Physiology of the small intestine Flashcards Preview

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Flashcards in Physiology of the small intestine Deck (23)
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1

What glands in the small intestine secrete mucus?

Brunner's glands

2

What is the function of motilin hormone?

Stimulates migrating motor complexes (MMCs) via both the enteric and autonomic nervous systems.

3

What is the function of Vasoactive intestinal peptide (VIP) hormone?

Increases blood flow to the GI tract

4

What is the function of CCK (cholecystokinin) and secretin?

Inhibits gastric motility and secretion and controls pancreatic and biliary secretion.

5

What are the main secretions of the small intestine?

Mucus, water and hormones

6

Name the hormones secreted by the small intestine.

Motilin
Vasoactive intestinal peptide (VIP)
Gastric inhibitory peptide (GIP)
Cholecystokinin (CCK)
Secretin

7

What cells (x2) in the pancreas secrete enzymes/alkali?

Acinar cells - enzymes (zymogens) (activated by membrane bound enterokinase)
Duct cells - alkali

8

How is HCO3- secreted from the pancreatic duct into the intestinal lumen?
(CO2 + H2O H2CO3 HCO3- + H+)

HCO3- secreted into duct lumen
H+ are pumped out of duct cells and released into the blood

9

How are fats digested in the small intestine?

1) Fats are emulsified by bile salts and phospholipids
2)Triglycerides are digested by pancreatic lipase to monoglycerides and fatty acids.
3)Held in micelles

10

How are fats absorbed in the small intestine?

1) Monoglycerides and fatty acids diffuse into epithelial cell
2)Reassembled into triglycerides
3)Packaged into chylomicrons
4)Leave intestinal villus via its lymph vessel (thoracic duct - LSV)

11

Describe how starch is converted to monosaccharides.

Pancreatic amylase converts starch to maltose. Brush border enzymes (maltase, sucrose and lactase) break down products to glucose, fructose and galactose. Absorbed into blood.

12

How are dissacharides formed from monosaccharides?

Glycosidic bond by eliminating water

13

Glucose, galactose and fructose are absorbed from the intestinal lumen via what transporters and exit into the blood via which transporters?

Glucose + galactose - SGLT-1
Fructsoe - GLUT5 (facilitated diffusion)
All exit into blood via GLUT2 (facilitated diffusion)

14

How are proteins absorbed in the small intestine?

1) proteins digested by: trypsin, chymotrypsin and carboxypeptidase
2)Further by: dipeptidase and aminopeptidase into tri/dipeptides and free AAs
3)Enter epithelial cells and usually hydrolysed to AAs by cytosolic peptidase

15

Di/tripeptides and free AAs are absorbed from the intestinal lumen via what transporters and exit into the blood via which transporters?

AAs - Na+-amino acid cotransporters
Di/tripeptides - H+-dependent co-transporters
Exit into blood by facilitated diffusion

16

How is Ca2+ absorbed?

1) Enters intestinal lumen via Ca2+ channel
2)Ca2+ exits via both:
plasma membrane Ca2+-ATPase
Na+/Ca2+ exchanger

17

What 2 forms is dietary iron present as?

Haem iron
Free iron

18

How is haem iron abserbed into blood?

Haem is absorbed by receptor-mediated endocytosis then digested to release Fe3+.
Fe3+ reduced to Fe2+
Fe2+ exits via the transmembrane protein ferroportin 1.

19

How is free iron absorbed into blood?

Fe3+ reduced to Fe2+ by membrane ferrireductase (FR).
Fe2+ crosses membrane via divalent metal transporter 1 (DMT1).
Fe2+ exits via the transmembrane protein ferroportin 1.

20

How is vitamin B12 absorbed from the intestine?

Stomach - binds to R protein.
Duodenum/ jejunum - released and binds to intrinsic factor (IF)
Terminal ileum - vit B12-IF complex is absorbed by receptor-mediated endocytosis

21

Explain lactose intolerance

Bacteria ferments lactose into gases etc - bloating

22

Explain how excessive vomiting can lead to metabolic alkalosis.

leads to large losses of secreted acids from the body.

23

Explain how excessive diarrhea can lead to metabolic acidosis.

excessive loss of fluid (and hence NaHCO3) in faeces.