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Pathophys > GI > Flashcards

GI Flashcards

1
Q

when do food and nutrients become part of the internal environment?

A

once they are absorbed into the blood or lymphatics

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2
Q

what two parts of the small intestine are important for absorption?

A

jejunum and ileum

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3
Q

what are the 4 main parts of the GI system?

A

upper, middle, lower and accessory

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4
Q

what are the three components of the upper GI system? what are its two functions?

A

mouth, esophagus, stomach

initial receptacle and initiation of digestion

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5
Q

what is the middle GI system compromised of? what is its function?

A 
small intestine (duodenum, jejunum, and ileum);
this is where most digestive & absorptive processes occur
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6
Q

what are the three parts of the lower GI system? what are its two functions?

A

cecum, colon, and rectum; it is important for mass movement effects and storage for elimination

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7
Q

what are the three parts of the accessory GI system? what is its function?

A

salivary glands, liver, pancreas; produce secretion that aid in digestion

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8
Q

what part of the upper GI tract is called the “entrance foyer”? what is its primary function?

A

mouth; function is mastication

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9
Q

What connects the oropharynx to the stomach?

A

esophagus

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10
Q

how long is the esophagus? what is it made of and describe its flexibility

A

10 inches; it is muscular (upper 1/3 is completely skeletal striated, middle 1/3 is mixed, lower 1/3 is completely smooth) and collapsible

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11
Q

what occurs in esophageal smooth muscle that helps move food along the tube?

A

peristalsis

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12
Q

what does the epithelial layer of the esophagus do?

A

its made of striated squamous epithelium which lubricates and protects the surface

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13
Q

what is the upper sphincter of the upper GI tract called? how about the lower one?

A

upper: pharyngoesophageal
lower: gastroesophageal

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14
Q

what is the pharyngoesophageal sphincter made of? what is its function?

A

circular layer of striated muscle; function: relaxes to open esophagus so food can enter

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15
Q

where is the gastroesophageal sphincter located? what does it pass through?

A

about 3 cm above the stomach; it passes through a “hiatus” which is the opening through the diaphragm into the stomach

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16
Q

describe how contraction and relaxation work in terms of the gastroesophageal sphincter

A

it remains contracted (tonic) causing an area of high pressure to keep contents in the stomach; it relaxes when eating

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17
Q

what does the esophageal hiatus do?

A

aids in the maintenance of high pressure area around lower sphincter to prevent reflux of stomach contents

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18
Q

what is a hiatal hernia? what happens to the body if its a severe one?

A

a protrusion of stomach up through the hiatus; you can get GERD and maybe damage to esophageal walls or ulcers

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19
Q

what type of hiatal hernia is the most severe and pt needs to go to the OR right away?

A

traumatic hiatal hernia; happens more rapid than usual gradual onset

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20
Q

how much fluid is secreted into the GI tract daily?

A

about 7000 ml

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21
Q

how much fluid of total secreted per day leaves the stool? what happens to the rest of it?

A

50-200 ml; remainder is absorbed in the small and large intestines

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22
Q

what are the GI secretions similar in concentration to?

A

similar to sodium and potassium in extracellular fluid

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23
Q

what are GI secretions mostly made up of?

A

water

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24
Q

where does the secreted GI fluid come from?

A

the extracellular space/compartment; so excessive secretion or impaired absorption will impact this space

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25
Q

what is the largest endocrine organ in the body?

A

GI tract

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26
Q

what are two hormones secreted by the stomach?

A

gastrin and ghrelin

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27
Q

what is gastrin produced by? what does it stimulate? what are two effects does it have?

A

produced by G cells in the antrum of the stomach; stimulates gastric acid secretion; growth producing (trophic) effect on the SI & colon mucosa AND acid secreting (oxyntic) effect on gland area of the stomach

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28
Q

what is ghrelin?

A

peptide hormone produced by endocrine cells in mucosal layer of fundus (stomach)

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29
Q

what activity does ghrelin increase? what is its effect?

A

ghrelin has potent growth hormone-releasing activity; stimulatory effect on food intake (increases appetite) and digestive function WHILE reducing energy expenditure (we keep the fat)

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30
Q

what does ghrelin stimulate secretion of?

A

GH secretion

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31
Q

what are the four SI hormones?

A

secretin, cholecystokinin, GLP-1, GIP

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32
Q

what is secretin secreted by? what is its secretion stimulated by? what does it inhibit? what does it stimulate/cause?

A

secreted by S cells in the duodenum and jejunum; stimulated by acidic chyme in the SI; inhibits gastrin release (turns off gastric acid secretion); stimulates the pancreas to secrete fluid with high bicarbonate and low chloride concentrations

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33
Q

what two things is cholecystokinin important for? what is it secreted by? what are its two functions?

A

important for fat digestion and absorption; secreted by I cells in the intestinal mucosa; functions- stimulates pancreatic enzyme secretion and increases pancreatic bicarb response to low circulating levels of secretin

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34
Q

what does cholecystokinin increase the effect of? what does it stimulate in the bile duct? what two things does it regulate?

A

action of secretin; stimulates biliary secretion of fluid and bicarb; regulates gallbladder contraction and gastric emptying

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35
Q

what is the incretin effect?

A

increase insulin after an oral glucose load after a predominantly carb meal

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36
Q

what is GLP-1 secreted by? what does it suppress? what does it slow and decrease? what does it increase?

A

secreted by L cells in the distal small bowel; suppressed glucagon release; slows gastric emptying, decreased appetite and body weight; increases net glucose clearance

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37
Q

what secretes GIP?

A

K cells in the upper gut (mainly jejunum)

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38
Q

what is saliva produced by?

A

salivary glands

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39
Q

what are the four salivary glands?

A

parotid, submaxillary, sublingual, and buccal glands

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40
Q

what are the three functions of saliva?

A

1) . protection and lubrication: sublingual and buccal glands
2) . antimicrobial: enzyme lysozyme
3) . initiates digestion of starches: ptyalin and amylase in saliva

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41
Q

what nervous system primarily regulates saliva?

A

ANS

parasympathetic: increases saliva flow
sympathetic: decreases flow

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42
Q

what are the gastric glands called? where are these located? what two cells do these glands contain?

A

oxyntic (gastric) glands; located in proximal 80% of the stomach (body and fundus); contains parietal and chief cells

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43
Q

what do parietal cells secrete?

A

HCL into the stomach to digest food/break down proteins (important for proton pump) and intrinsic factor

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44
Q

what is intrinsic factor important for?

A

B12 absorption (deficiency can lead to pernicious anemia)

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45
Q

what do chief cells secrete?

A

pepsinogen, which is converted to pepsin when exposed to low pH of gastric juices

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46
Q

what three things do G cells secrete?

A

mainly mucus, gastrin hormone, and some pepsinogen

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47
Q

where are chief and parietal cells found?

A

bases of gastric pits (body and fundus of the stomach)

48
Q

what three substances stimulate the parietal cells to secrete HCL? where are each of these substances found?

A

acetylcholine (PNS), gastrin (pyloric glands in the lower stomach), and histamine (released by ECL cells which are stimulated by gastrin)

49
Q

what do enterochromaffin-like (ECL) cells do?

A

release histamine which binds to parietal cell on H2 receptors

50
Q

what glands contain G cells?

A

pyloric glands

51
Q

what does pepsin do?

A

breaks down and digest protein in food

52
Q

what does the small intestine secrete and what does it receive secretions from?

A

secretes digestive juices; receives secretions from liver and pancreas

53
Q

what two things in the SI are important for secretions?

A

Brunner glands and intestinal mucosa

54
Q

where are Brunner glands found?

A

at the site where the stomach contents and liver and pancreatic secretions enter the duodenum

55
Q

what do brunner glands secrete? what NS is it influenced by? describe innervation

A

secretes alkaline mucus; influenced by ANS: sympathetic activity decreases mucus production (area is left susceptible to irritation)

56
Q

what two types of fluid does the small intestine intestinal mucosa secrete?

A

crypts of lieberkuhn and fluid with surface enzymes

57
Q

what do crypts of lieberkuhn produce?

A

serous fluid (pH 6.5-7.5) which acts as vehicle for absorption

58
Q

what is the purpose of the SI intestinal secretion fluid with surface enzymes?

A

aid in absorption. contains peptidases that separate amino acids and disaccharides split sugars

59
Q

what does the large intestine secrete?

A

only mucus

60
Q

what NS influences LI secretions?

A

ANS: parasympathetic increases mucus (mucus in stools is ONLY for movement)

61
Q

what are three major functions of gut microflora?

A

1) . metabolic activities that salvage energy and absorbable nutrients
2) . trophic effects on intestinal epithelial cells
3) . protection of the colonized host against invasion by pathogenic organisms

62
Q

how do broad spectrum ABX impact the gut?

A

disrupts microbial balance and allows overgrowth of pathogen species

63
Q

what 3 probiotics can be helpful in UC?

A

lactobacilli, bifidobacterial, nonpathogenic E coli

64
Q

what ABX is commonly used to treat C Dif?

A

flagyl

65
Q

what are the three main parts of digestion?

A

hydrolysis, enzyme cleavage, and fat emulsification

66
Q

what is hydrolysis (component of digestion)?

A

breakdown of compound via chemical reaction involving water (secrete 7-8 L of water in tract daily)

67
Q

what is fat emulsification (component of digestion)?

A

break down fat globules into fat droplets where enzymes can work more effectively at digesting them

68
Q

what is absorption?

A

process of moving nutrients and other materials from the external environment of GI tract to internal environment

69
Q

absorption is accomplished through what two processes?

A

active transport and diffusion

70
Q

describe the shape of the SI to accommodate for its large surface area

A

circular folds with fingerlike-projected villi

71
Q

what do fats rely on for absorption?

A

lymphatic system- transported to systemic circulation by this way

72
Q

what are enterocytes? where are they found? what do they secrete?

A

they are cells on the villi that are important for digestion and absorption; they secrete brush border enzymes that aid in digestion of carbs and proteins

73
Q

what are the four carb disaccharides?

A

starch, sucrose, lactose, and maltose

74
Q

what must the disaccharides be broken into so that they can be absorbed in the SI?

A

monosaccharides (glucose, fructose, galactose)

75
Q

what does amylase do? what two places is it found?

A

it breaks down starch into a-dextrins, maltose, and maltotriose; found in mouth and pancreas

76
Q

what do brush border enzymes do?

A

convert disaccharides into monosaccharides

77
Q

sucrose is broken into what two things? how about lactose and maltose?

A

sucrose- glucose and fructose
lactose- glucose and galactose
maltose- two glucose molecules

78
Q

what happens when carbs cant be broken down?

A

they remain osmotically active particles and cause diarrhea

79
Q

what is trehalose broken down into?

A

two glucose molecules

80
Q

how is fructose transported?

A

across SI mucosa by facilitated diffusion (along concentration gradient, doesn’t require energy)

81
Q

how are glucose and galactose transported?

A

by active transport against a concentration gradient (NA/K ATPase pump and ATP as energy source)

82
Q

how is water absorbed during carb absorption?

A

linked to absorption of osmotically active particles glucose and sodium

83
Q

what absorbs the 3 monosaccharides?

A

intestinal epithelial cells

84
Q

what are the three fats?

A

triglycerides, cholesterol, and phospholipids

85
Q

what is most fat intake in the form of?

A

triglycerides- containing long chain fatty acids

86
Q

what are medium chain TGs used for tx of?

A

malabsorption syndrome bc they only have 6-10 carbon atoms and are more completely broken down in pancreatic lipase (which allows them to be absorbed easier)

87
Q

what enzyme breaks down TGs?

A

pancreatic lipase

88
Q

what act as a carrier system for fatty acids and fat soluble vitamins?

A

bile salts

89
Q

what are the 4 fat soluble vitamins?

A

A, D, E, K

90
Q

what are micelles?

A

transport digestive products of lipids to the villi where they are absorbed (bile salts form them)

91
Q

what is the major site of fat absorption? where does fat absorption begin and end?

A

upper jejunum; begins in the stomach and ends in the SI

92
Q

patients with impairment in the release of bile will likely have impaired what? what type of pts is this seen in?

A

digestion of fats; cholecystitis pts

93
Q

what does obstruction of lymphatics impair?

A

transport of fat after absorption from gut

94
Q

what happens to the fat that isn’t absorbed?

A

excreted in the stool

95
Q

what does steatorrhea mean?

A

fatty stool

96
Q

what three things are proteins broken into?

A

amino acids, dipeptides, and tripeptides

97
Q

what enzyme starts protein breakdown?

A

pepsin in the stomach

98
Q

what four pancreatic enzymes contribute to protein breakdown?

A

trypsin, chymotrypsin, carboxypeptidase, and elastase

99
Q

pepsin and pancreatic enzymes are secreted in what form?

A

precursor molecules that must be converted to active form

100
Q

what enzymes degrade proteins into peptides?

A

brush border enzymes

101
Q

how are peptides transported across the mucosal membrane?

A

sodium linked process that uses Na/K ATPase pump for energy

102
Q

what are the three functions of the gallbladder?

A

1) . store bile that is made by the liver
2) . concentrates bile
3) . ejects bile when its stimulated (usually 30 mins after meal)

103
Q

should you do a GB ultrasound if a pt has eaten recently?

A

no, GB is smushed down bc it already ejected bile

104
Q

how does CCK impact the gallbladder and sphincter of Oddi?

A

causes the gallbladder to contract and sphincter to relax

105
Q

what is anorexia? what is it influenced by?

A

loss of appetite; influenced by hunger, hypothalamus (desire for food), smell, emotional factors, drugs, disease

106
Q

what does nausea result from? what two things can cause it? what ANS manifestations is it frequently accompanied by?

A

stimulation of medullary vomiting center; distension of duodenum or upper SI; watery salivation, vasoconstriction, pallor, sweating, inc HR

107
Q

what type of mechanism is vomiting?

A

protective- limits damage from ingested noxious agents

108
Q

vomiting involves what two medullary centers in the brain?

A

vomiting center and chemoreceptor trigger zone

109
Q

what is the vomiting center?

A

vomiting is reflexive, dorsal area of the reticular formation of the medulla near sensory nuclei of the vagus

110
Q

what three places does the vomiting center receive signals from?

A

GI tract/other organs (inflammation, distention, or irritation of organs), cerebral cortex, and vestibular apparatus (motion sickness)

111
Q

where is the chemoreceptor trigger zone located? it mediates vomiting in response to what?

A

floor of 4th ventricle- exposed to both CSF and blood; in response to blood-borne drugs or toxins

112
Q

what are three neuromediators of nausea/vomiting? what three places are these receptors found?

A

dopamine, serotonin, and opioid receptors; found in GI tract, vomiting center, chemoreceptor trigger zone

113
Q

what do dopamine antagonists do?

A

depress vomiting caused by stimulation of the chemoreceptor trigger zone (prochlorperazine - Compazine)

114
Q

what do serotonin antagonists do?

A

(ondansetron - Zofran) can reduce the nausea and vomiting caused by chemotherapy and radiation therapy

115
Q

what do ACH receptors in the vestibular center mediate?

A

mediate the N/V from motion sickness.

116
Q

what do Norepi receptors in vestibular center do?

A

stabilize and resist motion sickness

117
Q

what is Dramamine/dimenhydrinate?

A

strong CNS anticholinergic effect – acts on norepinephrine receptors in vomiting center and areas related to vestibular system

Pathophys (13 decks)

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