REVISION GUIDE GI: DIGESTION AND ABSORPTION Flashcards Preview

PHASE 1 REVISION GUIDE > REVISION GUIDE GI: DIGESTION AND ABSORPTION > Flashcards

Flashcards in REVISION GUIDE GI: DIGESTION AND ABSORPTION Deck (91)
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1

what is the primary site for digestion and absorption?

the small intesine

2

what are the 2 types of digestion?

mechanical
chemical

3

what processes occur in absorption in the small intestine?

simple diffusion
facilitated diffusion
active transport
endocytosis
paracellular transport

4

what are the adaptations of the epithelial lining of the small intestine?

has villi and microvilli - increase SA
has cell surface of enterocytes by membrane bound enzymes

5

what are the 3 ways that peptides modulate GI tract function?

endocrine (hormonal)
paracrine
neurocrine

6

what are the criteria for the endocrine modulation of GI tract function?

- physiological event (eg eating) must provide stimulus to one part of the GI tract that alters the activity of the others
- the effect must remain after the removal of nervous input
- the substance must be identified chemically
- actions may be antagonised/blocked
- synthesised endogenously
- released at a specific site in the blood stream in response to stimulus

7

how do paracrine modulate GI function?

activated by detection of nutrients
the mediator acts upon the immediate area around the cell

8

what is the neurocrine modulation of GI tract function?

sensory neuron activates an interneuron and activates a secretory motor neuron
this releases a neurotransmitter into the cleft activating adjacent cells
this can happen over a short or long distance

9

what is the result of negative feedback loop of stomach and duodenal digestion regulation?

acid activates D cells which release somatostatin - this acts to reduce the further release of acid
it inhibits G cells production of gastrin
it inhibits ECL cells release of histamine
it directly inhibits the release of acid from parietal cells
it stops chief cells production of pepsinogen

10

what is directly released as a result of duodenal digestion regulation?

nervous input from the brain
luminal contents

11

what is indirectly released as a result of duodenal digestion regulation?

distension of the gut
release of another hormone

12

what are the hormones that are involved in duodenal digestion regulation?

gastrin
secretin
gastric inhibitory peptide
cholecystokinin
vasoactive intestinal peptide

13

what is the general effect of duodenal hormones?

they tend to inhibit stomach function
decreased stomach activity leads to increased duodenal absorption/ digestion

14

where is gastrin produced in the duodenum?

- secreted by G cells in duodenum in response to proteins

15

what is the effect of gastrin?

it promotes stomach motility
it stimulates production of gastric acid and enzymes

16

where is secretin produced in the duodenum?

released from duodenal S cells in response to high acid levels
it is released when chyme arrives in duodenum

17

what is the effect of secretin in the duodenum?

- increases secretion of bile from liver and gallbladder
- increases secretion of HCO3- and enzymes from pancreas
- increases pH of chyme and promotes digestion
- reduces gastric motility
-reduce gastric secretory rates

18

when is gastric inhibitory peptide secreted by the duodenum?

secreted when fats and carbohydrates enter the duodenum

19

what is the effect of gastric inhibitory peptide in the duodenum?

inhibits gastric activity
increases insulin activity
stimulates duodenal gland activity
stimulates lipid synthesis
increase glucose use by skeletal muscles

20

where is CCK produced?

released from I cells in duodenum, jejunum, less so from ileum

21

when is CCK secreted?

why chyme arrives in the duodenum
especially when high quantities of lipids and proteins

22

what are the pancreatic effects of CCK?

accelerates release of enzymes
increases HCO3- secretion

23

what are the liver and gallbladder effects of CCK?

sphincter of oddi relaxation
gallbladder contraction

24

what is the effect of CCK on gastric activity?

it inhibits gastric activity and feeds to CNS to reduce sensation of hunger

25

what is the effect of vasoactive intestinal peptide?

stimulates the secretion of intestinal glands
dilates regional capillaries
inhibits acid production in stomach
dilation of capillaries allows more efficient absorption

26

how much protein does a healthy adult require per day?

40 - 50g

27

why are amino acids zwitterions?

they have both positive and negative groups on the same molecule

28

what is the pH of stomach acid?

HCl - pH 2
[H+] > 150mM

29

how much stomach acid is produced per day?

approx. 2 litres per day

30

how is stomach acid produced?

1. H2O dissociates into H+ OH- in parietal cells
2. CO2 and H2O create HCO3- and H+ (via carbonic anhydrase)
3. H+ are pumped into stomach lumen by H+/K+ATPase (pumps 1 H+ and 1 K+ exchanged)
4. HCO3- is secreted into capillary in exchange for Cl-
5. Cl- diffuse into stomach lumen through Cl- channels
6. in the stomach lumen H+ and Cl- react to form HCl