Chapter 5- Gastric Emptying, Digestion, Absorption Flashcards
1
Q
what is the GI tract’s function?
A
to provide the body with nutrients
2
Q
what is the purpose of digestion
A
break down into smaller particles
3
Q
what is the purpose of absorption?
A
transport of nutrients from intestine via lymph or blood vessels
4
Q
what is the purpose of elimination ?
A
elimination of waste, undigested food
5
Q
where does digestion start ?
A
in mouth
6
Q
what is the function of the mouth ?
A
mechanical digestion
7
Q
what is the function of salivary glands ?
A
secretion of fluid and digestive enzymes
8
Q
what is the function of stomach?
A
secretion of HCl and proteases
9
Q
what is the function of pancreas
A
secretion of digestive enzymes and bicarbonate
10
Q
what is the function of liver
A
secretion of bile acids
11
Q
what is the function of gallbladder
A
temporary storage and concentration of bile
12
Q
what is the function of small intestine ?
A
digestion of food, absorption of water, nutrients, electrolytes
13
Q
what is the function of large intestine
A
absorption of electrolytes
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
15
Q
what is the function of esophagus ?
A
push down bolus
16
Q
is swallowing possible in space or upside down ?
A
yes thanks to peristalsis in esophagus
17
Q
what is GERD ?
A
esophageal sphincter doesn’t work, acid goes into esophagus
18
Q
what is the function of the pyloric sphincter ?
A
controls amount of chyme going in small intestine
19
Q
what people are more affected by GERD ?
A
runners and cyclists
20
Q
what are the three parts of the stomach?
A
fundus, corpus, antrum
21
Q
what is the function of stomach corpus ?
A
secrete mucus, pepsinogen, HCl
22
Q
what is the function of stomach antrum?
A
secret mucus, pepsinogen, gastrin
23
Q
what are the three parts of small intestine ?
A
duodenum, jejunum, ileum
24
Q
where in the small intestine is the majority of digestion ?
A
duodenum
25
what is the function of duodenum
majority of digestion
26
what is the function of jejunum
little digestion, majority of absorption
27
what is the function of ileum
majority of absorption
28
which part of the small intestine doesnt digest
the ileum
29
what does bicarbonate secreted by pancreas do ?
it is a base that neutralizes acidic chyme
30
what are the purpose of the folds of Kerkring in the small intestine ?
they increase the surface area of the intestine 3x
| covered by villi which increase TSA 10x
31
what is the brush border ?
cover the villi and increase TSA of small intestine 20x
32
what is the TSA of small intestine ?
250 m^2 (tennis court)
33
how big are villi ?
1 mm
34
what are 2 diseases affecting the brush border ?
lactose intolerance / celiac disease, causing diarrhea (less absorption because brush border wiped out)
35
what is a lacteal ?
found in each villi, transports insoluble fat particles via lymphatic vessels
36
how does water-soluble particles get transported in villi ?
transport or diffusion into blood vessels across membranes of epithelial cells that cover the villi, and then transported to liver via hepatic portal vein
37
how much time does food spend in GI tract
1-3 days
38
what is transit time ?
time food spends in GI tract
39
what is transit time for small intestine
3-10h depending on motility
40
when does peristalsis increase
after a meal
41
what does bile consist of ? (6)
```
water
electrolytes
bile salts
cholesterol
lecithin
bilirubin
```
42
where is bile released ?
through hepatic duct into duodenum
43
when does bile secretion increase ?
after a meal, esp if a lot of fat
44
what does bile do ?
emulsify fat
45
in large intestine, what is chyme called ?
feces
46
what are the 3 components of large intestine
colon
rectum
anal canal
47
what are 2 functions of large intestine
absorption of electrolytes and temporary storage of feces
48
where does digestion of carbs start ?
in mouth
49
which enzyme breaks down starch ?
amylase
50
where are the two places amylase is made
saliva and pancreas
51
lactose intolerance = insufficiency of
lactase
52
what enzyme breaks down lactose
lactase
53
what enzyme breaks down sucrose
sucrase
54
we can only absorb this kind of CHO
monosaccharides, so we have to break CHO down
55
what secretes it and what is the function of gastrin
stomach
| stimulates HCl production and pepsinogen production
56
what secretes it and what is the function of secretin
small intestine
| stimulates water and bicarbonate secretion in pancreatic juice
57
what secretes it and what is the function of cholecystokinin
small intestine
| stimulates secretion of enzymes in pancreatic juice, gall bladder contractions
58
what CHO can't be digested ?
cellulose, found in fiber
59
where does digestion of fats start depending on their size
small and med FA in mouth (coconut and palm oil)
| long FA in intestine after emulsification
60
why is gastric lipase not fully efficient ?
bc it is in water, and fats are insoluble
61
what form do fat particles take on ?
micelles, with hydrophobic legs in middle bc gut is an aqueous environment
62
where does digestion of proteins start ?
in stomach
63
what does HCl do ?
denatures proteins, making bonds between aa exposed to enzymes
64
where does it work and what does it do: protease
stomach/ small intestine
| active form from inactive precursor
65
where does it work and what does it do: pepsin
subcategory of protease
| secreted as pepsinogen from stomach wall, activated with HCl and converted into pepsin which hydrolyzes protein
66
what stimulates HCl-pepsinogen?
food
67
pepsin = ____% of protein digestion
10-20
68
majority of digestion is in
small intestine
69
what do peptidases do ?
catabolize short chains into <3AA
70
describe carb digestion in stomach
none, bc amylase deactivated
71
which enzymes digest carbs in small intestine ?
pancreatic amylase and brush border enzymes
72
which enzymes digest fiber in large intestine ?
bacterial enzymes
73
describe protein absorption in large intestine
none
74
what three main substances hydrolyze protein
acid, pepsin, trypsin
75
when do proteins get completely broken down to amino acid
small intestine
76
what three lipases break down fat
lingual, pancreatic and gastric lipase
77
describe fatty acids in large intestine
none
78
how do CHO and protein get to liver?
from small intestine to portal vein to liver
79
how do fats get to blood ?
lymph vessels
80
what are the three main carbs that result from digestion ?
glucose, fructose, galactose
81
describe transport of fructose in absorption from lumen to epithelial cell
sodium-independent GLUT5 transporter on membrane of epithelial cell
82
describe transport of glucose and galactose into epithelial cell for absorption
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
describe transport of monosaccharides out of epithelial cell and into capillary
GLUT 2 accepts all three monosaccharides on contraluminal side of epithelial cell (no need for special sodium dependent transporter)
84
where in the body can glucose transporters be found
everywhere
85
in skeletal muscle, what are the two glucose transporters and when are they active ?
GLUT 1 at rest or low blood insulin
| GLUT 4 when glucose and insulin are high or muscle is active
86
when is glut 4 used in skeletal muscle ?
when glucose and insulin are high or during exercise
87
how is absorption different without bile salts for fat ?
with bile salts (micelles), fat absorption 97%
| without, 50%
88
how do fats get into blood ?
transport into villi and diffuse across membrane of epithelium into epithelial cells
89
for small and medium chain fatty acids, how does absorption happen ?
diffusion because more water soluble. then, bound to albumin and transported into blood
90
what percentage of bile is recycled
94%
91
for long chain fatty acids, how does absorption happen ?
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
what is the structure of a chylomicron
fatty sides in center, polar parts form the surface, allowing transport of blood into aqueous blood.
93
what does lipoprotein lipase do ?
digests TG into fatty acids for storage by breaking down chylomicrons and causing fatty acids to go into adipocytes where they are reesterified
94
what percentage of amino acids and peptides are absorbed ?
99%
67% as peptides
33% as aa
95
how many brush border transporters needed for aa
7
96
between a big aa chain and a small one, who is absorbed first ?
big, with more affinity
97
between a essential or non essential aa, who is absorbed first ?
essential
98
peptides vs aa, who is absorbed first ?
peptides
99
how do peptides get into epithelial cell ?
transported against a concentration gradient (need H+) carrier-mediated transport.
100
what happens to peptides in epithelial cell ?
broken down to aa by dipeptidase and tripeptidase and then aa transported to liver
101
how do aa get into epithelial cell ?
Na-dependent transport, then Na gets pumped out with Na+ K ATPase pump, and amino acids transported to liver via portal vein
102
what becomes of aminoacids in villi ?
may be used for protein synthesis (apoproteins, digestive enzymes, hormones, N-containing compounds, glutamine)
103
how does the liver use aa ? (amino acid pool turnover)
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
where does most water absorption take place ?
in duodenum of small intestine by simple diffusion
105
what law does water absorption obey ?
law of osmosis
106
what is an osmole (mOsm)
number of solute particles
107
what is osmolality
mOsm/kg (number of solute/kg)
108
what is osmolarity
mOsm/L
109
in gut, water moves according to ________
osmolarity
110
if you drink something with high osmolarity, what happens ?
body will want to dilute it and drags water to gut- diarrhea, cramping
111
when is higher osmolarity: gastric fluid/blood or fruit juice and coca cola ?
fruit juice and coca cola (600)
| compared to 300
112
water in intestine by secretions is what volume and where does it come from
7L
| from salivary glands, stomach, gallbladder, pancreas, intestine
113
what is the volume of daily water intake ?
2L
114
what is total daily water absorption ?
7+2=9L
115
with diarrhea, will you have more or less absorption of water ?
less, more fluid loss
116
where does most vitamin absorption take place ?
jejunum and ileum
117
what are 4 fat soluble vitamins ?
A, D, E, K
118
what are 2 water soluble vitamins ?
B and C
119
how are fat soluble vitamins absorbed ?
with FA, incorporated into chylomicrons and transported in lymph system
120
where is most of the absorption for fat soluble vitamins ?
small intestine
121
how are water soluble vitamins absorbed ?
diffusion
122
how are fat soluble vitamins stored ?
similar to fat, in body
123
how are water soluble vitamins stored ?
they are not, excess excreted in urine
124
how are minerals absorbed in small intestine ?
not well
125
what does mineral absorption depend on ?
chemical form
126
state %absorption of heme iron
15
127
state %absorption of non heme iron
2-10
128
state %absorption of calcium
35
129
state %absorption of magnesium
20-30
130
state %absorption of zinc
14-41
131
after what can absorption of vitamin take place ?
after digestion separates vitamin from coenzyme
132
how is the amount of bacteria in the gut dependent on the pH?
the higher the pH, the more bacteria there will be (so more in the small intestine and colon than the stomach)
133
how much bacteria in gut do we have at birth ?
GI is sterile at birth
134
at what age do we start having bacteria in the gut ?
3-4 weeks
135
what are the three functions of gut bacteria ?
digest CHO, proteins, lipids that escape digestion and absorption
ferment cellulose
produce vitamin K, B12, thiamin, riboflavin
136
what 4 vitamins are made by gut bacteria ?
vitamin K, B12, thiamin, riboflavin
137
folic acid absorption requires which enzyme ?
conjugase
138
are bacteria in gut primarily anaerobes or aerobes ?
anaerobes
139
how long does food take to leave stomach after digestion
1-4h
140
what causes gastric emptying ?
contractions from pacemaker cells of stomach increase intragastric pressure, pushing chyme through pyloric sphincter
141
what is chyme
food mixed with stomach acid
142
what kind of signals does the stomach get that controls gastric emptying? (2)
positive
- nervous signals caused by stretching and extension of the stomach wall
- gastrin release
143
what signals does the duodenum get that controls gastric emptying ? what are their purpose ?
negative feedback due to receptors that detect acidity, osmolarity
prevent dumping of excessive chyme into intestine
144
what is the enterogastric reflex ?
in duodenum, receptors monitor acidity, osmolarity
| when they are stimulated, the pylorus increases contractions, preventing dumping of excess chyme into intestine
145
what psychological factors can affect gastric emptying
smell and sight of food, thought of a food
146
how does volume of food ingested affect gastric emptying
stomach walls extend to a certain extent to accommodate larger volumes, but when maximal distension is reached, pressure increases.
147
how does exercise intensity affect gastric emptying
rate not affected by exercise up to 80%VO2max, where there may be a reduction
148
how does osmolarity affect gastric emptying
increased beverage osmolarity increases gastric secretions which reduce emptying and decrease water absorption
149
how does energy density affect gastric emptying
some nutrients like fat have an inhibitory effect on gastric emptying
150
how does meal or beverage temperature affect gastric emptying
extreme temperature decreases the rate
151
how does stress affect gastric emptying
reduced, due to stress hormones
152
who has slower gastric emptying- women or men ?
women
153
what other factors may cause gastric emptying rates to change
hyperthermia or dehydration
154
30-50% of these people have GI problems
distance runners
155
what are 3 upper GI problems
heartburn
bloating
vomiting
156
what are 4 lower GI problems
urge to poop
loose stool
diarrhea
bleeding
157
what are 4 related GI problems
nausea
dizziness
side ache
urge to urinate
158
what are 3 causes of GI problems
physiological
mechanical
nutritional
159
what are 2 physiological causes of GI problems
reduced blood flow to GI
| increased anxiety
160
what are 2 mechanical causes of GI problems
impact and posture
161
what are 5 nutritional causes of GI problems
fiber, fat, protein, fructose, dehydration
162
what are 5 ways to prevent GI problems
```
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
```
