Block VIII - Digestive Flashcards Preview

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Flashcards in Block VIII - Digestive Deck (38)
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1
Q

What is the major function of gastrointestinal system?

A

To digest and absorb nutrients

2
Q

What is the effect of histamine on acid secretion in the stomach?

A

Increases acid secretion

3
Q

In parietal cells, what processes mediate HCl secretion?

A

H and C; are secreted separately via two different pathways. H is generated from water and CO2 in parietal cells with the help of carbonic anhydrase, and secreted by H/K ATPase pump in lumen. Cl transferred into the cell by basolateral HCO3/Cl exchanger, exit into lumen via Cl channel

4
Q

In the stomach, H ions are secreted in exchange for what?

A

K

5
Q

What is secretin?

A

Secretin is a hormone secreted by the endocrine cells of the small intestine, it stimulates the pancreas to release bicarbonate ions

6
Q

What is the advantage of enzymatic hydrolysis?

A

Enzymatic hydrolysis is faster than hydrolysis without an enzyme

7
Q

Cholecystokinin is released in what cells in the presence of fats?

A

The duodenal mucosal cells

8
Q

What is the role of bile salts in digestion?

A

Emulsifying agnets for large fat droplets in the upper intestinal tract

9
Q

In what form are dietary carbohydrates absorbed in the small intestine?

A

Monosaccharides (note: sucrose and lactose are disaccharides)

10
Q

Where do dietary carbohydrates go after absorption?

A

The are transported to the liver via the hepatic portal vein after breakdown to simple monosaccharides

11
Q

What is required for efficient absorption of fats in the alimentary tract?

A

The presence of pancreatic lipase

12
Q

Is the polysaccharide cellulose digested in the body?

A

Yes, it is partially digested by bacteria in the colon. However cellulose cannot be digested by small intestinal enzymes

13
Q

Where are the products of digestion absorbed?

A

The products of digestion are absorbed across the intestinal epithelial cells

14
Q

In what form is dietary lipid absorbed by the SI transported in the lymph?

A

Chylomicrons

15
Q

What are the stimuli for GI reflex?

A

Distension of the wall by the volume of the luminal contents, increase in chyme concentration of specific digestion products, increase of chyme osmolarity, increase of chyme acidity

16
Q

What cells does the submucosal plexus directly act on?

A

Endocrine and secretory cells

17
Q

Is GI activity regulated by short and long neural reflexes?

A

Yes

18
Q

If enteric nervous system is a part of autonomic nervous system, do they use epi, norepi, and ach as their transmitters only?

A

No. Enteric nervous system is similar to CNS, using as much as 30 different neurotransmitters

19
Q

What is secreted by gastric chief cells?

A

Pepsinogen

20
Q

What volume of fluid is secreted daily into the GI tract?

A

7000 ml

21
Q

Where do water and electrolytes absorbed in the GI tract?

A

SI

22
Q

Where are exocrine and endocrine cells located in the GI tract?

A

The epithelial layer

23
Q

What is the advantage of the existence of proenzymes for pancreatic enzymes?

A

To facilitate safe storage

24
Q

What is the function of microvilli in the SI?

A

Greatly increase SA for absorption of nutrients

25
Q

What are the substances/condition that stimulates acid secretion in the stomach?

A

Gastrin, histamine, acetylcholine, distension of the stomach

26
Q

Where is gastrin secreted?

A

Antrum of the stomach

27
Q

What do micelles consist of?

A

Bile salts, fatty acids, phospholipids, 2-monoglycerides

28
Q

Is vitamin B12 a water-soluble vitamin?

A

Yes, it binds to the intrinsic factor (IF) which is secreted by the parietal cells of the stomach. The IF-vitamin B12 is absorbed by endocytosis at ileum

29
Q

What is the size of micelles?

A

3-10 nm

30
Q

Do bile salts directly hydrolyze lipids?

A

No, bile salts facilitate digestion and absorption of lipids but do not themselves digest

31
Q

What is the function of pancreatic lipase?

A

Pancreatic lipase is specific to hydrolyze triglycerides

32
Q

Which enzyme converts oligopeptides into individual amino acids?

A

Caboxypeptidases A and B

33
Q

What is the process of secondary active transport of glucose?

A

ATP is hydrolyzed by the basolateral Na-K ATPase for active transport of Na across the basolateral membrane into the interstitial fluid. The Na gradient provides the energy for glucose entry carried by glucose transporter (SGLUT-1) at the brush border

34
Q

What mechanisms by which Na can be absorbed in intestinal epithelial cells?

A

Na enter the cells from the apical membrane by Na/Cl co-transport and Na/H exchanger, Na channels, co-transported with amino acids or monosaccharide. Sodium exits the cells at basolateral membrane by Na/K ATPase

35
Q

What is the effect of sympathetic stimulation on the digestive process?

A

Decrease the intestinal motility

36
Q

Is bile salt recycling?

A

Yes about 90% of excreted bile salts are reabsorbed by secondary active transport of the ileum

37
Q

What is membrane digestion?

A

Membrane digestion is carried out at the external surface of the membrane of microvilli by the enteric and absorbed enzymes. Therefore the final stages of digestion are integrated and the initial stages of transport begin. Brush-border oligosaccharidases break oligosaccharides into onosaccharides (fructose, glucose, galactose)

38
Q

Are small peptides (bipeptides, tripeptides) absorbed in SI?

A

Yes, intestinal enterocytes contain special transporters to take up amino acids and small peptides