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BMS150 Post-MT2 > Physiology of the Gastrointestinal Tract and Introduction to Gut Microbiome > Flashcards

Physiology of the Gastrointestinal Tract and Introduction to Gut Microbiome Flashcards

1
Q

Big picture functions of the GI Tract?

A
  1. Transporting food by-products
  2. Breaking down and absorbing food by-products
  3. Decontaminating the food and maintaining appropriate relationship with live non-human cells
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2
Q

3 basic movements that take place along the GIT?

A
  1. Peristalsis
  2. Segmentation
  3. Migrating motor complex (MMC)
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3
Q

Waves of smooth muscle contraction that propel food bolus throughout entire GI tract?

A

Peristalsis

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4
Q

What produces rhythm of peristalsis? Where is it located?

A

Interstitial cells of Cajal (ICC) - in myenteric plexus

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5
Q

Peristalsis involves _____ behind (proximal) the food bolus and _______ in front (distal) of the food bolus

A

Contraction; Relaxation

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6
Q

Function of peristalsis?

A

Propel food further along the GI tract

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7
Q

Some problems with Peristalsis? (3)

A
  • Esophageal spasms
  • Atonic colon
  • Gastroparesis
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8
Q

Coordination of smooth muscle cells and interstitial cells of Cajal?

A

Segmentation

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9
Q

Where does segmentation occur?

A

Within the Small and Large Intestines

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10
Q

Function of segmentation?

A

Promotes mixing food particles to increase their interaction between villi and promotes absorption

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11
Q

Small movement, almost a vibration, that occurs predominantly during fasting 1.5-2 hr intervals

A

Migrating motor complex (MMC)

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12
Q

Where does MMC occur mainly?

A

Stomach and Small Intestine

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13
Q

What is MMC movement promoted by?

A

Motilin - secreted by Mo-cells in teh duodenum

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14
Q

Function of MMC?

A

Self-cleaning mechanism = dislodges food and bacteria from walls

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15
Q

What may a lack of MMC cause?

A

SIBO

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16
Q

What are the “pacemakers of the GI Tract”?

A

Interstitial Cells of Cajal (ICC)

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17
Q

Where are ICC’s found?

A

Throughout the entire GI Tract

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18
Q

ICC’s form a network with each other and smooth muscles via _______, as well as ______

A

Gap junctions; enteric motor neurons

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19
Q

What triggers smooth muscle contractions of ICCs?

A

Spike potentials

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20
Q

Additional factors that can increase the excitability of smooth muscle? (3)

A
  • Muscle stretch (distention)
  • Acetylcholine
  • Other GI hormones
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21
Q

What can decrease excitability of smooth muscles? What does it cause?

A

Norepinephrine - causes hyperpolarization

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22
Q

What is the enteric nervous system composed of?

A

Sensory, motor, and interneurons

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23
Q

What is the enteric nervous system organized into? (2)

A
  • Submucosal plexus and Myenteric plexus
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24
Q

Where is the Submucosal plexus located?

A

Located between the layers of submucosa and circular muscle (only present in SI and LI)

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25
Q

Function of the submucosal plexus? (4)

A
  • Regulate motility
  • Regulate local blood flow
  • Regulate secretions
  • Regulate epithelial cell function
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26
Q

Where is the Myenteric plexus located?

A

Between longitudinal and circular muscles (entire GI)

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27
Q

What is the function of the myenteric plexus?

A

Regulate motility

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28
Q

Nerves that connect the ENS and CNS? (3)

A
  • Vagus Nerve
  • Pelvic Splanchnic Nerves
  • Thoracic Sympathetic Trunk
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29
Q

Secretions promoting motility? (5)

A
  • I-cells = CCK
  • Enterochromaffin cells = serotonin
  • G-cells = gastrin
  • Mo-cells = motilin
  • Beta-pancreatic cells = insulin
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30
Q

Secretions reducing motility? (4)

A
  • S-cells = secretin
  • D-cells = somatostatin
  • Pancreatic cells = Pancreatic peptide YY
  • Alpha-pancreatic cells = glucagon
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31
Q

What is digestion?

A

Breaking down macromolecules into smaller molecules to increase absorption

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32
Q

Two types of digestion?

A
  1. Mechanical
  2. Chemical
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33
Q

What is mechanical digesiton?

A

Physically chewing/cutting/crushing/churning food to decrease vol and increase SA

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34
Q

Parts of the GI tract that help with mechanical digestion?

A

Mouth and Stomach

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35
Q

What is chemical digestion?

A

Chemical processes that allows absorption of food particles

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36
Q

Two types of chemical digesiton?

A
  1. Enzymatic digestion
  2. Lipid solubilization
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37
Q

What is enzymatic digestion?

A

Enzymes break macronutrients down into smaller and smaller particles through the process of hydrolysis

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38
Q

What is lipid solubilization?

A

Emulsifiers secreted by the liver emulsify ingested lipids so that enzymes can break them down to smaller, absorbable molecules

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39
Q

Enzymes/secretions present in the mouth to aid in digestion? (3)

A
  • Salivary amylase
  • Mucus
  • Water
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40
Q

Contributing organs/structures for digestion in the mouth? (2)

A
  • Salivary glands
  • Teeth
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41
Q

What is being digested in the mouth?

A

Carbohydrates (all other are being broken down into smaller particles)

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42
Q

Enzymes/secretions present in the stomach to aid in digestion? (3)

A
  • HCl
  • Lipase
  • Pepsin
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43
Q

Contributing nerve for stomach digestion?

A

Vagus nerve promotes HCl release

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44
Q

What is being digested in the stomach?

A

Proteins, fats, carbs - limited digestion other than proteins

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45
Q

What is the most important site of chemical digestion?

A

Small intestine

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46
Q

Enzymes/secretions present in the small intestine to aid in digestion? (3)

A
  • Bile acids
  • Pancreatic enzymes
  • Brush border enzymes
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47
Q

Contributing organs/structures to small intestine digestion?

A
  • Liver contributes bile
  • Pancreas releases numerous enzymes including lipase and amylase
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48
Q

What is being digested in the small intestine?

A
  • Proteins (bb enz. Pancreatic enz.)
  • Carbs (bb enz. and amylase)
  • Lipids (lipase and bile acids)
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49
Q

The movement of any substance across the mucosal epithelium of the alimentary tract and into the bloodstream (most substances) or lymphatics (lipids)?

A

Absorption

50
Q

What is absorption largely dependent on?

A

The health of the villus and microvilli of enterocytes in the small intestine

51
Q

What occurs in carbohydrate digestion?

A

Polysaccharides are broken down into monosaccharides

52
Q

What monosaccharides can be transported across the epithelial cells of the small intestine? (3)

A

Galactose, Glucose, Fructose

53
Q

How are glucose and Galactose transported into the enterocyte?

A

Na+/glucose (galactose) co-transporter (SGLT1)

54
Q

What does SGLT1 depend on?

A

High [Na+] in the lumen to power transport of hexose

55
Q

How is fructose transported into the enterocyte?

A

GLUT-5 = passive transporter

56
Q

How are the monosaccharides transported out the basolateral side of the enterocyte?

A

GLUT-2 and GLUT-5

57
Q

Where are majority of proteins absorbed?

A

The duodenum and jejunum

58
Q

Transporters for individual amino acids?

A

Na+ symporters

59
Q

How are dipeptides and tripeptides transported into the enterocyte?

A

PepT1 Transporter

60
Q

What does the PepT1 transporter rely on?

A

H+ concentration gradient

61
Q

What happens to di- and tripeptides in the enterocyte?

A

They’re hydrolyzed into amino acids

62
Q

Nucleic acids are broken down into sugars, purines, and pyrimidines - how are the bases absorbed?

A

Nucleoside transporters

63
Q

What fatty acids can passively diffuse through enterocyte (unmodified)?

A

FFAs that are 10-12 C long

64
Q

What happens to fatty acids that are > 10-12 C long?

A

They’re re-esterified once in the enterocyte

65
Q

How is cholesterol transported into the enterocyte?

A

NPC1L1 transporter

66
Q

What are FFA’s and cholesterol that are coated with proteins, more cholesterol and phospholipids

A

Chylomicron

67
Q

Why does chylomicron enter the lymphatics?

A

Too large to pass between endothelial cells into blood stream

68
Q

Impaired fat digestion and absorption resulting in high amount of fat in the stool

A

Steatorrhea

69
Q

What are the fat soluble vitamins? What do they depend on for absorption?

A

A,D,E,K
Depend on incorporation into micelle

70
Q

Where are most vitamins and nutrients absorbed?

A

Duodenum

71
Q

Where is Vitamin B12 absorbed?

A

Ileum

72
Q

What do most B vitamins and Vitamin C require for absorption?

A

Na+ co-transporter

73
Q

Where does Iron absorption occur? Via what?

A

Occurs within duodenum via divalent metal transporter 1 (DMT1)

74
Q

How is iron transported out of the enterocyte?

A

Ferroportin 1 and hephaestin

75
Q

In the plasma Fe2+ is converted to Fe3+ and is transported by _____

A

transferrin

76
Q

What is the microbiome?

A

The collection of all organisms living on and in a given environment or habitat

77
Q

What organisms are most/least prevalent in the microbiome?

A

viruses > bacteria > fungi

78
Q

What is the distribution of microbiota determined by? (4)

A
  • pH
  • O2 access
  • temperature
  • tropism
79
Q

Most common bacteria in mouth?

A

Spirochaetes

80
Q

Most common bacteria in the Esophagus?

A

Streptococci and Lactobacilli

81
Q

Most common bacteria in the stomach?

A

H. pylori

82
Q

Most common bacteria in the small intestine?

A

Lactobacilli

83
Q

Most common bacteria in the large intestine?

A
  • Bifidobacteria
  • Lactobacilli
  • Enterococci
84
Q

Where is the most diversity in the microbiome in the body?

A

Large intestine

85
Q

93.5% of gut bacteria belong to what phyla? (4)

A
  • Firmicutes
  • Bacteroidetes
  • Proteobacteria
  • Actinobacteria
86
Q

What 2 bacteria contribute most to the gut microbiome?

A

Firmicutes and Bacteroidetes

87
Q

Examples of Firmicutes? (2)

A
  • Lactobacillus
  • Enterococcus
88
Q

Examples of Bacteroidetes? (2)

A
  • Bacteroides
  • Prevotella
89
Q

Examples of Proteobacteria? (5)

A
  • Helicobacter
  • E. coli
  • Shingella
  • Salmonella
  • Yersina
90
Q

Example of Actinobacteria? (1)

A
  • Bifidobacterium
91
Q

8 functions of gut microbiome?

A
  1. Harvesting energy
  2. Strengthen gut integrity
  3. Shape intestinal epithelium
  4. Regulate immune function
  5. Regulate intestinal motility
  6. Protection against pathogens
  7. Production of some nutrients
  8. “Endocrine organ”
92
Q

Gut microbiome development if C-section?

A
  • Less Bacteroides
  • More clostridium
93
Q

Gut microbiome development if vaginal birth?

A

More characteristic of mothers microbiota

94
Q

Gut microbiome development if breastfed?

A

Bifidobacterium high

95
Q

Gut microbiome development if formula-fed?

A
  • Bifidobacterium low
  • higher diversity and altered ratios of other bacteria
96
Q

Gut microbiome development if under-fed?

A

Increased entero-pathogens

97
Q

What happens with a childs gut flora by 2.5 years old?

A

Composition, diversity, and functional capabilities similar to that of an adult

98
Q

What factors can influence the composition of the gut microbiota?

A
  • Genetics
  • Diet
  • Medications
99
Q

Dietary impact on gut microbiome of diet rich in starch, fiber, and plants vs. sugar, starch, animal proteins

A

Starch/fiber/plant = Prevotella present
sugar/starch/animal = prevotella largely absent

100
Q

Why is Prevotella important?

A

Produces short chain fatty acids (SCFA’s)

101
Q

Microbiome metabolites? (4)

A
  • Short-chain fatty acids (SCFAs)
  • Trimethylamine (TMA)
  • Bile acids
  • Indoles
102
Q

Examples of SCFAs produced? (3)

A

Acetate, Propionate, Butyrate

103
Q

When are SCFAs’ produced?

A

During fermentation of indigestible carbohydrates (fibers)

104
Q

How do SCFAs promote intestinal integrity? (4)

A
  1. Regulating luminal pH
  2. Regulate mucus production
  3. Produce fuel for the epithelial cells
  4. Modify mucosal immune function
105
Q

How do SCFAs influence overall metabolism? (4)

A
  1. Appetite regulation
  2. Energy expenditure
  3. Glucose homeostasis
  4. Immuno-modulation
106
Q

Microbiome metabolite that has been linked to increasing RF for atherosclerosis and thrombosis?

A

Trimethylamine (TMA)

107
Q

Microbiome metabolite that has been correlated to changes in energy metabolism?

A

Bile acids

108
Q

Microbiome metabolite that is produced by Trp metabolism and maintains intestinal barrier and influences immune function?

A

Indoles

109
Q

What can be metabolized into TMAs?

A
  • Choline
  • Phosphatidylcholine
  • L-carnitine
110
Q

Healthy/Beneficial changes made by non-pathogenic E. coli?

A

Increase epithelial mucus secretion and reduce epithelial permeability

111
Q

Healthy/Beneficial changes made by non-pathogenic Lactobacillus rhamnossus?

A

Increase expression of occludin and
ZO-1 proteins

112
Q

Healthy/Beneficial changes made by non-pathogenic L. rheuteri?

A

Increase epithelial cell proliferation

113
Q

Pathogenic changes in Salmonella entetica?

A

Reduced ZO-1 and occludin proteins and tight junction complexes

114
Q

Pathogenic changes in Clostridium difficile?

A

Reduced mucin production

115
Q

Pathogenic changes in Enterovirus E11?

A

Direct cytotoxicity

116
Q

Bacteria increased when constipated? Decreased?

A

I: Bacteroides and Enterobacter
D: Bifidobacterium and Prevotella

117
Q

Bacteria increased in diarrhea? Decreased?

A

I: Prevotella
D: Bifidobacterium, Bacteroides, Lactobacillus

118
Q

Mechanism of action interferes with bacterial cell activity (including replication) without directly causing death

A

Bacteriostatic

119
Q

Mechanism of action directly kills the bacteria

A

Bactericidal

120
Q

Antibiotic is able to effect different types of bacteria’s including gram positive, gram negative, and others (spirochetes, atypical)

A

Broad spectrum

121
Q

Negative effects of antibiotics on gut microbiome? (3)

A
  • Reduce species diversity
  • Altered metabolic activity
  • Select the antibiotic-resistant organisms
122
Q

When does antibiotic associated diarrhea (ADD) typically occur?

A

Initially during treatment or up to 2 months following discontinuation

BMS150 Post-MT2 (17 decks)

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