GI Physiology Flashcards
1
Q
what are nutrients
A
substances in food needed for growth, maintenance, and repair
2
Q
what are the macronutrients
A
three major nutrients
carbohydrates
lipids/fat
proteins
3
Q
what are the micronutrients
A
two other nutrients that are required but in small amounts
vitamins
minerals
4
Q
what are essential nutrients
A
nutrients that must be eaten because the body cannot synthesize these from other nutrients
5
Q
what are the functions of carbohydrates
A
primary energy source for the body, especially for brain and muscles
stored as glycogen in liver and muscles
6
Q
where is glycogen stored
A
liver and muscles
7
Q
what are the two types of carbohydrates
A
simple sugars
complex carbohydrates
8
Q
what are the simple sugars
A
monosaccharides and disaccharides
comes from fruits, milk, honey
9
Q
what are the complex carbohydrates
A
polysaccharides, starch, and fiber
10
Q
where are carbs absorbed
A
duodenum and jejunum
11
Q
what is glucose
A
fuel most used by cells to make ATP
12
Q
what is excess glucose used for
A
converted to glycogen or fat, then is stored
13
Q
what is glycogenolysis
A
biochemical process of the breakdown of glycogen into glucosew
14
Q
when does glycogenolysis occur
A
occurs when the glucose level drops in the blood
15
Q
where does glycogenolysis occur
A
occurs in the liver in muscle cells
16
Q
what are the two enzymes used to regulate glycogenolysis
A
phosphorylase kinase and glycogen phophorylase
17
Q
what is gluconeogenesis
A
biochemical process of the synthesis of glucose from non-carbohydrate sources
specifically of amino acids and liquids
18
Q
when does gluconeogenesis occur
A
when all glycogen stores are used up
19
Q
where does gluconeogenesis
A
occurs in the liver and kidney
20
Q
what is glycogen synthesis
A
biochemical process of synthesizing glycogen from glucose
21
Q
when does glycogen synthesis occurs
A
when there is sufficient glucose in the blood and the excess glucose is stored as glycogen
22
Q
where does glycogen synthesis occur
A
liver and muscle cells
23
Q
what are the most abundant form of fat
A
triglycerides
24
Q
what are examples of saturated fats
A
animal fats
tropical oils
25
what are examples of trans fats
processed and fried food such as margarine, spreads, vegetable shortening, fast food
26
what are examples of unsaturated fats
nuts, plant oils, certain fish
27
what structure is the cholesterol that we need made in
liver
28
what foods are cholesterol found in
egg yolk, meats, organs meats, shellfish, and meat products
29
how are lipids digested
bile emulsifies fats
lipases break them down into fatty acids and monoglycerides
30
where are lipids absorbed
through enterocytes, re-formed into triglycerides and transported via chylomicrons
31
what is the purpose of adipose tissue
protection, insulation, and fuel storage
32
what is important about phospholipids
makes up the phospholipid bilayer
essential for myelin sheaths
33
what is important about cholesterol in the body
stabilizes membranes
precursor of bile salts
steroid hormones
34
what is the importance of prostaglandins in the body
used for smooth muscle contraction
blood pressure control
inflammation
35
what is the major fuel source for hepatocytes and skeletal muscle
lipids
36
what are the dietary requirements for lipids
fats --> 20-35% of total caloric intake
saturated fats --> limited to 10% or less of total fat intake
cholesterol --> not required in diet
37
what is lipogenesis
triglyceride synthesis that occurs when cellular ATP and glucose levels are high
38
where are lipids stored
50% in adipose
50% is deposited in other areas
39
where is lipolysis
breakdown of stored fats into glycerol and fatty acids; reverse of lipogenesis
40
what are ketone bodies
formed with the metabolism of large amounts of fatty acids
accumulation of ketone bodies in blood can lead to ketosis
common in starvation and diabetes mellitus
41
what is ketoacidosis
happens when there is a build up of acids due to ketosis and causes dangerously low pH levels
42
how is cholesterol transported
through lipoproteins --> transported water-insoluble cholesterol and triglycerides through the blood
43
what are two types of transport lipoproteins
HDLs
LDLs
44
what are HDLs
high density lipoproteins; high protein content
transport excess cholesterol from peripheral tissues to liver to be broken down and secreted into bile
45
what are LDLs
low-density lipoproteins
have the highest cholesterol count
transport cholesterol to peripheral tissues for membranes, storage, or hormone synthesis
46
what are the poor types of cholesterol
LDLs
47
what are considered complete proteins
animal products
soybeans
48
what are considered incomplete proteins
legumes
nuts
cereals
(they lack essential amino acids)
49
what are the uses of proteins in the body
structural materials like keratin, collagen, elastin, and muscle proteins
immune function
tissue repair
50
what are the fat soluble vitamins
A, D, E, K
51
where are the fat soluble vitamins stores
liver and adipose tissue
52
what are the water-soluble vitamins
vitamins C and B-complex
53
what is special about vitamin B12
it is so large it requires intrinsic factor in the stomach to help break it down
54
where are vitamins and minerals absorped
small intestines
55
how are dangerous free radicals neutralized
through antioxidants found in Vitamin C, E, and A
56
what foods are high in Vitamin C and A that help reduce free radicals
broccoli, cauliflower, brussel sprouts
57
where are free radicals found
UV lights
radiation
air pollution
metabolism in the body
58
what are the four functions of the GI system
digestion
motility
absorption
secretion
59
what is the function temporalis
elevation and retraction
60
what is the function of the masseter
elevation
61
what is the function of the lateral pterygoid
protrusion
side to side
62
what is the function of the medial pterygoid
elevation
side to side
63
what is the importance of the lingual frenulum
helps with tongue mobility
can also affect speech and eating if the tongue is ties
64
what is the importance of the labial frenulum
lip ties
helps with lip mobility during speech
65
what supplies the tooth with all the nutrition and blood supply
root canal
66
how many baby (decidious) teeth are we born with
20; erupt between 6 and 24 months
67
how many permanent teeth do we get
32; erupt around 6-12 years of age
68
how are teeth classified
according to shape
incisors
canines
premolars
69
what are incisors
chisel shaped for cutting
70
what are canines
fanglike teeth that tear or pierce
71
what are premolars (bicuspids)
broad crowns with rounded cusps, used to grind or crush
72
what is the muscularis externa
found in the myenteric plexus; has smooth parasympathetic and sympathetic innervation
it is responsible for coordinating peristalsis
73
what are the layers of the GI tract
mucosa
submucosa
muscularis externa
serosa
74
what is the innermost layer of the GI tract
mucosa; made up of epithelial cells
75
what do the epithelial cells secrete in the GI tract
secrete acid
bicarb (HCO3)
digestive enzymes
hormones --> enteroendocrine cells
mucus
76
what are the two layers of the mucosa
lamina propria and muscularis mucosa
77
what is found in the lamina propria of the mucosa layer in GI tract
loose connective tissue
78
what is the function of the muscularis mucosa
helps with the movement of peristalsis
79
what is found in the submucosa
submucosal plexus
this is responsible for regulating secretions and local functions
contains more blood and lymphatic vessels
80
what layer of the GI tract faces the abdominal cavity
serosa
81
what is serosa made up of
visceral peritoneum
82
what are the three phases of digestion
cephalic phase
gastric phase
intestinal phase
83
what is the cephalic phase
initiated when sensory receptors in our brain sense food either from sight, smell, taste, or thought
it is mediated by the vagus nerve
tells stomach to start secreting Hcl
84
what is the gastric phase of digestion
once we have chewed our food, we start gastric phase --> bolus
stomach distention activates the stretch receptors and help stimulate the release of gastrin
stomach secretes more acid
85
what is the intestinal phase
occurs once the digested chyme enters the duodenum
presence of acid and a stretch in the duodenum triggers intestinal phase
86
what are the hormones of the GI tract
secretin
CCK
gastrin
GIP
ghrelin
leptin
acetylcholine
87
what are the hormones that are produced in the small intestine
secretin
CCK
GIP
88
where is gastrin produced
antrum of the stomach
89
where is ghrelin produced
stomach
90
where is leptin produced
fat cells --> adipocytes
91
where is acetylcholine produced
vagal nerve (CNS)
92
what needed for release of secretin
acid in the small intestine
93
what is the target organ/response for secretin
inhibits acid secretion and motility in the stomach
stimulates bicarb secretion from the pancreas to begin to neutralize stomach acid
94
what is needed for CCK to be released
amino acids and fatty acids in the small intestine
95
what is the target organ/response for CCK
digestive enzymes from the pancreas cause gallbladder to contract
this relaxes sphincter of Oddi to allow liver secretions to flow into small intestine
96
what is needed to release gastrin
amino acids, peptides in the stomach
97
what is the goal of gastrin
helps prep the stomach to digest
it increased acid secretion in the stomach and increases motility
98
what is GIP
glucose-dependent insulinotrophic peptide
inhibits acid production in stomach; stimulates insulin release from the pancreas
99
what is needed to stimulate GIP
glucose and fat in the small intestine
100
when is ghrelin produced
when the stomach is empty
low blood glucose
also inhibited in the circadian rhythm
101
what is the end goal for ghrelin
stimulates hunger signals from the stomach
102
what is the function of leptin
helps regulate energy balance
tells our body that we are full --> satiety
103
what is the function of acetylcholine in the GI tract
helps coordinate peristalsis
104
what is needed to release leptin
increased fat stores in the body
105
what two cranial nerves are needed for salivation
VII (facial)
IX (glossopharyngeal)
trigger the parotid, submandibular, and sublingual glands
106
what enzymes are found in the mouth/saliva
lysozyme
amylase
lipase
107
what is the function of lysozyme in the mouth
helps kill bad bacteria
108
what does saliva do
starts the breakdown of food
moistens, compacts food into a bolus
109
what does the bolus become once digested/entered into the stomach
chyme
110
how do we swallow (what changes in our mouth to initiate swallowing)
soft palate elevates
nasal cavity closes off air
epiglottis closes to inhibit respiration
111
where do the impulses come from in the brain when we start to swallow
medulla
112
what is the importance of rugae
increases surface area for digestion of chyme
113
what is product is mostly digested in the stomach
proteins
114
what cells secrete hcl and where are they found
parietal cells; found in mucosal layer
115
what are chief cells
release pepsinogen for protein digestion
116
what stimulates the production of Hcl in the stomach
gastrin
117
what inhibits Hcl from continuing to be produced
somatostatin also the presence of Hcl
118
how is Hcl produced in the stomach
parietal cells contain carbonic anhydrase enzymes that forms carbonic acid
carbonic acid breaks apart easily to form bicarb and H+
H+ is absorbed into the lumen
Cl- is exchanged for bicarb and enters the parietal cell which passively flow into the lumen which ultimately produce Hcl
119
how does pepsinogen become pepsin
when it enters the acidic lumen environment from the presence of Hcl it becomes activated
120
what is peristalsis
coordinated wave-like contractions and relaxations of smooth muscle in the GI tract
121
what are the four steps of peristalsis
initiation
contraction
mixing
emptying
122
what occurs during initiation of peristalsis
stretching; sensed and activated by enteric nervous system
123
what is contraction in peristalsis
fundus begins to close, and chyme moves down towards the pylorus
muscularis externa contracts behind the chyme to help push it forward
124
what is the mixing phase in peristalsis
retropulsion of food for further breakdown and mixing of gastric acid and enzymes
125
what is the emptying phase in peristalsis
movement of food to pyloric sphincter to allow small amounts of chyme to enter the duodenum
126
who is susceptible to gastroparesis
diabetics; there is neuropathy and a lack of coordination in peristalsis which slows everything down
127
when the chyme enters the small intestine, what does it come in contact with
brush border and microvili
128
what is the brush border/microvilli
helps increase surface area to increase absorption in the small intestine
129
what secretes mucus in the small intestine
goblet cells
130
what are lacteals
lymphatic vessels that connect to the small intestine to aid in fat absorption
131
what are the functional exocrine units of the pancreas
acinar cells
duct cells
132
what are acinar cells
release digestive enzymes
133
what are duct cells
secrete bicarb in response to secretin stimulation
use carbonic anhydrase to create bicarb buffer
134
how is bicarb exchanged in the pancreas
through the CFTR channel
bicarb is exchanged for chloride; helps us stay charge neutral
135
what is important about the CFTR in cystic fibrosis
there is a decrease in bicarb because the CFTR is not functioning correctly
impacts their acidity and water movement throughout the body
increases the number of cysts and scaring in the pancreas
136
what stimulates the release of enzymes in the acinar cells
CCK from the gallbladder
137
what triggers the duct cells to release bicarb
secretin
138
what are proteases
pancreatic enzymes the breakdown proteins
139
what are peptidases
pancreatic enzymes that breakdown proteins
140
what two enzymes do we monitor to check function of pancreas
lipase (mostly)
amylase
141
what is found in the pancreas that makes the enzymes active
epithelial cells have membrane-bound enterokinase which cleaves trypsinogen to trypsin
trypsin then activates the other inactive enzymes
142
what is the function unit of the liver
lobule
143
what are the liver cells called
hepatocytes
144
what is contained in a lobule
portal triads = bile duct, hepatic portal vein, and hepatic artery
145
how are substances absorbed into the liver
through the portocaval system; specifically the hepatic sinusoids
it is then processed in the hepatocytes
146
what are the four enzymes of the liver
ALT
AST
ALP
GGT
147
what is the function of ALT
amino acid breakdown
148
what is the function of AST
amino acid breakdown
also found in the heart and muscles
149
clinical significance of ALT
increased in liver damage
150
clinical signifance of AST
increased in liver damage and heart/muscle problems
151
what is the function of ALP
breakdown of molecules that are important for bone and bile health
152
clinical significance of ALP
increased in liver problems, bile duct issues, or in bone disease
153
function of GGT
amino acid transport and antioxidant in cells
154
clinical significance of GGT
increased in liver or bile duct problems
especially elevated in alcohol use
155
what is bile made of
bicarb
cholesterol
phospholipids
bile salts
organic waste
bilirubin/bile pigments
156
what gives our stool it's characteristic brown color
bilirubin from bile
157
how is bile released
fatty acids in the duodenum trigger an increase of CCK
CCK causes gallbladder to contract and sphincter of Oddi to relax
increase bile flow into the duodenum and increase bile flow into the common bile duct
158
how are carbohydrates absorbed/digested in the small intestine
through brush border enzymes and amylase
broken down from polysaccharides to monosaccharides (glucose, fructose, and galactose)
transported via glucose transporters
159
how are proteins digested/absorbed in the small intestines
partially broken down in the stomach through pepsin
then proteases and peptidases in the interstitial lumen and in brush borders break everything down into amino acids and other peptide fragments
160
how are fats/triglycerides digested and absorbed in the small intestine
partially broken down in mouth and stomach through gastric lipase
needs to undergo emulsification
161
what is the process of emulsification
enzymatic digestion through pancreatic lipase breaks triglycerides into micelles, then it is absorbed/reassembled and packaged into chylomicrons
162
how are micelles and fatty acids transported
reabsorbed into the chylomicrons and transported via the lacteals
163
what is the biggest metabolic function of the large intestine
maintaining the balance between good bacteria and bad bacteria
164
how does the body release irritant acids and gases
the large intestine ferments the indigestable carbohydrates and proteins
165
what is the defecation reflex
the process of having a bowel movement is stimulated by distention in the rectum
166
how do parasympathetic signals trigger defecation
stimulates the contraction of the sigmoid colon and rectum to relax the internal anal canal
167
how does the external anal canal function
we have voluntary control of the external anal canal to expel feces
we can assist this process by doing valsalva's maneuver
168
what is valsalva's maneuver
closing of the glottis
contraction of diaphragm
contraction of abdominal wall muscles
all cause increase intra-abdominal muscle which can help open up the external anal canal
