Digestion 3: Secretion Flashcards Preview

PSL301 > Digestion 3: Secretion > Flashcards

Flashcards in Digestion 3: Secretion Deck (111):
1

secretion

release of materials from cells that line the lumen of the GI

2

Where do secretion products end up?

- ISF: paracine action
- blood stream
- lumen of GI

3

where can goblet cells be found?

small & large intestines

4

which cells secrete mucus in the stomach?

Foveolar cells

5

largest endocrine system in the body is...

enteroendocrine cells (EEC)
- cells that secrete hormones in the GI

6

there are ___ types of EECs, and ___ types of GI hormones

18-20;
18-20

7

EEC function is influenced by...

- GI contents
- ANS

8

describe EECs

single cells scattered throughout the length of the GI; secrete hormones

9

Goblet cells refer to...

mucus secreting cells that is shaped like a goblet (more like a comma ",")

10

we take in about __ L of fluid a day, but there is __ L of fluid entering the GI tract in total due to...

2L;
7L;
secretions from the liver, pancreas, etc.

11

how much is secreted & absorbed in toe GI tract per day?

9 L total input

12

secretions into the GI include...

- saliva
- bile
- gastric secretions
- pancreatic secretions
- intestinal secretions

13

secretions into the GI = ___x the volume of ____

2x;
plasma

14

how are fluids removed from the GI?

- absorption: small (main effect) & large intestines
- excretion: feces (small effect)

15

How is SA in the GI increased?

1) folds (3x)
2) hills & valleys (10x)
3) microscopic protrusions (20x)

16

SA increase method that can be found in the stomach

folds & valleys (no hills!)

17

rugae

folds on the inside of your stomach to allow expansion

18

valleys in the stomach =

gastric pits

19

gastric pits = opening to...

gastric gland

20

entrance to gastric glands are within the ___

rugae

21

anatomy: upper curve of the stomach

fundus

22

anatomy: antrum

nearly closed cavity located immediately before the stomach outlet. It is lined by mucosa and it does not produce acid

23

hills & valleys =

hills = villi
valleys = crypts

24

SA increase methods that can be found in the small intestines

- folds (plica or valvulae conniventes)
- hills (villi)
- valleys (crypts of Lieberkuhn)
- microscopic protrusions (microvilli)

25

differences between rugae and plica

plica is in small intestines, and is permanent

26

Crypts of Lieberkuhn extend to...

into the mucosa of the small & large intestines

27

SA increase in large intestines

1) folds (haustra)
2) valleys (crypts of Lieberkuhn) - no hills!

28

haustration

when food pushes the haustra outwards, creating bulges & increased SA

29

what causes haustra in the large intestines?

lack of resistance underlying the circular muscle in the large intestine during segmentation

30

what can haustration be classified as?

motility pattern

31

microvilli is supported by...
why?

microfilaments;
allow microvilli to waves around to increase flow in small intestines

32

celiac disease

- immune disease where patients allergic to gluten
- microvilli are shorter → less SA → less absorption of nutrients → malnutrition

33

where are goblet cells found in the small intestines?

between the epithelial cells making up the villi

34

salivary gland is made up of...

1) parotid gland
2) sublingual gland
3) submandibular gland

35

saliva contains....

- water
- electrolytes
- bicarb
- mucus
- IgA antibody
- lysozyme
- defensins
- enzymes (salivary amylase & lingual lipase)

36

function of saliva

- protection
- lubrication (try to prevent secondary peristalsis)
- taste
- digestion

37

defensins

antimicrobial proteins that break bac't cell walls

38

salivation is controlled by...

CNS (salivary center in medulla)

39

conditioned response to salivation vs. unconditioned response

unconditioned: mechanoreceptors & chemoreceptors sense food in the mouth

conditioned response: see, smell, etc. becomes associated with taste of food

40

conditioned response to salivation

sight/smell of food → cerebral cortex → salivary center (medulla) → salivation

41

salivary center is at...

pons / medulla

42

effect on salivation: PNS vs. SNS

PNS: lots of watery saliva
SNS: small amount of thick saliva

43

PNS control on salivation (process)

salivary center → CN VII, IX → salivary glands → watery saliva

44

SNS control on salivation (proess)

thoracic spinal cord → pelvic nerves → superior cervical ganglion → post-ganglion fibres → salivary glands → thick saliva

45

what secretory cells are found in the stomach (order from lumen → gastric pit → gastric gland)?

- mucous cells
- parietal cells
- chief cells
- enterochromaffin-like cells
- D cells
- G cells

46

mucous cells secrete...

- mucus
- bicarb

47

parietal cells secrete...

- HCl
- intrinsic factor

48

chief cells secrete...

- pepsinogen
- gastric lipase

49

enterochromaffin-like cells secrete...

histamine

50

D cells secrete...

somatostatin

51

G cells secrete...

gastrin

52

physical layer of production in the stomach is ___, while chemical layer of production is ___

mucus;
bicarb

53

Zollinger-Ellison syndrome

hyperacidic stomach that breaks down protective barriers and damages cells of the stomach

54

pH of stomach lumen

2

55

symptoms of ZE syndrome

- GERD
- nausea
- pain
- malnutrition
- heartburn

56

GERD

reflux of acidic chyme up the esophagus → dull chest pain

57

function of HCl in stomach

- kill bacteria
- denature protein
- activate pepsinogen

58

function of intrinsic factor

binds to vit B12 → proper absorption in ileum

59

vit B12 is also known as...

cobalamin

60

How does parietal cells secrete HCl?

1) water dissociates to H+ and OH-
2) H+ is pumped into lumen by H/K-ATPase
3) OH- + CO2 → bicarb (catalyzed by CA)
4) bicarb leave on basolateral side using Cl/bicarb-exchanger
5) Cl- is pumped into lumen by Cl-transporter
6) Cl joins with H in lumen to form HCl

61

Alkaline tide

build up of bicarb in ISF of stomach (parietal cells), so blood leaving the stomach is very basic

62

how to activate pepsinogen?

- Acid in stomach
- Pepsin (activates itself)

63

function of gastrin

- stimulates secretion of acid, histamine, pepsinogen, mucus
- increase stomach motility & mass movements (gastrocolic reflex)

64

what stimulates release of gastrin?

peptides in the lumen of the stomach

65

G cells are mostly found in ___ region of the stomac

pyloric

66

2 ways in which gastrin can stimulate the release of HCl (and describe)

1) directly: gastrin → bloodstream → parietal cells → secrete HCl

2) indirectly: gastrin → bloodstream → enterochromaffin-like cells (ECL) → histamine → parietal cells → secrete HCl

67

gastrin is responsible for ___ reflex

gastrocolic

68

cause of ZE syndrome

hypersecretion of gastrin
- gastrin secreting tumour in pancreas

69

which cells in the pancreas secrete things? where are they secreted into?

- acinar cells
- duct cells

secreted into pancreatic duct

70

what do acinar cells secrete?

- pancreatic amylase, lipase, nuclease, inactive protease

71

proteases secreted by acinar cells

- trypsinogen
- chymotrypsinogen
- procarboxypeptidase
- proelastase

72

duct cells secrete...

- bicarb
- water

73

pancreatic secretions into the small intestines is controlled by...

sphincter of Oddi

74

How are pancreatic enzymes activated in the small intestines?

by enterokinase / enteropeptidase

75

enterokinase

enzymes embedded in brush border that is required for the activation of proteases secreted by the pancreas

76

how is bicarb secreted in the GI tract? (slide 20)

1) water + CO2 dissociate → bicarb + H (catalyzed by CA)
2) bicarb goes into lumen via bicarb/Cl-exchanger
3) H leaves the cell via NHE
4) NKCC transporter pumps stuff into lumen
5) Cl leaves cell via CFTR to lumen
6) Na leaves the cell to ISF via Na/K-ATPase

77

Why is the blood leaving the pancreas / small intestines acidic?

bicarb is secreted in lumen while H is secreted into ISF
- this balances alkaline tide from stomach

78

CFTR

cystic fibrosis transmembrane regulator

79

how is water secreted in the GI tract?

- Na attracted to lumen because it's very negative from bicarb and Cl-
- water is attracted to solutes in lumen
- both transported to lumen via paracellular pathway

80

only way for Cl to exit in the lumen is...

CFTR

81

Why do people with cystic fibrosis have to ingest ____? Why?

pancreatic enzymes;
- defective CFTR channels
- no watery bicarb (only thick mucus from duct cells)
- mucus blocks pancreatic duct
- no enzymes can reach small intestines
- no digestion

82

bile is made up of...

- bile salts
- lecithin
- cholesterol
- bilirubin
- bicarb

83

where does bile come from?

- synthesized by liver
- diet
- secretions from duct cells
- remainders from body (e.g. bilirubin, cholesterol)

84

bile salt recycling =

enterohepatic circulation

85

bile salt recycling happens ___ x per day

5 - 15

86

define: enterohepatic circulation

cycling between the liver and small intestines
- connected by hepatic portal vein

87

primary bile acids are synthesized by...

liver

88

secondary bile acids are syntheiszed by...

bacterial conversion in intestines

89

bile acid → bile salt

conjugation with glycine or taurine (amino acids)

90

difference between bile acid vs. bile salt

bile acid is lipophilic, so it wants to leave the lumen;
bile salt is conjugated, so can be soluble in the lumen

91

process of bile salt recycling

1) liver makes primary bile acids
2) gets conjugated and enters small intestines
3) return to hepatic portal vein by...
- passive transport
- active transport
- bacteria mediated absorption (→ bile acids or continue → secondary bile acids)
4) goes back to liver

92

bacteria mediated absorption

convert bile salt → bile acids so it can easily cross epithelial membrane

convert the bile salt → bile acid → secondary bile acid → reabsorbed or lost in feces

93

fate of secondary bile acids

reabsorbed or lost in feces

94

secondary bile acids (specific names and fate)
[MAYBE NOT ACCURATE]

- deoxycholic acid (reabsorbed)
- lithocholic acid (lost)

95

what hormone is released by the stomach?

gastrin

96

what hormones are released from small intestines?

- secretin
- CCK
- GIP
- Motilin
- GLP-1

97

glucose-dependent insulintropic protein is secreted from...

K cells (mostly jejunum, some duodenum)

98

why is GIP secreted?

in response to mixed meal (glucose, fat, protein)

99

effect of GIP

- increase insulin
- decrease acid

100

motilin is secreted by...

M cells

101

when is motilin secreted?

during fasting

102

function of motilin

regulates migrating motor complex (MMC)

103

secretin is secreted by...

S cells in duodenum

104

function of secretin

decrease acid in small intestines
- more pancreatic bicarb
- less gastric acid secretion
- less gastric emptying

105

CCK is secreted by...

I cells in duodenum and jejunum

106

CCK is secreted in response to...

fatty acids & AA in small intestines

107

CCK causes...

- contraction of gall bladder (more bile)
- increased release of pancreatic enzymes (increase small intestines)
- decreased gastric acid secretion & gastric emptying (slow stomach)

108

GLP-1 (glucagon-like peptide-1) is secreted by...

L cells of the ileum

109

GLP-1 is secreted in response to...

fatty acids & cabs in the small intestines

110

effects of GLP-1

- decreased gastric acid secretion & emptying (slows stomach)
- increased insulin & B-cell growth; decreased glucagon

111

GLP-1 causes feeling of...

satiation