalamus
Satiety center
31
Stimulates appetite; found at the lateral hypothalamic area
Appetite/hunger center
32
Sends signal to satiety and hunger centers
Arcuate nucleus
33
Release POMC to decrease appetite
Anorexigenic neurons
34
Release neuropeptide Y to increase appetite
Orexigenic neurons
35
Stimulates anorexigenic neurons and inhibits orexigenic neurons
Leptin (fat cells), insulin, GLP-1
36
Inhibits anorexigenic neurons
Ghrelin (gastric cells)
37
Inhibits Ghrelin
Peptide YY
38
Contractions due to subthreshold slow waves; constant level of contraction or tone without regular periods of relaxation; seen in the orad stomach, lower esophageal, ileocecal and internal anal sphincters
Tonic contractions
39
Contractions due to spike potentials; periodic contractions followed by relaxation, for mixing and propulsion; seen in the esophagus, gastric antrum and small intestines
Phasic contractions
40
Slow waves are slow, oscillating membrane potentials that are not true action potentials. This is due to the GI pacemaker called:
Interstitial cells of Cajal
41
Depolarization of slow waves is due to:
Sodium influx
42
Slowest frequency of slow waves is seen in the:
| Fastest frequency of slow waves is seen in the:
Slowest: stomach (3/min)
Fastest: small intestines (12/min)
43
Spike potentials are true action potentials. Depolarization is due to:
Calcium influx (threshold: -40mV)
44
What is the most common stimulus for GI peristalsis
Distention
45
What is the myenteric reflex?
Muscles upstream contract, muscles downstream exhibit receptive relaxation
46
What is the law of the gut?
Myenteric reflex + anal direction of peristalsis
47
How long does it take to transfer material from pylorus to ileocecal valve and ileocecal valve to colon, respectively?
3-5 hours, 8-15 hours
48
What substance begins CHO digestion while chewing?
Amylase
49
Where is the swallowing center located?
Medulla
50
What are the 3 phases of swallowing?
Oral phase: triggers reflex when food is at the pharynx
Pharyngeal phase: soft palate pulled upward, glottis covered, UES relaxes
Esophageal phase: UES closes, primary and secondary esophageal peristalsis occurs
51
What is the capacity of the stomach?
1.5 L
52
What substance increases the distensibility of the orad stomach?
Cholecystokinin
53
Normal gastric emptying time is:
3 hours
54
Gastric emptying is fastest when food is isotonic and liquid. What is the size required to enter the duodenum?
55
What 2 substances are inhibitors of gastric emptying?
Fat (due to CCK), H+ in the duodenum
56
Back and forth movement with no net forward motion, mixes chyme with pancreatic enzymes
Segmentation contraction
57
Propels chyme toward large intestine
Peristaltic contraction
58
Characteristic of the circular and longitudinal muscles that when one is contracted, the other is relaxes and vice versa
Reciprocally innervated
59
Sac-like segments due to segmental contractions of the large intestines
Haustra
60
Part of the large intestine for absorption of water
proximal colon
61
Part of the large intestine for storage of feces
distal colon
62
Occur 1-3x a day to move colonic contents over long distances (from transverse colon to sigmoid colon)
Mass movements
63
Urge to defecate happens once rectum is ___% filled
25%
64
Color of feces is due to the pigment:
| Combustible material present in feces:
Stercobilin
| Methane
65
Food in the stomach increases peristalsis in the ileum and relaxation of the ileocecal sphincter
Gastroileal reflex
66
Food in the stomach increases peristalsis in the colon and frequency of mass movements
Gastrocolic reflex
67
Vomiting is a wave of reverse peristalsis that begins from:
small intestines
68
Vomiting center is located in the:
Medulla
69
Vomiting center receives information from the following:
vestibular system, back of the throat, GI tract and the CTZ
70
Incomplete vomiting; closed UES
retching
71
Most acidic among the GI secretions:
Gastric secretion (pH 1.0 - 3.5)
72
Most alkaline among the GI secretions:
Brunner's gland secretion (pH 8.0 - 8.9)
73
Produces the most amount of GI secretion/day
Small intestines (1800 mL)
74
Produces the least amount of GI secretion/day
Brunner's glands and large intestines (200 mL each)
75
Substance found in saliva responsible for initial digestion of starch and lipids respectively
Starch: ptyalin
Lipids: lingual lipase
76
These cells produce the "initial saliva"
Acinar cells
77
These cells produce the "final saliva"
Ductal cells
78
Saliva: serous secretion
Parotid gland
79
Saliva: mixed secretion
Submandibular and sublingual glands
80
Saliva: effect of parasympathetic NS
increases salivation
81
Saliva: effect of sympathetic NS
decreases salivation
82
Saliva: initial saliva is high in:
Na, Cl
83
Saliva: final saliva is high in:
HCO3, K
84
Saliva: hormone involved in absorbing Na at the ductal cells
Aldosterone
85
Saliva: at high flow rates, saliva has:
High Na, Cl, low K and high HCO3
86
Saliva: at low flow rates, saliva has:
Low Na, Cl, High K and low HCO3
87
What is peculiar about HCO3 secretion in saliva?
It does not follow contact-time rule. (increase salivary gland stimulation --> increase flow rate --> increase HCO3 secretion)
88
What is the only essential secretion of the stomach?
Intrinsic factor (for Vitamin B12 absorption)
89
Gastric cells and secretions:
| contains mucus neck cells, parietal cells and chief cells
Oxyntic glands (body)
90
Gastric cells and secretions:
| contains G cells, mucus cells
Pyloric glands (antrum)
91
Gastric cells and secretions:
| secretes mucus an dHCO3
Mucus cells, mucus neck cells
92
Gastric cells and secretions:
| secretes HCl and IF
Parietal cells/oxyntic cells
93
Gastric cells and secretions:
| secretes Gastrin
G cells
94
Gastric cells and secretions:
| secretes Serotonin
Enterochromaffin cells
95
Gastric cells and secretions:
| secretes Histamine
Enterochromaffin-like cells
96
Gastric cells and secretions:
| secretes Pepsinogen
Chief/peptic cells
97
Chloride enters the gastric parietal cell in exchange for bicarbonate in a process called:
Alkaline tide
98
What are the 3 substances that stimulate HCl secretion?
Histamine (H2 receptors), Ach (M3 receptors), Gastrin (CCKB receptors)
99
What are the inhibitors of HCl secretion?
Low pH (
100
What are the 3 phases of HCl secretion?
Cephalic phase, gastric phase, intestinal phase
101
What phase produces the highest HCl secretion?
Gastric phase (60%) (Cephalic phase: 30%, intestinal phase: 10%)
102
What substances protects the mucosa from HCl and pepsin?
HCO3, mucus
103
What are the protective factors against PUD?
Prostaglandins, mucosal blood flow, growth factors
104
What are the damaging factors?
H. pylori, NSAIDs, stress, smoking, alcohol
105
What are the essential pancreatic secretions?
Pancreatic amylase, lipase, protease, trypsin inhibitor (prevets autodigestion)
106
Most common component of bile:
Water
107
Active component of bile:
Bile salts
108
What are the primary bile acids?
Cholic acid, chenodeoxycholic acid
109
What are the secondary bile acids?
Deoxycholic acid, lithocholic acid
110
What are the bile salts?
Glycodeoxycholic acid, Taurodeoxycholic acid
| Glycolithocholic acid, Taurolithocholic acid
111
Site of synthesis of bile
Liver
112
Site of storage and concentration of bile
Gallbladder
113
CCK and Ach causes gallbladder______
contraction
114
CCK causes relaxation of the ________
sphincter of Oddi
115
94% of bile salts are recirculated back to the liver using Na-bile salt co-transporter in the terminal ileum. This process is called the:
Enterohepatic circulation
116
The process of chemical breakdown of ingested foods into absorbable molecules
Digestion
117
The movement of nutrients, water, and electrolytes from the lumen of the intestine into the blood
Absorption
118
How do you absorb glucose and galactose from lumen to intestinal cell?
SGLT-1
119
How do you absorb fructose from lumen to intestinal cell?
GLUT-5
120
How do you absorb glucose, galactose, and fructose from intestinal cell to the blood?
GLUT-2
121
```
Digestion of carbohydrates:
Mouth: ______
Stomach: None
Small intestine: ________
Only _______ are absorbed
```
Mouth: ptyalin
Small intestine: pancreatic amylase, brush border enzymes, disaccharidases
Only monosaccharides are absorbed
122
Digestion of proteins:
Mouth: None
Stomach: _______
Small intestines: _______
Stomach: Pepsin
| Small intestine: Enterokinase, trypsin
123
In the denaturation of proteins, only secondary, tertiary and quaternary structures are denatured. Primary structures are not denatured due to its covalent bonds. Primary structures are only broken by:
Proteases
124
What is the optimum pH for pepsin activity?
pH 1.0 - 3.0 (inactivated at pH > 5.0)
125
What is the optimum pH for pancreatic lipase activity?
pH 6.0
126
What is the basis of steatorrhea in Zolinger-Ellison syndrome?
Acidic pH deactivates pancreatic lipase --> decreased digestion of fats
127
What is the basis for osmotic diarrhea in lactose intolerance?
E.coli in the gut utilizes the lactose and gives off acids as waste products --> acids attract water
128
Is pepsin essential for protein digestion?
No
129
Is trypsin essential for protein digestion?
Yes
130
Triglycerides are absorbed from lumen to intestinal cell via: ______; it is absorbed from intestinal cell to lacteals via: ______
Micelles, chylomicrons
131
Bile salts inactivates pancreatic lipase. What pancreatic coenzyme is secreted to prevent this from happening?
Procolipase --> Colipase
132
What is the only product of triglyceride metabolism that is NOT hydrophobic?
Glycerol
133
What type of fatty acids go directly to the portal vein instead of the lacteals?
Short-chain and medium-chain fatty acids
134
Main site for water absorption:
Jejunum
135
Potassium is absorbed and secreted at the following sites respectively
small intestines, large intestines
136
Primary ion secreted in the intestinal lumen
Chloride (Na and H2O follows)
137
Needed to absorb vitamin B12
Intrinsic factor
138
Needed to absorb calcium
1,25 (OH)2 cholecalciferol/calcitriol/active vitamin D
139
Needed to absorb iron
Vitamin C
140
Part of the metabolism of these vitamins involve colonic flora
Vitamin K, Vitamin B1, B2, B12
141
What is the central organ for metabolism?
Liver
142
The liver is ___% of total body weight, and receives ___% of cardiac output
2% of total body weight; received 25% of CO
143
Red blood cells is converted to what in the reticuloendothelial system?
RBC --> Hemoglobin --> Biliverdin --> Bilirubin
144
Bilirubin metabolism: what form of bilirubin is seen in the bloodstream?
Bilirubin-albumin complex
145
Bilirubin metabolism: in the liver, conjugation of bilirubin happens due to what enzyme?
UDP glucuronyl transferase
146
Bilirubin metabolism: What form of bilirubin is released to the bile?
Conjugated bilirubin
147
Bilirubin metabolism: What form of bilirubin is seen in the terminal ileum, and colon respectively?
Terminal ileum: urobilinogen
| Colon: urobilin, stercobilin
148
In the classic lever lobule model, the liver is hexagonal in shape. At the center is the _____ and at the borders is the ______
Center: central vein
Borders: portal triad
149
In the liver acinus model, this zone is most prone to toxins, but receives the most O2 and nutrients
Zone 1
150
In the liver acinus model, this zone is least prone to toxins, but receives the least O2 and nutrients
Zone 3
151
The liver can undergo regeneration of its lost mass up to ____%.
70%
152
Special liver cells seen in the space of Disse for vitamin A storage and involved in liver fibrosis
Ito cells/hepatic stellate cells/perisinusoidal cells
153
Special liver cells seen in the liver sinusoids and act as antigen presenting cells/ liver macrophages
Kuppfer cells
