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
2
Q
what two parts of the small intestine are important for absorption?
A
jejunum and ileum
3
Q
what are the 4 main parts of the GI system?
A
upper, middle, lower and accessory
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
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
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
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
8
Q
what part of the upper GI tract is called the “entrance foyer”? what is its primary function?
A
mouth; function is mastication
9
Q
What connects the oropharynx to the stomach?
A
esophagus
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
11
Q
what occurs in esophageal smooth muscle that helps move food along the tube?
A
peristalsis
12
Q
what does the epithelial layer of the esophagus do?
A
its made of striated squamous epithelium which lubricates and protects the surface
13
Q
what is the upper sphincter of the upper GI tract called? how about the lower one?
A
upper: pharyngoesophageal
lower: gastroesophageal
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
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
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
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
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
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
20
Q
how much fluid is secreted into the GI tract daily?
A
about 7000 ml
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
22
Q
what are the GI secretions similar in concentration to?
A
similar to sodium and potassium in extracellular fluid
23
Q
what are GI secretions mostly made up of?
A
water
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
25
what is the largest endocrine organ in the body?
GI tract
26
what are two hormones secreted by the stomach?
gastrin and ghrelin
27
what is gastrin produced by? what does it stimulate? what are two effects does it have?
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
28
what is ghrelin?
peptide hormone produced by endocrine cells in mucosal layer of fundus (stomach)
29
what activity does ghrelin increase? what is its effect?
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)
30
what does ghrelin stimulate secretion of?
GH secretion
31
what are the four SI hormones?
secretin, cholecystokinin, GLP-1, GIP
32
what is secretin secreted by? what is its secretion stimulated by? what does it inhibit? what does it stimulate/cause?
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
33
what two things is cholecystokinin important for? what is it secreted by? what are its two functions?
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
34
what does cholecystokinin increase the effect of? what does it stimulate in the bile duct? what two things does it regulate?
action of secretin; stimulates biliary secretion of fluid and bicarb; regulates gallbladder contraction and gastric emptying
35
what is the incretin effect?
increase insulin after an oral glucose load after a predominantly carb meal
36
what is GLP-1 secreted by? what does it suppress? what does it slow and decrease? what does it increase?
secreted by L cells in the distal small bowel; suppressed glucagon release; slows gastric emptying, decreased appetite and body weight; increases net glucose clearance
37
what secretes GIP?
K cells in the upper gut (mainly jejunum)
38
what is saliva produced by?
salivary glands
39
what are the four salivary glands?
parotid, submaxillary, sublingual, and buccal glands
40
what are the three functions of saliva?
1) . protection and lubrication: sublingual and buccal glands
2) . antimicrobial: enzyme lysozyme
3) . initiates digestion of starches: ptyalin and amylase in saliva
41
what nervous system primarily regulates saliva?
ANS
parasympathetic: increases saliva flow
sympathetic: decreases flow
42
what are the gastric glands called? where are these located? what two cells do these glands contain?
oxyntic (gastric) glands; located in proximal 80% of the stomach (body and fundus); contains parietal and chief cells
43
what do parietal cells secrete?
HCL into the stomach to digest food/break down proteins (important for proton pump) and intrinsic factor
44
what is intrinsic factor important for?
B12 absorption (deficiency can lead to pernicious anemia)
45
what do chief cells secrete?
pepsinogen, which is converted to pepsin when exposed to low pH of gastric juices
46
what three things do G cells secrete?
mainly mucus, gastrin hormone, and some pepsinogen
47
where are chief and parietal cells found?
bases of gastric pits (body and fundus of the stomach)
48
what three substances stimulate the parietal cells to secrete HCL? where are each of these substances found?
acetylcholine (PNS), gastrin (pyloric glands in the lower stomach), and histamine (released by ECL cells which are stimulated by gastrin)
49
what do enterochromaffin-like (ECL) cells do?
release histamine which binds to parietal cell on H2 receptors
50
what glands contain G cells?
pyloric glands
51
what does pepsin do?
breaks down and digest protein in food
52
what does the small intestine secrete and what does it receive secretions from?
secretes digestive juices; receives secretions from liver and pancreas
53
what two things in the SI are important for secretions?
Brunner glands and intestinal mucosa
54
where are Brunner glands found?
at the site where the stomach contents and liver and pancreatic secretions enter the duodenum
55
what do brunner glands secrete? what NS is it influenced by? describe innervation
secretes alkaline mucus; influenced by ANS: sympathetic activity decreases mucus production (area is left susceptible to irritation)
56
what two types of fluid does the small intestine intestinal mucosa secrete?
crypts of lieberkuhn and fluid with surface enzymes
57
what do crypts of lieberkuhn produce?
serous fluid (pH 6.5-7.5) which acts as vehicle for absorption
58
what is the purpose of the SI intestinal secretion fluid with surface enzymes?
aid in absorption. contains peptidases that separate amino acids and disaccharides split sugars
59
what does the large intestine secrete?
only mucus
60
what NS influences LI secretions?
ANS: parasympathetic increases mucus (mucus in stools is ONLY for movement)
61
what are three major functions of gut microflora?
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
how do broad spectrum ABX impact the gut?
disrupts microbial balance and allows overgrowth of pathogen species
63
what 3 probiotics can be helpful in UC?
lactobacilli, bifidobacterial, nonpathogenic E coli
64
what ABX is commonly used to treat C Dif?
flagyl
65
what are the three main parts of digestion?
hydrolysis, enzyme cleavage, and fat emulsification
66
what is hydrolysis (component of digestion)?
breakdown of compound via chemical reaction involving water (secrete 7-8 L of water in tract daily)
67
what is fat emulsification (component of digestion)?
break down fat globules into fat droplets where enzymes can work more effectively at digesting them
68
what is absorption?
process of moving nutrients and other materials from the external environment of GI tract to internal environment
69
absorption is accomplished through what two processes?
active transport and diffusion
70
describe the shape of the SI to accommodate for its large surface area
circular folds with fingerlike-projected villi
71
what do fats rely on for absorption?
lymphatic system- transported to systemic circulation by this way
72
what are enterocytes? where are they found? what do they secrete?
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
what are the four carb disaccharides?
starch, sucrose, lactose, and maltose
74
what must the disaccharides be broken into so that they can be absorbed in the SI?
monosaccharides (glucose, fructose, galactose)
75
what does amylase do? what two places is it found?
it breaks down starch into a-dextrins, maltose, and maltotriose; found in mouth and pancreas
76
what do brush border enzymes do?
convert disaccharides into monosaccharides
77
sucrose is broken into what two things? how about lactose and maltose?
sucrose- glucose and fructose
lactose- glucose and galactose
maltose- two glucose molecules
78
what happens when carbs cant be broken down?
they remain osmotically active particles and cause diarrhea
79
what is trehalose broken down into?
two glucose molecules
80
how is fructose transported?
across SI mucosa by facilitated diffusion (along concentration gradient, doesn't require energy)
81
how are glucose and galactose transported?
by active transport against a concentration gradient (NA/K ATPase pump and ATP as energy source)
82
how is water absorbed during carb absorption?
linked to absorption of osmotically active particles glucose and sodium
83
what absorbs the 3 monosaccharides?
intestinal epithelial cells
84
what are the three fats?
triglycerides, cholesterol, and phospholipids
85
what is most fat intake in the form of?
triglycerides- containing long chain fatty acids
86
what are medium chain TGs used for tx of?
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
what enzyme breaks down TGs?
pancreatic lipase
88
what act as a carrier system for fatty acids and fat soluble vitamins?
bile salts
89
what are the 4 fat soluble vitamins?
A, D, E, K
90
what are micelles?
transport digestive products of lipids to the villi where they are absorbed (bile salts form them)
91
what is the major site of fat absorption? where does fat absorption begin and end?
upper jejunum; begins in the stomach and ends in the SI
92
patients with impairment in the release of bile will likely have impaired what? what type of pts is this seen in?
digestion of fats; cholecystitis pts
93
what does obstruction of lymphatics impair?
transport of fat after absorption from gut
94
what happens to the fat that isn't absorbed?
excreted in the stool
95
what does steatorrhea mean?
fatty stool
96
what three things are proteins broken into?
amino acids, dipeptides, and tripeptides
97
what enzyme starts protein breakdown?
pepsin in the stomach
98
what four pancreatic enzymes contribute to protein breakdown?
trypsin, chymotrypsin, carboxypeptidase, and elastase
99
pepsin and pancreatic enzymes are secreted in what form?
precursor molecules that must be converted to active form
100
what enzymes degrade proteins into peptides?
brush border enzymes
101
how are peptides transported across the mucosal membrane?
sodium linked process that uses Na/K ATPase pump for energy
102
what are the three functions of the gallbladder?
1) . store bile that is made by the liver
2) . concentrates bile
3) . ejects bile when its stimulated (usually 30 mins after meal)
103
should you do a GB ultrasound if a pt has eaten recently?
no, GB is smushed down bc it already ejected bile
104
how does CCK impact the gallbladder and sphincter of Oddi?
causes the gallbladder to contract and sphincter to relax
105
what is anorexia? what is it influenced by?
loss of appetite; influenced by hunger, hypothalamus (desire for food), smell, emotional factors, drugs, disease
106
what does nausea result from? what two things can cause it? what ANS manifestations is it frequently accompanied by?
stimulation of medullary vomiting center; distension of duodenum or upper SI; watery salivation, vasoconstriction, pallor, sweating, inc HR
107
what type of mechanism is vomiting?
protective- limits damage from ingested noxious agents
108
vomiting involves what two medullary centers in the brain?
vomiting center and chemoreceptor trigger zone
109
what is the vomiting center?
vomiting is reflexive, dorsal area of the reticular formation of the medulla near sensory nuclei of the vagus
110
what three places does the vomiting center receive signals from?
GI tract/other organs (inflammation, distention, or irritation of organs), cerebral cortex, and vestibular apparatus (motion sickness)
111
where is the chemoreceptor trigger zone located? it mediates vomiting in response to what?
floor of 4th ventricle- exposed to both CSF and blood; in response to blood-borne drugs or toxins
112
what are three neuromediators of nausea/vomiting? what three places are these receptors found?
dopamine, serotonin, and opioid receptors; found in GI tract, vomiting center, chemoreceptor trigger zone
113
what do dopamine antagonists do?
depress vomiting caused by stimulation of the chemoreceptor trigger zone (prochlorperazine - Compazine)
114
what do serotonin antagonists do?
(ondansetron - Zofran) can reduce the nausea and vomiting caused by chemotherapy and radiation therapy
115
what do ACH receptors in the vestibular center mediate?
mediate the N/V from motion sickness.
116
what do Norepi receptors in vestibular center do?
stabilize and resist motion sickness
117
what is Dramamine/dimenhydrinate?
strong CNS anticholinergic effect – acts on norepinephrine receptors in vomiting center and areas related to vestibular system
