Gastrointestinal Physiology (Part 2) Flashcards Preview

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Flashcards in Gastrointestinal Physiology (Part 2) Deck (73)
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1

What are the ultimate functions of the GI tract?

digestion and absorption

2

Define digestion

The chemical breakdown of ingested foods into absorbable molecules

3

Define absorption

The movement of nutrients, water, and electrolytes from the lumen of the intestine into the blood

4

What are the 2 paths for absorption?

- cellular path
- paracellular path

5

Describe the cellular path for absorption

The substance must cross the luminal membrane, enter the intestinal epithelial cell, and then be extruded from the cell across the basolateral membrane into blood

6

Describe the paracellular path for absorption

Substances move across the tight junctions between intestinal epithelial cells, through the lateral intercellular spaces, and into the blood.

7

The surface of the small intestine is arranged in longitudinal folds called what?

Folds of Kerckring

8

What increases the surface area of the small intestine?

Villi and microvilli

9

Where are villi the longest and the shortest? Why?

Longest in the duodenum, where most digestion and absorption occurs.
Shortest in the terminal ileum.

10

What covers the surface of the villi?

epithelial cells

11

The apical surface of the epithelial cells is further expanded by what?

microvilli

12

What is the microvillar surface called?

the brush border

13

What are the 3 types of ingested carbohydrates?

- polysaccharides
- disaccharides
- monosaccharides

14

What type of carbohydrate is the only one that the intestinal epithelial cells can absorb? What does this mean?

Monosaccharides

Therefore, to be absorbed, all ingested carbohydrates must be digested to monosaccharides.

15

What are the 3 monosaccharides?

- glucose
- galactose
- fructose

16

Describe the process of starch digestion

1) alpha-amylase digests the interior 1,4-glycosidic bonds in starch
2) this results in the formation of 3 disaccharides (alpha dextrins, maltose, and maltotriose)
3) these disaccharides are further digested to monosaccharides by the intestinal brush-border enzymes
4) the end result is glucose

17

What are the 3 disaccharides in food?

- trehalose
- lactose
- sucrose

18

Do trehalose, lactose, and sucrose require the amylase digestive step?

No, since they are already in the disaccharide form

19

What is trehlaose digested into?

2 molecules of glucose

20

What is lactose digested into?

glucose and galactose

21

What is sucrose digested into?

glucose and fructose

22

How is glucose absorbed by intestinal epithelial cells?

via a Na+ dependent cotransporter

23

How is galactose absorbed by intestinal epithelial cells?

via a Na+ dependent cotransporter

24

How is fructose absorbed by intestinal epithelial cells?

via facilitated diffusion

25

What is an example of failure to digest a carbohydrate to an absorbable form?

lactose intolerance

26

Describe the basis behind lactose intolerance

The brush-border lactase is deficient or lacking, which means lactose is not digested to glucose and galactose

27

Proteins must be digested to one of 3 absorbable forms, what are they?

- amino acids
- dipeptides
- tripeptides

28

Where does protein digestion begin? By way of what?

In the stomach by way of pepin

29

Protein digestion is completed where? By way of what?

In the small intestine with pancreatic and brush-border proteases

30

What are the 2 classes of proteases?

- endopeptides
- exopeptides