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RUSVM Physiology II > Final Exam GI Physiology: GI Tract Absorption > Flashcards

Final Exam GI Physiology: GI Tract Absorption Flashcards

1
Q

What are the 9 general factors that influence the absorption or secretion of substances across membranes?

A
  1. Size
  2. Solubility
  3. Charge
  4. Concentration gradient
  5. Electrical gradient
  6. Available energy
  7. Area of membrane
  8. Transport protein availability
  9. Permeability of tight junctions
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2
Q

Why does the flow of water across intestinal mucosa decrease from duodenum to ileum to large intestine?

A

The tight junctions get gradually less “leaky”

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3
Q

How is absorption throughout the intestines similar to absorption in the proximal tubule?

A

Both are isosmotic

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4
Q

How is secretion by the GI tract different from secretion in the nephron?

A

GI tract secretes isotonic fluids into the lumen

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5
Q

How is flow through tight junctions accomplished?

A

Via active transport and facilitated transport (like in the nephron)

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6
Q

Does absorption take place in the mouth? In the esophagus?

A

Absorption does NOT take place at either of these organs

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7
Q

Can volatile fatty acids in their associated forms cross the rumen and reticulum (cecum and colon) mucosa?

A

Yes!

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8
Q

What are the 3 main VFAs?

A

Acetic, Proprionic, Butyric

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9
Q

The small intestine is a major site of _______ in the GI tract.

A

absorption

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10
Q

What are the electrolyte absorption mechanisms available in the GI tract?

A 
Basolateral Na+- K+ ATPase pumps
Na+-H+ antiports
Cl- HCO3- antiports 
Na+ uniports
Na+glucose symports
Na+ amino acid symports
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11
Q

What do Basolateral Na+- K+ ATPase pumps do?

A

Pumps sodium into the basolateral interstitum to maintain a low cytoplasmic [Na+].

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12
Q

What do Na+-H+ antiports do?

A

A way of putting sodium into the absorptive cells of the GI tract. H+ secreted into lumen as Na+ is absorbed.

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13
Q

What do Cl- HCO3- antiports do?

A

A way of putting sodium into the absorptive cells of the GI tract.

HCO3- is secreted into lumen as Cl- is absorbed

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14
Q

What do Na+ uniports do?

A

A way of putting sodium into the absorptive cells of the GI tract.

Na+ enters and Cl- follows paracellularly

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15
Q

What do Na+glucose symports do?

A

A way of putting sodium into the absorptive cells of the GI tract.

Glucose diffuses into the basolateral interstitium and Cl- follows paracellularly.

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16
Q

What do Na+ amino acid symports do?

A

A way of putting sodium into the absorptive cells of the GI tract.

Amino acids diffuse into basolateral interstitium and Cl- follows paracellularly.

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17
Q

How is K+ absorbed in the small intestine?

A

Via simple diffusion (after osmosis) and solvent drag through tight junctions

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18
Q

What ports become abundant in the COLON?

A

Na+ uniports

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19
Q

The colon ______ K+.

A

secretes

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20
Q

What does the presence of aldosterone do at the activity of colon basolateral Na+K+ ATPase?

A

Aldosterone INCREASES the activity of colon basolateral Na+K+ATPase which INCREASES Na+ and H20 absorption, and INCREASES K+ secretion

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21
Q

Bacterial toxins can BLOCK electrolyte antiports. What does this do to the animal?

A

Inhibits water absorption

Promotes diarrhea and dehydration in young animals especially. This can lead to mortality.

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22
Q

Bacterial toxins can block electrolyte antiports. What do they do to Na+glucose and Na+amino acid symports?

A

Bacterial toxins do not affect these symports.

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23
Q

Because bacterial toxins do not block sodium-glucose and sodium-amino acid symports, what is an effective means of preventing life-threatening diarrhea?

A

ORS! Oral Rehydration Solutions rich in glucose and amino acids can prevent life-threatening diarrhea.

24
Q

What promotes increased absorption of Ca++, Mg++, and (PO4)2-?

A

Calcitriol

25
Q

What does calcitriol promote the absorption of?

A

Calcium, magnesium, and phosphate ions

26
Q

What substance antagonizes the action of calcitriol?

A

CORTISOL is an antagonist of Calcitriol

27
Q

In order to be absorbed, ingested polysaccharides must be hydrolyzed by an enzyme called ________ .

A

Amylase

28
Q

T or F: Amylase CAN attack terminal glycosidic bonds.

A

False. Amylase cannot attack terminal glycosidic bonds

29
Q

What are the two end products of hydrolyzation of ingested polysaccharide by amylase?

A

Maltose and maltotriose

30
Q

Can maltose and maltotriose (hydrolysis products of ingested polysaccharides) be absorbed across the mucosal membrane?

A

NO, maltose and maltotriose cannot be absorbed across the mucosal membrane.

31
Q

What is responsible for the hydrolysis of maltose and maltotriose?

A

Brush border oligosaccharides (glucoamylase and dextrinase)

32
Q

What are ingested disaccharides (sucrose and lactose) hydrolyzed by?

A

Brush border sucrase hydrolyzes sucrose and lactose. The end products are glucose and fructose.

33
Q

What are ingested disaccharides (sucrose and lactose) hydrolyzed by other than brush border sucrase?

A

Brush border lactase also hydrolyzes sucrose and lactose. The end products are glucose and galactose.

34
Q

How are glucose and galactose absorbed?

A

Via Na+glucose symport

35
Q

How is fructose absorbed?

A

Via facilitated diffusion

36
Q

How do glucose, galactose and fructose exit, so they can ultimately enter portal circulation?

A

Glucose, galactose and fructose exit via BASOLATERAL PORTS which facilitate their diffusion.

37
Q

What is ingest protein hydrolyzed by?

A

Pancreatic proteases

Results in amino acids and oligopeptides

38
Q

What are oligopeptides hydrolyzed by?

A

Brush border oligopeptidases

Results in amino acids, dipeptides and tripeptides

39
Q

How are amino acids absorbed?

A

Via Na+amino acid symports

40
Q

How are dipeptides and tripeptides absorbed?

A

Via symports with intracellular peptidases

Results in amino acids

41
Q

How do amino acids exit in order to ultimately enter portal circulation?

A

Amino acids exit via basolateral ports which facilitate their diffusion

42
Q

Colostrum is rich in antibodies and contains a trypsin inhibitor. What does this trypsin inhibitor do?

A

It inhibits proteolysis in the small intestine

43
Q

How long postpartum does the trypsin inhibitor in colostrum work?

A

No more than 2 days postpartum

44
Q

What do absorptive cells do when encountered by colostral antibodies within 2 days postpartum?

A

Absorptive cells endocytose colostral antibodies intact!

45
Q

What is ingested triacylglycerol (lipid) emulsified by?

A

Bile acids and phospholipid lecithin emulsify triacylglycerol.

Results in small droplets of triacylglycerol

46
Q

What are the small droplets of triacylglycerol hydrolyzed by?

A

Pancreatic enzymes (lipase, colipase, phospholipase, and cholesterolesterase) hydrolyze the small droplets of triacylglycerol.

47
Q

What is the result of hydrolysis of small triacylglycerol lipid droplets by pancreatic enzymes?

A 
Free fatty acids
Monoacylglycerols
Glycerol
Cholesterol
Lysolecithin
Fat soluble vitamins
48
Q

How are mixed micelles formed?

A

By using bile acids, phospholipids and products of small droplet triacylglycerol lipid hydrolysis.

49
Q

What is the “core” of mixed micelles made up with?

A

LCFA (long chain fatty acids), MG (monoacylglycerol), lysolecithin, cholesterol, and fat soluble vitamins

50
Q

Are short chain and medium chain fatty acids found in the core of a mixed micelle?

A

NO. Only LONG CHAIN FATTY ACIDS

51
Q

Is glycerol a component of the core of a mixed micelle?

A

NO. Glycerol is not found in mixed micelles, even though it is a products of lipid hydrolysis.

52
Q

Micelles diffuse from lumen to _________ ________ membrane.

A

Mucosal cell membrane. The contents are diffused readily.

53
Q

Where are most micellar contents absorbed?

A

In the JEJUNUM

54
Q

Where are bile acids reabsorbed?

A

In the TERMINAL ILEUM

55
Q

What happens to the products of lipid hydrolysis once within the mucosal cell (brought here by mixed micelle)

A

They are RE-ESTERIFIED to form:

Triacylglycerols
Cholesterolester
Phospholipid

56
Q

What happens to the re-esterified triacylglycerol, cholesterolester, and phospholipid inside the mucosal cell?

A

They are put together with ingested fat soluble vitamins, cholesterol, phospholipids and proteins to make a heterogenous lipid droplet called a CHYLOMICRON

57
Q

Chylomicrons are too big to be taken up by small intestinal capillaries. Instead, they are taken up by ______ and transferred to plasma via the ________ duct.

A

LACTEALS take up chylomicrons and are transferred to plasma via the THORACIC DUCT

RUSVM Physiology II (17 decks)

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