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Physiology > Gastrointestinal Physiology > Flashcards

Gastrointestinal Physiology Flashcards

1
Q

Muscle layer responsible for decreasing the diameter of the lumen

A

Inner circular muscle layer

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2
Q

Muscle layer responsible for shortening the segment of the GI tract

A

Outer longitudinal layer

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3
Q

Found between submucosal and inner circular muscle layer; for secretion, absorption, and contraction of muscularis mucosae

A

Meissner’s plexus (submucosal plexus)

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4
Q

Found between the inner circular and outer longitudinal muscle layers; for motility

A

Auerbach’s plexus (myenteric plexus)

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5
Q

What innervates the muscularis mucosa?

A

Meissner’s plexus

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6
Q

Which layer is NOT seen in the esophagus?

A

Serosa

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7
Q

Strongest layer of the esophagus

A

Submucosa

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8
Q

3 muscle layers found in the stomach

A

Inner oblique, middle circular, outer longitudinal

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9
Q

What is the significance of the inner oblique layer?

A

causes retropulsion for more mixing of chyme

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10
Q

The myenteric/Auerbach plexus is mainly excitatory except for which regions?

A

Pyloric sphincter and Ileocecal valve

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11
Q

VIP is responsible for the relaxation of these 4 structures:

A

lower esophageal sphincter, orad stomach, pyloric sphincter, ileocecal valve

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12
Q

Peyer’s patches contain secretory IgA and is found where:

A

lamina propria of mucosa layer of ileum

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13
Q

Brunner’s glands contain HCO3-rich fluid and is found where:

A

submucosa of the duodenum

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14
Q

Extrinsic parasympathetic innervation from the esophagus to the upper large intestine is from what nerve?

A

Vagus nerve

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15
Q

Extrinsic parasympathetic innervation from the lower large intestines to anus is from what nerve?

A

Pelvic nerves

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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

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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

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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

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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

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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

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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

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22
Q

Most potent stimuli for gastrin secretion

A

Phenylalanine, tryptophan, methionine

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23
Q

Neurocrine from vagus nerve to G cells which increases gastrin secretion

A

GRP/Bombesin

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24
Q

GI hormone classified as an incretin

A

Glucose-dependent Insulinotropic Peptide

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25
Q

A candidate GI hormone secreted by the pancreas in response to CHO, CHON, lipids that inhibits pancreatic HCO3 and enzymes.

A

Pancreatic polypeptide

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26
Q

A candidate GI hormone secreted by the intestinal cells in response to hypoglycemia which stimulates glycogenolysis and gluconeogenesis.

A

Enteroglucagon

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27
Q

A candidate GI hormone secreted by L-cells of small intestines which stimulates insulin secretion

A

Glucagon-like peptide (GLP-1)

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28
Q

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

A

Somatostatin

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29
Q

A GI paracrine secreted by mast cells of gastric mucosa which increases H+ secretion, and potentiates gastrin and Ach action

A

Histamine

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30
Q

Inhibits appetite; found at the ventromedial hypothalamus

A

Satiety center

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31
Q

Stimulates appetite; found at the lateral hypothalamic area

A

Appetite/hunger center

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32
Q

Sends signal to satiety and hunger centers

A

Arcuate nucleus

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33
Q

Release POMC to decrease appetite

A

Anorexigenic neurons

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34
Q

Release neuropeptide Y to increase appetite

A

Orexigenic neurons

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35
Q

Stimulates anorexigenic neurons and inhibits orexigenic neurons

A

Leptin (fat cells), insulin, GLP-1

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36
Q

Inhibits anorexigenic neurons

A

Ghrelin (gastric cells)

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37
Q

Inhibits Ghrelin

A

Peptide YY

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38
Q

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

A

Tonic contractions

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39
Q

Contractions due to spike potentials; periodic contractions followed by relaxation, for mixing and propulsion; seen in the esophagus, gastric antrum and small intestines

A

Phasic contractions

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40
Q

Slow waves are slow, oscillating membrane potentials that are not true action potentials. This is due to the GI pacemaker called:

A

Interstitial cells of Cajal

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41
Q

Depolarization of slow waves is due to:

A

Sodium influx

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42
Q

Slowest frequency of slow waves is seen in the:

Fastest frequency of slow waves is seen in the:

A

Slowest: stomach (3/min)
Fastest: small intestines (12/min)

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43
Q

Spike potentials are true action potentials. Depolarization is due to:

A

Calcium influx (threshold: -40mV)

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44
Q

What is the most common stimulus for GI peristalsis

A

Distention

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45
Q

What is the myenteric reflex?

A

Muscles upstream contract, muscles downstream exhibit receptive relaxation

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46
Q

What is the law of the gut?

A

Myenteric reflex + anal direction of peristalsis

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47
Q

How long does it take to transfer material from pylorus to ileocecal valve and ileocecal valve to colon, respectively?

A

3-5 hours, 8-15 hours

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48
Q

What substance begins CHO digestion while chewing?

A

Amylase

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49
Q

Where is the swallowing center located?

A

Medulla

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50
Q

What are the 3 phases of swallowing?

A

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

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51
Q

What is the capacity of the stomach?

A

1.5 L

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52
Q

What substance increases the distensibility of the orad stomach?

A

Cholecystokinin

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53
Q

Normal gastric emptying time is:

A

3 hours

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54
Q

Gastric emptying is fastest when food is isotonic and liquid. What is the size required to enter the duodenum?

A
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55
Q

What 2 substances are inhibitors of gastric emptying?

A

Fat (due to CCK), H+ in the duodenum

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56
Q

Back and forth movement with no net forward motion, mixes chyme with pancreatic enzymes

A

Segmentation contraction

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57
Q

Propels chyme toward large intestine

A

Peristaltic contraction

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58
Q

Characteristic of the circular and longitudinal muscles that when one is contracted, the other is relaxes and vice versa

A

Reciprocally innervated

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59
Q

Sac-like segments due to segmental contractions of the large intestines

A

Haustra

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60
Q

Part of the large intestine for absorption of water

A

proximal colon

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61
Q

Part of the large intestine for storage of feces

A

distal colon

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62
Q

Occur 1-3x a day to move colonic contents over long distances (from transverse colon to sigmoid colon)

A

Mass movements

63
Q

Urge to defecate happens once rectum is ___% filled

A

25%

64
Q

Color of feces is due to the pigment:

Combustible material present in feces:

A

Stercobilin

Methane

65
Q

Food in the stomach increases peristalsis in the ileum and relaxation of the ileocecal sphincter

A

Gastroileal reflex

66
Q

Food in the stomach increases peristalsis in the colon and frequency of mass movements

A

Gastrocolic reflex

67
Q

Vomiting is a wave of reverse peristalsis that begins from:

A

small intestines

68
Q

Vomiting center is located in the:

A

Medulla

69
Q

Vomiting center receives information from the following:

A

vestibular system, back of the throat, GI tract and the CTZ

70
Q

Incomplete vomiting; closed UES

A

retching

71
Q

Most acidic among the GI secretions:

A

Gastric secretion (pH 1.0 - 3.5)

72
Q

Most alkaline among the GI secretions:

A

Brunner’s gland secretion (pH 8.0 - 8.9)

73
Q

Produces the most amount of GI secretion/day

A

Small intestines (1800 mL)

74
Q

Produces the least amount of GI secretion/day

A

Brunner’s glands and large intestines (200 mL each)

75
Q

Substance found in saliva responsible for initial digestion of starch and lipids respectively

A

Starch: ptyalin
Lipids: lingual lipase

76
Q

These cells produce the “initial saliva”

A

Acinar cells

77
Q

These cells produce the “final saliva”

A

Ductal cells

78
Q

Saliva: serous secretion

A

Parotid gland

79
Q

Saliva: mixed secretion

A

Submandibular and sublingual glands

80
Q

Saliva: effect of parasympathetic NS

A

increases salivation

81
Q

Saliva: effect of sympathetic NS

A

decreases salivation

82
Q

Saliva: initial saliva is high in:

A

Na, Cl

83
Q

Saliva: final saliva is high in:

A

HCO3, K

84
Q

Saliva: hormone involved in absorbing Na at the ductal cells

A

Aldosterone

85
Q

Saliva: at high flow rates, saliva has:

A

High Na, Cl, low K and high HCO3

86
Q

Saliva: at low flow rates, saliva has:

A

Low Na, Cl, High K and low HCO3

87
Q

What is peculiar about HCO3 secretion in saliva?

A

It does not follow contact-time rule. (increase salivary gland stimulation –> increase flow rate –> increase HCO3 secretion)

88
Q

What is the only essential secretion of the stomach?

A

Intrinsic factor (for Vitamin B12 absorption)

89
Q

Gastric cells and secretions:

contains mucus neck cells, parietal cells and chief cells

A

Oxyntic glands (body)

90
Q

Gastric cells and secretions:

contains G cells, mucus cells

A

Pyloric glands (antrum)

91
Q

Gastric cells and secretions:

secretes mucus an dHCO3

A

Mucus cells, mucus neck cells

92
Q

Gastric cells and secretions:

secretes HCl and IF

A

Parietal cells/oxyntic cells

93
Q

Gastric cells and secretions:

secretes Gastrin

A

G cells

94
Q

Gastric cells and secretions:

secretes Serotonin

A

Enterochromaffin cells

95
Q

Gastric cells and secretions:

secretes Histamine

A

Enterochromaffin-like cells

96
Q

Gastric cells and secretions:

secretes Pepsinogen

A

Chief/peptic cells

97
Q

Chloride enters the gastric parietal cell in exchange for bicarbonate in a process called:

A

Alkaline tide

98
Q

What are the 3 substances that stimulate HCl secretion?

A

Histamine (H2 receptors), Ach (M3 receptors), Gastrin (CCKB receptors)

99
Q

What are the inhibitors of HCl secretion?

A

Low pH (

100
Q

What are the 3 phases of HCl secretion?

A

Cephalic phase, gastric phase, intestinal phase

101
Q

What phase produces the highest HCl secretion?

A

Gastric phase (60%) (Cephalic phase: 30%, intestinal phase: 10%)

102
Q

What substances protects the mucosa from HCl and pepsin?

A

HCO3, mucus

103
Q

What are the protective factors against PUD?

A

Prostaglandins, mucosal blood flow, growth factors

104
Q

What are the damaging factors?

A

H. pylori, NSAIDs, stress, smoking, alcohol

105
Q

What are the essential pancreatic secretions?

A

Pancreatic amylase, lipase, protease, trypsin inhibitor (prevets autodigestion)

106
Q

Most common component of bile:

A

Water

107
Q

Active component of bile:

A

Bile salts

108
Q

What are the primary bile acids?

A

Cholic acid, chenodeoxycholic acid

109
Q

What are the secondary bile acids?

A

Deoxycholic acid, lithocholic acid

110
Q

What are the bile salts?

A

Glycodeoxycholic acid, Taurodeoxycholic acid

Glycolithocholic acid, Taurolithocholic acid

111
Q

Site of synthesis of bile

A

Liver

112
Q

Site of storage and concentration of bile

A

Gallbladder

113
Q

CCK and Ach causes gallbladder______

A

contraction

114
Q

CCK causes relaxation of the ________

A

sphincter of Oddi

115
Q

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:

A

Enterohepatic circulation

116
Q

The process of chemical breakdown of ingested foods into absorbable molecules

A

Digestion

117
Q

The movement of nutrients, water, and electrolytes from the lumen of the intestine into the blood

A

Absorption

118
Q

How do you absorb glucose and galactose from lumen to intestinal cell?

A

SGLT-1

119
Q

How do you absorb fructose from lumen to intestinal cell?

A

GLUT-5

120
Q

How do you absorb glucose, galactose, and fructose from intestinal cell to the blood?

A

GLUT-2

121
Q 
Digestion of carbohydrates: 
Mouth: \_\_\_\_\_\_
Stomach: None
Small intestine: \_\_\_\_\_\_\_\_
Only \_\_\_\_\_\_\_ are absorbed
A

Mouth: ptyalin
Small intestine: pancreatic amylase, brush border enzymes, disaccharidases
Only monosaccharides are absorbed

122
Q

Digestion of proteins:
Mouth: None
Stomach: _______
Small intestines: _______

A

Stomach: Pepsin

Small intestine: Enterokinase, trypsin

123
Q

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:

A

Proteases

124
Q

What is the optimum pH for pepsin activity?

A

pH 1.0 - 3.0 (inactivated at pH > 5.0)

125
Q

What is the optimum pH for pancreatic lipase activity?

A

pH 6.0

126
Q

What is the basis of steatorrhea in Zolinger-Ellison syndrome?

A

Acidic pH deactivates pancreatic lipase –> decreased digestion of fats

127
Q

What is the basis for osmotic diarrhea in lactose intolerance?

A

E.coli in the gut utilizes the lactose and gives off acids as waste products –> acids attract water

128
Q

Is pepsin essential for protein digestion?

A

No

129
Q

Is trypsin essential for protein digestion?

A

Yes

130
Q

Triglycerides are absorbed from lumen to intestinal cell via: ______; it is absorbed from intestinal cell to lacteals via: ______

A

Micelles, chylomicrons

131
Q

Bile salts inactivates pancreatic lipase. What pancreatic coenzyme is secreted to prevent this from happening?

A

Procolipase –> Colipase

132
Q

What is the only product of triglyceride metabolism that is NOT hydrophobic?

A

Glycerol

133
Q

What type of fatty acids go directly to the portal vein instead of the lacteals?

A

Short-chain and medium-chain fatty acids

134
Q

Main site for water absorption:

A

Jejunum

135
Q

Potassium is absorbed and secreted at the following sites respectively

A

small intestines, large intestines

136
Q

Primary ion secreted in the intestinal lumen

A

Chloride (Na and H2O follows)

137
Q

Needed to absorb vitamin B12

A

Intrinsic factor

138
Q

Needed to absorb calcium

A

1,25 (OH)2 cholecalciferol/calcitriol/active vitamin D

139
Q

Needed to absorb iron

A

Vitamin C

140
Q

Part of the metabolism of these vitamins involve colonic flora

A

Vitamin K, Vitamin B1, B2, B12

141
Q

What is the central organ for metabolism?

A

Liver

142
Q

The liver is ___% of total body weight, and receives ___% of cardiac output

A

2% of total body weight; received 25% of CO

143
Q

Red blood cells is converted to what in the reticuloendothelial system?

A

RBC –> Hemoglobin –> Biliverdin –> Bilirubin

144
Q

Bilirubin metabolism: what form of bilirubin is seen in the bloodstream?

A

Bilirubin-albumin complex

145
Q

Bilirubin metabolism: in the liver, conjugation of bilirubin happens due to what enzyme?

A

UDP glucuronyl transferase

146
Q

Bilirubin metabolism: What form of bilirubin is released to the bile?

A

Conjugated bilirubin

147
Q

Bilirubin metabolism: What form of bilirubin is seen in the terminal ileum, and colon respectively?

A

Terminal ileum: urobilinogen

Colon: urobilin, stercobilin

148
Q

In the classic lever lobule model, the liver is hexagonal in shape. At the center is the _____ and at the borders is the ______

A

Center: central vein
Borders: portal triad

149
Q

In the liver acinus model, this zone is most prone to toxins, but receives the most O2 and nutrients

A

Zone 1

150
Q

In the liver acinus model, this zone is least prone to toxins, but receives the least O2 and nutrients

A

Zone 3

151
Q

The liver can undergo regeneration of its lost mass up to ____%.

A

70%

152
Q

Special liver cells seen in the space of Disse for vitamin A storage and involved in liver fibrosis

A

Ito cells/hepatic stellate cells/perisinusoidal cells

153
Q

Special liver cells seen in the liver sinusoids and act as antigen presenting cells/ liver macrophages

A

Kuppfer cells

Physiology (13 decks)

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