Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MABS Physiology > 29 Digestive and Absorptive Functions of the GI Tract > Flashcards

29 Digestive and Absorptive Functions of the GI Tract Flashcards

1
Q

how are carbohydrates ingested?

A 
Starch
Disaccharides (mostly lactose and sucrose)
Monosaccharides (glucose and fructose)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

T/F, Only monosaccharides can be absorbed?

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Two phases of digestion?

A 
Luminal 
Brush border (brush border enzymes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

where does carbohydrate absorption occur?

A

Apical border

Basolateral border

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens at the apical border?

A

Sodium-coupled nutrient transport via SGLT-1 (sodium/glucose transporter-1):
Glucose
Galactose

Facilitated diffusion via GLUT 5:
Fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what happens at the basolateral border?

A

All monosaccharides use GLUT2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how does lactose intolerance work?

A

undigested lactose increases the osmolality of the gut which results in an increase in osmolality. The high osmolality leads to a concomitant increase in a a net water secretion causing diarrhea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is Hartnup disease?

A

Autosomal recessive

Difficulty in absorbing non-polar amino acids like tryptophan (which is necessary in the production of serotonin, melanin, and niacin)

  • Niacin deficiency results in pellagra
  • -4 D’s: Dehydration, Dermatitis, Dementia, Death
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the importance of micelles?

A

Enzymatic digestion takes place on the surface of emulsion droplet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name the disease based on characteristics below:

Autosomal recessive
Difficulty in absorbing non-polar amino acids like tryptophan (which is necessary in the production of serotonin, melanin, and niacin)

A

Hartnup disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is pellagra?

A

4 D’s: Dehydration, Dermatitis, Dementia, Death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

where does the enzymatic digestion of micelles take place?

A

Enzymatic digestion takes place on the surface of emulsion droplet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

products of digestion and micelles form this?

A

mixed micelles with bile salts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the functions of the mixed micelles?

A

Keep products in suspension
Prevent them from re-esterifying
Transport them to the epithelial surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what do micelles contain?

A

cholesterol, fat-soluble vitamins, monoglycerides and phospholipids with bile acids allowing for suspension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

where do the micelles travel?

A

to the apical membrane of the enterocytes and products of fat digestion enter cell by simple diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

without micelle formation, what happens to the free fatty acids?

A

some free fatty acids can be absorbed but not cholesterol and other lipid products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what happens to the lipid digestion products?

A

re-esterified with free fatty acid (FFA) within the cell cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

where are the chylomicrons formed?

A

in the cell (packed on the Golgi complex) and they contain a lipid core surrounded by phospholipids and Apolipoprotein B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

T/F, Fat-soluble vitamins are also incorporated into chylomicrons

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

describe the path of the chylomicrons?

A

they exit the cell via exocytosis and enter the lymphatic system (lacteals) (not the hepatic portal system like all other absorbed nutrients) and then are returned to vascular system by thoracic duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

where do the chylomicrons not exit?

A

not the hepatic portal system like all other absorbed nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how does fat malabsorption present?

A

as steatorrhea (fat in stools, often foul-smelling and floats in toilet) Give a possible cause for each condition and explain why it would lead to fat malabsorption.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are some symptoms and cases of fat malabsorption?

A
  • Low pH in duodenum
  • pancreatic insufficiency
  • Loss of surface area in intestines
  • Bacterial overgrowth
  • Bile salt deficiency
25
Q

what would cause the low pH in duodenum? why would this lead to malabsorption?

A

Increased H+ secretion (gastrinoma)
decreased bicarbonate secretion (pancreas disorders)

Digestive enzymes (except pepsin) function at a neutral pH; H+ is also damaging to epithelium preventing adequate function.

26
Q

what would cause pancreatic insufficiency?

why would this lead to malabsorption?

A

Chronic pancreatitis (decreased pancreas secretion); pancreatectomy, obstruction (tumor); impaired function (CF)

Pancreatic enzymes are critical for digestion. Gastric, salivary and intestinal enzymes are inadequate.

27
Q

what would cause the loss of surface area in intestines? why would this lead to malabsorption?

A

Celiac disease

Large surface area is critical for complete absorption. With insufficient surface chyme is propulsed along the GI tract with inadequate absorption.

28
Q

what would cause bacterial overgrowth?Why would it lead to malabsorption?

A

Motility disorders (slow motility), high pH, surgery

Bile salts get deconjugated in the presence of too many bacteria and lose their function and can get prematurely absorbed before the terminal ileum.

29
Q

what would cause a bile salt deficiency?Why would it lead to malabsorption?

A

Terminal ileum disease or resection

Bile acids need to be recycled via the enterohepatic circulation (liver cannot make up for high loss rates). Bile salts are critical for suspended fat in aqueous milieu and for micelle formation and fat absorption.

30
Q

what is the Shilling’s Test?

A

A test for pernicious anemia that is comprised of two phases

31
Q

describe the two phases that we test for pernicious anemia?

A

Phase 1 – Replete patient’s B12 then give radiolabeled B12. If no renal excretion then B12 malabsorption. Go to phase 2

Phase 2 – Give radiolabeled B12 and intrinsic factor. If renal excretion then pernicious anemia (IF deficiency). If no excretion then look for other causes of malabsorption.

32
Q

what is the difference between the phases?

A

Phase 1 – Replete patient’s B12 then give radiolabeled B12

Phase 2 – Give radiolabeled B12 and intrinsic factor

33
Q

In the intestines, where is iron stored?

A

At the apical border
Inside the cell
At the basolateral membrane

34
Q

at the apical border how is the heme form absorbed? what about the non-heme form?

A

Absorbed by the intestinal epithelium intact by facilitated transport

Fe3+ is insoluble at duodenal pH so it is reduced to Fe2+ and absorbed by active transport (Divalent metal transporter or DMT-1)

35
Q

what is the effect of tea on iron?

A

Tannic acid in tea can form insoluble complexes with iron and prevent absorption.

36
Q

what is heme released by inside the cell?

A

heme oxygenase

37
Q

so inside the cell, what is the term used to describe the protein that complexes with Fe2+? what is the complex called?

A

apoferritin; ferritin

38
Q

what is ferritin?

A

a storage form of iron and some iron stays in the enterocytes

39
Q

at the basolateral membrane, where is the iron transported?

A

to bloodstream where it is bound to transferrin and travels to the liver.

40
Q

what is the major storage site for iron?

A

the liver

41
Q

T/F, the liver synthesizes transferrin

A

T

42
Q

what is the main enzyme in the stomach used for protein digestion?

A

pepsin

43
Q

what is the main enzyme in the small intestine used for protein digestion?

A

trypsin(activated by enterokinase) used to activate:

chymotrypsin
elastase
carboxypeptidase A/B
*all pancreatic proteases

44
Q

what are the three phases of protein digestion?

A

Gastric
Proteins digested to peptides and oligopeptides

Lumen of intestines
Peptides digested to oligopeptides

Brush Border
Oligopeptides digested to aa’s, di-and tripeptides

45
Q

what are the ultimate products of protein digestion?

A

Amino Acids

Di- and tripeptides

46
Q

how are amino acids transported at the luminal membrane?

A

Cotransport with Na+

Depends on gradient created by Na+/K+ ATPase

47
Q

how are Di and Tripeptides transported at the luminal membrane?

A

Cotransport with H+ (PEPT1)

H+ source is Na/H exchanger (NHE)

48
Q

how are di and tripeptides processed in the cell? at the basolateral membrane?

A

into AA’s by peptidase; amino acids and transported via facilitated diffusion

49
Q

what is the medical condition for patients who cannot form chylomicrons?

A

Abetalipoproteinemia, Fat can enter the cell but cannot be absorbed into the system. Epithelial cells appear swollen with fat on histologic section.

50
Q

what could cause Low pH in duodenum?

A

Increased H+ secretion (gastrinoma), decreased bicarbonate secretion (pancreas disorders)

51
Q

what could cause Pancreatic insufficiency?

A

Chronic pancreatitis (decreased pancreas secretion); pancreatectomy, obstruction (tumor); impaired function (CF)

52
Q

what could cause Loss of surface area in intestines?

A

Celiac disease

53
Q

what could cause Bacterial overgrowth?

A

Motility disorders (slow motility), high pH, surgery

54
Q

what could cause Bile salt deficiency?

A

Terminal ileum disease or resection

55
Q

T/F, Fat soluble vitamins are also incorporated into chylomicrons?

A

T

56
Q

what is pellagra?

A

Pellagra is due to vitamin B3 (niacin) deficiency. It presents with the 3 D’s: dermatitis, diarrhea and psychiatric manifestations (Dementia, Delirium or Depression)

57
Q

Causes of lipid malabsorption can cause fat soluble vitamin deficiencies, what vitamin?

A

ADEK

58
Q

what percent of calcium is absorbed from the GI tract?

A

40%, mostly absorbed in the duodenum and jejunum, regulated by PTH and circulating plasma concentration and relies on Vitamin D absorption

59
Q

what are the three roles of Vitamin D?

A

Increases luminal absorption
Upregulates Calbindin D synthesis
Increases Ca-ATPase activity

MABS Physiology (57 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions