Term
| GI tract length in live individual |
|
Definition
|
|
Term
| GI tract length in deceased individual |
|
Definition
| 30 feet - due to muscle relaxation. |
|
|
Term
|
Definition
Parotid gland
(located in front of your ears, on your cheek)
Sublingual gland
Submandibular gland |
|
|
Term
|
Definition
- Mostly water
- Some enzymes
- Bicarbonate |
|
|
Term
| The GI tract, starting at the mouth. |
|
Definition
Mouth
Pharynx
Esophagus
(esophageal sphincter)
Stomach proper
(pyloric sphincter)
Small intestine
Duodenum
Jejunum
Ileum
(iliocecal sphincter)
Large intestine
Cecum
Ascending large intestine
Transverse colon
Descending column |
|
|
Term
| Is the lumen inside or outside the body? |
|
Definition
Outside the body. It goes directly from a source exposed to the outside, the mouth, to another that is exposed to the outside, the large intestine.
Sphincters close off the internal areas of the GI tract from the external area. The esophageal sphincter faces the outside (the esophagus and mouth) and the anal sphincter. |
|
|
Term
| Where are the largest concentrations of bacteria found in the GI tract? |
|
Definition
The mouth and some in the esophagus.
In the large intestine. |
|
|
Term
| What are the accessory organs? |
|
Definition
- Salivary glands
- Pancreas
- Liver |
|
|
Term
| What are accessory glands |
|
Definition
They're not part of the GI tract directly - however, the either secrete digestive juices or play a very important part in the activation of digestive juices.
The accessory organs:
- Salivary glands
- Pancreas
- Liver |
|
|
Term
| Is the gall bladder an accessory organ? |
|
Definition
| No. it's basically a bile storage organ - it receives the bile, absorbs the fluid from the bile - making it more concentrated, then secretes it into the common bile duct. |
|
|
Term
|
Definition
A vestigial organ that lies just below the cecum.
Commonly infected - must be removed when it is so. |
|
|
Term
| Overall functions of the digestive system? |
|
Definition
To provide continuous supply of water, electrolytes, and nutrients.
It requires:
Digestion, breakdown of food
Absorption, specialized absorptive epithelial cells
Secretion, digestive enzymes/secretions by exocrine cells
Motility, smooth muscle propelled transit of food
Excretion, of undigested food stuffs
Immune barrier function, keep bacteria outside of body. |
|
|
Term
| Where does most absorption take place? |
|
Definition
| In the duodenum of the small intestine. |
|
|
Term
Enzymes from which section of the GI tract is primarily responsible for digestion of food?
a) The mouth
b) The stomach
c) The small intestine
d) The large intestine |
|
Definition
|
|
Term
| Gastrointestinal functions are controlled by what general mechanisms? |
|
Definition
| Paracrine, nervous, hormonal. |
|
|
Term
| What is the first stop of blood on the way away from the stomach? |
|
Definition
|
|
Term
| True or false: there are endocrine cells lining the gut alongside absorptive epithelial cells. |
|
Definition
|
|
Term
| Endocrine cells lining the gut secrete hormones. How, however, can they be hormones? Where do they act? |
|
Definition
They actually act back on the stomach.
However, hormones must travel to act on the target tissue (definition of hormone).
The pathway:
Secreted by the endocrine cells, enters into stomach capillary network and travels through the blood stream to the liver wherein the hormones undergo their final activation before traveling to their target sites through the blood stream. |
|
|
Term
| Chemoreceptors of the gut |
|
Definition
| Stimulated by elevated pH levels. |
|
|
Term
|
Definition
| Stimulated by elevated osmolality. |
|
|
Term
| What is the GI tract regulated by? |
|
Definition
Chemoreceptors
Osmoreceptors
Mechanoreceptors
Neural reflexes (ANS)
Enteric nervous system
Hormones |
|
|
Term
| What region of your GI tract is innervated by both branches of the autonomic nervous system |
|
Definition
|
|
Term
| What is the short neural reflex? |
|
Definition
| Chemo/osmo/mechanoreceptors innervate the enteric nervous system, resulting in increased motility and secretion. It does not depend on interaction with higher neural centers. |
|
|
Term
| What is the long neural reflex? |
|
Definition
| What is the long neural reflex? |
|
|
Term
| Which branch of the autonomic nervous system increases contractility and secretion? |
|
Definition
|
|
Term
| Where is the striated muscle of the GI tract located? |
|
Definition
| The upper 3/4 of the esophagus (including the pharynx) and the anal sphincter. |
|
|
Term
| Where in the spinal cord does the parasympathetic nervous system branch from? Where are its primary and secondary neurons located? |
|
Definition
Preganglionic nerves exit the spinal cord at cranial nerve X (the vagas nerve) and in the sacral (pelvic nerve) regions.
They innervate the gut ganglia (myenteric plexus) as well as the striated muscle found in the upper 3/4 of the esophagus and the anal sphincter. |
|
|
Term
| Where in the spinal cord does the sympathetic nervous system branch from? Where are its primary and secondary neurons located? |
|
Definition
Primary neurons exit the spinal column to synapse on the ganglionic chain.
From here, secondary neurons lead to the secondary ganglia: the coeliac ganglion, superior mesenteric ganglion and inferior mesenteric ganglion.
The secondary ganglion then send fibers that innervate the gut. |
|
|
Term
| Secondary ganglion of the sympathetic nervous system pertaining to the gut |
|
Definition
The coeliac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion |
|
|
Term
| How does the parasympathetic nervous system increase motility and secretion? |
|
Definition
| Increases motility due to excitatory synapses on longitudinal and circular muscles. Some of these also innervate both endocrine and secretory cells. |
|
|
Term
| Name the functional layers of the small intestine? |
|
Definition
Longitudinal muscles
Myenteric plexus (ganglia)
Outer/inner circular muscles
Deep muscular plexus (no ganglia)
Submucous plexus (ganglia)
Mucosal plexus
Membrane mucosae
Mucosa |
|
|
Term
| Where, in the functional layers of the small intestine, would you find the ganglia? |
|
Definition
| Within the myenteric plexus and the submucous plexus |
|
|
Term
| Which of the functional layers of the small intestine lacks ganglia. |
|
Definition
Deep muscular plexus.
Within the smooth muscle (long/circular) layers. |
|
|
Term
| Where are the GI tract pacemaker cells found? What are they called? |
|
Definition
ICC networks -- found predominantly in the myenteric plexus between the myenteric plexus neurons and the longi/circular muscle cells.
There is also an intermuscular ICC network in the deep muscular plexus.
Those ICCs found in the myenteric plexus are those that set the frequency - ie they pull the less dominant ICC cells to increase their frequency. |
|
|
Term
| Which network takes over pacemaker responsibilities if there is damage to the myenteric plexus neurons? |
|
Definition
| The deep muscular plexus intersticiall cell network. |
|
|
Term
| Are there ICC cells in the submucosal plexus? |
|
Definition
|
|
Term
| Smooth muscle cells communicate with each other directly by means of what? |
|
Definition
|
|
Term
| ICC's communicate with each other by means of what type of communication? |
|
Definition
|
|
Term
| How large of a molecule can pass through a gap junction? |
|
Definition
|
|
Term
|
Definition
| Interstitial cells of cajal |
|
|
Term
| What type of receptor is a requirement for the proper development of nerve ganglia and ICC's? |
|
Definition
c-kit
-- it's a receptor type tyrosine kinase which binds to ligand stem cell factor |
|
|
Term
| If a mouse lacks ICC's, it can be ascertained that they likely lack what receptor? |
|
Definition
| That they miss the c-kit receptors |
|
|
Term
| True or false: all of the hormones in the GI tract are peptides |
|
Definition
|
|
Term
| True or false: all the peptides in the GI tract are hormones. |
|
Definition
False.
All hormones there may be peptides, but not all peptides are hormones. |
|
|
Term
| What are the mediators of the GI tract? |
|
Definition
Mediators: peptides, derivatives of amino acids, or non-peptides from various sources.
Modulated by: Hormones (endocrines), paracrines, neurocrines or immune/juxtacrine factors. |
|
|
Term
|
Definition
Mediators of the GI tract.
Released in response to neural activity and chemical and mechanical signals triggered by foodstuff, act at a DISTANT SITE. (must go through blood stream to liver, be cleaved to be activated, proceed to target site) |
|
|
Term
| Which mediators act in the immediate vicinity of release? |
|
Definition
| Paracrine/immune/neurocrine substances |
|
|
Term
| Which types of mediators have quick-removal mechanisms to limit their duration of action? |
|
Definition
| Paracrine mediators are readily metabolised or reabsorbed to limit duration of activity. |
|
|
Term
| Which are the most important GI hormones? |
|
Definition
Gastrin
CCK
Secretin
GIP
Motilin |
|
|
Term
| True or false: upon leaving the GI tract, nutrient rich blood goes to the liver to be processed before being directed into the general blood stream. |
|
Definition
| False - the blood first goes to the liver through the portal vein, then goes to the heart. |
|
|
Term
| What criteria defines a GI hormone? |
|
Definition
1) Must alter the activity at a different site than that of release.
2) Effect must persist even if neural connections have been severed.
3) The substance should be able to elicit the expected physiological effect when injected intravenously.
4) Identified chemically and have structure confirmed by synthesis. |
|
|
Term
| What are the sources of the five GI hormones? |
|
Definition
Gastrin - ANTRUM, duodenum, jejunum
CCK - DUODENUM, JEJUNUM, ileum
Secretin - DUODENUM, jejunum, ileum
GIP - DUODENUM, JEJUNUM
Motilin - DUODENUM, JEJUNUM |
|
|
Term
|
Definition
A hormone that acts on the brain and is found at its highest concentrations when we are fasting.
It encourages us to seek out food. |
|
|
Term
| Where is gastrin released ? |
|
Definition
ANTRUM (mostly)
Duodenum
Jejunum (least) |
|
|
Term
|
Definition
DUODENUM (most)
JEJUNUM (most)
Ileum (least) |
|
|
Term
| Where is Secretion released? |
|
Definition
DUODENUM (most)
Jejunum
Ileum |
|
|
Term
|
Definition
| DUODENUM, JEJUNUM (equally) |
|
|
Term
| Where is motilin released? |
|
Definition
|
|
Term
| Which of the five GI hormones promotes growth of mucosa and the pancreas? |
|
Definition
|
|
Term
| Which cells produce gastrin? |
|
Definition
g-cells
-- first located in the antrum of the stomach. Found all the way to the jejunum. |
|
|
Term
|
Definition
I-cells
--- in duodenum and jejunum - neurons for it are found in the ileum and colon. |
|
|
Term
| Secretin is produced by what cells? |
|
Definition
S-cells
--- in the small intestine |
|
|
Term
| GIP cells are produced by what cells? |
|
Definition
K-cells
--- in the duodenum and jejunum |
|
|
Term
| What cells produce motilin? |
|
Definition
| Endocrine cells in the upper GI tract that have yet to be named. |
|
|
Term
| True or false: endocrine cells will secrete several hormones |
|
Definition
|
|
Term
| Which gastrointestinal hormone stimulates the release of insulin? |
|
Definition
GIP
-glucose-dependent insulinotropic peptide |
|
|
Term
| Which gastrointestinal hormone stimulates the production and release of acid? |
|
Definition
|
|
Term
| What are the different morphology of gastrointestinal endocrine cells? |
|
Definition
"Open" endocrine cells contact with lumen
"closed" endocrine cells, no contact with lumen
"open" endocrine cells in human jejunum amid enterocytes |
|
|
Term
| The five established GI hormones are secreted by what morphology of gastrointestinal endocrine cells. |
|
Definition
|
|
Term
| Name the key paracrine agents and their roles. Also, if known, where (or what kinds of cells) produce them. |
|
Definition
1) Histamine
Not a peptide - is a derivative of histidine.
Produced by ECL cells, Released by gastrin
Stimulates acid secretion by stomach.
Potentiates actions of ACh and gastrin on acid secretion
Antacid medications cimetidine (tagamet) and ranitidine (zantac) block H2 histimine receptors.
2) Somatostatin
GI peptide
Produced by D cells
Inhibits gastrin release when antral mucosa is acidified and directly inhibits gastric acid secretion from parietal cells.
Distributed in gastric/duodenal mucosa/pancreas
Inhibits release of ALL gut hormones |
|
|
Term
| Which hormonal agent also functions as a juxtacrine/immune mediator? |
|
Definition
|
|
Term
|
Definition
Key endocrine agent, GI peptide, produced by D cells.
Distributed in gastric/duodenal mucosa/pancreas
Inhibits gastrin release when antral mucosa is acidified and directly inhibits gastric acid secretion from parietal cells.
Inhibits release of ALL gut hormones |
|
|
Term
|
Definition
Not a peptide - is a derivative of histidine.
Produced by ECL cells, Released by gastrin
Stimulates acid secretion by stomach.
Potentiates actions of ACh and gastrin on acid secretion
Antacid medications cimetidine (tagamet) and ranitidine (zantac) block H2 histimine receptors. |
|
|
Term
| Function of substance P in GI |
|
Definition
| Found in brain and GI tract mucosa, stimulates intestinal motility and gallbladder contraction |
|
|
Term
|
Definition
| Stimulates motility - found in the brain and gut (excitatory) |
|
|
Term
| Effect of VIP in the gut -- where in the gut its found. |
|
Definition
Found in mucosa and muscle of the gut
Function is to relax the gut smooth muscle |
|
|
Term
| GRP function and location |
|
Definition
Found at gastric mucosa - function is to increase gastrin release.
GRP = gastrin releasing peptide. |
|
|
Term
|
Definition
Function similarly to a paracrine hormone. (diffusing across synapse)
May stimulate or inhibit release of endocrines or paracrines (GRP {vagal stimulates release}) mediates vagal release of gastrin. |
|
|
Term
| Acetylcholine stimulates the release of what and from what cells? |
|
Definition
| Acetylcholine stimulates acid secretion from gastric parietal cells |
|
|
Term
| Location and activity of enkephalins |
|
Definition
Found in mucosa and muscle
Increases the smooth muscle tone |
|
|
Term
What are the four basic functions of the digestive tract?
Are there any other key ones? |
|
Definition
Motility
Digestion
Absorption
Secretion
(excretion and immune barrier function) |
|
|
Term
| Describe the immune barrier function of the GI tract |
|
Definition
There is a presence of immune cells, in lymphoid tissue, in the lamina appropria.
These immune cells are T and B lymphocytes, macrophages and dendritic cells.
They sample the status of the lumen of the gut if there's pathogenic bacteria / toxins then the immune system mounts a response to avoid you becoming more ill. |
|
|
Term
| Name the GI sphincters, starting at the mouth. |
|
Definition
Upper esophageal sphincter
Lower esophageal sphincter
Pyloric sphincter
Sphincter of oddi
Ileocolic sphincter
Anal sphincter (external/internal) |
|
|
Term
|
Definition
| Blocks the digestive juices of the pancreas from constantly leaking into the duodenum. |
|
|
Term
| Upper esophageal sphincter |
|
Definition
| Is under voluntary control for swollowing. Keeps air from entering the GI tract. |
|
|
Term
| Where is striated muscle found in the GI tract? |
|
Definition
Upper third of the esophagus is striated muscle.
The upper esophageal sphincter is striated circular muscle.
The external anal sphincter is striated muscle. |
|
|
Term
| Where does the involuntary movement of food begin? |
|
Definition
| At the upper esophageal sphincter - once it moves past this point, its movement is under the control of paristalsis. |
|
|
Term
| What are the names of the layers that make up the walls of the GI tract - name them from the outermost inwards? Is it the same structure throughout? |
|
Definition
It is generally the same structure throughout the GI tract.
Serosa (lubricating layer that produces water secretions)
Musculus externa
Outer longitudinal muscles
Myenteric plexus (ENS cell body location)
Inner circular muscles
submucosa
Submucous plexus (project into m. epithelial cells, +
secretions)
Mucosa (made up of layers of smooth muscle)
Muscularis mucosa --undulations of villi
Lamina propria - contains lymphatic vessels (lacteal),
capillaries, arteries and veins
Epithelial cells - endocrine, absorptive etc. |
|
|
Term
| What are the facets that regulate GI functions? |
|
Definition
Autonomous smooth muscle functions
ICC (muscle like but not contractile)
Slow wave potentials
Pacesetter cells
Intrinsic nerve plexus
Myenteric plexus and submucous plexus
Extrinsic innervation
Sympathetic/parasympathetic activity
Gastrointestinal hormones
Immune/paracrine factors
Histimine
Substance P |
|
|
Term
| ICC's work on which muscle |
|
Definition
| On the longitudinal and circular muscles. |
|
|
Term
| Which plexus contains the pacemaker ICC's? |
|
Definition
|
|
Term
Which of the following is false: The syncytium of the GI tract can have the following layouts:
- Circular muscle to circular muscle
- Longitudinal muscle to longitudinal muscle
- Circular muscle to longitudinal muscle
- ICC to circular muscle
- ICC to longitudinal muscle |
|
Definition
| Longitudinal to circular muscles are not connected by gap junctions. It is the ICC's or proximal muscle that feeds information forward in each independent muscle type. |
|
|
Term
| What modulates the frequency of paristalsis? |
|
Definition
| The coupling between pacemaker cells (ICC) modulates frequency |
|
|
Term
| Where is the highest frequency for muscle rhythmicity in the GI tract? |
|
Definition
|
|
Term
| Which organ in the GI tract has the highest frequency for muscle rhythmicity? |
|
Definition
|
|
Term
| Which organ in the GI tract has the lowest frequency form muscle rhythmicity? |
|
Definition
| The stomach and the colon. |
|
|
Term
| The force and duration of contractions in the GI tract is proportional to what? |
|
Definition
| To the frequency of action potentials. |
|
|
Term
The force and duration of contractions in the GI tract is proportional to what:
a) The frequency of the slow wave
b) The frequency of action potentials
c) The magnitude of the influx of calcium
d) The magnitude of the influx of potassium |
|
Definition
| B - frequency of action potentials. |
|
|
Term
Which of the following is the correct effect on myenteric plexus neurons by stretch, acetylcholine, parasympathetics
a) Increases membrane potential
b) Increase Force/duration of contraction
c) Hyperpolarizes membrane potential
d) Decrease force/duration of contraction
e) A and B
f) A and D
g) None of the above |
|
Definition
Answer is E.
By increasing the membrane potential (making it more positive) it reaches action potential threshold more easily.
The increase in frequency of AP's increases the force/duration of contraction. |
|
|
Term
Which of the following is the correct effect on the myenteric plexus neurons by norepinephrine, sympathetics, nitric oxide.
a) Increases membrane potential
b) Increase Force/duration of contraction
c) Hyperpolarizes membrane potential
d) Decrease force/duration of contraction
e) A and B
f) C and D
g) None of the above |
|
Definition
Answer if F.
Causes hyperpolarization. |
|
|
Term
| What are the different motility patterns? Where do you find them? |
|
Definition
Peristalsis
- Sequential contraction of smooth muscle, primarily in the esophagus.
Segmentation
- Mostly duodenum - increases absorption
Mass movement
- Large intestine - occurs 3/4 times a day.
MMC (migrating motor complex)
- Seen when fasting, when [motilin] increases.
- Acts in lower part of stomach - ileum.
- Prevents retrograde movement + clearing indigestible foods.
Receptive relaxation
- Seen in the upper portion of the stomach.
- Mediated by NO.
- when you swollow, NO is released and the upper part of the stomach relaxes right away.
- Involves ENS and extrinsic autonomic NS -- cutting off the vagas nerve may cause issue with this. |
|
|
Term
| Substances found in saliva |
|
Definition
Lingual lipase
Amylase
Mucins
IgA
Lysozyme
Lactoferrin |
|
|
Term
| Which neural branch controls saliva flow |
|
Definition
| Neural regulation is primarily by the autonomic nervous system. |
|
|
Term
| Which substances are the primary secretagogues? |
|
Definition
| Acetylcholine and Ne/Epinephrine |
|
|
Term
| True or false: only the parasympathetic nervous system causes the secretion of saliva |
|
Definition
|
|
Term
|
Definition
"dry mouth" caused by impaired salivary secretions.
Could be caused by
○ sjogrens syndrome-autoimmune attack of salivary glands.
○ Drug side effects
○ Head/neck radiation to tumors
Presents with:
Tooth decay, esophageal erosions due to lowered pH, difficulty lubricating/swallowing food, opportunistic infections |
|
|
Term
GERD
Symptoms and treatment |
|
Definition
Gastroesophageal reflux disease
Symptoms:
Esophagitis + erosion of mucosa/ulcers
Lumen stricture
Columnar cells replace squamous epithelium
Adenocarcinoma
Treatment:
Proton pump inhibitors
H2 histimine receptor antagonists |
|
|
Term
Where do the innervations for swallowing originate from in the brain? Afferently and efferently
What about paristalsis? |
|
Definition
Afferent: sensory inputs from pharynx activates area in the medulla (brain stem) - the swallowing center
Efferent:
Pharynx and striated muscle via nucleus ambiguus (somatic motor type)
Smooth muscle via dorsal motor nucleus (visceral motor type)
Paristalsis - sequential neural impulses from the center. |
|
|
Term
| Describe esophageal peristalsis |
|
Definition
When you first swallow theres a relaxation of the upper esophageal sphincter (contracting as soon as food passes) and funda (upper part of stomach).
Upon swollowing, coincidently, the lower esophageal sphincter relaxes due to NO/VIP which relaxes the circular muscle layer in the LES in anticipation of the food entering the upper gut region. Behind the bolus, there is a contraction due to release of ACh. |
|
|
Term
| What is primary and secondary paristalsis? |
|
Definition
Primary paristalsis
- Occurs when you initially swallow food.
Secondary paristalsis
- Gets rid of excess food stuck in the esophagus |
|
|
Term
| Which part of the stomach functions as a storage area |
|
Definition
| The fondus and body of the stomach |
|
|
Term
| Which neurotransmitter or molecule is responsible for the relaxation of circular muscle? |
|
Definition
|
|
Term
| Which neurotransmitter or molecule is responsible for the contraction of circular muscle? |
|
Definition
|
|
Term
| What triggers esophageal peristalsis? |
|
Definition
Distention or luminal acidity.
Primarily mediated by ENS - but there are vagal efferent/afferent complexes coming from the brain stem. |
|
|
Term
|
Definition
- Storage
- Regulate release of chyme into duodenum
- Secrete HCl -- enzymes beginning protein digestion
- Secrete Grehlin (fasting) - control of feeding
- Churn and mix food with digestive secretions |
|
|
Term
| Where are the cells that release ghrelin? |
|
Definition
| Within the body and the fondus of the stomach |
|
|
Term
|
Definition
| Ghrelin is a hormone that is released by fondus/body portion of the stomach during fasting and right before eating. It acts in the hypothalamus, at the appetite center of the brain. Stimulates appetite. |
|
|
Term
| Where is gastrin released from? |
|
Definition
| From the G-cells of the antrum/pylorus region. |
|
|
Term
|
Definition
| Contains parietal cells and produces acid, which is then secreted into the stomach. |
|
|
Term
|
Definition
| Parietal cells - stimulates acid production |
|
|
Term
| Where does the major mixing of foods occur? |
|
Definition
| In the antrum and the pylorus. |
|
|
Term
| As more food enters the stomach, what stimulates the more vigorous contractility pattern? |
|
Definition
| The distention of the antrum/pylorus region causes the activation of mechanoreceptors, causing vigorous contractility pattern. |
|
|
Term
| How is the bolus moved through the stomach? |
|
Definition
Tonic contractions of fundus and body (little mixing)
Phasic contractions of the proximal and distal antrum ("antral pump") **retropulsion occurs here. |
|
|
Term
| Where does retropulsion become important? |
|
Definition
| In the stomach, in the antrum region. It's phasics contractions cause retropulsion which allows for the pulverization of the bolus into smaller and smaller pieces. |
|
|
Term
| The frequency or pace of the contractions of the stomach is mediated by what? |
|
Definition
By ICC. Interstiatial cells of cajal.
3 c/min |
|
|
Term
| Protein digestive products stimulate the release of what GI hormone? |
|
Definition
| Amino acids cause the release of gastrin in the antrum G-cells. |
|
|
Term
| Describe the vagovagal reflex in the stomach |
|
Definition
During the gastric phase of digestion, when the bolus has entered the stomach and has caused the distention of the fundus and body causes antrum mechanoreceptors to be activated.
These act on vagal afferents, goes up to higher processing centers then back down vagal efferents, synapsing on an acetylcholine antagonised interneuron which then stimulates the release of NO and VIP.
NO and VIP relaxes the fondus and body of the stomach. |
|
|
Term
| Fat digestion products causes the release of what GI hormone? What is that hormones actions? |
|
Definition
CCK.
Reduces the muscle contractility in the fondus
(vasovagal reflex) |
|
|
Term
True or false:
CCK is released in the antrum of the pylorus in response to the presence of glucose/protein/fats |
|
Definition
False.
CCK is released in response to the presence of glucose/protein/fats in the duodenum. |
|
|
Term
| What would be the symptoms in an individual who's afferent vagal nerve to their stomach and their duodenum has been cut? |
|
Definition
There would be decreased relaxation of the fondus when food entered the stomach. Therefore, the bolus would cause an increase in pressure much more quickly than it would otherwise.
So receptive relaxation would be greatly inhibited.
Also causes a decrease or delay in gastric emptying. |
|
|
Term
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Definition
Acidic gastric chyme entering the duodenum activates chemoreceptors in the wall of the duodenum are activated.
These chemoreceptors are part of the enteric nervous system, which communicates with the antrum/pylorus portion of the ENS to decrease the rate of gastric emptying. (short reflex) |
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Term
| When acid is present in the duodenum, what is (are) the response(s)? |
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Definition
1) ENS short reflex to pyloric antrum / pylorus
2) Secretin secretion, activation, then decreases antrum circular muscle contraction, increases the tonic contraction of the circular muscle of the pyloric sphincter |
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Term
| What stimulates gastrin release in the duodenum? Where does it act and what are gastrins functions in the stomach? |
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Definition
The presence of protein digestion products in the duodenum stimulates the release of gastrin.
Also, the release of gastrin-releasing-peptide releases gastrin as well
- Increases pyloric smooth muscle contractions
- Increases gastric juice secretions
- Increases mixing by increasing antral contractions. |
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Term
| What stimulates the release of CCK in the duodenum? Where does it act and what are CCK's functions in the stomach? |
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Definition
Products of fat digestion stimulate release of CCK alongside GIP.
Both cause increase in muscle contractions of pyloric sphincters (delay gastric emptying)
+ decrease in acid secretion.
+ inhibits gastrin release |
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Term
| What is enterogastrone? What is its action? |
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Definition
It's a GI hormone that hasn't actually been named yet.
Seems to cause decrease in gastric emptying and reduction in HCl secretion. |
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Term
| What are the enterogastrones? |
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Definition
GI hormones that are released from the duodenal mucosa by acid, fatty acid, or hyperosmotic solutions.
*activity is to inhibit acid secretion and gastric emptying.
Hormones:
GIP - released by fatty acids, acts at parietal cells to inhibit acid secretion.
Secretin - inhibits gastric acid secretion
Cholecystokinin (CCK) - inhibits gastric emptying and inhibits gastrin release. |
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Term
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Definition
Condition where gastric emptying is impaired.
Causes:
• Systemic diseases (long standing diabetes mellitus) (neuropathy, damage to ICC's)
• Injury to vagus nerve
• Medications (opiates; anticholinergics)
• Gastric cancer
• Peptic ulcer disease
Treatment/management:
Eat small meals
Liquids better tolerated than solid |
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Term
| Gastric secretions in the stomach come from what glands? |
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Definition
| The oxyntic gland and the pyloric gland. |
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Term
| People who have a gastric bypass may be in danger of having a deficiency in what vitamin? |
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Definition
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Term
| Where is the intrinsic factor released from |
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Definition
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Term
| What do chief cells secrete |
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Definition
| Pepsinogen and gastric lipase. |
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Term
| What do ECL cells secrete? What stimulates this? |
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Definition
| ECL cells secrete histamine. Histamine causes an increase in acid secretion. |
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Term
| What is secreted by the oxyntic gland? |
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Definition
Mucus
Enzymes
HCl
Grehlin (hormone) |
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Term
| What is secreted by the pyloric gland? |
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Definition
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Term
| What are the different cell types found in the mucus lining of the stomach |
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Definition
Superficial epithelial cells
Mucous neck cells
Parietal cells
Chief cells
Endocrine cells |
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Term
| Where is somatostatin released? What is its action? |
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Definition
Released from D-cells when pH is low enough to trigger it.
Acts on nearby antrum G-cells and INHIBITS them, reducing gastrin release and reducing gastric acid secretion.
This occurs during the interdigestive phase* |
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Term
List the following as either will increase secretion of acid or decrease secretion of acid in the antrum:
a) Luminal H+
b) Vagal stimulation via acetylcholine
c) Peptides/amino acids present in lumen
d) Vagus stimulation of G cells via GRP |
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Definition
a) Directly stimulates D cells to secrete somatostatin. INHIBITS gastrin release from G cells
b) Inhibits somatostatin release from D cells -- INCREASES acid secretion
c) Directly stimulates G cells to release gastrin -- INCREASES acid secretion
d) Stimulates gastrin release -- INCREASES acid secretion |
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Term
List the following as either will increase secretion of acid or decrease secretion of acid in the fundus:
a) Vagal stimulation via ACh on parietal cells
b) Vagal stimulation via ACh on ECL cells
c) Gastrin stimulation on ECL cells
d) Gastrin stimulation on parietal cells |
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Definition
a) Increases acid secretion
b) Increases acid secretion
c) Causes release of histamine, increasing acid secretion.
d) Stimulates parietal cells to increase acid secretion directly. |
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Term
| What's the difference between actively secreting parietal cells and those that are not? |
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Definition
Resting:
Elaborate system of intracellular membranes and abundant mitochondria
Secreting:
Amplified apical membrane from fusion of tubulovesicles and secretory canaliculi
Tubulovesicles contain proton pumps, so inserting them into the apical membrane increases overall density of H^+ receptors.
Apical membrane invaginate and interdigitate |
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Term
| On which membrane do the GI hormones act on parietal cells. |
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Definition
| The receptors are found on the basolateral membrane. |
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Term
| Which receptors are found in the basolateral membranes of parietal cells? By what secondary messenger does it act? |
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Definition
M3 - ACh receptor -- increased Ca
H2 - histamine receptor -- increased cAMP
CCK-B - gastrin receptor -- increased Ca |
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Term
| Describe the release of acid from parietal cells on a molecular level from the perspective of the transport systems within each membrane. |
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Definition
Basolateral membrane:
- Bicarbonate (out of cell), chloride (into cell) exchanger
- Sodium/potassium exchanger (Na in, K out)
Apical membrane:
- Potassium channel (out)
- Chloride channel (out)
- Potassium (in)/hydrogen (out) transporter
○ Note, Cl and H out makes HCl
When the receptors (M3, H2, CCK-B) on the basolateral membrane are filled, there is an increase in the activity of carbonic anhydrase that converts CO2 and H2O into bicarbonate |
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Term
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Definition
| Refers to an event where, during HCl secretion from parietal cells of the stomach, also secretes bicarbonate ions across their basolateral membranes and into the interstitial fluid, temporarily increasing pH. |
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Term
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Definition
Also known as "zollinger-ellison syndrome"
- Extragastric endocrine tumor whose cells undergo unregulated secretion of large amounts of GASTRIN (massive release of acid)
○ Non-beta cell tumors of pancreas
○ Duodenal tumors |
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Term
| Patients with gastrinoma present with what types of symptoms? |
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Definition
Peptic and duodenal ulcers, diarrhea, steatorrhea (fatty stool), hypokalemia
Show low blood potassium levels (hypokalemia) |
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Term
| What pharmacotherapy would be useful to alleviate the symptoms of gastrinomas |
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Definition
| H2 antagonists or proton pump inhibitors which directly inhibit the transport of hydrogen, reducing gastric acid secretion. |
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