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Gastrointestinal > Absoprtion + Digestion > Flashcards

Absoprtion + Digestion Flashcards

1
Q

What type of carbs can be absorbed?

A

Only monosaccharides

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2
Q

What is needed for glucose to be absorbed in SI?

A

Na+

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3
Q

How do we digest starch?

A
  • amylase breaks down a 1-4 bonds of straight chain > maltose
  • maltase breaks down maltose in 2 glucose
  • isomaltase breaks down a 1-6 bonds of branches
  • glucose is absorbed
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4
Q

How do we digest lactose?

A

Lactase breaks down lactose into glucose + galactose to be absorbed

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5
Q

How do we digest sucrose?

A

Sucrase breaks down sucrose into glucose + fructose to be absorbed

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6
Q

How are monosaccharides absorbed?

A
  • Na+ + glucose + galactose enter enterocyte via SGLT1 (Na+ is needed for this to occur)
  • fructose enters via GLUT5
  • glucose, galactose + fructose exit on basolateral membrane via GLUT2 into venous drainage of small intestine
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7
Q

How are proteins digested?
- stomach
- intestinal lumen
- brush border

A

Stomach:
- chief cells secrete pepsinogen
- converted to pepsin due to acidic environment
- proteins broken down to oligopeptides + amino acids

Intestinal lumen:
- pancreas releases proteases in inactive form (zymogens)
- enteropeptidase coverts trypsinogen into trypsin
- trypsin activates the other inactive proteases

Brush border:
- short peptides enter enterocytes via PepT1
- amino acids co transported with Na

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8
Q

What are the major proteases secreted by the pancreas in their inactive + active form?
What are the two groups?

A

Endopeptidases:
- trypsinogen > trypsin
- chymotrypsinogen > chymotrypsin
- proelastase > elastase

Exopeptidases:
- pro-carboxypeptidase A > carboxypeptidase A
- pr-carboxypeptidase B > carboxypeptidase B

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9
Q

Describe protein digestion in the stomach

A
  • chief cells secrete pepsinogen
  • converted to pepsin due to acidic environment
  • proteins broken down to oligopeptides + amino acids
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10
Q

Describe protein breakdown in the intestinal lumen

A
  • pancreas releases proteases in inactive form (zymogens)
  • enteropeptidase converts trypsinogen into trypsin
  • trypsin activates the other inactive proteases
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11
Q

What are the different groups of proteases and what’s the difference between them?

A
  • Endopeptidases: break bond in the middle of chain > shorter polypeptides
  • Exopeptidases: break bond at end of chain > amino acids + short peptides
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12
Q

How are proteins absorbed in the small intestine?

A
  • short peptides enter enterocytes via PepT1
  • amino acids co transported with Na+
  • amino acids + short peptides enter venous drainage
  • or cytosolic peptidases act on short peptides in enterocytes
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13
Q

What does SGLT1 transport?

A

Glucose + galactose into enterocyte
Need Na+ to work

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14
Q

What does GLUT5 transport?

A

Fructose into enterocyte

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15
Q

What does GLUT2 transport?

A

Glucose
Galactose
Fructose
Into venous drainage

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16
Q

What does PepT1 transport?

A

Dipeptides
Tripeptides
Into enterocyte

17
Q

What ion is responsible for water absorption?

A

Na+

18
Q

What ion is responsible for water secretion?

A

Cl-

19
Q

Outline water secretion

A
  • Cl- enters cells via NKCC contransporters
  • increase in cAMP > increased Cl- secretion through CFTR protein
  • Na+ drawn through tight junctions into lumen
  • water follows
20
Q

What anaemia can vit B12 deficiency cause?

A

Megaloblastic anaemia

21
Q

Causes of vitamin B12 deficiency

A
  • lack of intrinsic factor
  • hypochlorhydria
  • inflammation of terminal ileum e.g. Crohn’s disease
  • inadequate intake in diet (uncommon)
22
Q

What is hypochlorydria?

A

Low stomach acid production

23
Q

Outline lactose intolerance

A
  • deficiency in lactase enzyme
  • lactose not broken down so is not digested
  • bring water into gut lumen > diarrhoea
  • in colon,lactose is fermented in gut > flatulence and bloating
24
Q

How is irritable bowel syndome diagnosed?

A

In absense of documented abnormalities

25
Q

Symptoms of irritable bowel syndrome

A

Abdominal pain
Bloating
Flatulence
Diarrhoea/constipation
Renal urgency

26
Q

What demographic does IBS commonly effect?

A
  • females > males 2:1
  • 20-40 year olds
  • associated with psychological disorders
27
Q

What is coeliac disease?

A

Immunological response to gluten (gliadin fraction)

28
Q

What effect does coeliac disease have on the gut?

A

Damages mucosa:
- flattening of villi
- hypertrophy of crypts
- lymphocytes in epithelium
vvv this causes vvv
- impaired digestion
- malabsorption

29
Q

Symptoms of coeliac disease

A

Malabsorption > diarrhoea
Weight loss
Bloating
Flatulence
Aneamia
Neurological symptons

30
Q

Investigations of coeliac disease

A
  • blood test > IgA tissue transglutaminase
  • upper GI endoscopy: duodenal biopsy to look at mucosal pathology > reduced or absent villi, crypt hyperplasia
31
Q

Treatment of coeliac disease

A

Gluten free diet

32
Q

What routes can water move?

A

Trans cellular
Paracellular

33
Q

Symptoms of vitamin B12 deficiency

A

Neurological issues
Anaemia
Glossitis
Mouth ulcers

34
Q

When does lactase expression decrease?

A

After the age of 2

35
Q

What monosaccharides can be absorbed?

A

Glucose
Fructose
Galactose

36
Q

What skin finding can you get secondary to coeliac disease?

A

Dermatitis herpetiformis

37
Q

What blood test is used for coeliac disease?

A

IgA tissue transglutaminase

38
Q

What is seen in a duodenal biopsy in a patient with coeliac disease?

A

Villa atrophy
Crypt hyperplasia
Increased intraepithelial lymphocytes

Gastrointestinal (27 decks)

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