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Semester 3-GI > Lecture 11-Intestines > Flashcards

Lecture 11-Intestines Flashcards

1
Q

What are the roles of the intestines?

A

Absorb nutrients, water and electrolytes paracellularly or transcellularly

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2
Q

What contributes to the large SA of the small intestine?

A

Villi, microvilli and plicae circulares

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3
Q

True or false: monosaccharides and disaccharides are absorbed by the small intestine

A

FALSE - only monosaccharides

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4
Q

Where does final breakdown of sugars occur?

A

Brush border

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5
Q

Which bonds are between glucose molecules in amylose?

A

Alpha 1, 4

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6
Q

Which bonds are between glucose molecules in amylopectin?

A

Alpha 1, 4 between the straight chains and alpha-1, 6 between the branches

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7
Q

Which enzyme breaks alpha-1,4 bonds?

A

Amylase

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8
Q

Which enzyme breaks alpha-1,6 bonds?

A

Isomaltase

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9
Q

Which channel on the apical membrane allows the entry of glucose into the cell?

A

SGLT-1 (moves with Na+)

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10
Q

Which channel transports glucose out of the enterocyte?

A

GLUT-2

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11
Q

Which channel on the apical membrane allows fructose to enter the cell and by which mechanism?

A

GLUT-5 by facilitated diffusion

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12
Q

Complete the sentence: in the stomach, pepsinogen from ______ cells is converted to pepsin by ___

A

Chief

HCl

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13
Q

What converts trypsinogen to trypsin?

A

Enteropeptidase

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14
Q

What does trypsin do?

A

Activates other proteases

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15
Q

What are the two groups of proteases?

A
  • endopeptidases: breaks bonds in the middle of the polypeptide
  • exopeptidases: breaks bonds at the end of the polypeptide
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16
Q

Give examples of each group of proteases

A
  • endopeptidases: trypsin, chymotrypsin, elastase

- exopeptidases: carboxypeptidase

17
Q

True or false: most protein products are ingested as di/tripeptides

A

TRUE

18
Q

How are protein products absorbed in the small intestine?

A
  • Na+/AA co-transporter on apical membrane

- di/tripeptides moved by H+ co-transporter (PepT1) and converted to AA by cytosolic peptidases

19
Q

True or false: Na/K ATPase is present on the basolateral membranes of the small and large intestines

A

TRUE

20
Q

How does Na+ enter the cell in the small intestine?

A

Na+ co-transporter

21
Q

How does Na+ enter the cell in the large intestine?

A

Na+ channels induced by aldosterone

22
Q

How is calcium absorbed when Ca2+ intake is low?

A

Active transcellular absorption:

  • Ca2+ enters the cell via facilitated diffusion
  • Ca2+ ATPase removes the ion from the basolateral membrane
23
Q

What is required for the active transport of Ca2+?

A

Vitamin D

24
Q

How is calcium absorbed when intake is high?

A

Passive paracellular absorption

25
Q

What is needed for iron absorption?

A

Gastric acid

26
Q

How is iron absorbed when levels are low?

A

Binds to transferrin and transported to stores (Hb and ferritin complexes in bone marrow, liver and spleen)

27
Q

How is iron absorbed when levels are high?

A

Iron in ferritin complexes

28
Q

How are water soluble vitamins absorbed?

A

By Na+ co-transport

29
Q

Where is vitamin B12 absorbed?

A

Terminal ileum, bound to intrinsic factor

30
Q

What is the basis of oral rehydration therapy?

A

Uptake of Na+ generates an osmotic gradient for water to follow and glucose uptake stimulates Na+ uptake so a mix of glucose and Na+ stimulates maximum water uptake

31
Q

What is Coeliac disease?

A

Intolerance to gliadin fraction of gluten found in wheat, rye and barley

32
Q

What are the symptoms of coeliac disease?

A
  • diarrhoea
  • flatulence
  • weight loss
  • sensory loss in hands
33
Q

Describe the pathophysiology of coeliac disease

A

Immune response, damage to mucosa of intestines:

  • absence of villi so loss of SA -> diarrhoea
  • lengthening of crypts
  • lymphocytes infiltrate epithelium -> malabsorption
34
Q

What are the investigations conducted to confirm coeliac disease?

A
  • upper GI endoscopy
  • biopsy
  • bloods
35
Q

How can coeliac disease be treated?

A

Avoid gluten

Semester 3-GI (14 decks)

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