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60 > L28 - control of GI secretion > Flashcards

L28 - control of GI secretion Flashcards

1
Q

what are the major body secretory systems

A
  1. salivary glands
  2. stomach
  3. pancreas
  4. bile system
  5. intestine
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2
Q

define endocrine

define exocrine

A

secretion into blood

secretion into GI lumen

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3
Q

name the 3 salivary glands

A
  1. parotid gland
  2. submandibular gland
  3. sublingual gland
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4
Q

describe composition of parotid gland secretion

A

serous (watery)

high amylase

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5
Q

describe composition of submandibular gland secretion

A

serous & mucous

high [lysozyme]

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6
Q

describe composition of sublingual gland secretion

A

mainly mucus

some serous

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7
Q

describe general composition of saliva

A 
water
mucins (glycoproteins)
lysozymes
amylase
lipase
cells
calcium phosphate
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8
Q

what are mucins

A

glycoproteins

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9
Q

what cells secrete initial saliva and where

A

acinar cells in the acinus (bottom of gland)

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10
Q

what is the ionic composition of primary saliva

A 
Na
Cl 
K 
HCO3
amylase
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11
Q

where does modification of the ionic content of saliva occur

A

intercalated duct

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12
Q

what is reabsorbed from the primary saliva

A

Na

Cl

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13
Q

what is further secreted into/remains in the primary saliva

A

K

HCO3

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14
Q

what happens to saliva composition when flow rate is increased

A

less time to modify / reabsorb /secrete

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15
Q

what controls flow rate?

A

neuronal input

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16
Q

what controls saliva secretion

A

PNS and SNA - salivary centres in medulla

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17
Q

what stimulates saliva secretion

A

smell & sight of food

pressure & taste receptors in mouth

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18
Q

does PSNS or SNS have greater effect on salivary secretion

A

PSNS

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19
Q

what type of saliva is stimulated by
PSNS
SNS

A

serousy

mucousy

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20
Q

list the functions of saliva (5)

A
  1. lubrication (aids speech and swallowing)
  2. protection (cooling, antimicrobial)
  3. taste (dissolves food)
  4. maintenance of teeth (alkaline pH prevents decay)
  5. digestion (amylase, lipase)
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21
Q

list the gastric secretions

A
  1. HCL
  2. Pepsin
  3. lipase
  4. mucus & HCO3
  5. intrinsic factor
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22
Q

function of HCL (gastric secretion)

A

optimum pH for stomach enzymes
dissolves food
kills bacteria

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23
Q

what is pepsins optimum pH

what is its function

A

2-3

digestion of proteins

24
Q

function of mucus and HCO3 gastric secretion

A

forms a layer around stomach wall protecting cells from degradation

25
Q

function of intrinsic factor gastric secretion

A

aids vitamin b12 absorption

26
Q

what factors control HCL secretion into stomach

A

increasing : will increase secretion
ACh (neuronal)
Gastrin (endocrine)
histamine (paracrine)

decreasing : will increase secretion
somatostatin (endocrine)
secretin (endocrine)

27
Q

what is alkaline tide and its purpose

A
  1. Cl is extracted from blood (at stomach) so it can be secreted as HCL
  2. HCO3 replaces this lost Cl- in the blood
  3. this makes the blood here more alkaline
28
Q

what cells secrete HCL

A

gastric parietal cells

29
Q

what receptors are found on gastric parietal cells

A

Histamine
ACh
Gastrin

30
Q

what are the phases of gastric secretion in order

A
  1. cephalic phase
  2. gastric phase
  3. intestinal phase
31
Q

what is secreted by the pancreas

A

digestive enzymes
HCO3
water

32
Q

what is function of HCO3 secreted by pancreas

A

neutralises chyme

33
Q

list the digestive enzymes secreted by the pancreas and what they degrade

A

amylase - polysaccharides
lipase - fats
ribonuclease/deoxyribonuclease - nucleic acids
trypsin/chymotrypsin/carboxypeptidase - proteins

34
Q

how are degradative enzymes stored in the pancreas

A

as inactive forms (zymogens)

35
Q

what pancreatic cells secrete HCO3 and mucin and what stimulates them to do so

A

Centroacinar (epithelial) cells

secretin

36
Q

what does secretin stimulate the secretion of from the pancreas

A

HCO3 and mucin

37
Q

what effect does high rate of secretion (flow rate) have on pancreatic juice composition

A

will mainly contain Na and HCO3

38
Q

what is secreted from the fundus of stomach

A

lipase

39
Q

what is secreted from the antrum of stomach

A

mucus
pepsinogen
gastrin

40
Q

what is secreted from body of stomach

A

mucus
pepsinogen
HCL

41
Q

what is secreted from the chief cells of gastric glands

A

pepsinogen

lipase

42
Q

what is secreted from enteroendocrine cells of gastric glands

A

gastrin

somatostatin

43
Q

what is secreted from parietal cells of gastric glands

A

HCL

intrinsic factor

44
Q

what effect does low rate of secretion (flow rate) have on pancreatic juice composition

A

will mainly contain Na and Cl

45
Q

what stimulates pancreatic secretion

A

secretin
cholecystokinin (CCK)
PSNS

46
Q

when is secretin released

A

in response to H+ in duodenum

47
Q

when is CCK released

A

in response to fats and AA in duodenum

48
Q

what stimulates PSNS to increase pancreatic secretion

A

stomach and duodenum distension

49
Q

what inhibits pancreatic secretion

A

somatostatin

50
Q

describe bile composition

A 
bile salts
lecithin 
HCO3- 
cholesterol 
bile pigments 
trace metals
51
Q

what blood waste materials are found in bile

A

cholesterol
trace metal
bile pigments

52
Q

what is the function of bile salts and lecithin

A

fat digestion

53
Q

how is bile secretion regulated

A
  1. when food is in the SI the bile duct opens (under hormonal control via CCK)
  2. bile released into SI
54
Q

what hormone regulates bile secretion

A

cholecystokinin (CCK)

55
Q

how is the release of pancreatic bicarbonate into the duodenum stimulated

A
  1. H+ in duodenum stimulates secretin

2. secretin stimulates release of pancreatic bicarbonate

60 (27 decks)

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