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GI Final > Digestion/Absorption > Flashcards

Digestion/Absorption Flashcards

1
Q

Folds of Kercking

A

Longitudinal folds on luminal surface of small intestine

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2
Q

Brush border

A

Increases surface area and is site of activity for numerous digestive enzymes

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3
Q

Enterocytes

A
  • Epithelial cells

- Focusing on digestion, absorption, secretion

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4
Q

Goblet cells

A

Mucus-secreting cells for protection

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5
Q

Paneth cells

A

Part of mucosal defenses against infection that secrete agents to destroy bacteria or produce inflammation

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6
Q

Effect of terminal ileal resection?

A
  • Abolished bile salt and Vitamin B12 absorption
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7
Q

Carb Digestion (mouth)

A
  • Some starch broken down
  • Salivary amylase
  • Starch broken into maltose and polymers of glucose
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8
Q

Carb digestion (SI)

A
  • Most starch breakdown occurs here
  • Pancreatic amylase *
  • Starch – maltose and polymers of glucose
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9
Q

Maltose becomes

A

Glucose + Glucose

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10
Q

Trehalose becomes

A

Glucose + Glucose

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11
Q

Lactose becomes

A

Galactose + Glucose

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12
Q

Sucrose becomes

A

Glucose + Fructose

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13
Q

Monosaccharide transporters from lumen to duodenal epithelial cell?

A

SGLT1 + GLUT5

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14
Q

SGLT 1

A

secondary active transporter for glucose and galactose (from lumen to epithelial cell)

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15
Q

GLUT 5

A

facilitated diffusion for fructose (from lumen to epithelial cell)

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16
Q

GLUT 2

A

facilitated diffusion into blood (from epithelial cell to blood)

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17
Q

Transporters from epithelial cell to blood

A
  • Na/K ATPase

- GLUT 2

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18
Q

What results from lactose intolerance?

A

Lactose stays in lumen, holds H2O in lumen and osmotic diarrhea results

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19
Q

D-xylose test

A
  • Pt ingests 25 g D-xylose and urine collected for 5 hrs
  • 4g+ in urine = absorbed properly
  • < 4 g in urine = not properly absorbed (some absorption disorder present)
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20
Q

Endopeptidases

A

hydrolyze interior bonds

pepsin, trypsin, chymotrypsin, elastase

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21
Q

Exopeptidases

A

hydrolyze one amino acid at a time from carboxyl end

carboxypeptidase A/B

22
Q

Protein digestion (stomach)

A
  • 10-20% breakdown occurs here (not essential)

- Pepsin (pepsinogen activated at pH 2,3)

23
Q

Protein digestion (pancreas)

A
  • Proteins broken down into di/tri peptides

- Trypsin, chymotrypsin, carboxypeptidase, elastase

24
Q

Role of trypsin and chymotrypsin in protein digestion

A

Cleaves into small polypeptides

25
Q

Role of carboxypeptidase in protein digestion

A

Cleaves AA into carboxyl ends

26
Q

Protein digestion (SI)

A
  • Aminopolypeptidase, dipeptidases

- AA/peptides absorbed into enterocytes

27
Q

What enzyme(s) activate zymogens?

A

Trypsin or enterokinase (trypsinogen)

28
Q

Co-transport of AAs in SI

A

Travel with Na+ in co-transporters

Peptides travel w/ H+

29
Q

Chronic pancreatitis

A

Deficiency of pancreatic enzymes (ie. lack of proteases)

30
Q

Congenital trypsin absence

A

No trypsin… no functional pancreatic enzymes

31
Q

Cystinuria

A
  • Defect in/absence of Na+/AA cotransporters

- Dibasic AA (Cys, Lys, Arg, Orn) transporters specifically

32
Q

Hartnup disease

A
  • SI cannot absorb neutral AAs

- Sx resemble pellagra (dementia, diarrhea, dermatitis)

33
Q

Cystic Fibrosis

A
  • CFTR-regulated Cl- channel on apical membrane w/ mutation
  • Mutation causes loss of HCO3- secretion (enzymes cannot move from ducts – pancreatitis)
  • Autodigestion of pancreas possible
34
Q

Biggest issue with lipid digestion

A

Insolubility of lipids

35
Q

Lipid digestion (stomach)

A
  • Lingual/gastric lipase act on TAGs (10% TAG absorption)

- Time required for CCK to act… so CCK inhibits gastric emptying to allow time for more mixing and GB emptying

36
Q

Lipid digestion (SI)

A
  • Majority of digestion here
  • Bile salts emulsify fats
  • Variety of enzymes secreted into SI to facilitate digestion
37
Q

Pancreatic lipase

A
  • Secreted as active

- Inactivated by bile salts w/o colipase (which is activated by trypsin to displace bile salts)

38
Q

Cholesterol ester hydrolase

A
  • Secreted as active
  • catalyzes production of free cholesterol
  • TAG – glycerol
39
Q

Phospholipase A2

A
  • Secreted as proenzyme

- Breaks down phospholipids

40
Q

Steps in fat absorption

A
  1. Solubilization by micelles (apical side)
  2. Diffusion of micellar content across apical membrane
  3. Reesterification
  4. Chylomicron formation
  5. Exocytosis of chylomicrons into lymphatics (through BL)
41
Q

Component needed for lipid absorption

A

ApoB (w/o it you get abetalipoproteinemia)

42
Q

Key indication of lipid absorption issue

A

Steatorrhea

43
Q

Key theme of lipid absorption issue

A

Improper acidity of duodenal contents (too much acid/not enough HCO3-)

44
Q

Factors causing bile salt deficits

A
  • Ileal resection

- Small intestinal bacterial overgrowth (bacteria deconjugate bile salts, which impairs micelle formation)

45
Q

Problems with tropical sprue

A
  • Loss/decreased number of intestinal epithelial cells
  • Reduced microvilli surface area
  • Fat soluble vitamins also afected
  • Diarrhea main indication
46
Q

Small intestine bacterial overgrowth

A
  • Inappropriate growth of bacteria
  • Malabsorption
  • Breath test can indicate methane or hydrogen
47
Q

Common causes of pernicious anemia

A
  1. Atrophic gastritis (chronic inflammation – loss of parietal cells)
  2. Autoimmune metaplastic atrophic gastritis (immune systems attacks IF)
48
Q

Significance of gastric bypass/gastrotomy

A
  • Loss of parietal cells – loss of IF – Pernicious anemia
49
Q

Iron Absorption

A
  • Liver secretes apotransferrin into bile
  • Apotransferrin binds with Fe/Hb to form transferrin
  • Vitamin C aids in process
  • Fe3+ to Fe2+
50
Q

Main site of absorption for most nutrients/vitamins

A

Small intestine

GI Final (13 decks)

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