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Biomedical Physiology > The Digestive System Part 2 > Flashcards

The Digestive System Part 2 Flashcards

1
Q

*Label this diagram of the stomach

A

there

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2
Q

what areas of the stomach secrete

A

the fundus, the body and the antrum

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3
Q

what type of mucosa does the body of the stomach contain

A

oxyntic mucosa

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4
Q

what type of glands does the antrum contain

A

the pyloric glands

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5
Q

what are the two sphincters present in the stomach called

A

the gastroeosophageal and the pyloric

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6
Q

what does the luminal surface of the stomach have

A

deep folds

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7
Q

where does a peristaltic contraction originate and to where does it go towards

A

a peristaltic contraction originates in the upper fundus and sweeps down towards the pyloric sphincter

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8
Q

where does the peristaltic contraction become vigorous

A

the contraction becomes more vigorous as it reaches the thick muscles antrum

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9
Q

what is the function of the strong antral peristaltic contraction

A

it propels the chyme forward

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10
Q

what two types of contraction occur in the stomach

A

regular peristaltic contractions - ber. strong peristaltic contractions - antrum

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11
Q

what does ber stand for

A

basal electrical rhythm

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12
Q

list three functions of the stomach

A

stores ingested food until emptied into the small intestine, secretes hcl and enzymes, converts contents into chyme

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13
Q

what is the mucosal lining of the stomach divided into

A

the oxyntic mucosa and the pylorid gland area based on the differences in glandular secretion

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14
Q

*label this diagram of the excocrine secretory cells

A

there

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15
Q

what is an exocrine gland

A

a gland that secretes its products into ducts

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16
Q

what is the function of the mucous cells present lining the gastric pits and the entrance of the glands

A

they secrete a thin, watery mucus - alkaline mucous

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17
Q

what is the function of the mucous cells when secreting the alkaline mucous

A

a protective function

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18
Q

what is the stimulus for the mucous cells to begin secreting alkaline mucous

A

a mechanical stimulation

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19
Q

what do chief cells release

A

pepsinogen

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20
Q

what is the function of the pepsinogen that the chief cells release

A

once the pepsinogen is activated, it digests protein

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21
Q

what is the stimulus for the cheif cells to release the pepsinogen

A

acetylcholine and gastrin

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22
Q

what do the parietal cells secrete

A

they secrete hcl and intrinsic factor

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23
Q

what stimulates the parietal cells to secrete hcl

A

acetylcholine, gastrin and histamine

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24
Q

what is the function of intrinsic factor

A

to absorb vitamin b12

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25
Q

what do exocrine secretions collectively make up

A

gastric digestive juice

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26
Q

what are the three endocrine/paracrine secretory cells

A

enterochromaffin-like cells (ecl cells), g cells and d cells

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27
Q

what is the function of enterchromaffin-like cells

A

to release histamine

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28
Q

what is the stimulus for ecl cells to release histamine

A

acetylcholine and gastrin

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29
Q

what is the function of the histamine that is secreted by the ecl cells

A

to stimulate the parietal cells

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30
Q

what do g cells release

A

they release gastrin

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31
Q

what is the stimulus for the g cells to produce gastrin

A

protein products and acetylcholine

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32
Q

what is the function of the gastrin produced by the g cells

A

to stimulate the perietal/chief/ecl cells

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33
Q

what do the d cells produce

A

they produce somatostatin

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34
Q

what is the stimulus for the d cells to produce somatostatin

A

acid

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35
Q

what is the function of the d cells producing somatostatin

A

to inhibit parietal/g/ecl cells

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36
Q

are enterochromaffin-like ecl cells stimulatory or inhibitory

A

they are stimulatory

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37
Q

are g cells stimulatory or inhibitory

A

they are stimulatory

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38
Q

are d cells stimulatory or inhibitory

A

they are inhibitory

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39
Q

what are the two functions of the peristaltic contractions

A

mixing of the gastric contents and the driving force for gastric emptying

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40
Q

The intensity of an- tral peristalsis can vary markedly under the influence of differ- ent signals from what

A

both the stomach and duodenum; thus, gastric emptying is regulated by both gastric and duodenal factors

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41
Q

what factors of the stomach increase the rate of motility and emptying of the gastric contents

A

volume of chyme, fluidity of chyme and distension of stomach

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42
Q

what factors of the duodenum decrease the rate of motility and emptying of the gastric contents

A

fat, acid, hypertonicity and distension

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43
Q

the presence of one or more stimuli in the duodenum activates appropriate duodenal receptors which trigger either one of two types of responses. what are the two types of responses

A

a hormonal or a neural response

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44
Q

the neural response is mediated through both the intrinsic nerve plexuses and the autonomic nerves, what are these reflexes collectively termed

A

the enterogastric reflex

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45
Q

what type of reflex is the intrinsic nerve

A

short reflex

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46
Q

what type of reflex are the autonomic nerves

A

long reflex

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47
Q

the hormonal response involves the release from the small intestine mucosa of several hormones collectively known as the

A

enterogastrones

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48
Q

where does the blood carry the enterogastrones and for what function

A

the blood carries these hormones to the stomach where they inhibit antral contractions to reduce gastric emptying

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49
Q

what are the two most important enterogastrones

A

secretin and cholecytokinin (cck)

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50
Q

what cells produce secretin

A

s cells

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51
Q

what cells produce cck

A

I cells

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52
Q

where are the s cells and I cells producing the enterogastrones found

A

in the duodenum and jejenum

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53
Q

what are two other factors which may impact on gastric motility and emptying

A

emotion and intense pain

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54
Q

what effect does emotion have on gastric motility and emptying

A

emotion alters the ans balance, it stimulates/inhibits motility and emptying

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55
Q

what affect does intense pain have on gastric motility and emptying

A

intense pain increases the sympathetic activity, decreasing the motility and emptying

56
Q

what three regions make up the small intestine

A

the duodenum, the jejunum and the ileum

57
Q

how would you describe the small intestine

A

as a coiled hollow tube roughly 8-10feet long

58
Q

what is the small intestine the primary site of

A

the primary site of digestion and absorption

59
Q

what three specialisations increase the absorptive surface of the small intestine

A

circular folds, villus and microvilli

60
Q

the circular folds of the small intestine increase the absoptive surface by how much

A

3-fold

61
Q

the villus of the small intestine increase the absorptive surface area by how much

A

10 fold

62
Q

list four features of the villus in the small intestine

A

epithelial cells cover the surface. they have a connective tissue core. there is a capillary network. there is a terminal lymphatic vessel

63
Q

what do the microvilli form

A

a brush border

64
Q

by how much do the microvilli increase the absorptive surface of the small intestine

A

20 fold

65
Q

the microvilli of the small intestine have membrane bound enzymes, list three

A

enterokinases, disaccaridases and aminopeptidases

66
Q

the surface modifications of the small intestine - the circular folds, the villi and the microvilli - altogether increase the overall absorptive surface area by how much

A

600 fold

67
Q

what are the three secretions into the duodenum

A

the intestinal juice, the pancreatic juice and bile

68
Q

roughly how much intestinal juice is secreted into the duodenum per day

A

1.5 litres per day

69
Q

what cells secrete intestinal juice

A

exocrine cells in the small intestine mucosa

70
Q

what do the exocrine cells in the small intestine mucosa secrete which makes up the intestinal juice

A

aqueous salt and mucus secretion

71
Q

what is the aqueous salt and mucus secretion secreted by the exocrine cells in the small intestine making up the intestinal juice called

A

the succus entericus

72
Q

roughly how much pancreatic juice is secreted daily

A

1-2 litres a day

73
Q

what two cells are involved in secretions making up the pancreatic juice

A

acinar cells and duct cells

74
Q

what do the acinar cells release

A

pancreatic enzymes that digest all three food stuffs

75
Q

what are the three pancreatic enzymes that the acinar cells secrete

A

pancreatic proteolytic enzymes, pancreatic amylase and pancreatic lipase

76
Q

give an example of a pancreatic proteolytic enzyme released by acina cells

A

trypsinogen

77
Q

what do proteolytic enzymes digest

A

protein

78
Q

what do amylase enzymes digest

A

carbohydrate

79
Q

what do pancreatic lipase digest

A

fat

80
Q

what do the duct cells of the pancreas secrete

A

aqueous alkaline solution

81
Q

what is the aqeuous alkaline solution secreted by the duct cells rich in

A

NaHCO3

82
Q

the pancreatic exocrine secretion is under hormonal control, what happens when there is acid in the duodenal lumen

A

it results in an increase release of secretin from the duodenal mucosa. the secretin is carried by the blood to the pancreatic duct. this releases in an increased secretion of aqueous NaHCO3 solution into the duodenal lumen

83
Q

what is the function of the NaHCO3 being released into the duodenal lumen

A

to neutralise the acid in the duodenal lumen

84
Q

when there are fat and protein products in the duodenal lumen, which cells secrete more substance and which substance do they secrete

A

i cells secrete more cck from the duodenal mucosa

85
Q

when there is fat and protein in the duodenal lumen, more cck is carried by the blood to the pancreatic acinar cells, what happens next

A

an increased secretion of pancreatic digestive enzymes into the duodenal lumen takes place which digests the fat and protein products

86
Q

roughly how much bile is secreted into the duodenum on a daily basis

A

250ml-1litre per day

87
Q

where is bile synthesised and secreted from

A

liver

88
Q

where is bile stored

A

in the gall bladder

89
Q

what is the main function of bile salts

A

to aid in fat digestion and absorption

90
Q

what are dietary carbohydrates converted into

A

monosaccharides

91
Q

where does digestion of carbohydrates begin

A

in the mouth

92
Q

what enzyme is present in the mouth for carbohydrate digestion

A

salivary amylase

93
Q

what does salivary amylase cconvert glycogen and starch into in the mouth

A

oligosaccharides

94
Q

what enzymes are present in the small intestine for the digestion of carbohydrates

A

pancreatic amylase and disaccharidases

95
Q

what role do the disaccharidases have

A

they convert disaccharides into monosaccharides

96
Q

what role does pancreatic amylase have

A

convert glycogen, oligosaccharides and starch into disaccharides

97
Q

glucose and galactose are absorbed in the small intestine by what type of transport

A

secondary active transport in which symport carriers such as the sodium and glucose co transporter SGLT is involved

98
Q

how do glucose and galactose leave the enterocyte

A

by facilitated diffusion through the glut-2 passive transporter

99
Q

how does fructose enter an enterocyte - by which type of transporter

A

glut-5 which is a passive transporter, so it enters by facilitated diffusion

100
Q

how does fructose leave an enterocyte into the interstitial fluid

A

through the glut-2 passive transporter, so it exits by facilitated diffusion

101
Q

how do carbohydrates enter the blood, in which form do they have to be broken down to

A

monosaccharides enter the blood

102
Q

what must proteins be digested into

A

amino aids

103
Q

digestion of proteins begins where

A

in the stomach

104
Q

gastric pepsin in the stomach converts proteins into what

A

large polypeptides

105
Q

what three types of enzymes do we have in the small intestine

A

pancreatic proteolytic enzymes, aminopeptidases and intracellular peptidases

106
Q

what converts dipeptides to amino acids

A

dipeptidases

107
Q

in protein absorption, small peptides are absorbed at the apical membrane by which two methods

A

symporter driven by H+ and Na+ - tertiary active transport

108
Q

how do small peptides pass through the basolateral membrane

A

by facilitated diffusion which is passive

109
Q

how do amino acids enter the enterocyte via the apical membrane

A

by na+ co transporters - symporters- secondary active transport

110
Q

how do amino acids leave through the basolateral membrane

A

via a passive transporter, facilitated diffusion

111
Q

what are proteins broken into to enter the blood capillary

A

amino acids

112
Q

why are lipids a challenge to digest

A

lipids are hydrophobic so chemical and physical transformations must take place before they are digested and absorbed

113
Q

why does the insolubility of fat in water present a special problem in digestion

A

because fat must be transferred from the watery chyme through the watery bodily fluids, even though fat is not water soluble

114
Q

what is lipid converted into

A

monoglycerides and free fatty acids

115
Q

what enzyme aids in digestion of lipids

A

pancreatic lipase

116
Q

why are micelles key in the absorption of lipids

A

micelles are water-soluble particles that can carry the end products of fat digestion. the monoglycerides and free fatty acids passively diffuse from the micelles through the lipid component of the epithelial cell membranes to enter the interior of these cells.

117
Q

bile secretion is modulated by what three regulatory systems

A

chemical regulation, hormonal regulation and neural regulation

118
Q

what is used in the chemical regulation of the secretion of bile

A

bile salts

119
Q

what hormone is used for the seretion of bile

A

secretin

120
Q

what nerve is used in bile secretion

A

vagus nerve

121
Q

what four substances make up the bile - (they form a aqeuous alkaline fluid)

A

bile salts, cholesterol, lecithin and bilirubin

122
Q

what two parts make up bile salts

A

a lipid soluble part and a water soluble part

123
Q

where do bile salts adsorb onto

A

the surface of fat droplets

124
Q

the mixing movements of the small intestine result in the breaking up of

A

fat droplets

125
Q

what prevents the bile salts and lipid from re-coalescing in the small intestine

A

the water soluble surface

126
Q

what two components of bile are involved in the formation of micelles which are water soluble

A

bile salts and lecithin

127
Q

describe the core of a micelle

A

hydrophobic - consisting of monoglycerides and free fatty acids

128
Q

describe the shell of a micelle

A

hydrophillic

129
Q

what is the function of the micelle

A

to transport h2o insoluble substances to the enterocytes

130
Q

what does the lipid empulsion formed allow

A

This lipid emulsion prevents the fat droplets from coalescing and thereby increases the surface area available for attack by pancreatic lipase.

131
Q

what is the function of pancreatic lipase

A

Lipase hydrolyzes the triglycerides into monoglycerides and free fatty acids.

132
Q

what happens when a micelle approaches the apical membrane of a enterocyte

A

When a micelle approaches the absorptive epithelial surface, the monoglycerides and fatty acids leave the micelle and passively diffuse through the lipid bilayer of the luminal membranes.

133
Q

what happens to the free fatty acids and the monoglycerides once they enter an enterocyte after diffusion across the apical membrane

A

The monoglycerides and free fatty acids are resyn- thesized into triglycerides inside the epithelial cells.

134
Q

what happens to the triglycerides in the enterocyte

A

These triglycerides aggregate and are coated with a layer of lipoprotein from the endoplasmic reticulum to form water-soluble chylomicrons.

135
Q

how do chylomicrons leave the basal membrane of the enterocyte

A

Chylomicrons are extruded through the basal membrane of the cells by exocytosis.

136
Q

chylomicrons are unable to cross the basement membrane of the capillaries so where do they go instead

A

Chylomicrons are unable to cross the basement membrane of capillaries, so instead they enter the lymphatic vessels, the central lacteals.

Biomedical Physiology (19 decks)

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