Final Exam GI Physiology: GI Tract Absorption Flashcards Preview

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Flashcards in Final Exam GI Physiology: GI Tract Absorption Deck (57)
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1

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

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

2

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

The tight junctions get gradually less "leaky"

3

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

Both are isosmotic

4

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

GI tract secretes isotonic fluids into the lumen

5

How is flow through tight junctions accomplished?

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

6

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

Absorption does NOT take place at either of these organs

7

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

Yes!

8

What are the 3 main VFAs?

Acetic, Proprionic, Butyric

9

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

absorption

10

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

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

11

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

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

12

What do Na+-H+ antiports do?

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

13

What do Cl- HCO3- antiports do?

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

HCO3- is secreted into lumen as Cl- is absorbed

14

What do Na+ uniports do?

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

Na+ enters and Cl- follows paracellularly

15

What do Na+glucose symports do?

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

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

16

What do Na+ amino acid symports do?

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

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

17

How is K+ absorbed in the small intestine?

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

18

What ports become abundant in the COLON?

Na+ uniports

19

The colon ______ K+.

secretes

20

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

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

21

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

Inhibits water absorption

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

22

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

Bacterial toxins do not affect these symports.

23

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

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

24

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

Calcitriol

25

What does calcitriol promote the absorption of?

Calcium, magnesium, and phosphate ions

26

What substance antagonizes the action of calcitriol?

CORTISOL is an antagonist of Calcitriol

27

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

Amylase

28

T or F: Amylase CAN attack terminal glycosidic bonds.

False. Amylase cannot attack terminal glycosidic bonds

29

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

Maltose and maltotriose

30

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

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