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EXCI 445 > Chapter 5- Gastric Emptying, Digestion, Absorption > Flashcards

Chapter 5- Gastric Emptying, Digestion, Absorption Flashcards

1
Q

what is the GI tract’s function?

A

to provide the body with nutrients

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2
Q

what is the purpose of digestion

A

break down into smaller particles

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3
Q

what is the purpose of absorption?

A

transport of nutrients from intestine via lymph or blood vessels

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4
Q

what is the purpose of elimination ?

A

elimination of waste, undigested food

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5
Q

where does digestion start ?

A

in mouth

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6
Q

what is the function of the mouth ?

A

mechanical digestion

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7
Q

what is the function of salivary glands ?

A

secretion of fluid and digestive enzymes

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8
Q

what is the function of stomach?

A

secretion of HCl and proteases

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9
Q

what is the function of pancreas

A

secretion of digestive enzymes and bicarbonate

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10
Q

what is the function of liver

A

secretion of bile acids

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11
Q

what is the function of gallbladder

A

temporary storage and concentration of bile

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12
Q

what is the function of small intestine ?

A

digestion of food, absorption of water, nutrients, electrolytes

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13
Q

what is the function of large intestine

A

absorption of electrolytes

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14
Q

what are the 3 purposes of chewing

A
  • mechanically reduces the size of food particles, increasing rate of gastric emptying
  • increases surface area of food, more digestive enzymes released
  • mixes food with saliva and digestive enzymes
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15
Q

what is the function of esophagus ?

A

push down bolus

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16
Q

is swallowing possible in space or upside down ?

A

yes thanks to peristalsis in esophagus

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17
Q

what is GERD ?

A

esophageal sphincter doesn’t work, acid goes into esophagus

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18
Q

what is the function of the pyloric sphincter ?

A

controls amount of chyme going in small intestine

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19
Q

what people are more affected by GERD ?

A

runners and cyclists

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20
Q

what are the three parts of the stomach?

A

fundus, corpus, antrum

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21
Q

what is the function of stomach corpus ?

A

secrete mucus, pepsinogen, HCl

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22
Q

what is the function of stomach antrum?

A

secret mucus, pepsinogen, gastrin

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23
Q

what are the three parts of small intestine ?

A

duodenum, jejunum, ileum

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24
Q

where in the small intestine is the majority of digestion ?

A

duodenum

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25
Q

what is the function of duodenum

A

majority of digestion

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26
Q

what is the function of jejunum

A

little digestion, majority of absorption

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27
Q

what is the function of ileum

A

majority of absorption

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28
Q

which part of the small intestine doesnt digest

A

the ileum

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29
Q

what does bicarbonate secreted by pancreas do ?

A

it is a base that neutralizes acidic chyme

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30
Q

what are the purpose of the folds of Kerkring in the small intestine ?

A

they increase the surface area of the intestine 3x

covered by villi which increase TSA 10x

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31
Q

what is the brush border ?

A

cover the villi and increase TSA of small intestine 20x

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32
Q

what is the TSA of small intestine ?

A

250 m^2 (tennis court)

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33
Q

how big are villi ?

A

1 mm

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34
Q

what are 2 diseases affecting the brush border ?

A

lactose intolerance / celiac disease, causing diarrhea (less absorption because brush border wiped out)

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35
Q

what is a lacteal ?

A

found in each villi, transports insoluble fat particles via lymphatic vessels

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36
Q

how does water-soluble particles get transported in villi ?

A

transport or diffusion into blood vessels across membranes of epithelial cells that cover the villi, and then transported to liver via hepatic portal vein

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37
Q

how much time does food spend in GI tract

A

1-3 days

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38
Q

what is transit time ?

A

time food spends in GI tract

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39
Q

what is transit time for small intestine

A

3-10h depending on motility

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40
Q

when does peristalsis increase

A

after a meal

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41
Q

what does bile consist of ? (6)

A 
water
electrolytes
bile salts
cholesterol
lecithin
bilirubin
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42
Q

where is bile released ?

A

through hepatic duct into duodenum

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43
Q

when does bile secretion increase ?

A

after a meal, esp if a lot of fat

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44
Q

what does bile do ?

A

emulsify fat

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45
Q

in large intestine, what is chyme called ?

A

feces

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46
Q

what are the 3 components of large intestine

A

colon
rectum
anal canal

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47
Q

what are 2 functions of large intestine

A

absorption of electrolytes and temporary storage of feces

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48
Q

where does digestion of carbs start ?

A

in mouth

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49
Q

which enzyme breaks down starch ?

A

amylase

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50
Q

where are the two places amylase is made

A

saliva and pancreas

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51
Q

lactose intolerance = insufficiency of

A

lactase

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52
Q

what enzyme breaks down lactose

A

lactase

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53
Q

what enzyme breaks down sucrose

A

sucrase

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54
Q

we can only absorb this kind of CHO

A

monosaccharides, so we have to break CHO down

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55
Q

what secretes it and what is the function of gastrin

A

stomach

stimulates HCl production and pepsinogen production

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56
Q

what secretes it and what is the function of secretin

A

small intestine

stimulates water and bicarbonate secretion in pancreatic juice

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57
Q

what secretes it and what is the function of cholecystokinin

A

small intestine

stimulates secretion of enzymes in pancreatic juice, gall bladder contractions

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58
Q

what CHO can’t be digested ?

A

cellulose, found in fiber

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59
Q

where does digestion of fats start depending on their size

A

small and med FA in mouth (coconut and palm oil)

long FA in intestine after emulsification

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60
Q

why is gastric lipase not fully efficient ?

A

bc it is in water, and fats are insoluble

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61
Q

what form do fat particles take on ?

A

micelles, with hydrophobic legs in middle bc gut is an aqueous environment

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62
Q

where does digestion of proteins start ?

A

in stomach

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63
Q

what does HCl do ?

A

denatures proteins, making bonds between aa exposed to enzymes

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64
Q

where does it work and what does it do: protease

A

stomach/ small intestine

active form from inactive precursor

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65
Q

where does it work and what does it do: pepsin

A

subcategory of protease

secreted as pepsinogen from stomach wall, activated with HCl and converted into pepsin which hydrolyzes protein

66
Q

what stimulates HCl-pepsinogen?

A

food

67
Q

pepsin = ____% of protein digestion

A

10-20

68
Q

majority of digestion is in

A

small intestine

69
Q

what do peptidases do ?

A

catabolize short chains into <3AA

70
Q

describe carb digestion in stomach

A

none, bc amylase deactivated

71
Q

which enzymes digest carbs in small intestine ?

A

pancreatic amylase and brush border enzymes

72
Q

which enzymes digest fiber in large intestine ?

A

bacterial enzymes

73
Q

describe protein absorption in large intestine

A

none

74
Q

what three main substances hydrolyze protein

A

acid, pepsin, trypsin

75
Q

when do proteins get completely broken down to amino acid

A

small intestine

76
Q

what three lipases break down fat

A

lingual, pancreatic and gastric lipase

77
Q

describe fatty acids in large intestine

A

none

78
Q

how do CHO and protein get to liver?

A

from small intestine to portal vein to liver

79
Q

how do fats get to blood ?

A

lymph vessels

80
Q

what are the three main carbs that result from digestion ?

A

glucose, fructose, galactose

81
Q

describe transport of fructose in absorption from lumen to epithelial cell

A

sodium-independent GLUT5 transporter on membrane of epithelial cell

82
Q

describe transport of glucose and galactose into epithelial cell for absorption

A

a sodium dependent monosaccharide transporter (SGLT). eg glucose transported with 2 sodium ions into cell and then the sodium ions are actively transporter back into lumen through a Na+ K+ ATPase pump

83
Q

describe transport of monosaccharides out of epithelial cell and into capillary

A

GLUT 2 accepts all three monosaccharides on contraluminal side of epithelial cell (no need for special sodium dependent transporter)

84
Q

where in the body can glucose transporters be found

A

everywhere

85
Q

in skeletal muscle, what are the two glucose transporters and when are they active ?

A

GLUT 1 at rest or low blood insulin

GLUT 4 when glucose and insulin are high or muscle is active

86
Q

when is glut 4 used in skeletal muscle ?

A

when glucose and insulin are high or during exercise

87
Q

how is absorption different without bile salts for fat ?

A

with bile salts (micelles), fat absorption 97%

without, 50%

88
Q

how do fats get into blood ?

A

transport into villi and diffuse across membrane of epithelium into epithelial cells

89
Q

for small and medium chain fatty acids, how does absorption happen ?

A

diffusion because more water soluble. then, bound to albumin and transported into blood

90
Q

what percentage of bile is recycled

A

94%

91
Q

for long chain fatty acids, how does absorption happen ?

A

micelles are formed within the intestinal lumen, performing a ferrying function. diffusion through lipid membrane, and then FA are reesterified into the epithelial cell endoplasmic reticulum. then, the TG are combined with cholesterol and phospholipids to form chylomicrons. chylomicrons move through lacteals in villi and transport through the lymphatic system to the subclavian veins

92
Q

what is the structure of a chylomicron

A

fatty sides in center, polar parts form the surface, allowing transport of blood into aqueous blood.

93
Q

what does lipoprotein lipase do ?

A

digests TG into fatty acids for storage by breaking down chylomicrons and causing fatty acids to go into adipocytes where they are reesterified

94
Q

what percentage of amino acids and peptides are absorbed ?

A

99%
67% as peptides
33% as aa

95
Q

how many brush border transporters needed for aa

A

7

96
Q

between a big aa chain and a small one, who is absorbed first ?

A

big, with more affinity

97
Q

between a essential or non essential aa, who is absorbed first ?

A

essential

98
Q

peptides vs aa, who is absorbed first ?

A

peptides

99
Q

how do peptides get into epithelial cell ?

A

transported against a concentration gradient (need H+) carrier-mediated transport.

100
Q

what happens to peptides in epithelial cell ?

A

broken down to aa by dipeptidase and tripeptidase and then aa transported to liver

101
Q

how do aa get into epithelial cell ?

A

Na-dependent transport, then Na gets pumped out with Na+ K ATPase pump, and amino acids transported to liver via portal vein

102
Q

what becomes of aminoacids in villi ?

A

may be used for protein synthesis (apoproteins, digestive enzymes, hormones, N-containing compounds, glutamine)

103
Q

how does the liver use aa ? (amino acid pool turnover)

A

excess aa stripped of carbon skeleton. amino groups combine with CO2 to make urea, sent to kidneys
use carbon skeletons to make FA or glucose or energy

104
Q

where does most water absorption take place ?

A

in duodenum of small intestine by simple diffusion

105
Q

what law does water absorption obey ?

A

law of osmosis

106
Q

what is an osmole (mOsm)

A

number of solute particles

107
Q

what is osmolality

A

mOsm/kg (number of solute/kg)

108
Q

what is osmolarity

A

mOsm/L

109
Q

in gut, water moves according to ________

A

osmolarity

110
Q

if you drink something with high osmolarity, what happens ?

A

body will want to dilute it and drags water to gut- diarrhea, cramping

111
Q

when is higher osmolarity: gastric fluid/blood or fruit juice and coca cola ?

A

fruit juice and coca cola (600)

compared to 300

112
Q

water in intestine by secretions is what volume and where does it come from

A

7L

from salivary glands, stomach, gallbladder, pancreas, intestine

113
Q

what is the volume of daily water intake ?

A

2L

114
Q

what is total daily water absorption ?

A

7+2=9L

115
Q

with diarrhea, will you have more or less absorption of water ?

A

less, more fluid loss

116
Q

where does most vitamin absorption take place ?

A

jejunum and ileum

117
Q

what are 4 fat soluble vitamins ?

A

A, D, E, K

118
Q

what are 2 water soluble vitamins ?

A

B and C

119
Q

how are fat soluble vitamins absorbed ?

A

with FA, incorporated into chylomicrons and transported in lymph system

120
Q

where is most of the absorption for fat soluble vitamins ?

A

small intestine

121
Q

how are water soluble vitamins absorbed ?

A

diffusion

122
Q

how are fat soluble vitamins stored ?

A

similar to fat, in body

123
Q

how are water soluble vitamins stored ?

A

they are not, excess excreted in urine

124
Q

how are minerals absorbed in small intestine ?

A

not well

125
Q

what does mineral absorption depend on ?

A

chemical form

126
Q

state %absorption of heme iron

A

15

127
Q

state %absorption of non heme iron

A

2-10

128
Q

state %absorption of calcium

A

35

129
Q

state %absorption of magnesium

A

20-30

130
Q

state %absorption of zinc

A

14-41

131
Q

after what can absorption of vitamin take place ?

A

after digestion separates vitamin from coenzyme

132
Q

how is the amount of bacteria in the gut dependent on the pH?

A

the higher the pH, the more bacteria there will be (so more in the small intestine and colon than the stomach)

133
Q

how much bacteria in gut do we have at birth ?

A

GI is sterile at birth

134
Q

at what age do we start having bacteria in the gut ?

A

3-4 weeks

135
Q

what are the three functions of gut bacteria ?

A

digest CHO, proteins, lipids that escape digestion and absorption
ferment cellulose
produce vitamin K, B12, thiamin, riboflavin

136
Q

what 4 vitamins are made by gut bacteria ?

A

vitamin K, B12, thiamin, riboflavin

137
Q

folic acid absorption requires which enzyme ?

A

conjugase

138
Q

are bacteria in gut primarily anaerobes or aerobes ?

A

anaerobes

139
Q

how long does food take to leave stomach after digestion

A

1-4h

140
Q

what causes gastric emptying ?

A

contractions from pacemaker cells of stomach increase intragastric pressure, pushing chyme through pyloric sphincter

141
Q

what is chyme

A

food mixed with stomach acid

142
Q

what kind of signals does the stomach get that controls gastric emptying? (2)

A

positive

  • nervous signals caused by stretching and extension of the stomach wall
  • gastrin release
143
Q

what signals does the duodenum get that controls gastric emptying ? what are their purpose ?

A

negative feedback due to receptors that detect acidity, osmolarity
prevent dumping of excessive chyme into intestine

144
Q

what is the enterogastric reflex ?

A

in duodenum, receptors monitor acidity, osmolarity

when they are stimulated, the pylorus increases contractions, preventing dumping of excess chyme into intestine

145
Q

what psychological factors can affect gastric emptying

A

smell and sight of food, thought of a food

146
Q

how does volume of food ingested affect gastric emptying

A

stomach walls extend to a certain extent to accommodate larger volumes, but when maximal distension is reached, pressure increases.

147
Q

how does exercise intensity affect gastric emptying

A

rate not affected by exercise up to 80%VO2max, where there may be a reduction

148
Q

how does osmolarity affect gastric emptying

A

increased beverage osmolarity increases gastric secretions which reduce emptying and decrease water absorption

149
Q

how does energy density affect gastric emptying

A

some nutrients like fat have an inhibitory effect on gastric emptying

150
Q

how does meal or beverage temperature affect gastric emptying

A

extreme temperature decreases the rate

151
Q

how does stress affect gastric emptying

A

reduced, due to stress hormones

152
Q

who has slower gastric emptying- women or men ?

A

women

153
Q

what other factors may cause gastric emptying rates to change

A

hyperthermia or dehydration

154
Q

30-50% of these people have GI problems

A

distance runners

155
Q

what are 3 upper GI problems

A

heartburn
bloating
vomiting

156
Q

what are 4 lower GI problems

A

urge to poop
loose stool
diarrhea
bleeding

157
Q

what are 4 related GI problems

A

nausea
dizziness
side ache
urge to urinate

158
Q

what are 3 causes of GI problems

A

physiological
mechanical
nutritional

159
Q

what are 2 physiological causes of GI problems

A

reduced blood flow to GI

increased anxiety

160
Q

what are 2 mechanical causes of GI problems

A

impact and posture

161
Q

what are 5 nutritional causes of GI problems

A

fiber, fat, protein, fructose, dehydration

162
Q

what are 5 ways to prevent GI problems

A 
avoid: 
milk containing lactose
high fiber foods the day of or day before competition (no digestion could cause discomfort) 
aspirin and NSAIDs
high fructose drinks
dehydration

EXCI 445 (13 decks)

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