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HL Bio > D2 digestion > Flashcards

D2 digestion Flashcards

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Biology 101 flashcards
1
Q

is digestive juice secreted continuously?

A

no – its coordinated w presence of food in part of the gut (vol and when)

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2
Q

3 mechanisms that control the secretion of digestive juices

A

mechanical
hormonal
nervous

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3
Q

describe the process of nervous control of secretion of digestive juices

A

sight/smell/taste food = medulla sends nerve impulses via VAGUS nerves = stimulate secretion of saliva and stomach wall cells

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4
Q

parasympathetic vs sympathetic control of digestive juices (nervous)

A

parasym = speed up digestion when food is ingested

sym = slows down digestion when no foods available

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5
Q

2 mechanical functions for control of digestive juice secretion

A
  • stomach contraction
  • peristalsis
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6
Q

name the 4 hormones that make up hormornal control of secretion of digestive juices

A
  1. secretin
  2. cholecystokinin
  3. gastrin
  4. somatostatin
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7
Q

how does secretin control secretion of digesive juices

A
  • produced by special cells in SI in response to acid fluid
  • release of alkali
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8
Q

where are secretin, cholecystokinin, gastrin, and somatostatin secreted from

A

special cells in SI

SI

G cells in stomach, duodenum and pancreas

special cells in stomach, duodenum, pancreas

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8
Q

how does cholecystokinin control secretion of digestive juices

A
  • presence of food in SI
  • release of bile
  • secretion of pancreatic enzymes
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9
Q

how does gastrin control the secretion of digestive juices

A

physical stimulation – presence of food
chemical stimulation – protein

release of gastric acids and enzymes

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10
Q

how does somatostatin control the secretion of digestive juices

A

prevents release of acid

prevents release of gastrin, CCK, secretin (basicall cancels out the other 3 hormones)

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11
Q

outline the mechanism of secretion control 6

A
  1. sight/smell = secretion of gastric juices
  2. food in stomach = wall stretched = further secretion
  3. protein = gastrin secreted = further secretion
  4. gastrin secretion slows at 3.5 pH, stops at 1.5 pH (protein in food acts as buffer to stomach acid)
  5. partially digested chyme enters duodenum = proteins = secrete gastrin = more juice
  6. chyme (low protein but w fatty acids and glu) = secretin + cholecytokinin = decr gastric juice secretion
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12
Q

define exocrine gland

A

have DUCTS that carry their secretory product to surface of body / lumen of gut

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13
Q

what do saliva glands secrete and what is the effect

A

saliva – mouth

amylase + mucus

starch –> maltose

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14
Q

what do gastric glands secrete and whats the effect

A

gastric juice – stomach

pepsin + HCl

proteins –> polypeptides
acidic enviro –> kills bacteria

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15
Q

what does the pancreas secrete and whats the effect (exocrine gland)

A

pancreatic juice – SI

amylase + proteases + peptidases + lipases + nucleases

starch –> maltose
proteins/polypeptides –> polypeptides + peptides + AAs
triglycerides –> fatty acids + glycerol
nucleotides –> pentose sugars + Pi + bases

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16
Q

whats the pH of the stomach

A

2.0

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17
Q

function of saliva

A

lubricating the mouth, throat, food bolus

amylase = digestion of starch

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18
Q

outline the path of pancreatic juices 2`

A

transported by pancreatic duct

enters intestine in duodenum

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19
Q

what cells secrete mucus

A

goblet cells

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20
Q

what is the function of mucus

A

forms an effective barrier to HCl and proteases = prevents self digestion (autolysis)

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21
Q

what is chyme

A

food mixed with gastric juice and churned by muscle action = semi-liquid

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22
Q

what did william beaumont discover and establish

A

the role of gastric secretions

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23
Q

how was gastric activity first observed and studied

A

through a opening from stomach interior to outside the body (bc gunshot)

gastric juice collected and tested w diff foods

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24
Q

how is stomach acid produced

A

by combination of H+ ions and Cl- ions produced by epithelial cells (parietal cells) of stomach lining

release of H+ ions thru protein carriers = intake of K+ ions from stomach lumen (needs ATP)

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25
Q

what does stomach acid do to protease ensymes

A

activation

pepsinogen (inactive) – HCl removes 44 AA –> pepsin (Active)

proteins –> peptides

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26
Q

purpose of acid conditions in stomach?

A

favour hydrolysis reactions, helps to control pathogens ingested with food

27
Q

what happens in stomach pH falls to low

A
  • stomach wall endangered
  • secretin and somatostatin = inhibit gastrin secretion = decr acid
  • inhibitory drugs presecribed (eg PPI)
28
Q

when do stomach ulcers form

A

when stomach lining is disrupted

29
Q

symptoms of gastric ulcers

A

tummy owie + hearburn + nausea + shit blood sometimes

30
Q

causes of gastric ulcers

A

excess secretion of gastric acid
+ presence of Helicobacter pylori

31
Q

what prevents H.pylori from being reached by immune response

A

the mucus layer

32
Q

what does H. pylori attach to

A

cells of stomach mucosa (underneath mucus lining)

33
Q

why cant H+ ions reach H.pylori

A

its neutralised by HCO ions and ammonium ions (from bacterias secretion of urease = action on urea)

34
Q

what is gastritis

A

inflammation at site of h.pylori infection

35
Q

what could be a further outcome of h.pylori infection

A

goblet cells fail = decr secretion of mucus = stomach lining exposed to HCl and protease

36
Q

3 ways h.pylori ulcers are treated

A
  • amoxicillin
  • clarithromycin
  • proton pump inhibitor
37
Q

how does amoxicillin treat in gastric ulcers

A

is an antibiotic

directly inhibits synthesis of bacterial cell walls

38
Q

how does clarithromycin treat stomach ulcers

A

is also an antibiotic

prevents growth of bacteria – inhibits translation = no protein synthesis

39
Q

how do proton pump inhibitors treat stomach ulcers (short)

A

inhibits acidification

40
Q

impact of proton pump inhibitors

A

blocks proton pump (the hydrogen-potassium one)
in parietal cells of gastric gland = decr H+ secretion into lumn = decr hcl prod

may encourage growth of gut microflora

41
Q

wall of SI contains _______ muscle tissue

A

involuntary

42
Q

what does the innermost surface of the SI consist of

A

epithelium layer (mucosa)
- contains many goblet cells

43
Q

what does mucus from goblet cells do

A

adheres to cells lining the gut

protects gut from mechanical damage, resists self-digestion

44
Q

what cells does the epithelium of the villi contain many of!

A

goblet cells

45
Q

name the 4 components of cross section of small intestine wall (Starting from innermost)

A
  1. mucosa: enterocytes
  2. submucosa
  3. circular muscle layer + longditudinal muscle layer
  4. serosa
46
Q

what are enterocytes

A

cells that have microvilli – digest and absorb substances

47
Q

name the 5 adaptations of the villi

A
  1. microvilli
  2. large number of mitochondria
  3. pinocytotic vesicles
  4. basal channels betw epithelial cells
  5. tight junctions
48
Q

how does microvilli improve food absorption

A

foldings on cell surface (Facing lumen) = incr surface area

49
Q

how do pinocytotic vesicles impvoe food absorption

A

in villus – fluid taken up/released in tiny vesicles across plasma membrane

(basically cell drinking)

50
Q

what do tight junctions do in the villus

A

bind the individual epithelial cells tgt = only way into tissues is thru epithelium

basal channels below tight junctions

51
Q

why is insoluble fibre important

A

incr faecal mass = stinulates peristaltic movements

(non digestible carbs – cellulose, lignin)

52
Q

materials not absorbed are _______ as __________

A

egested

faeces

53
Q

main constituents of insoluble fibre

A

cellulose and lignin

54
Q

what are the benefits of a high fibre diet

A
  • improved bowel movement (Stimulates movement of chyme thru gut)
  • slows absorption of glucose = decr risk of diabetes
  • decr disease of large intestine
55
Q

why cant humans digest celluose

A

we dont have cellulase :(

56
Q

what bacteria is cholera caused by

A

Vibrio cholerae

57
Q

how is cholera aquired

A

drinking water contaminated with shit from infected ppl

  • large no. req. – more than 108-109
58
Q

what toxin does cholera release

A

enterotoxin

59
Q

what is the effect of enterotoxin (simple)

A

loss of irons = loss of water

60
Q

symptoms of cholera

A

massive loss of body fluid = dehydration

vomiting, diarrhea

weakness, incr thirst, seizures, drop in blood pressure, decr urine, kidney failure

61
Q

how does cholera enterotoxin work in DETAIL 4

A
  1. enterotoxin consists of two-protein complex
  2. B part – binds to binding site (glycolipid on plasma membranes of epithelial cells)
  3. A part – activates enzyme systems of plasma membrane = secretion of Cl ions into gut lumen = sodium ion uptake inhibited
  4. hypersecretion of CL ions = water loss
62
Q

treatment of cholera

A

immediate administration of dilute solution of electrolytes (oral rehydration salts)

= rebalance fluid and ions lost

63
Q

challenges in treating cholera

A

ppl weakened by food shortage

drinking water may need to be carreid some distance (inaccessible)

boiling water to make it safe requires scarce fuel

64
Q

__________ water makes it safe from cholera

A

boiling

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