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Y2 GI > Small and Large Intestine > Flashcards

Small and Large Intestine Flashcards

1
Q

parts of small intestine

A

duodenum, jejunum, ilieum

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2
Q

function of SI

A

helps to further digest food coming from the stomach.
It absorbs nutrients and water
move food along

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3
Q

what increases surface area in the small intestine?

A

cylindrical, circular folds (plicae), villi, microvilli

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4
Q

what is the function of villus and crypt cells in SI

A

villus - absorbs, crypt - secretes Cl and water

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5
Q

what is the importance of H2O secretion in digestion

A
  • maintain lumenal contents in liquid state
  • promotes mixing of nutrients w digestive enzymes
  • aids nutrient presentation to absorbing surface
  • dilutes and washes away toxins
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6
Q

what transporter does Cl go through at the apical membrane in SI

A

CFTR

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7
Q

what regulates the transportation of Cl through the membrane in SI

A

Adenylate cyclase

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8
Q

what are the 2 types of movement in s intestine

A

segmentation and peristalsis

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9
Q

what is segmentation

A
  • contraction ↔ relaxation of short segments
  • contraction moves chymes (up&down) into areas of relaxation
  • relaxed areas then contract and push chyme back
  • thorough mixing of contents w digestive enzymes
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10
Q

what generates segmentation contractions

A

depolarisation generated by pacemaker cells in longitudinal muscle

basic electrical rhythm produces oscillations in membrane potential → threshold → AP → contraction

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11
Q

what is the frequency of segmentation determined by

A

BER (basic electrical rhythm), decreases as move down tract

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12
Q

what determines strength of contraction in segmentation

A

AP frequency

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13
Q

what effect does parasym and symp have on contraction in segmentation

A

para - inc contraction,

symp - dec

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14
Q

when does peristalsis start

A

following absorption of nutrients, segmentation stops and p starts

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15
Q

what is the migrating motility complex

A

patterns of peristaltic activity travelling down small intestine,

starts in gastric antrum

ends in terminal ileum

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16
Q

what does the MMC migrating motility complex do

A

move undigested material into large int

limit bacterial colonisation of small int

17
Q

what hormone is involved in initiation migrating motility complex

A

Motilin

18
Q

what is the law of the intestine

A

bolus always moves down to colon, mediated by myenteric plexus

19
Q

what is the gastroileal reflex

A
  • opening of ileocaeceal valve
  • chyme enter large int
  • distention of colon
  • reflex contraction of ileocaecal valve ( prevents backflux into small int)
20
Q

structure of large int, parts and epithelium

A

ascending, transverse, descending, sigmoid

muscularis externa - circular muscle layer complete but longitudinal not

21
Q

what are the 3 bands around the colon

A

teniae coli

22
Q

what does the colon do

A
  • no important nutrient absorption

- transports Na from lumen into blood, absorption of water, dehydrates chyme, solid faecal pellets

23
Q

what is the importance of long residence time in colon

A

what is the importance of long residence time in colon

24
Q

what does bacteria do in colon

A 
breakdown cellulose
Bacterial fermentation of undigested carbohydrate
- short chain FA
- Vitamin K
- gas
25
Q

what is the anus closed by

A
  • internal anal sphincter (smooth muscle under automatic control)
  • external anal sphincter (skeletal muscle under voluntary control)
26
Q

what reflex gives you the urge to defaecate and why

A

defaecation reflex

distention of rectal wall produced by mass movement of faecal material into rectum → mechanoreceptors

27
Q

what is the defaecation reflex

A
  • under parasymp control via pelvic splanchnic nerves
  • contraction of rectum
  • relaxation of internal and contraction of external anal spinchter
  • inc peristaltic activity in colon, inc pressure on spinchter → relax under voluntary control → faeces come out
28
Q

what causes constipation

A

distention of rectum

29
Q

what causes diarrhoea

A

too frequent passage of faeces which are too liquid, causes dehydration
enterotoxigenic bacteria

30
Q

enterotoxigenic bacteria

A

Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells

inc H2O secretion

elevate intracellular second messengers

H2O secretions swamps absorptive capacity of villus cells

31
Q

how do you treat Secretory Diarrhoea

A

Give sodium/glucose solution

rehydration

oral rehydration therapy

Y2 GI (7 decks)

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