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Alimentary System: Pathology SA > Microbiota of the Gastrointestinal Tract > Flashcards

Microbiota of the Gastrointestinal Tract Flashcards

1
Q

What factors caused the variation of bacteria going down the GI tract

A

Transit time vs growth rate of bacteria

Different pH

Exposire to toxins

Different oxygen concentrations

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2
Q

Define obligate anerobes

A

bacteria that cannot grow in the presence of oxygen

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3
Q

Define facultative anaerobes

A

Bacteria grow in the presence or absence oxygen

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4
Q

Where does the vast majority of bacteria live

A

Large intestine

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5
Q

What is functions of the GIT Microbiota

A

Metabolism of dietary components

Production of essential metabolites to maintain health

Development of the immune system

host signalling

modifications of host secretions

Defence against pathogens

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6
Q

What do the gut microbes grow upon

A

The fibre that we eat

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7
Q

Where is the energy absorbed from the breakdown of dietary fibre by gut microbes

A

Large intestine

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8
Q

What else can GIT microbes use for growth

A

endogenous (host derved) substrates

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9
Q

What is the benefit of GIT bacteria breaking down dietary fibre

A

Improves faecal bulking, eases passage, results in shorter transit time

releases additional phytochemicals

Maintains slightly acidic pH

produces essential supply of short chain fatty acids

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10
Q

What are the three short chain fatty acids released

A

Butyrate

Propionate

Acetate

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11
Q

What is the function of butyrate

A

Epithelia cell growth and regeneration

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12
Q

What is the function of propionate

A

Glucogeness in the liver

satiety signalling

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13
Q

What is the fate and the function of acetate

A

Transported in the blood to peripheral tissue for lipogenesis

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14
Q

Where does majority of fermentation occur in the large intestine

A

The right side - Ascending colon

its carbohydrate rich

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15
Q

What is the varying pH of the large intestine

A

Ascending -Right side is slightly acidic

desending -Left side is pH neutral (has higher pH than ascending)

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16
Q

What has the greatest influence on gut bacterial growth and activity

A

diet and age

17
Q

What does a diverse balanced diet give you

A

A diverse balanced microbiota

and a diverse balanced products

18
Q

What is the ways bacterial defend you against pathogens

A

Barrier effect

Active competitive exclusion

produce active compounds that kill incoming pathogen s

19
Q

How does active competitive exclusion work in defence of pathogens

A

large number
Commensal bacteria close to epithelium
block and prevent adhesion/colonisation
by pathogens

20
Q

How does the barrier effect work in defence against pathogens

A

The inner mucus layer forms barrier between the luminal bacterial poplation and the epithelial cells and prevents pathogen penetration

21
Q

What happens if bacteria penetrate the epithelium

A

Normal immune response = homeostasis

22
Q

What occurs if there is a dysregulated immune response

A

Inflammation

23
Q

Why is there a higher risk of disease in the distal colon

A

Due to higher pH, so there is less pathogen fermentation

and its slower transit time mens there is a higher exposure to harmful compounds

24
Q

Where is protein fermentation most likely to occur

A

distal colon (descending)

25
Q

What is produced in protein fermentation

A

Branched short chain fatty acids

Gases - NH3 H2S

Phenols
indoles
Amines

26
Q

What is produced in carbohydrate fermentation

A

Short chain fatty acids

Gases - CO2, H2, CH4

27
Q

How does the immune system and the gut microbiota exist

A

In co-evoloution

As the microbiota shapes the development go the immune system, and the immune system shapes the gut microbiota - basically priming each other

28
Q

What are Toll like receptors

A

Receptors that specifically recognise bacterial components in the innate immune system

That determine self from foreign pathogens

29
Q

What is the major function f the short chain fatty acids produced in bacterial fermentation

A

Important signalling molecules

30
Q

What is FFAR2 receptor activated by and what its result

A

activated by acetate, propionate > butyrate, results in GLP-1 secretion

(inhibits fat accumulation)

31
Q

What is FFAR receptor activated against and what is the result

A

activated by propionate and butyrate, results in PYY secretion
(improves insulin resistance and satiety signalling to brain)

32
Q

What is GPR109A receptor activated by and what is the result

A
  • activated by butyrate
    suppresses colonic inflammation and carcinogenesis
    (anti-inflammatory cytokines eg. IL-10)
33
Q

What occurs when the immune system can no longer distinguish between harmful detrimental pathogens and the commensal bacteria

A

Auto-Immune disease

34
Q

What can dysbiosis (microbial imbalance) of gut microbiota lead to

A

can disrupt the homeostasis

and can lead to gut inflammation

Alimentary System: Pathology SA (27 decks)

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