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GI > Large intestine > Flashcards

Large intestine Flashcards

1
Q

What are taeniae coli?

A

Three longitudinal muscle bands equally spaced around the colon that mean its easier to contract the circular muscle

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2
Q

What are haustra?

A

small pouches that give the colon its segmented appearance, because the taeniae coli are shorter than the large intestine

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3
Q

What are the appendicies epiploicae?

A

Fatty tags

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4
Q

What is the difference between the surface of the small intestine and colon?

A

Surface of colon is flat and smooth, whereas the small intestine has lots of vili

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5
Q

Why is mucus secreted into the large intestine?

A

faecal material is compact and less liquidy so mucus needs to facilitate its passage

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6
Q

What secretes mucus onto the surface of the large intestine?

A

pit glands

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7
Q

how does the ilioceaecal valve open?

A

Pressure opens valve and allows material to flow through

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8
Q

When does the iliocaecal valve close? why?

A

When the caecum is expanded, to prevent backflow and prevent bacterial flora from colon entering the ileum

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9
Q

What is meant by the term flutter valve?

A

one way valve

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10
Q

Is contraction of the colon slow or fast? what is the direction of food?

A

Slow

Food is moved back and forth

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11
Q

What is a mass movement?

A

A large peristaltic wave that moves material a long way.

Houstra briefly disappear as all circular muscle is involved in peristalsis

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12
Q

What controls the motility of the colon?

A

Enteric nervous system

Also enteroendocrine and neurocrine influence from cells releasing 5-HT and Peptide YY

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13
Q

What is the role of peptide YY in motility?

A

Feeds back to earlier parts of the bowel if movement needs to slow down (i.e. if fats haven’t been absorbed by SI and have moved into the colon) –> ILEAL BREAK

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14
Q

What is the ileal break?

A

presence of undigested lipids in distal ileum and proximal colon releases peptide YY which slows gastric emptying and small bowel peristalsis

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15
Q

What is the role of gastrocolic and ortocolic reflexes?

A

Trigger mass movements of the colon
Gastrocolic - triggers colon activity when we eat to clear space

Orthocolic - when you go from horizontal to vertical in the morning it triggers colonic motility

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16
Q

What does the digestion in the colon?

A

Bacteria - because we can no longer digest anything

17
Q

What do bacteria digest fibre to?

A

Short chain fatty acids e.g. methane,

18
Q

What do bacteria digest urea and amino acids to?

A

ammonia

19
Q

What to bacteria digest bilirubin to?

A

urobilinogen and stercobilins

20
Q

What to bacteria digest cysteine and methionine to?

A

Hydrogen sulphide

21
Q

What do bacteria digest primary bile acids to?

A

Secondary bile acids

22
Q

What do bacteria digest conjugated bile acids to?

A

unconjugated bile acids

23
Q

What gases are released during fermentation in the colon?

A

nitrogen
hydrogen
Co2

24
Q

How are short chain fatty acids picked up?

A

Active transport using a Na+ linked co transporter

25
Q

What are fatty acids used for in the colon?

A

Energy source for colonocytes

26
Q

How is salt absorbed in the colon?

A

Epithelial sodium channels (ENaC) allows transcellular sodium transport
Na+ flows passively and generates an electrical gradient, and Cl- flows paracellularly
water follows paracellularly

27
Q

What stimulates salt absorption?

A

Aldosterone

28
Q

What two things mainly cause secretion in the colon?

A

cAMP

Ca2+

29
Q

How does C.Diff cause excess water loss?

A

Increases Ca2+
More Cl- flows into lumen, Na+ and water follow
Secretory diarrhoea

30
Q

How do cholera are E.coli cause secretory diarrhoea?

A

increase cAMP which causes Cl- secretion into lumen, Na+ and water follow

31
Q

What determines the balance between potassium secretion and absorption in the colon?

A

aldosterone (tends to favour passive secretion)

and cAMP

32
Q

Why is potassium secretion in the colon usually passive?

A

Usually a negative charge in the lumen because of Cl- secretion

33
Q

Why are they rectal valves?

A

Slow down the movement of material

34
Q

What type of muscle is the internal anal sphincter?

A

Smooth - reflex

35
Q

What type of muscle is the external anal sphincter?

A

skeletal - voluntary

36
Q

What is anal sampling?

A

a small amount of faeces enters the anus through the internal anal sphincter

37
Q

How does sitting or squatting facilitate the passage of fences?

A

increases the rectosigmoid angle

38
Q

What is Hirschsprung’s disease?

A

no ganglia in colon

colon becomes grossly dilated because there is no reflex relaxation - you can’t defecate

GI (10 decks)

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