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GI Final > Digestion and absorption Processes in the GI Tract > Flashcards

Digestion and absorption Processes in the GI Tract Flashcards

1
Q

cellular absorption

A

lumen to apical membrane to intestinal epithelial cells to basolateral membrane to blood
transporters in membranes

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2
Q

paracellular absorption

A

intestinal epithelial cells to lateral intercellular space to intestinal epithelial cells
tight junctions

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3
Q

cavital (luminal) digestion

A

refers to digestion resulting from the action of enzymes secreted by the salivary glands stomach and pancreas

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4
Q

membrane (contract) digestion

A

refers to hydrolysis by enzymes synthesized by epithelial cells

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5
Q

structure of the intestinal mucosa

A

kerckring - longitudinal folds
villi and microvilli increase surface area of the small intestine (longer in duodenum and shorter in ileum)
all increase the intestine total surface area by 600 fold

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6
Q

enterocytes

A

function in digestion, absorption and secretion
turnover rate cells are replaced 3-6 days
susceptible to irradiation and chemotherapy

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7
Q

goblet cells

A

mucus secreting cells

physical chemical and immunologic protection

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8
Q

paneth cells

A

part of the mucosal defense against infection

secrete agents that destruct bacteria or produce inflammatory responses

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9
Q

pinocytosis

A

at the base of the microvilli

major mechanism in the uptake of proteins

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10
Q

passive diffusion

A

particles move through pores in the cell membrane or through intercellular spaces

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11
Q

barriers crossed during absorption into enterocyte

A 
unstirred layer of fluid 
glycocalyx 
apical membrane 
cytoplasm of the cell 
basolateral membrane 
basement membrane 
wall of blood capillary or lymphatic vessel
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12
Q

end products of carbohydrate digestion

A

only monosaccharides are absorbed by the enterocytes

glucose, glactose, and fructose

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13
Q

transport mechanisms in absorption of carbohydrates

A

co-transport and facilitated diffusion

SLGT1 - secondary active transport

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14
Q

lactose intolerance

A

failure to digest carbohydrates
brush border lactase is deficient or lacking
undigested lactose remains in the lumen and holds water and causes osmotic diarrhea
undigested and unabsorbed lactose is fermented into methane and H gas causing excess gas

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15
Q

Stomach proteases - endopeptidase

A

pepsin
trypsin
chymotrypsin
elastase

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16
Q

stomach proteases - exopeptidases

A

carbocypeptidase A

carboxypeptidase B

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17
Q

small intestine proteases

A 
trypsin
chymotrypsin
elastase
carboxy peptidase A
carboxy peptidase B
18
Q

transport mechanism in absorption of proteins

A

4 separate cotransporters - neutral, acidic, basic, and imino AA
4 separate facilitated diffusion mechanisms - one each for neutral acidic basic and imino AA

19
Q

chronic pancreatitis and cystic fibrosis

A

deficiency of pancreatic enzymes

20
Q

congenital trypsin absence

A

in the absence of trypsin it seems like all the pancreatic enzyme are gone

21
Q

cystinuria

A

defect in or absence of Na amino acid cotransporters
transporter for di basic amino acids is absent from the SI and kidney
genetic disorder
as a result of the intestinal deficiency amino acids are secreted in feces

22
Q

hartnup disease

A

cannot absorb neutral aa
recessive genetic disorder
symptoms resemble those caused by pellaga (deficiency of niacin)
symptoms - diarrhea, mood changes, neurologic problems, red, scaly skin rash, usually which skin is exposed to sunlight , photosensitivity, short stature, uncoordinated movements
urine same have high excretion of neutral aa

23
Q

mutations in cystic fibrosis transmembrane conductance regulator

A

regulated anion channel that is located at the apical surface of the duct cells
loss of bicarb secretion

24
Q

insolubility of lipids

A

lipids need to be solubilized in micelles and transported to the apical membrane of intestinal epithelial cells for absorption

25
Q

stomach and lipid digestion

A

lingual and gastric lipases initiate lipid digestion in the stomach
CCK allows sufficient time for lipids to get digested properly by slowing gastric emptying

26
Q

small intestine and lipid digestion

A

most lipid digestion occurs in the small intestine
bile salts emulsify lipids
pancreatic enzymes are secreted into the small intestine to complete the digestive work

27
Q

pancreatic lipase

A

inactivated by bile slats colipase solves this problem

28
Q

colipase

A

secreted as inactive form it is activated by trypsin

once activated it binds to pancreatic lipase displacing bile salts

29
Q

cholesterol ester hydrolase

A

in addition to catalyze the production of cholesterol it also hydrolyzes triglycerides to produce glycerol

30
Q

phospholipase A2

A

proenzyme is activated by trypsin

31
Q

mechanism for processing lipids

A 
solubilization by micelles 
diffusion of micellar contents across apical membrane 
reesterfication 
chylomicron formation 
exocytosis of chylomicrons
32
Q

abnormalities of pancreatic enzyme secretion

A

failure to secrete adequate amounts of pancreatic enzymes
regulation of acidity of duodenal contents is critical for the integrity of pancreatic enzyme function
Zollinger-Ellison syndrome
Pancreatitis

33
Q

deficiency of bile salts

A

interferes with the formation of micelles
ileal resection interrupts the enterohepatic circulation of bile salts
small intestinal bacterial over growth

34
Q

decreased intestinal epithelial cells

A

tropical sprue - lipid absorption is impaired because the surface area for absorption is decreased

35
Q

fat soluble vitamins (A, D, E and K)

A

same mechanism of absorption as lipids

36
Q

water soluble vitamins (B1, B2, B3, B12, C, biotin, folic acid, nicotinic acid, and pantothenic acid)

A

absorbed via Na dependent cotransport mechanism in the small bowel

37
Q

Vitamin B12

A

form complexes with other proteins in order to be absorbed

38
Q

pernicious anemia

A

type of vitamin B12 anemia
stomach does not produce enough IF which decreases B12
due to atrophic gastritis and autoimmune conditions

39
Q

absorption of vitamin D

A

D3 from diet
converted to 15 hydroxy D3 in liver
converted to 1,2 dihydroxy D3 and 24,25 dihydroxy D3 in liver
leads to increase gut Ca2 absorption, bone calcification, bone reabsorption

40
Q

abnormalities of vitamin D absorption

A

inadequate Ca2 absorption - rickets and osteomalacia

no D3 and no 1,23 dihydroxy D3

GI Final (8 decks)

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