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74 Cards in this Set

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What organ secretes the most fluid?
Stomach
the largest total amount of fluid secretion into the gut occurs in the __________
small intestine
What is the serous component of secretion?
water, electrolytes (nature of electrolyte varies)
What is the protein component of secretion? (very general)
Enzymes necessary for digestion of nutrients. Mucus
What is the purpose of mucus?
1) lubricates chyme
2) Provides buffering of pH in food and chyme leaving stomach
what are the mucus glands like?
single cells interspersed with epithelium lining (e.g., goblet cells). Mucous adheres and protects glands
What type of glands are common in the stomach, have invaginations of epithelium (pits) leading to the secretory cells?
tubular
what type of glands are composed of acini and ducts?
Compound glands
What is the primary secretion? the secondary?
What the acini secrete (into center of acinus which goes into the ducts). 2ndary is what the ducts themselves add + the primary (modify electrolyte and water component)
Is the primary secretion iso, hypo, or hypertonic? the secondary?
Primary - iso
Secondary - hypo
What is the effect of rate of flow ?
The more time fluid is in contact with the ducts, the greater opportunity for electrolyte exchange.

FAST flow rates, ducts can't really do much, and saliva resembles primary secretion.

At SLOW flow rates, the ducts have more chance to act, and the final product is very hypotonic (the ducts remove NaCl)
How does the parasympathetic and sympathetic ns. act on secretion? What is the saliva like for each?
both increase flow, a rare example where they do the same thing. Sympathetic secretion is really mucusy (less serous component). Parasympathetic is more serous/watery
what are the salivary enzymes?
1) salivary amylase
2) lingual lipase

NO protein digestion until stomach.
What kind of hormonal control of salivary secretion is there?
NONE
What kind of environment does salivary amylase prefer? Does it continue working in the stomach?
Prefers an alkaline environment (ph = 7-10). When it enters the stomach about half is broken down. When it gets to small intestine it becomes active again.
What kind of environment does lingual lipase prefer? Does it continue working in the stomach?
Optimum pH is 4.0. continues to digest while food is in stomach.
What kind of environment does intestinal lipase prefer?
Prefers a BASIC pH
What cellular things cause secretion? (2)
1) some use adenylyl cyclase --> cAMP. increase in cAMP causes secretion. Example : VIP and secretin.

2) Some use the DAG/IP3 system. this causes Ca2+ release, and a rise in ca2+ stimulates secretion.

Example: ACh, CCK, tachykinins
What role does mucous play in salivary function?
lubricates, neutralizes pH. mucus is alkaline.
What role does alpha amylase/ptyalin play in salivary function?
starts breakdown of starches/carbohydrates
What role does lingual lipase play in salivary function?
starts lipid digestion
What role does lysozyme play in salivary function?
Antibacterial fx
What role does IgA play in salivary function?
Immune protection
What role do growth factors play in salivary function?
Protective, allow for repair
What role does the serous component play in salivary function?
taste/sensory stimulation/pH neutralization
what type of secretions (mucus or serous) do the following glands have:
1) Parotid
2) sublingual
3) submandibular/submaxillary
1) serous ONLY
2) mucus and serous (mostly mucus)
3) mucus and serous (mostly serous)
regarding neural control of saliva secretion, which (parasymathetic or sympathetic) component of ANS is involved with VIP?
Parasympathetic.
What converts pepsinogen --> pepsin?
H+
What is responsible for secreting H+ into stomach?
Parietal cells release H+ via the H+/K+/ATPase (prot0n pump).
The H+/K+ ATPase transports one hydrogen ion (H+) from the cytoplasm of the parietal cell in exchange for one potassium ion (K+) retrieved from the gastric lumen. As an ion pump the H+/K+ ATPase is able to transport ions against a concentration gradient using energy derived from the hydrolysis of ATP.
How does the proton pump work?
In parietal/oxyntic cells, the H+/K+/ATPase pumps one H+ ion out of cell (and into gastric lumen) and one K+ ion into cell (against concentration gradients of both), using ATP.
what secretes pepsinogen?
Chief cells
where are parietal cells located?
fundus and corpus of stomach
why do proton pump inhibitors (PPIs) take awhile to start working?
The H+ in the parietal cell takes awhile to be made by the cell and then used up
Why is pernicious anemia seen sometimes when a person has stomach problems?
Parietal cells also release intrinsic factor which is necessary for absorption of B12 in ileum. If these don't release it, B12 deficiency causes pernicious anemia.
What does mucus do in stomach?
Secreted by mucus neck cells in surface epithelium and neck. Promotes movement of HCl to where it needs to be. Prevents stomach from autodigestion/forms a protective layer.
What part of oxyntic/parietal cells increase drastically when cell is stimulated?
the canaliculi (invaginations of apical membrane that increase surface area because this is where the H is released). Allows cell to secrete acid more rapidly.
What are the neural components of acid secretion? (2)
1) Enteric: Nerves of ENS directly stimulate parietal and peptic cells.

2) vagus/parasympathetic has multiple effects:

a) enterochromaffin-like cells activated by vagus --> release histamine --> stimulates parietal cell --> H+ is secreted.

b) Stimulates enteric neuron that stimulates gastric secretion (via GRP)

c) Stimulates chief cell directly ---> pepsin

d) stimulates parietal cell directly --> H+
what role does histamine play in acid secretion?
the vagus nerve activates enterochromaffin-like cells ---> they release <b>histamine </b> --> histamine stimulates parietal cell via paracrine mode --> H+ is secreted
What neuron type uses Gastrin Releasing Peptide (GRP)? In response to what?
An enteric neuron uses it in response to vagal stimulation. It, of course, causes release of gastrin
what is gastrin released into?
blood. it's hormone
what three things stimulate the parietal cell?
1) Gastrin
2) ACh
3) Histamine
What stimulates release of somatostatin?
When gastric contents empty, the stomach pH drops (they were acting as a buffer.) the drop in pH to ~2 stimulates release of Sts
What does somatostatin do?
* Somatostatin suppresses the release of gastrointestinal hormones
o Gastrin
o Cholecystokinin (CCK)
o Secretin
o Motilin
o Vasoactive intestinal peptide (VIP)
o Gastric inhibitory polypeptide (GIP)
o Enteroglucagon
* Decrease rate of gastric emptying, and reduces smooth muscle contractions and blood flow within the intestine[5]
* Suppresses the release of pancreatic hormones
H+ stimulates ____________ release, which in turn causes a decrease in ________ secretion.
somatostatin; H+
What phase of acid secretion is characterized by preparation for a meal, when site or smell of food activates vagal reflex --> stimulation of parietal cell and gastrin release
cephalic phase
what is the phase of gastric secretion where the actual presence of the meal causes max acid secretion. It's a vagovagal reflex.
gastric
In the gastric phase, what is the main stimulus for gastrin release?
distension of the antrum.
what phase of gastric secretion is characterized by chyme moving into the intestine, its presence inhibiting H+ secretion.
Intestinal
How can CCK act as a competitive antagonist to gastrin?
Because they're in the same family they can stimulate the same receptors. At high [CCK], gastrin receptors are activated by CCK, just not as well. Net result is decrease of H+ secretion because gastrin can't bind and maximally activate its own receptors.
Chyme is (hyper, hypo, isosmotic) when it leaves the intestine
hyper
How does the gastroduodenal system reverse the problem of hyperosmolarity of chyme?
Releases lots of hyposmotic bicarb solution
what is dumping syndrome?
when gastric contents enter the small intestine too rapidly. results in nausea and cramps.
what are the endocrine components of pancreas?
insulin, glucagon, somatostatin pancreatic polypeptide.

comes from islets of langerhans
what are the serous exocrine components of pancreatic secretion?
water and bicarb
What are the protein exocrine components of pancreatic secretion?
Lipolytic (e.g., lipase), Amylase, proteolytic.

there's a bunch of them
what neural components stimulate release of pancreatic secretions? humoral?
Neural : ACh, VIP, GRP
Humoral: Secretin, CCK
What happens to the composition of pancreatic juice as the secretory rate increases?
The [bicarb] and [Cl-] at very low rates resembles plasma: higher Cl- than bicarb.

As the flow rate increases, the [bicarb] increases and [Cl-] decreases. It's the opposite of plasma.
What does secretin regulate?
The duodenal secretions that neutralize acid delivered into duodenum
What role do the cystic fibrosis transmembrane regulator channels play in secretion?
Secretion of water into the crypt enterocyte is generally considered to be coupled to the secretion of chloride ion via a Cl- ion channel. (CFTR)
What causes the release of PP (pancreatic polypeptide)? Where is it released from?
Vagal stimulation causes its release from endocrine cells of pancreatic islets into pancreatic portal system.


The function of PP is to self regulate the pancreas secretion activities (endocrine and exocrine), it also has effects on hepatic glycogen levels and gastrointestinal secretions.
What causes PYY to be released and what does it do?
Fat in ileum and colon cause its release. It inhibits meal-stimulated GI functions (eg secretion, gastric emptying, transit rate, motility)
During what phase of Pancreatic Secretion is there the most activity (secretion?)
Intestinal.
What mediates the Intestinal phase of pancreatic secretion?
CCK, secretion, hormones, enteropancreatic reflexes
What 2nd messengers mediates the effects of CCK/gastrin?
Ca2+
What 2nd messenger mediates the effect of VIP/secretin?
cAMP
What is the analog in secretory/acinar cells to excitation-contraction coupling in SM cells?
Stimulus-secretion coupling
Where does cholera toxin act? What does it do?
It permanently activates the Gprotein coupled with intestinal epithelial cell receptors. This in turn leads to secretion of H2O, Na+, K+, Cl-, and HCO3- into the lumen of the small intestine resulting in rapid dehydration and other factors associated with cholera, including a rice-water stool.
What do the duodenal glands secrete?
serous fluid (Water + electrolyte) similar to plasma except higher in bicarb.
What does secretin do?
Increases secretion from duodenal glands in order to neutralize the acid coming into the duodenum from the stomach
SSt, Opioid and SNS
inputs are ______________ ;
cholinergic are _______________
inhibitory;excitatory
What regulates secretion of the enterocytes?
enteric neurons primarily from submucosal plexus
What is the neurotransmitter of the IPAN (intrinsic primary afferent neuron?)?
Calcitonin Gene Related Peptide (CGRP)
What activates IPANs?
5HT and prostaglandins
Is there a similar pattern of secretion from gastric, biliary, and pancreatic fluid during the interdigestive period (similar to the MMC)
Yes, it comes in bursts, functioning to keep the gut clear and ready for next meal