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GI > Digestion/Absorption > Flashcards

Digestion/Absorption Flashcards

1
Q

What are the two types of digestive activity?

A

Cavital/Luminal

Membrane/Contact

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2
Q

What is cavital/luminal digestion?

A

Digestion occurring as result of enzymes secreted from salivary glands, stomach, and pancreas

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3
Q

What is membrane/contact digestion?

A

Digestion occurring due to enzymes present within enterocytes brush borders that digest on “contact”

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4
Q

What are 3 functional cells of intestinal epi and what is their function?

A

Enterocytes- digest, absorb, and secrete (high turnover rate)

Goblet cells- secrete mucus for protection

Paneth cells- secrete agents against bacteria

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5
Q

What is transmural movement? What is the pathway?

A

Transmural movement- movement from lumen to blood

Lumen -> unstirred fluid layer -> glycocalyx -> apical membrane -> cytoplasm -> basolateral membrane -> capillary wall

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6
Q

What are the 3 end products of carbohydrate digestion? What types of carbohydrates are absorbed?

A

End products- glucose, galactose, fructose

Only monosaccharides are absorbed

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7
Q

What type of digestion occurs when starches are converted to disaccharides and by what enzyme?

What type of digestion occurs when disaccharides are converted to monosaccharides?

A

Starch to disaccharide via amylase- cavital/luminal

Disaccharide to monosaccharide- membrane/contact

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8
Q

What enzyme is used and what are the products when the following products are digested?

Trehalose, Lactose, Sucrose

A

Trehalose via trehalase- glucose-glucose
Lactose via lactase- glucose-galactose
Sucrose via sucrase- glucose-fructose

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9
Q

Explain mechanism of carbohydrate absorption from lumen to blood

A

SGLT1- is a Na/Glucose or galactose apical transporter
GLUT5- is a fructose apical transporter
GLUT2- is a glucose, galactose, fructose basolateral transporter

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10
Q

What is the cause of lactose intolerance?
Why does lactose intolerance cause osmotic diarrhea?
Why does lactose intolerance cause excessive gas?

A

Absence of lactase in brush border (membrane digestion)
Undigested lactose holds onto water leading to diarrhea
Undigested lactose ferments into methane causing gas

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11
Q

Explain the D-xylose test and what it is looking for

A

Fast overnight, give oral D-xylose, and collect urine samples to look for any xylose

Testing for absorptive capacity of proximal SI

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12
Q

What enzyme digests protein in the stomach? How it the enzyme activated?

A

Pepsin, activated by low pH, digestions proteins within the stomach

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13
Q

What small intestinal enzyme digests proteins? How is it activated?

A

Trypsin, activated by enteropeptidase in brush border, is a small intestinal enzyme that digests proteins

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14
Q

What is the difference between pancreatic endo and exopeptidases? How are they activated?

A

Endopeptidases break interior bonds
Exopeptidases break external bonds

All pancreatic peptidases are activated by trypsin

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15
Q

What are the pancreatic endopeptidases?

A

Trypsin, chymotrypsin, and elastase

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16
Q

What are the pancreatic exopeptidases?

A

Carboxypeptidase A and B

17
Q

How are proteins absorbed into enterocytes?

How are proteins absorbed into blood?

A

Into cell- 4 separate co-transporters for neutral, acidic, basic, and imino AAs

Into blood- 4 separate facilitated transporters for neutral, acidic, basic, and imino AAs

18
Q

What causes cystinuria? What is the result?

A

Cystinuria is due to defective co-transporters and thus AA are not absorbed from the lumen into enterocytes
As a result AA will be present in feces

19
Q

What is Hartnups disease? What are symptoms?

A

Hartnups disease is an autosomal recessive genetic disorder where individuals can’t absorb neutral AA

Symptoms- diarrhea, tryptophan in urine, and niacin deficiency resulting in red scaly rashes

20
Q

What is cystic fibrosis? What enzyme deficiencies is it associated with? What else is it associated with and why does it lead to acute/chronic pancreatitis?

A

Cystic fibrosis is mutation of CFTR (Cl channel) that is associated with pancreatic enzyme deficiencies

Associated with decreased HCO3 secretion and an inability to flush out enzymes leading to pancreatitis

21
Q

Where does a majority of lipid digestion occur and why?

A

Most lipid digestion occurs in the small intestines due to bile being released there and emulsifying lipids which enhances lipase action due to an increased SA

22
Q

Explain the relationship between pancreatic lipase, colipase, trypsin, and bile

A

Pancreatic lipase is inactivated by bile

Colipase is activated by trypsin and will bind to pancreatic lipase to activate it

23
Q

Explain the absorption of lipids

A

Digested lipids are packaged into micelles which are absorbed across brush borders. Then lipids are reesterified leading to chylomicron formation and chylomicron exocytosis

24
Q

What is the cause of abetalipoproteinemia?

A

Absence of ApoB means one can not make chylomicrons and thus cannot absorb lipids

25
Q

What are some possible causes of bile salt deficiency?

A

Ileal resection

SI bacterial growth as result of decreased gastric acid secretion or decreased gastric motility

26
Q

What is the cause of tropical sprue? Why does it lead to steatorrhea? What vitamin deficiencies is it associated with?

A

Unknown cause
Decreased epi cells -> decreased microvilli -> decreased lipid absorption -> steatorrhea
Associated with folate and vit b12 deficiency

27
Q

What is the cause of Celiac sprue?
What is the effect on the intestines?
What deficiencies is it associated with?

A

Celiac sprue is due to Ab against gliadin (wheat protein)
Results in destruction of villi and hypertrophy of crypts
Associated with vitamin and iron deficiency

28
Q

What vitamins are fat soluble and how are they absorbed?

A

Vitamins A, D, E, K

Absorbed by same mechanism as lipids

29
Q

How are water solube vitamins absorbed?

A

Water soluble vitamins are absorbed via a Na dependent cotransporter

30
Q

Explain the absorption of Vit B12

A

Vit B12 binds R protein in stomach and enters duodenum where it binds IF which has receptors in the distal ileum which allow for vit B12 absorption

31
Q

What are vit B12 deficiencies associated with?

A

Demyelination- vit b12 is cofactor for myelination

Pernicious anemia- RBC fail to mature

32
Q

What are some possible underlying causes of pernicious anemia?

A

Atrophic/chronic gastritis- chronic inflammation of gastric mucosa results in parietal cell destruction which releases IF

Autoimmune disorder creates anti-IF Abs

GI (10 decks)

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