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PHGY 210 > digestion post midterm 2 > Flashcards

digestion post midterm 2 Flashcards

1
Q

what signal is sent to the NS to cause secretion and vasodilation even the food enters the stomach

A

vago-vagal activation during the cephalic phase

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2
Q

what does distention in the stomach activate?

A

-activates local enteric reflex and vago-vagal reflex

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3
Q

what are the products of proteins released during protein digestion?

A

secretogogues

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4
Q

what are secretogogues?

A

which are AA or partially digestied proteins

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5
Q

what do secretogogues act on?

A

act on gastrin releasing G-cells which sit in the antrum of the stomach.

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6
Q

what does gastrin effec?

A

effects parietal cells to produce HCl

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7
Q

what type of hormone is gastrin?

A

peptide hormone

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8
Q

what is gastrin released by?

A

released by endocrine cells in the antrum of the stomach by G cells

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9
Q

what causes for gastrin to be released?

A
  • Secretogogues
  • Local enteric reflexes (distention in the antrum)
  • Vagally-mediated reflexes (vago-vagal reflexes)
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10
Q

what regulates gastrin release?

A

itself as it is self regulated

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11
Q

what type of feedback mechanism regulates gastrin?

A

positive feedback and negative feedback

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12
Q

what happens if the pH of the stomach drop below 2?

A

gastrin release gets inhibited

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13
Q

what will a low stomach pH cause?

A

release of the somatostatin cells which will inhibit the parietal cells from releasing HCl

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14
Q

what is the tropic effect of gastrin

A

stimulates production of more parietal cells

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15
Q

where is histamine present in the stomach?

A

in the gastric mucosa

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16
Q

what does histamine elicit?

A

large volumes of gastric juices with lots of HCl

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17
Q

how does gastrin ellicit large volumes of gastric juices with lots of HCl?

A

it sensitized the parietal cells to other stimuli

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18
Q

what can the the blocking of background release of histamine cause

A

inhibit acid secretion in response to ACh and Gastrin

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19
Q

what are H2 blockers used for?

A

used to decrease HCl secretions

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20
Q

how can ulcers be treated?

A

using H2 blockers or as H+/K+ATPase blockers

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21
Q

what is the impact of secretogogues as the food enters the duodenum?

A

secretogogues will enter circulation and cause a hormone to stimulate a final push of HCl secretion by the parietal cell.

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22
Q

what inhibits gastric secretions?

A

the enterogastrone hormone complex

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23
Q

what does the enterogastrone hormone complex control?

A

antral peristalsis & secretion

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24
Q

what are some preintesinal changes made to food?

A

o Meal is reduced to a semi-liquid consistency

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25
Q

what happens to the osmotic pressure before it reaches the intestine

A

unchanged

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26
Q

what happens to the cyme before it reaches the intestines

A

its acidified

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27
Q

what is limited at the level of the stomach?

A

digestion

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28
Q

what is digested in the stomach?

A

polysaccharides –> disaccharides by salivary amylase
proteins –> polypeptides by gastric pepsin
lipids into DG/MG by lingual lipases

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29
Q

what happens to chyme once it reaches upper intestine?

A

must be neutralized

osmotic pressure must be equilibrated

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30
Q

where does absorption take place?

A

begins in the upper intestine

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31
Q

where do the pancreatic ducts lead to

A

to the duodenum

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32
Q

what does the pancreas secrete?

A

pancreatic juices

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33
Q

what is contained in pancreatic juices?

A

many digestive enzymes

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34
Q

what does the exocrine portion of the pancreas contain?

A

acini

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35
Q

what is contained in acini

A

duct cells and acinar cells

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36
Q

what is secreted by acinar cells?

A

digestive enzymes

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37
Q

what is secreted by duct cells?

A

bicardbonate rich fluid

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38
Q

what enzymes are contained in the pancreatic juices?

A 
pancreatic amylase
trypsin
chymotrypsin
elastase
pancreatic lipase
ribonuclease
diribonuclease
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39
Q

what breaks down trypsinogen into trypsin?

A

enterokinase

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40
Q

what is the function of trypsin?

A

it breaks down other pancreatic enzymes such as chymotrypsin, protelastase, procarboxypeptidase

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41
Q

what does the pancreas produce in order to inhibit trypsin?

A

trypsin inhibitor

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42
Q

why would the pancreas produce trypsin inhibitor?

A

to ensure that any trypsin in the pancreas is broken down

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43
Q

what volume of pancreatic juices are secreted daily?

A

0.5-1.5L/day

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44
Q

what is the osmolarity of pancreatic juices?

A

isotonic ~300mOsm

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45
Q

what is the main electrolyte found in pancreatic juice?

A

HCO3-

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46
Q

what is the pH of pancreati juice?

A

7.2-8.2

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47
Q

what is the concentration of enzymes in pancreatic juices?

A

~3g%

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48
Q

what is the function o amylase?

A

breaks down polysaccharides into disaccharides

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49
Q

how must CHO be broken down in order to be absorbed?

A

as monosaccharides

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50
Q

how are proteases first released as?

A

proenzymes

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51
Q

why must proteases be secreted into an inactive form?

A

in order to prevent the breakdown of the pancreatic cells themselves

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52
Q

at what pH is needed for lipases to function?

A

~8

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53
Q

what is produced by the liver and needed to break down fats?

A

bile salts

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54
Q

what is released by the exocrine secretions of the pancreased?

A

cells release large volume of pancreatic juice rich in HCO3- and small volume of juice rich in pancreatic enzymes

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55
Q

what is the largest gland in the body?

A

the liver

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56
Q

what are the main functions of the liver?

A

storage, synthesis, detoxification, metabolism

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57
Q

what is secreted by the liver?

A

bile

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58
Q

where is bile released?

A

via the hepatic duct and enter common bile duct and then into the SI

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59
Q

what sphincter needs to be open to allow bile to enter through the SI?

A

sphincter of Oddi

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60
Q

what do the lobules of the liver contain?

A

hepatocytes

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61
Q

how much bile is secreted daily?

A

0.5-1L

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62
Q

what ion is most prominent in bile?

A

HCO3-

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63
Q

what is the pH of bile?

A

7.8-8.2

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64
Q

what is contained in bile?

A

disgestive enzymes

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65
Q

what concentration of solids is found in bile

A

3g%

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66
Q

what solids are found in bile?

A

bile salts
bile pigments
cholesterol
phospholipids

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67
Q

is bile secretion continuous or intermittent?

A

continuous

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68
Q

is the enterance of bile in the duodenum continuous of intermittent?

A

intermittent

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69
Q

how much bile enters the SI daily?

A

<500-700 ml

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70
Q

what is the function of the gall bladder?

A

concentrate and store bile

71
Q

how does the liver synthesize bile salts?

A

from cholesterol

72
Q

what are the main fucntions of bile salts?

A

Facilitate digestion, transport and absorption of Fat (including cholesterol) by forming water-soluble complexes with fats and fat soluble vitamins

73
Q

what are the fat soluble vitamins?

A

ADEK

74
Q

are bile salts polar, non polar, amphipatic?

A

amphipatic

75
Q

what does the amphipatic nature of bile salts allow?

A

it allows to form miscells through aggregation

76
Q

where would vitamins and choelsterol be found in the micelle?

A

at the core of it

77
Q

what is the function of micelles produced by bile salts?

A

Stabilizes the emulsions so they can be acted on by the lipases

78
Q

how much bile salts are contained in the body?

A

3.5g

79
Q

how much bile salts is synthesized daily?

A

0.5g

80
Q

how much bile salts get released daily?

A

15-20g

81
Q

how can so much bile be released and so little secreted daily?

A

bile is recycled and returned to the liver via enterohepatic circulation

82
Q

how often does the bile salt pool get recirculated dailyy?

A

a few times a day

83
Q

what happens by the time they reach the distal ileum

A

bile salt is reabsorbed

84
Q

what are the main functions of bile salts

A

regultaes hepatic bile flow
regulates the synthesis of new bile salts
keeps cholesterol in solution

85
Q

how is heptatic bile flow regulated?

A

via positive feedback mechanisms

86
Q

what would happen to bile secretion if the ileum is removed?

A

less bile is secreted since, less bile is returned

87
Q

through what feedback mechanisms does bile synthesis occur?

A

negative feedback, more that is returned less is synthesized

88
Q

what happens if cholesterol precipitates?

A

it may give rise to gallstones

89
Q

how much is solubility of cholesterol increased in bile?

A

2x10^6

90
Q

what is the role of bile salts intraintestinally?

A

act as a detergent and help for emulsions

aids in transport of fat soluble vitamins

91
Q

what is the role of bile salts in the colon?

A

inhibits sodium transport and water absoption`

92
Q

what happens if we have too much bile salts in the colon?

A

diarrhea

93
Q

what are agents which cause the liver to secrete a larger volume of bile

A

choleretics

94
Q

what are Agents which cause an increase in the emptying of the gall bladder

A

colagogues

95
Q

what is the law of reciprical action?

A

If the gall bladder is contracted, the sphincter of Oddi will be relaxed and vice versa

96
Q

how does bile travel from site of production to the organs it needs to reach

A

The liver produces bile which enters the SI via the sphincter of Oddi, travels via hepatic circulation
From the hepatic portal vein from IT -> liver ->IVC ->Heart

97
Q

by the time we reach what part of the GIT will most of the bile salts have been reabsorbed?

A

by the time they reach the distal ileum

98
Q

how much bile cann the gallbladder store?

A

50-100ml

99
Q

what does the gallbladder do to bile?

A

it concentrates its solids, reduces their pH, increases viscosity

100
Q

what is the concentration of solids in the gallbladder?

A

10-20g%

101
Q

can the gallbladder synthesize bile salts?

A

no

102
Q

what is a cholecystectomy?

A

it involves the removal of a gallbladder

103
Q

what happens if the gallbladder is removed?

A

hepatic bile is generally sufficent to break down lipids, however, eating less lipid richs foods would be better

104
Q

after all the salivary, gastric, pancreatic and hepatic digestion in what state are CHO?

A

they still need to be broken down into monosaccharides

105
Q

after all the salivary, gastric, pancreatic and hepatic digestion in what state are proteins?

A

proteins still need to be broken down into AA, di/tripeptides

106
Q

after all the salivary, gastric, pancreatic and hepatic digestion in what state are fats?

A

fats have been broken down into FA/MG/DG and so no need for further steps

107
Q

what is secreted by the small intestine?

A

water
mucous
ions

108
Q

where are the enzymes contained in the SI contained and what are they called?

A

brush border enzymes which are attached to the villli of the cells

109
Q

what process is used in the SI to aid in mechanical digestion?

A

segmentation

110
Q

how does chemical digestion take place in the SI?

A

Occurs as chyme mixes with the pancreatic juices, intestinal juices and bile

111
Q

why is it important to have invaginations and outpushing in the membrane of the SI?

A

o Large surface area for secretion, digestion and absorption

112
Q

what takes place in the villi region of the SI?

A

Complete digestion and absorption

113
Q

what are villi contained in villi cells?

A

• Enterocytes in villi synthesize digestive enzymes which remain in the brush border

114
Q

what enzymes are secreted in the SI?

A 
Enterokinase (lumen)
Amylase
Lipases
Aminopeptidase
Dipeptidase
Disaccharases
-Sucrase
-Maltase
-Isomalatase
-Lactase
115
Q

where are intestinal cells born?

A

in the crypt region

116
Q

when do cells matin in the SI?

A

Cells mature as they move up to the villi region

117
Q

how long is cell turnover in the SI?

A

~3-5 days

118
Q

what happens to intestinal cells once they reach the tip of the SI?

A

apoptose

119
Q

where does absoprtion take place in the SI?

A

in the lumen of the intestine

120
Q

what allows for proximity with the circulatory system in the villi of the SI?

A

capillary loop and lacteal

121
Q

how are fats carried and absorbed in circulation in the SI?

A

fats will complex with chylomicorns and be carried by lacteals into lymphatic system until they reach circulation

122
Q

through what system does the contents of the capillary loop flow through?

A

flows through the hepatic system

123
Q

where does the contents of the lacteals drain into?

A

contents of the lacteal travel through the greater lymphatic vessels and drain into the left subclavian veins

124
Q

how are lipids tranported?

A

through lipoproteins

125
Q

why is it difficult to transport lipids through blood?

A

due to their hydrophobic nature

126
Q

what are the different classes of lipoproteins?

A

chylomicrons
VLDL
LDL
HDL

127
Q

what do crypt cells lack?

A

• Lack digestive enzymes

128
Q

what do crypt cells secrete?

A

secrete a large volume (3L/Day) of alkaline fluid known as succus entericus

129
Q

how much volume is secreted in the SI daily?

A

~3L

130
Q

what is the most prominent ion in the SI?

A

HCO3-

131
Q

what is the ph in the small intestine?

A

7.5-9

132
Q

how much is secreted in the colon?

A

a very small volume

133
Q

what is the pH in the colon?

A

• Alkaline
o [HCO3-] = 100-150 mEq/L
o [K]= 100-150 mEq/L

134
Q

what is there alot of in the colon?

A

bacteria and mucin

135
Q

what lack in the colon?

A

digestive enzymes and no nutrient absorption

136
Q

what regulates intestinal secretions of the colon?

A
  • Local enteric reflexes
  • Vago-vagal reflexes
  • Hormonal factors
137
Q

what is being absorbed through the process of nutrient absorption?

A

the majority is resabsorbed material

138
Q

what are the sites of exchange characterized by?

A

Very large surface area of small intestine

Intimate contact with blood vessels

139
Q

how does absorption take place?

A 
o	Simple diffusion
o	Facilitated diffusion
o	Active transport
o	Pinocytosis (take nutients into the cells)
o	Osmosis
140
Q

what factors may limit absorption?

A

need for adequate digestion, absorption, transit time and cofactors and transporters

141
Q

what are factors that influence adequate digestion?

A

the amount of enzymes, the activity of the enzymes, optimal pH and composition, proper motility

142
Q

how much daily secretions needs to be rebasorbed daily?

A

~7L

143
Q

how much content is taken in by the mouth?

A

~2000mL fluid and 500g solids

144
Q

how much is excreted by the body

A

~50g and 100mL

145
Q

from the solids excreted in the body what are is proportions?

A
  • 30% bacteria
  • 30% undigested fiber
  • 10-20% lipids
  • 10-20% inorganic matter
146
Q

overall how many L does the body need to absorb daily?

A

9L

147
Q

does the body only need to absorb fluid?

A

no alot of the fluids also contain ions which also need to be absorbed

148
Q

how manu L are absorbed in the SI daily? what is the max capacity of the SI?

A

7l

Max: 15L

149
Q

how manu L are absorbed in the colon daily? what is the max capacity of the colon?

A

2L

max: 4-5L

150
Q

how much proteins are released in the lumen daily? what happens to them?

A

50g enzymes
30g cells
thus overall the 80g of proteins need to be broken down into AA to be reused

151
Q

by how much is the surface area increased by the vili and microvili

A

villi: 30x
microvilli: 600x

152
Q

what is the rate of the post prandial blood flow to the intestine?

A

1-2L/day

153
Q

why are villi efficent in absorption?

A

: each villus has a capillary loop and lacteal

154
Q

why is it not a good idea to exercise after a fat meal?

A

slow rate of lymphe flow: 1-2mL/minute

155
Q

what is mostly absorbed by the duodenum?

A 
Iron 
Ca2+
CHO
PROTEINS
Na+
lipids
156
Q

what is mostly absorbed in the jejunum?

A

CHO
PROTEINS
Na+
lipids

157
Q

what is mostly absorbed by the ileum?

A 
CHO
VIT B12
PROTEINS
BILE SALTS
Na+
Lipids
158
Q

what breaks down lactose?

A

lactase

159
Q

what % of CHO is lactose?

A

6%

160
Q

what is lactose broken down into?

A

galactose and glucose

161
Q

what % of CHO is starch?

A

60%

162
Q

what % of CHO is sucros?

A

30%

163
Q

what type of protein is more rapidly absorbed?

A

oligopeptides

164
Q

how much protein is taken in daily?

A

~35-200g

165
Q

what happens to MG ready to be absorbed?

A
  • FA from monoglycerides are taken up by the micelles and will enter the enterocytes and reform TG which will join to the chylomicrons and transported by the lacteal into the lymphatic system
  • The glycerol portion of the MG is taken into the blood directly
166
Q

what is the high efficency of the GIT a result of?

A

effective coordination of activities (neural, homonal,motor, secretory, enzymatic) within an organ between organs

167
Q

how does the body function in response to a meal?

A
  • secretory activity before and after

- motor activity will receive, accomodate and convey the meal

168
Q

what is the transit time in the colon?

A

hours to days

169
Q

what is the transit time in the SI?

A

several hours

170
Q

what is the transit time in the stomach?

A

minutes to hours

171
Q

what is the transit time in the esophagus?

A

seconds

172
Q

what is the transit time in the pharynx?

A

<1s

173
Q

what is the transit time in the GIT relative to?

A

the fucntion of the given organ

PHGY 210 (11 decks)

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