Gastrointestinal Flashcards
1
Q
Epthelial cells are specialied in different part of the GI tract for ________or _________
A
secretion or absorption
2
Q
Contraction causes a change in the surface area for secretion or absorption
A
Muscularis mucosa
3
Q
Contraction causes a decrease in diameter of the lumen of the GI tract
A
Circular muscle
4
Q
Contracion causes shortening of a segment of the GI tract
A
Longitudinal muscle
5
Q
Comprise the enteric nervous system of the GI tract
Integrate and coordinate the motility, secretory, and endocrine funcrions of the GI tract
A
Sumbmucoasl (meissner plexus) and myenteric plexus
6
Q
the _____________of the GI tract comorises both extrinsic and intrinsic nervous systems
A
ANS
7
Q
Extrinsic innervation
A
PNS and SNS
8
Q
carry information from the brain ste and spinal cord to the GI tract
A
Efferent fibers
9
Q
Carry sensory information from chemoreceptors and mechanoreceptors in the GI tract to the brain stem and spinal cord
A
Afferent fibers
10
Q
_______________is usually excitatory on the functions of the GI tract
A
Parasympathetic
- carried via the vagus and pelvic nerves
- Preganglionic PS fibers synapse in the yenteric and submucosal plexus
- cell bodies in the ganglia of the plexuses then send information to the smooth muscle, secretory cells, and endocrine cells of the GI tract
11
Q
The _______ innervates the esophagus, stomach, pancreas, and upper large intestine
A
Vagus nerves
- Reflexes in which both afferent and efferent pathways are contained in the vagus nerve are called vasovagal reflexes
12
Q
the _____ innervates the lower large intestine, rectum, and anus
A
Pelvic nerve
13
Q
___________ is usually inhibitory on the functions of the GI tract.
A
Sympathetic nervous system
- Fibers originate in the spinal cord between T8 - L2
- Preganglionoc sympathetic cholinergic fibers synapse in the prevertebral ganglia
- Postganglionic sympathetic adrenergic fibers leave the prevertebral gangla and synapse in the myenteric and submucosal plexues. Direct postganglionic adrenergic innervation of blood vessels and some smooth muscle cells also occurs
- Cell bodies in th eganlia of the plexuses then send information to the smooth muscle, secretory cells and endorcrine cells of the GI tract
14
Q
Coordinates and relays information from the PNS and SNS to the GI tract
A
Intrinsic nervous system (enteric nervous system)
- uses local reflexes to relay within the GI tract
- controls most functions of the GI tract, especially motility and secretion, even in the absence of extrinsic innervation
15
Q
Primarily controls the motility of the GI smooth muscle
A
Myenteric plexus (Auerbach plexus)
16
Q
Primarily controls secretion and blood flow
Receives sensory information and chemoreceptors and mehanoreceptors in the GI tract
A
Submucosal Plexus (Meissner plexus)
17
Q
“official” GI hormones
A
gastrin
cholestokinin
seccretin
glucose insulinotropic eptide (GIP)
18
Q
Increases H+ secretion. Stimulates growth of gastric mucosa
A
gastrin
- Stimulus:
- small peptides and amino acids
- distention of stomach
- vagus (via GRP)
- inhibited by H+ in stomach
- Inhibited by somatostatin
- Gastrin -CCK family
19
Q
Stimulates cobtraction of gallbladder and relaxation of sphincter of Oddi.
Increase pancreatic enzyme and HCO3 secretion
Increase growth of exocrine pancreas/gallbladder
Inhibits gastric emptying
A
CCK
- Stimulus
- small peptides and amino acids
- fatty acids
- gastrin-CCK family
20
Q
Increase pancreatic HCO3 secretion
Increase Biliary HCO3 secretion
Decrease gastric H+ secretion
A
Secretin
- Stimulus
- H+ in duodenum
- Fatty acids in the duodenum
- Secretin-glucagon family
21
Q
Increase insulin secretion
Decrease gastric H+ secretion
A
GIP
- Stimulus
- fatty acids, amino acids, and oral glucose
- secretin-glucagon family
22
Q
Site of secretion of gastrin
A
G cells of the stomach
23
Q
Site of secretion of CCK
A
I cells of duodenum and jejunum
24
Q
Site of secretion of Secretin
A
S cells of duodenum
25
Site of secretion of GIP
Duodenum and jejunum
26
little gastrin have _______ amino acids
Big gastrin have \_\_\_\_\_\_\_\_\_- ammino acids
17
34
27
All biologic activity of gastrin resides in the\_\_\_\_\_\_\_\_\_\_\_\_
four C-terminal amino acids
28
Gastrin inncreases H secretion by gastric ___________ cells
parietal
29
Paatients with ________ have hypertrophy and hyperplasia of the gastric mucosa
gastrin secreting tumors
30
The most potent stimuli for gastrin secretion are _______ and \_\_\_\_\_\_\_\_
Phenylalanine and tryptophan
31
Vagal stimulation is mediated by \_\_\_\_\_\_\_\_\_\_\_\_
gastrin releasing peptide
* Atropine does not block vagally mediated gastrin secretion because the mediator of vagal effect is GRP, not ACh
32
Inhibitors of gastrin secretion
H+ in the lumen of the stomach
Somatostatin
33
Occurs when gastrin is secreted by non-B cell tumors of the pancreas
Zollinger-Ellison syndrome
34
Homologous to gastrin
CCK
35
the biologic activity of CCK resides in the \_\_\_\_\_\_\_\_\_\_\_\_\_
C terminal hepatapeptide
* 5 C-terminal amino acids are the same in CCK and Gastrin
36
T/F. triglycerides stimulate the release of CCK
false
they cannot cross intestinal membrane
37
homologous to glucacon
Secretin
* 14 of the 27 amino acids in secretin are the same as those in glucagon
* All of the amino acids are required for biologic activity
38
Homologous to secretin and glucagon
GIP
39
More effective in causing insulin release (ORAL/IV glucose)
oral
40
Candidate hormones
secreted by the GI tract
* Motilin
* increases GI motility and is involved in interdigestive myoelectric complexes
* Pancreatic poypeptide
* inhibits paancreatic secretion
* GLP-1
* bind to pancreatic B cells and stimulates insulin secretion
41
Released from endocrine cells in the GI mucosea
diffuse ofver short distances to act on target cells located in the GI tract
paracrines
* Somatostatin
* histamine
42
Secreted by cells throughout the GI tract in rsponse to H in the lumen. Its secretion is inhibited by vagal stimulation
inhibits the release of all GI hormones
inhibits gastric H secretion
Somatostatin
43
secreted by mast cells of the gastric mucosa
increases gastric H secretion directly and by potentiating the effects of gastrin and vagal stimualtion
Histamine
44
synthesied in neurons of the GI tract, moved by axonal transport down the axons, and released by action potential in the nerves
diffuses across the synaptic cleft to target ce;;s
Neurocrines
* vasoactive intestinal peptide (VIP)
* GRP (bombesin)
* enkephalins
45
homologous to secretin
released from neurons in the mucosa and smooth muscle of the GI tract
relaxation of GI smooth muscle, including the LES
stimulates pancreatic HCO3 secretion and inhibits gastric H secretion
VIP
46
secreted by pancreatic islet cell tumors and is presumed to mediate pancreatic cholera
VIP
47
released from vagus nerbes that innervate the G cells
stimulates gastrin release from G cells
GRP (bombesin)
48
secreted from nerves in the mucosa and smooth muscle of the Gi tract
stimulates contraction of GI smooth muscles, particularly the LES, pyloric sphincter, and ileocecal sphincters
inhibit intestinal secretion of fluid and electrolytes
Enkephalins (met-enkephain and leu-enkephalin)
49
Hormone assciated with the use of opiates in the teatment of diarrhea
Enkephalins (met and leu)
50
satiety center
ventromedial nucleus of the hypothalamus
51
Feeding center
lateral hypothalamic area of the hypothalamus
52
Release proopiomelanocortin in the hypthalamic centers and cause decreased appetite
Anorexigenic neurons
53
release neuropeptide Y in the hypothalamic centers and stimulate appetite
Orexigenic neurons
54
secreted by fat cells. It stimulates anorixegic neurons and inhibts orexigenic neurons
Leptin
55
secreted by gastric cells. It stimulate orexigenic neurons and inhibits anorexigenic neuros, thus increasing appetie
ghrelin
56
Contractile tissue of the GI tract is almost exclusively ____________ with te exception of pharynx, upper one thir of esophagus, and external anal sphincter all of which are striated muscles
Unitary smooth muscle
57
Depolariation of the ____________ leads to contraction of a ring of smooth muscle and a decrease in diameter of the segment of the GI tract
circular muscle
58
occur in the lower esophagus, gastric antrum, and small intestine, which contract and relax periodically
Phasic contractions
59
Occur in the lower esophageal sphincter, orad stomac, and ileocecal and internal anal sphincters
Tonic contractions
60
slow waves are ___________ inherent to the smooth muscle cells of some parts of the GI tract
osclillating membrane potentials
* occur spontaneously
* originae in the **intestitial cells of cajal**
* not action potentials although they determine the pattern of action of potentials
61
Mechanism of slow wave production
* cyclic opening of calcium channels followed bu opening of K channels
* Depolarization during each slow wave brings the membrane potential of smooth muscle cells closer to threshold and therefore increases the probability that action potentials will occur
* Action potentials, produced on top of the background of slow waves then intitiate phaseic contractions of the smooth muscle cells
62
sets the maximum frequency of contractions for ach part of the GI tract
frequency of slow waves
* lowest in the **stomach**
* highest in the **duoddenum**
* not influenced by neural or hormonal input
63
lubricates food by mixing it with saliva
decrease the sie of food particles to facilitate swallowing and to begin the digestive process
Chewing
64
The swallowing refelx is coordinated in the \_\_\_\_\_\_\_\_\_\_\_
Medulla
* fibers in the vagus and glossopharyngeal nerves carry information between the gI tract
1. the nasopharynx closes and at the ame time, **breathing is inhibited**
2. the laryngeal muscles contract to close the glottis and elevate the larynx
3. **peristalsis begins in the pharynx** to propel the food bolus toward the esophagus. simultaneously, the **upper esophageal sphincter relaxes** to permit the food bolus to enter the esophagus
65
Because the esophagus is located in the thorax, intreaesophageal pressure equal thoracic pressure which is _______ than atospheric pressure.
lower
66
Esophageal motility
1. the UES relaxes to permit swallowed food to enter te esophagus
2. the upper esophageal sphincter then contracts so that food will not reflux nto the pharynx
3. A **primary peristaltic contraction** creates an area of high pressure behind the food bolus.**gravity** accelerates movement
4. A **seconday peristaltic contraction** clears the esophasugs of any remaining food
5. The lower esophageal sphincter relaxes mediated vagally and the nuerotransmmitte is **VIP**
6. the orad region of the stomach relaxes (**"receptive relaxation")** to allow the food bolus to enter the stomach
67
may ccur if the tone of the lower esophageal sphincter is decreased and gastric ocntent reflux into the stomach
GERD
68
May occur if the lower esophageal sphincters dows not relax during swallowing and food accumulates in the esophagus
Achaalsia
69
Three layers of smooth muscle in the stomach
* longitudinal
* circular
* oblique
70
Three anatomic regions of the stomach
fundus
body
antrum
71
The ______ of the stomach includes the fundus and the proximal body. This region contains **oxyntic** glands and is responsible for receiving the ingested meal
orad region
72
the _____ of the stomach includes the antrum and the distal body. This region is responsible for the conrations that mix food and propel it into the duodenu
Caudad
73
is a vasovagal refelx that is initiated by distension of the stomach and is abolished by vagotomy
receptive relaxation
* the orad of the stomach relaxes
* CCK paticipates by increasing distensibility of the orad stomach
74
Mixing and Digestion
1. Slow waves in the caudad stomach occur at a frequency of 3-5 waves/min. they depolarize the smooth muscle cells
2. If threshold is reached during the slowwaves, action potentials are fired, followed by contraction
3. thus, the frequency of slow waves, action potentials are fired, followed by contraction. Thus, the frequency of slow waves sets the maximal frequency of contraction
4. a **wave of contraction** closes the distal antrum, thus the caudad stomach contracts, food is propelled back into the stomach to be mixed (**retropulsion)**
5. Gastric contraction are **inceased by vagal stimulation and decreaed by sympathetic stimulation**
75
Even during fasting, stomach contractions called\_\_\_\_\_\_\_\_\_\_\_\_ occure at 90 minute intervals and clear the stomach of residual food
Migrating myoelectric complex
* Motilin is the mediator of these contractions
76
The rate if gastric emptying is fastest when the stomach contents are \_\_\_\_\_\_\_\_
Isotonic
77
\_\_\_\_\_ inhibits gastric emptying by stimulating the release of CCK
Fat
78
\_\_\_\_\_\_\_\_\_in the duodenum inhibits gastric emptying via direct neural redlexes
H+
79
Slow waves in the small intestine set the basic electrical rhythm, whic occurs at a frequency of
12 waves/min
80
\_\_\_\_\_\_\_\_\_\_\_increases intetsinal smooth muscle contraction
parasympathetic stimualtion.
| (sympathetic stimulation decreases it)
81
mix the intestinal contents
a section of small intestine contracts sending the intestinal in both orad and caudad directions,
Back and forth segment causes mixing without any net forward movement of the chyme
Segmentation contractions
82
are highly coordinated and propel the chyme through the small intestine toward the large instestine. Ideally, peristalsis occurs after digestion and absorption have taken place.
Peristaltic contractions
83
Peristaltic reflex
Coordinated y the enteric nervous system
1. Food in the intestinal lumen is sensed by enterochromaffin cells, which release serotonin **(5-HT)**
2. 5-HT bind to receptors in **intrinsic primary afferent neurons (IPANs)**, which initiate the peristaltic reflex
3. **Behind the food bolus**, excitatory transmitters cause contraction of circular muscle and inhibitory transmitters cause relaxation of longituinal muslces, **In front of the bous,** inhibitory transmitters cause relaxation of circular muscle and excitatory transmitters cause contraction of longitdinal muscle
84
mediated by extrinsic ANS and possibly gastrin
The presence of food in the stomach triggers increaed peristalsis in the ileum and relaxation of the ileocecal sphincter. As a result, the instestinal contents are delivered to the large intestine
Gastroileal reflex
85
saclike segments, appear after contractions of large intestines
Haustra
86
\_\_\_\_\_\_\_\_\_ in the proximal colon mix the contents and are responsible for the appearance of haustra
Segmentation contractions
87
Mass movements occur \_\_\_\_\_\_\_/day and cause the colonic contents to move distally for long distances (from transverse colon to the sigmoid colon)
1 to 3
88
Most colonic water absorption occurs in the \_\_\_\_\_\_\_\_
proximal colon
89
As the rectum fill with fecal material, it contracts and the internal anal sphincter relaxes
Rectosphincteric reflex
90
once the rectum is filled to about _______ of its capcity, there is an urger to defecate, However defecation is prevented because the _______ is tonically contracted
25%
external anal sphincter
91
The presence of food in the stomach increases the motilit of the colon and increases the frequency of mass movements
gastrocolic reflex
92
he gastrocolic has a rapid ________ component that is initiated when stomach is stretched by food
parasympathetic
93
the absence of the colonic enteric nervous system, results in constriction of the involved segment, marked dilatation and accumulation of intestinal cintents proximal to the constriction and severe constipation
Hirschprung disesase
94
The vomiting ceter in the \_\_\_\_\_\_\_\_is stimuated by tickling the back of throat, hastric distention and vestibualr stimulation (motion sickness)
medulla
95
The chemorecptor trigger zone in the __________ is activated by emetics, radiation, and vestibular stimulation
fourth ventricle
96
Summary of GI secretions
97
Functions of Saliva
* Initial starch digestion by a-amlase adn initial triglyceride digestion by lingual lipase
* Lubrication
* Protection
98
Characteristiccs of saliva
* High volume
* High K and HCO3
* Low Na and Cl
* Hypotonicity
* presence of a-amylase, lingual lipase and kallikrein
99
The composition of salivea varies with the \_\_\_\_\_\_\_\_\_
salivary flow rate
* The lowest flow rate
* lowest osmolarity
* lowest Na, Cl and HCO3
* Highest K concenration
* highest flow rate: (Up to 4 ml/min)
* closest to that of plasma
100
Saliva is formed by three major glands
parotid
submandibular
sublingual
101
Produces an initial salive with a composition similar to plasma
this initial plasma is isotonic
Acinus
102
The ducts modify the initial saliva by \_\_\_\_\_\_-
* Reabsorption of Na and Cl
* Secretes K and HCO3
* **Aldoseterone** acts on the ductal cells to increase reabsorption of sodium and the secretion of potassium
* saliva becomes **hypotonic** in the ductsbecause the ducts are relatively impermeable to water.
* the effect of flow rate on saliva composition is explained primarily by changes in the contact time available for reabsorption
103
Saliva production is controlled by \_\_\_\_\_\_\_\_\_\_\_\_
parasympatehtic and sympatheic
| (not GI hormones)
104
Salivar production is unique that it is increased by \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
BOTH PNS ans SNS
105
Increases saliva production by increasing transport porcesses in the acinar and ductal cells and by causing vasodilaton
parasympathetic stimulation (CN VII and IX)
106
Cholinergic receptors on acinar cells and ductal cells are \_\_\_\_\_\_\_\_\_\_\_\_---
muscarinic
107
The second messengar in parasympathethic stimualtion of salivary production is \_\_\_\_\_\_\_\_\_\_
Inositol 1,4,5 triphosphate (IP3)
and
Increased intracellular calcium
* Atropine innhibit the production of saliva and cause dry mouth
108
Inreases the production of saliva and the growth of salivary glands.
Sympathetic stimulation (effects are smaller than those of parasympathetic)
109
Receptors on acinar and ductal cells are \_\_\_\_\_\_\_\_
B-adrenergic
110
The second messenger on sympathetic stimulation of production of saliva is \_\_\_\_\_\_\_\_\_\_\_\_
cyclic adenosine monophasphate
111
Parietal cells secretes ________ and are found in \_\_\_\_\_\_\_\_
HCl and Intrinsic factor
Fundus of stomach
* stimulus
* gastrin
* vagal stimulation (ACh)
* Histamine
112
Chief cells secretes _______________ and are ound in the \_\_\_\_\_\_\_\_\_\_\_\_
Pepsinogen (converted to pepsin at low pH)
Body (fundus)
* Stimulus
* Vagal stimualtion (ACh)
113
G cells secretes ________ found in the\_\_\_\_\_\_\_\_\_\_
Gastrin
antrum
* Simulus
* Vagal stimulation (via GRP)
* small peptides
* inhibited by somatostatin
* inhibited by H in stomah (via stimulation of somatostatin release)
114
Mucous cells secretes ___________ found in the \_\_\_\_\_\_\_\_\_\_
Mucus, pepsinogen
* Stimulation
* Vagal stimulation (ACh)
115
Mechanism of gastric H+ secretion
* Parietal cells **secrete HCl** into the lumen of the stomach, and concurrently **absorbs HCO3** into the bloodstream
1. In the parietal cells, CO2 and H2O are converted to H and HCO3 catalyzed by **carbonic anhydrase**
2. H+ is secreted into the lumen of the stomach by the **H+-K pump (H-K-ATPase).** Cl is secreted along with H, thus the secretion product is HCl
3. The HCO3 produced in the cells is absorbed into the bloodstream in exhange for Cl **(Cl-HCO3 exchange).** As HCO3 is added to the venous blood, the pH of the blood increases **(Alkaline tide).**
116
Omeprazole inhibits the _______ and \_\_\_\_\_\_\_\_\_\_
H,K ATPase and Blocks H+ secretion
117
If vomiing occurs, gastric H+ never arrives in the small intestine, there is no stimulus for pancreatic HCO3 secretion, and the arterial blood \_\_\_\_\_\_\_\_\_\_\_\_\_
metabolic alakalosis
118
Increases H+ secretion by direct pathway and indirect pathway
Vagal stimulation
* Direct pathway
* The vagus nerve innervates **parietal cells** and stilmulates H+ secretion
* **ACh**
* **Muscarinic** receptors
* 2nd messenger : I**P3 and Increased intracellular Ca**
* Indirect pathway
* vagus nerves innervates the **G cells** and stimulates gastric secretion, which then stimulates H+ secretion by an endocrine action.
* Neurotransmitter : **GRP**
119
Cholinergic muscarinic antagonist, inhibits H+ secretion by blocking the direct pathway, which uses ACh
Atropine
* does not block H secretion completely because it does not inhibit the indirect pathway, which causes GRP as neurotransmitter
120
\_\_\_\_\_\_\_\_\_\_elimates both direct and indirect pathway
Vagotomy
121
released in response to eating a meal
stimulates H+ secretion by interacting with CCKb receptor on the parietal cells
also stimulates enterochromaffin-like cells and histamine secretion
gastrin
122
The second messenger for gastrin in the parietal cells
IP3/Ca
123
Released from ECL cells in the gastric mucosa and diffuses to the nearby parietal cells
stimualtes H secretion by activating H2 receptors on the parietal cell membrane
Histamine
* The H2 receptor is coupled to adenylyl cyclase via Gs protein
124
Second messenger for histamine
cAMP
125
H2 receptor blocking drugs suc as cimetiine,\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
inhibit secretion of H+ by blocking the stimulatory effect of histamine
126
Histamine potentiates the actions of _____ and _______ in stimulating H+ secretion
ACh and gastrin
127
ACh potentiates the action of _______ and ______ in stimulatng H+ secretion
Histamine and gastrin
128
Inhibition of gastric H+ secretion
* negative feedback
1. low pH (\<3 in the stomach)
2. somatostatin
* direct and indirect pathway
3. Prostaglandin
129
Somatostatin inhibits gastric H+ secretion via direct pathway through \_\_\_\_\_\_\_\_\_\_\_\_\_
binding to receptors on the parietal cells that are coupled to adenyly cyclase via **Gi protein** - \> decreasing cAMP
130
Somatostatin inhibits gastric H+ secretion via indirect pathway through \_\_\_\_\_\_\_\_\_\_\_\_\_
inhibiting release of histamine and gastrin
131
Prostaglandin inhibits gastric H+ secretion by \_\_\_\_\_\_\_\_\_\_\_\_\_\_-
activating **Gi protein**, inhibiting adenyly cyclase and decreasing cAMP levels
132
Gastric ulcers
* gastric mucosa is damaged
* Gastric H+ secresion is decreased
* Gastrin levels are increased
* H. pylori colonizes the gastric mucus and releases cytotoxins that damage the gastric mucosa
* H. pylori contans urease, which converts urea to NH3
133
Diagnostic tests for H. pylori involves\_\_\_\_\_\_\_\_--
drinking a solution of 13C- urea which is convertedd to 13CO2 by urease and measured in the expired air
134
Duodenal ulcers
duodenal mucosa is damaged
Gastric H+ secretion is increased. Excess H+ is delivered to the duodenum, damaging the duodenal mucosa
Gastrin secretion in response to a meal is increased
H. pylori is also a major cause of duodenal ulcer. H. pylori inhibits somatostain secretion and inhibits intestinal HCO3 secretion
135
Zollinger-Ellison syndrome
Occurs when a gastrin-secreting tumor of the pancrease causes increased H+ secretion
H+ secretion continues unabated because the gastrin secreted by pancreatic tumor calls is not subject to negative inhibition by H+
136
Contains a high concentration of HCO3, whose purpose is to neutralize the acidic chyme that reaches the duodenum
contains enymes essential for the digestion of protein, carnihydrate, and fat
Pancreatic secretion
137
Pancreatic juice is characterized by
* high volume
* virually the same Na and K concentrations as plasma
* Much higher HCO3 concentration than plasma
* much lower Cl concentraton than plasma
* sotonicity
* Pancreatic lipase, amylase, and proteases
138
The composition of tthe aqueous component of pancreatic secretion varies with the \_\_\_\_\_\_\_\_
flow rate
* at low rates
* isotonicc fluid (Na and Cl)
* at highrates
* isotonic fluid (Na and HCO3)
139
Pancreatic struccture that produce a small volume of initial pancreatic secretion, which is mainly Na and Cl
Acinar
140
Pancreatic structure that modify the initial pancreatic secretion bys ecreting HCO3 and absorbing Cl via a Cl-HCO3 exchange mechanism in the membrane
Ductal cells
141
secreted by S cells of the duodenum in response to H+ in the duodenal lumen
actis on the **pancreatic duct cells** to increase **HCO3** secretion
Secretin
142
the second messenger of secretin is \_\_\_\_\_\_\_\_\_\_
cAMP
143
secreted by the I cells of the duodenum in response to small peptides, amino acids, and fatty acids in the duodenal lumen
acts on the pancreatic **acinar cells** to i**ncease enzyme secretion**
CCK
* potentiates the effect of secretin on ductal cells to stimulate HCO3 secretion
144
the second messengers of CCK are\_\_\_\_\_\_\_\_\_
IP3 and increased intracellualr Calcium
145
Reeased in response to H+, small peptides, amino acids, and fatty acids in the duodenal lumen
stimulates enzyme secretion by the acinar cells and like, CCK potentiates the effect of secretin on HCO3 secretion
ACh (via vagovagal reflexes)
146
disorder of pancreatic secretions
results from adefect in Cl channels that is caused by a mutation in the cysticfibrosis transmembrane conductance regualtor (CFTR) gene
associated with a deficiency of pancreatic enzymes resulting in malabsorption and steatorrhea
Cystic fibrosis
147
Composition of bi;e
bile salts, phospholipids, cholesterol, and bile pigments
148
\_\_\_\_are ampipathic molecules. they orient themselves around droplets of lipid and keep the lipid droplets dispersed
Bile salts
* aid in the intestinal digestion and absorption of lipds by empulsifying and solubilizing them in micelles
149
Bile is produced continuoysly by \_\_\_\_\_\_\_\_
hepatocytes
150
\_\_\_\_\_\_\_\_\_ increase the foration of bile
Choleretic agents
151
Bile formation
1. **Primary bile acids** (cholic acid and chenodeoxycholic acid) are synthesized from cholesterol by hepatocyes
* In the instestine, bacteria convert a portion of each of the primary bileacids to **secondary bile acids** (deoxycholic acid and lithoholic acid)
2. Bile acids are conjugated with glycine or taurine to form their respective bile salts
3. Electrlytes and water are added to the bile
4. Bile is concentrated in the gallbladder as a rsult if isosmotic absorption of solutes and H2O
152
released in response to small peptides and fatty acids in the duodenum
tells the gallbladder that bile is needed to emulsify and absorb lipids in the duodenum
causes contraction of the gallbladder and relaxation of sphincter of Oddi
CCK
153
the terminal ileum contains \_\_\_\_\_\_\_\_\_, which is a secondary active transporte that recircualtes bile acids to the liver
Na-Bile acid contransporter
* because bile acids are not recirculated until thery reach the terminal ileum, bile acids are present for maximal absorption of lipids throughy the upper small intestine
154
the surface area for absorption in the small intestine is greatly incrased by the presene of the \_\_\_\_\_\_\_\_\_
brush border
155
Mechanism of Carbohydrate absorption
Na-dependendent cotransport (glucose, galactose)
Facilitated diffusion (fructose)
* small intestine
156
Mechanism of absorprion of proteins
Na-dependent contransport (amino acids)
H+ dependent cotransport (di and tripeptides)
* small intestine
157
Mechanism of absorption of Lipids
Micelles form with bile salts in intestinal lumen
Diffusion of fatty acids, monoglycerides, and cholesterol into cell
Re-esterification in cell to triglycerides and phospholipids
Chylomcirons form in cell (requires apoprotein) and are transfered to lymph
* Small intestine
158
Mechanism of absortption of fat soluble vitamins
Micelles with bile salts
159
Mechanism of absorption of water-soluble vitamins
(Vit. B12)
Na-dependent cotransport
Intrinsic factor-vitamin B12 complex
* Small intestine, ileum of small intestine
160
Mechanism of absortpion of bile acids
Na-dependent contransport
recirculated to liver
* Ileum of small intestine
161
mechanism of absorption of Calcium
Vit. D dependent (calbindin D-28K)
162
Mechanism of absorption of Fe2+
Binds to apoferritin in cell
circulates in blood bound to transferrin
* Small inetstine
163
only \_\_\_\_\_\_\_\_\_\_- are absorbed CHO.
monosaccharides
164
hydroyze 1,4 glycosidic bonds in starch, yieldng maltose, maltotriose, and a-limit dextrins
a-amylase
165
\_\_\_\_\_\_\_, _____ and\_\_\_\_\_\_\_ in the intestinal brush border then hydrolyze the oligosaccharids to glucose
maltase
a-dextrinase
sucrase
166
Results from the absence of brush border lactase and thus the inability to hydorlyze lactcose to glucose and galactose for absorption,
lactose intolerance
* Osmotic diarrhea
167
\_\_\_\_\_\_ degrade proteins by hyrdolyzing interior peptide bonds
Endopeptidases
168
\_\_\_\_\_\_ hydrolyze on amino acid at a time from the C terminus of proteins and peptides
Exopeptidases
169
Not essential for protein digestion
secreted as pepsinogen by the chief cells of the stomach
Pepsin
170
The optimum pH for pepsin is \_\_\_\_\_\_\_\_\_\_
between 1 and 3
171
Pancreatic proteases
Includes, trypsin chymotrypsin, elastase, caboxypeptidase A, and Carboxypeptidase B
Secreted in ananctive forms
172
Trypsinogen is activated to trypsin by a brush border enzyme
Enterokinase
173
Digestive products of protein can be absorbrd as \_\_\_\_\_\_,\_\_\_\_\_\_\_. and \_\_\_\_\_\_\_
Amino acids, dipeptides, and tripeptides
174
Free amino acids are absorbed via
Na-dependent amino acid cotransport in the luminal membrane. (analogous to the cotransporter for glucose and galactose)
* four separate carrirs
* neutral
* acidic
* basic
* imino
175
faster absorption (dipeptides and tripeptides or amino acids)?
Dipeptides and tripeptides
* via H-dependent cotransport
176
CCK ______ gastric emptying
Slows
177
In the intestinal cells, the product of lipid digestion are _______ to triglcyerides, cholesterol ester, and phospholipid and with apoproteins form Chylomicrons
re-esterified
178
Chylomicrons are transported out of the intestinal cells by \_\_\_\_\_\_\_\_\_\_\_
exocytosis
179
Malabsorption of lipid - steatorrhea can be caused by \_\_\_\_\_\_\_\_\_\_\_
* Pancreatic disease
* Hypersecretion of gastrin
* low duodenal pH inanctivates pancreatic lipase
* Ileal resection
* depletion of the bile acid pool
* bacterial overgrowth
* deconjugation of bile acids and their early absorption in the upper small instestine
* Decreased number of intestinal cells for lipid absorption (tropical sprue)
* Failure to synthesize apoprotein B
180
\_\_\_\_\_\_\_\_\_ attach the epithelial cells to one another at the luminal membrane
Tight junctions
181
Absorption of NaCl
1. Na moves into the intestinal cells, across the luminal membrane, and down its gradient.
* Passive diffusion
* Na-glucose or Na-amino acid cotransport
* Na-Cl cotransport
* Na-H exchange
2. Na is pumped out of the cell against its gradient by the Na-K pump in the basolateral membranes
3. Cl absorption accompanies Na absorption throghout the GI tract by
* Passive diffusion by a paracellular route
* Na-Cl cotransport
* Cl-HCO3 exchange
182
Absorption and secretion of K
* Dietary K is **absorbed in the small intestine** by passive diffusion via a paracellular route
* K is actively **secreted in the colon** by a mechanism similar to that for K secretion in the renal distal tubule
* Aldosterone
183
Absorption of water
* Secondary to solute absorption
* **isosmotic in the small intestine and gallbladder.** the emchanism for coupling solute and water absorption in these epithelia is the same as that in the **renal proximal tubule**
* In th **colon**, water permeability is much lower than in the small intestine, and feces may be hypertonic
184
The secretory mechanisms of electrolytes and water by the intestine are located in the\_\_\_\_\_\_\_\_\_
crypts
185
\_\_\_\_\_\_\_\_ is the primary ion secreted into the intestinal lumen
Chloride
* transported through Cl channels in the luminal membrnae that are regulated by cAMP
186
Sodum is secreted into the lumen by \_\_\_\_\_\_\_\_\_\_\_
passively following Cl
187
Causes diarrhea by stimulating Cl secretion
Vibrio cholerae
* cholera toxin catalyzes ADP ribosylation of the a-subunit of the Gs protein coupled to adenylyl cyclase
* Intracellualr cAMP increases, as aresult, Cl channels in the luminal membrane open
* Na and water follows Cl and lead to **secretory diarrhea**
188
Hemogloin is degraded to ________ by the RES
bilirubin
189
bilirubin is carried in the circulation bound to \_\_\_\_\_\_\_\_\_\_\_
albumin
190
In the liver, bilirubin is conjugated with glucuronic acid via the enzyme \_\_\_\_\_\_\_\_\_\_\_\_
UDP glucuronyl transferase
191
Phase I reactions are catalyzed by
cytochrome P450 enzymes
