Exam 4 - Digestive System Flashcards
What are the organs that make up the gastrointestinal tract
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum anus
What are the accessory organs of the digestive tract
pancreas, liver, gallbladder, salivary glands
What is another name for the digestive system
The alimentary system
What is each area of the digestive tract specialized for
Mouth/pharynx: digestion (mechanical and chemical), mastication, lubrication, and propulsion
Esophagus: conduit
Stomach: storage, digestion (churning, proteases, stomach acid)
Small intestine: Digestion and absorption
Large intestine: water and electrolyte balance
List and state the function of the sphincters in the body
Upper esophageal: swallowing
Lower esophageal: prevent gastric reflux into esophagus
Pyloric sphincter: partial regulation of gastric emptying, prevents duodenal-gastric reflux
ileocecal sphincter: separates large and small intestine
internal and external anal sphincters: control defication
Functions of accessory organs in relation to digestion
Liver: makes bile
Gallbladder: stores bile
Salivary glands: secretes mucous and amylase and saliva
Pancreas: secretes enzymes for digestion into lumen of small intestine
List and state function of cells of the mucousa
Surface cells: on villi of crypts of lieberkuhn, increase SA, minor digestive function
Goblet cells: secrete mucous
Stem/progeneter cells: at bottom, differentiate
Enteric endocrine cells: deepest part of crypt, secrete hormones into blood and secrete mucous
Undifferentiated cells: at bottom, turn into any cells
What must occur before food can be assimilated
Food must be digested into component molecules and absorbed into the blood/lymph
Carbohydrates: ingestion, digestion, and absorption
Ingested: 1/2 daily caloric intake as sugar or disaccharides
Digested: mouth - amylase small intestine - amylose (1,4): maltose and maltotriose amylopectin (1,6): alpha limited dextrins Villi - lactase: glucose and galactose Glucoamylase (1,4 gluc bonds) sucrase-isomaltase sucrase (1,4) isomalt (1,4 and 1,6)
Absorption:
lactose: Na+/gluco co-transporter
Fructose: GLUT5
GLUT2: basolat for gluc and galact
Proteins Ingestion, Digestion, and Absorption
Ingestion: 1/6 daily caloric intake as protein/large peptides
Digestion: stomach - pepsin small intestine trypsin and chymotripsin: oligosacch minimal carboxypeptidase: individual aa brush border: multiple peptidase to make individual aa
Absorption: apical (2nd active) aa: Na/aa co-trans di/tri: H+/peptide co-trans In cell all made aa Basolat (passive): aa channel down []
Lipids Ingestion, Digestion and Absorption
Ingestion: triglycerides
Digestion: small intestine only (no brush border)
lipase: breaks down on surface only
colipase: holds lipase to fat droplets until free fatty a and monoglyc
emulsification: churning and bile salts break down giant fat droplets into smaller so lipase works better
Absorption:
some: micelles in lumen
all eventually: passive diffusion thru membrane into cell and returned into triglyc
Absorptive process of Lipids
- Micelle to enterocyte
- reform triglyceride
- cholomicron
- exocytosed basolateral
- lacteals
- lymph vessels
- thoracic duct
- subclavian vein
Functions of the GI tract
Digestion
Excretion into the feces (via bile)
Water and electrolyte balance (no control)
Defense
Immunological - lymph nodes, mast cells, macrophages
Non-immunological: gastric acid, mucin, peristalsis
What is the source of fluid in the small intestine
Secretion by stomach and small intestine
Why is the immune system important to the GI tracct
it is all open to the external world which is a very large SA
Digestive Control and examples
Coordination of multiple secretory, enzymatic, and motor process (ex. acid in the stomach w/motor activity at the SAME TIME)
Neuronal, hormonal, and paracrine agents (thought of food, one hormone stim other)
Endocrine, neural and paracrine (ENS)
Where is the ENS located and what kinds of neurons does it have
The submucosal plexis is between the submucosa and mucosal layers
The myenteric plexis is between the outer longitudinal and next layer in
It is sensory, motor and interneurons
What are the functions of the Enteric Nervous System
controls vasoconstriction, secretion of secretory cells, and the mechano and chemoreceptors of the mucosa
Describe the brain-gut axis including descriptions of the innervations of the GI tract by the parasympathetic and sympathetic nervous systems
The brain gut axis is two way communication between the GI tract and the brain.
Parasymp is mainly responsible
Vagus nerve to majority acting as th epostgang of parasymp so releases ACh on M2 and M3 receptors
Pelvic Nerve to descending colon and beyond
Symp - no evidence
Describe the types of GI motor activity
Churning - mixing
Peristalsis - movement/propulsion forward
Reservior action - prevents anything from entering the small intestine while maintaining low P
Describe how sphincters regulate flow and their interactions with surrounding smooth muscle
Proximal stimulation = relaxation
Distal stimulation = contraction
Describe the stages of deglutition
Voluntary phase - tongue bushes the bolus towards oropharynx
Pharyngeal phase - soft palate closes off nasopharyns, pharyns and larynx are elevated
succesibe constriction of pharyngeal constrictors: pushes bolus through pharynx to esophagus and pushes epiglottis over larynx
Inferior pharyngeal constrictor contracts and upper esophageal relaxes - bolus enters
Esophageal phase - bolus moved by peristalsis; lower espoh sphincter opens when puper closes
Identify the functional separation for the stomach and duodenum
Allows for neutralization of stomach acid and proper functioning of the small intestine
Describe the actions of the internal and external anal sphincters when defecation is desired
P in rectum over time-
When fecal enters, increase P due to increase V
triggers reflex to cause rectal relaxation and increased cl (active contraction of rectal smooth, relax of smooth internal anal sphincter)
Skeletal muscles of external anal sphincter contracts due to proximal P on sphincter - involuntary reflex different than other sphincters
Describe the actions of the internal and external anal sphincters when defecation is not desired
P in rectum over time-
When fecal enters, increase P due to increase V
triggers reflex to cause rectal relaxation and increased cl (active contraction of rectal smooth, relax of smooth internal anal sphincter)
To defecate, must be voluntary conscious relaxation of external sphincter
Identify the steps necessary for defecation
1) relax of external anal sphincter
2) flexion of the hips
3) contraction of abdominal muscles
4) relaxation of the pelvic floor
List the main three functions of the stomach
Secretory
Motor
Hormonal
List the secretory products of the stomach (6)
Acid, mucous, pepsinogen, bicarbonate, water, intrinsic factor
List the 2 main hormones producted by the stomach
gastrin and somatostatin
What are the motor functions and stages of the stomach
Functions: secretory, motor, hormonal
1) receiving and providing temporary storage of dietary foods and liquids
2) mixing of food and water with gastric secretory products
3) grinding food so that it is smaller
4) regulating exit of retained material from the stomach into the duodenum
Histology of the stomach (cells)
Surface and neck mucus cells
Gastric pit - increase SA of stomach
Gastric Glands - chief cells (pepsinogen secretion), parietal cells (secrete HCl and Intrinsic factor), and enteroendocrine cells ( secrete things into blood)
Steps of acid secretion by parietal cells
Use CO2 to make H+
CA to make carbonic acid
then bicarb and H+ ions
Shift where Cl- enters cell w/H+
List the purposes for gastric acid
Kill pathogens, denature proteins, activate pepsinogen
Describe how acid secretion is regulated including the chemical messengers involved, the source of the secretogues, their pathways of activation, their mechanisms of action, and the stimuli for release of the secretogues
Direct control:
1) stimulated by ACh from para
1a) feed-forward to secrete before enters thru Vagus Nerve releasing ACh on M3 (Gq) of parietal cells and ECL
1b) negative feedbacck once in stomach - gastric distention activates vagus to brain and back
2) Gastrin from antrum G cells onto CCKB receptor on body of stomach
2a) stim by vagus nerve stim enteric nervous system releasing GRP
2b) stim by aa/peptide products on apical side to release gastrin and more acid
3) histamine from body endocrine cells (H2 receptor of parietal cell)
Indirect: ACh or Gastrin caused histamine release
Describe the inhibitors of acid secretion including their location of production, their pathways and mechanism for inhibition, and the stimuli for and/or inhibitors of their release (as much as stated in the lecture notes)
Somatostatin secreted from D cells by luminal acid or gastrin which then inhibits acid secretion by…
1) Parietal cell Gi receptor to decrease phosphorylation
2) Antagonizes intracellular effects of histamine
3) Indirectly inhibits gastrin and histamine secretion
- -Inhibited by ACh from ENS or Vagus
Prostaglandin inhibits acid secretion by….
1) acts on Gi receptors of parietal cell to directly reduce secretion
2) Indirectly reduce gastrin and histamine secretion
Describe acid secretion during the basal state and during the 3 phases in response to a meal (include all the steps found in each phase and rough percent of total acid secretion thatoccurs in each phase)
Basal state: interdigestive - highest at night (pH 3) and lowest in morning (pH 7)
Cephalic: first response to meal, 30% total secretion - feed-forward
activates Vagus nerve to release ACh to stomach
Gastric: second response 50-60% total secretion - distention stom activates local reflexes and the vago-vagal to release ACh on G, ECL, and parietal cells and GRP on G cells. Also digestion of protein
Intestinal- minor phase, 5-10% secretion- protein digestive products stim parietal to release gastric acid
Describe pepsinogens/pepsins where each are made, the stimuli for production of each and the mechanisms of action for the secretogue ,
including their function,
Released by chief cells when stimulated by ACh during the cephalic phase and by the vago-vagal reflex due to stom distention and ACh onto cells to release pepsinogen
Pepsinogen will become pepsin only if pH <5 & only active <3.5. Even more active <3
Function: cleaves proteins in middle and not at ends
Role of stomach in carbo and fat digestion
None
Describe the components, functions and mechanisms of the gastric diffusion barrier
Concentration gradient of H+ so that higher in lumen than cell and interstitial. pH mucous close to 7
All parts: apical mem cells impermeable to H+ and apical w/very tight junctions
All minus gastric glands:
[HCO3-] increase in mucous to protect surface of cells
Mucous gell layer = layer b/t lumen and cells
released by…
1) ACH by enteric mucous cells to secrete
2) Phys or Chem (acid, pepsins, and ethanol) irritation
3) Prostaglandins - cell irritated, releases prost, trigger mucous secretion
Describe the protection against acid mechanisms in the duodenum (2)
S cells sensitive to acid, secrete secretin to act in pancrease to stim release of bicarb.
Brunner’s glands of submucosa secrete bicarb if cells irritated
Describe the glands of pancreas and salivary glands
Exocrine pancreas: acinar cells that secrete into lumen of acinus to flow thru ducts
Salivary glands have same organization but w/alveolar cells, not acinar cells
Define acinus
Acinus: “grape-like”, the smallest secreting portion of a gland
Describe acinar cells
specialized for the prod of protein and secretion into lumen
Identify the form and function of duct cells
Duct cells are for secretion of fluid and transport of electrocytes
Identify the product and location of goblet cells
Goblet cells (pancreas) localized towards distal/secreting end of the ducts; also for secretion of fluid and transport of electrolytes
Identify the product of pancreatic acinar cells and the detailed mechanism/pathways for their release
Secrete digestive enzymes into lumen of small intestine
Makes proteins necessary for digestion, packages it up in vesicles, and releases it because of CCK to act on CCKA (Gq) or bc of ACh on M3 (Gq) - increass phosphorylation by PKC to cause vesicles to fuse w/membrane and secrete enzymes into lumen
non-primary: VIP and secretin (Gs) = weak stim of zymogens thru PKA
Describe the mechanisms and stimuli for pancreatic and salivary cells to secrete fluid (and NaCl)
Stimuli for secretion is ACh and CCK to acinar cells to release a Na/Cl- rich soln.
1) Na/Cl/K co-trans basolat
2) increased intra Cl- drives it apical plus Na+
Primary duct cell bicarb is secretin and it a HCO3-/Cl- exchange
Describe the pathways, inhibitors, and stimuli for pancreatic duct cell bicarbonate secretion
Most powerful secretion by secretin (Gs) to increase cyc AMP
Also secreted by ACh on M3 (Gq) to PKC to phos CFTR
Inhibited by Substance P
1) Secrete into lumen thru Cl-/bicarb exchanger
2) Lumen more - to drive Na+ thru tight junc, Na+/bicarb in lumen to increase Osm to drive in water,Next, take blood bicarb into cell, CA to make own bicarb, H+ transported by H+ pump and Na/H exchanger
Identify where most of the pancreatic fluid is produced (acini or ducts)
75% produced in the ducts
Identify the purpose of pancreatic bicarbonate production
Mainly to neutralize gastric acid, also help solubilize lipids
Identify the organ with the highest rate of protein synthesis and secretion
Pancreas 1.5 L/day fluid secretion
Identify what determines the level of pancreatic secretion
A balance between the factors that inhibit and stimulate secretion
Identify what types of proteins are secreted by the pancreas
More than 20 kinds of proteins secreted - most zymogens, others active
Protesases to digest proteins
Nucleases - to break down RNA and DNA
Amylase: break down carbohydrates
Lipase: fat breakdown
Describe pancreatic release of digestive enzymes in the basal state and during the three phases following a meal (include the stimuli and mechanisms employed during each phase and the approximate amount of enzyme released during each phase
Cyclic release of enzymes at a low level and then w/trigger there is redundant reg
Cephalic (sight, taste and smell) - feed-forward system, 25% total enzyme release
Vagus Nerve to ENS to cause ACh on M3 of acinar and duct cells
Gastric phase (food in stom) - feed-forward, 10-20% total release ACh (Main reg via vago-vagal reflex) and Gastrin (weak affin to CCKA receptor)
Intestinal - negative feedback, 50-80% total release;
Gastric acid stim duodenal S cells to release secretin - stim HCO3 and fluid secretion from pancreatic duct cells
Lipids and peptones stim duodenal I cells to release cholecystokinin which stim acinar cells to release digestive enzymes
Identify the purpose for redundancy in pancreatic secretion
It is a fail safe - digestion is very important so there are a variety of methods to ensure it can be done
State the approximate amount of the pancreas that can be removed before maldigestion occurs
80-90% can be removed
Identify all the functions for saliva that we discussed and be able to explain the function
Primary purpose: prevent dehydration of the oral mucosa and provide digestion for mastication and swallowing of ingested food
Also: oral hygine (lysozomes and IGA to kill bacteria and virus), taste, and initiation of carbohydrate digestion
Describe the secretory products of each of the different primary salivary glands
Parotid salivary gland: serous, mostly ions and water with high amylase
Sublingual: mucinous, more mucous with less amylase
Submandibular: mixture
Describe the role salivary duct cells play in the final saliva composition that enters the mouth
Salivary duct cells alter what was secreted by the acinar cells to create a hypotonic saliva rich in KHCO3 and low in NaCl
Acinar stim to secrete by ACh on M3 (Gq) to make an isotonic saline of Cl- and Na+ (too salty)
Duct cells absorb Na+ and Cl- and secrete K+ and HCO3-
Identify when salivary secretion is lowest and how much it can be increased of basal rates
During sleep it is at its lowest of 0.5 ml/day but it can increase 10 fold
Identify the main regulator of salivary secretion
The parasympathetic nervous system
Identify the pathways for parasympathetic control of salivation including stimuli for activation, location of salivatory nuclei and nerves involved
Para activates:
1) projects thru glossopharyngeal to parotid gland
2) Facial to submandibular and sublingual
Symp activates:
1) adrenal gland and release of epine - mior effect
Identify the effect of sympathetic activation on salivation
It causes salivation
Identify how stress can induce a dry mouth
Draw mouth causes parasympathetic withdraw causing dry mouth
Identify where most digestion occurs
Most digestion occurs in the small intestine
Identify the purpose of digestion
To break things down to an absorbable size so we can get the proper nutrients
Secretion and absorption of water
Interstitial epi cells are polar which is important for transporting accross the membrane
Secretion: 8.5L/day to small; absorbs 6.5 L/day and K+, Na+ and HCO3-
Colon gest 2L day, absorbs 1.9L and Na+ and Cl=
Absorption of Sodium in different parts of intestinal tract
Na+ abs in small and large intestine coupled w/Cl- usually
Mainly absorbed by vili expi in small and surface epi colon
Na+ to blood - via Na/K pump on basolat of epi
Jejunum & some ileum: co-trans dependent on electrogenic process in vilus epi (Na/H exchanger - H+ in lumen abs Na+ so cell keep pH at optimum level)
Ileum and prox dependent on parallel abs of Cl- (Counter trans Na/H and Cl-/HCO3-; H and HCO3- to lumen)
Distal colon: ENaC channels
Absorption of Cl- in diff parts of intestinal tracts
Small and large intestine - linked to Na+ reabs Voltage dependent Cl- absoprtion Na+ electrogenic absorption = negative lumen = draw Cl- in Distal colon (ENaC) and some in ileum w/co-trans
Identify the sources of protein that is digested and absorbed in the GI tract
70-90g/day of protein from diet
Other sources: endogenous enzymes, mucus, and sloughed epithelial cells
Identify the locations of macronutrient absorption and the relative importance of each location
Duodenum - most important
Jejunum - semi important
Ileum - only important to fats
Describe the mechanism for absorption of fat soluble vitamins
Vit A, D, E & K absorbed same way as lipids
Embedded into fats we consume, liberated as fats in lumen, simple diffusion across apical mem.
In enterocyte, goes into chylomicron and trans to liver to store it or release it in the blood
Describe the mechanism for absorption of water soluble vitamins
Most (B and C - not B12) facilitated diffusion or thru 2nd active trans (w/Na+) similar to ions, aa, and sugars
Describe the mechanism for absorption of Vit b12
Large and charged molecule that cannot go thru a channel
1) Bound to intrinsic factor in stomach, travels to ileum
2) Enterocytes of ileum have receptors for intrinsic factor
3) Binds and is endocytosed by receptor mediated endocytos
4) B12 liberated, intrinsic factor digested (in enterocyte)
5) In blood, transcolablbin 2 bound to B12
7) taken up by cells that need to divide (B12 necessary for thymine repro)
Describe the absorption of trace minerals and, in particular, iron
Iron - most needed; bound to heme from meat and easily absorbed into enterocyte
Ionized iron (ferric Fe3 and Ferrous Fe2)
1) Only co-trans w/H+ for Fe2, so Fe3 broken down
2) In cell, ferrus binds mobile ferrin
3a) stay
3b) some ionized iron passive trans across basolat and bind to transferrin to take Fe to cells that need it
4) equilibrium in free iron and bound
5) Once absorbed, no mechanisms to get rid of it
What would happen with high iron (in blood) and transferrin mostly bound
the free iron in blood is higher than free iron in the cell, so iron would not leave
Define hepatobiliary
Of the liver and gallbladder
Describe the blood flow of the liver following the movement of blood from the heart to the liver and back to the heart by all pathways
Portal system w/hepatic sinusoid as the capillary of the liver
1) Heart –> aorta –> hepatic artery (O2 rich) –> hepatic sinusoid –> central vein –> hepatic vein –> vena cava –> heart
2) Heart –> aorta –> small intestines (O2 poor) –> hepatic portal veins –> hepatic sinusoid –> central vein –> hepatic vein –> vena cava –> heart
Describe a portal acinus, what it is, how to outline one, the significance of them, and the zones
Functional division of the liver that is diamond in shape w/two axis - 1) b/t central veins, 2- b/t portal triads
Zone1: closest to portal triad (most O2)
Zone II: middle
Zone III: closest to central vein (least O2)
Identify the cell types found in the liver and their location and function and which are the most numerous//Identify the location of hepatocytes specialized for different functions and identify what those general functions are for the different locations
Hepatocytes: most common
periportal hepato - zone I - oxidative metabolism
pericentral hepato - zone III - conjugation rxns and other detoxifying
Endothelial cells (line sinusoids, veins, and arteries)
Kupffer cells in sinusoids (mixed macrophages)
Stellate cells - b/t hepato and sinusoid (store Vitamin A)
Identify the functions of bile and where it is produced
Bile is produced in the liver
primary funct: emulsify fats
other: assist in diluting and neutralizing gastric acid and excreting substances for excretion in the feces
Describe the flow of bile from the liver to the duodenum, including the important ducts/canaliculi, where it is stored and how it gets to the storage site, how it gets from the storage site to the duodenum, where the bile enters the duodenum and what structure regulates the entry of bile into the duodenum
1) made in hepatocytes
2) secreted apical mem to bile canaliculi
3) interlobar bile ducts (ducts in portal triads)
4) Right and left hepatic ducts
5) common bile ducts
6a) cystic duct (branch to gallbladder)
6b) Sphincter of Odi - to duodenum if it is open ie if there is fat in the duct
Describe the functions of the gallbladder
1) storage reservior (30-50ml/bile)
2) concentrative function ([] bile made by liver)
Describe bile secretion including where the bile salts secreted by the liver come from, the proportion that escapes recycling, what the bile salts are made from, and whether the bile salts are recycled more than once during a meal
Most bile salts reabsorbed by Na+/coupled transporters & sent to liver via portal vein and absorbed by hepato
95% recycled and reused during digestion of one meal
Liver makes new bile by uptake of cholesterol and production of cholesterol
Identify what gives bile, urine and feces their color and why feces is brown but urine is yellow
Bilirubin is a product of heme which is fairly non-polar so hard to get rid of in kidney
Liver makes it watersoluble and send it out thru bile
Makes urine yellow and in intestinal tract, cholanic bacteria break it down which is why feces is brown
- Identify what is secreted by duct cells and describe how it is secreted (refer back to the pancreas file) and what the stimulus for secretion is (hormone and what stimulates that hormone) Describe the secretion of bile including what stimulates production in the hepatocyte, where it is stored, how it is concentrated, the stimulus for secretion (hormone and what stimulates that hormone), and how the hormone causes secretion
Duct cells secrete a bicarbonate rich fluid in response to secretin, which is stimulated by the acid in the duodenum
If no need - bile diverted to gallbladder where 90% H2O removed so it is concentrated by absorbing Na/Cl thru counter (h/Na and Cl/HCO3-), then CA convert CO2 and H2O of lumen by CA
If need - I cells of duocenum secrete cholecystokinin, increse plasma CCK, acts on CCKA receptors to cause gallbladder contraction, increase bile flow to common bile duct and increase flow into duodenum. CCK also on sphincter of Odi to cause relax and increase flow into duodenum
Other functions of the liver
Biotransformations - metabloize compounds
Take sub across basolat mem of blood into cell to be chemically degraded
2 phases of transformation follow so it will be taken up
Phase 1: oxidize chem rxn using p-450 enzymes (drugs, bile acid synthesis, vitamin activation)
Phase 2: ROH and conjugates another molecule (large polar group)
Which stimulates ventilation to blow off excess Co2?
a) increased H+ from volatile sources
b) increased H+ non-volatile sources
c) both
d) neither
c) both
Vomiting causes loss of (H+ or HCO3-) while diarrhea causes loss of (H+ or HCO3-)
H+ vomit, HCO3- diarrhea
Which of the following are true of bicarbonate? Choose three.
a. It is freely filtered.
b. It is bound to proteins.
c. It is reabsorbed.
d. It is not reabsorbed.
e. It can be secreted.
f. It cannot be secreted.
freely filtered, reabsorbed, can be secreted
Water and CO2 come into tubular cells and are converted into bicarbonate and hydrogen ions. What is the fate of the bicarbonate and hydrogen ions?
Bicarb moved to blood, H+ secreted into the tubule
If the blood is acidic, the kidneys will respond by (choose three):
a. reabsorbing less bicarbonate
b. reabsorbing more bicarbonate
c. breaking down glutamate
d. not breaking down glutamate
e. make new bicarbonate
f. not make new bicarbonate
reabsorbing more bicarbonate, breaking down glutamate, make new bicarb
T or F Nueronal input is required for function of the ens
false
The __symp/para_NS_ stimulates secretions and increases mobility in the GI tract
para
___ acts in the brain to induce satiety
Cholecystokinin
Source of agents: ACh Histamine Gastrin Somatostatin Secretin Cholecystokinin (CCK)
ENS: ACh ECL: Histamine G: Gastrin D: Somatostatin S: Secretin I: Cholecystokinin (CCK)
ID the G protein each agent is linked to: ACh Histamine Gastrin Somatostatin Prostaglandins Secretin Cholecystokinin (CCK)
ACh - Gq Histamine - Gs Gastrin - Gq Somatostatin - Gi Prostaglandins - Gi Secretin - Gs Cholecystokinin (CCK) - Gq
Which of the following stimulate parietal cells to produce acid? Choose three.
a. Histamine
b. Gastrin
c. Somatostatin
d. Prostaglandins
e. Acetylcholine
Histamine, Gastrin and ACh
Acetylcholine from the enteric nervous system is stimulatory to all of the following except:
a. Chief cells
b. Mucus cells
c. ECL cells
d. Parietal cells
e. Somatostatin
f. Acinar cells
g. Duct cells
Somatostatin
Acidic conditions in the lumen of the small intestine _____________ the release of somatostatin and prostaglandins.
a. stimulate
b. inhibit
a - stimulate
Which of the following does prostaglandin inhibit the secretion of? Circle all that apply.
a. acid
b. histamine
c. gastrin
d. mucus cells
acid, histamine, and gastrin
What is the main secretagogue for duct cells?
secretin
Gastrin has a/an (stim/inhib) effect on ECL and parietal cells
stimulatory
Acidic chyme in the duodenum (stim/inhib) the release of secretin and CCK
stimulates
