Section 7: Salivary and Gastric Secretion and Esophageal and Gastric Motility Flashcards
Cell types of salivary gland:
serous, acinar, and mucous cells
Functions of saliva:
protects and digests
Protective aspects of saliva:
mucus, HCO3-, and antibacterial enzymes
Digestive aspects of saliva;
alpha-amylase, Lingual lipase (neither are essential for digestion)
True or False? Alpha-amylase is essential for digestion while lingual lipase is not.
F. neither are essential
What type of glands are salivary glands?
exocrine
Surface epithelial cells of the salivary glands produce:
0.5 to 1.0 L, most productive gland of the body, isotonic NaCl, NaHC03, KCl
True or False? Saliva is always hypertonic.
F. Hypotonic (a solution in which normal cells will increase in volume)
pH of saliva at rest and when stimulated:
6 vs. 9
mOsm/L of saliva at rest and when stimulated:
575 vs. 200 mOsm/L
ion concentrations in plasma, most to least:
Na+, Cl-, HCO3-, K+
Ion concentration in saliva when stimulated, most to least:
Na+, HCO3-, Cl-, K+
What are the two components of the model of salivary secretion?
acinar cells produce primary secretion and duct cells modify secretion
Functional unit of any salivary gland:
The “Salivon”, blind end set of epithelial cells, acing region, smooth muscle cells to contract secretions
Ion concentration in saliva when not stimulated, most to least:
K+, Cl-, Na+, HCO3-
What is found in the end piece of a salivary gland?
amylase-containg primary secretion, nearly isotonic total he plasma)
Where does modification of ionic content take place in the salivary gland?
Striated and excretory ducts
What types of secretions are released from acing cells?
Plasma-like
What drives Cl- secretion into the acing lumen through apical-membrane Cl- channels?
Cl- electrochemical gradient created by large intracellular stores
What happened to the acing fluid as it flows through the ducts?
modified
What are absorbed and what are secreted in the salivary gland duct between Na+, Cl-, K+, and HCO3-?
unstimulated absorption: Na+ and Cl-, unstimulated secretion: K+, and stimulated secretion: HCO3-
Unstimulated absorption of ___ occurs in the salivary gland duct.
Na+ and Cl-
Unstimulated secretion of ___ occurs in the salivary gland duct.
K+
Stimulated secretion of ___ occurs in the salivary gland duct.
HCO3-
What nerve enters the Otic Ganglion?
Jacobson’s nerve and Tympanic Plexus
Parasympathetic input from fibers of this nucleus stimulates the parotid gland to produce vasodilation and secrete saliva.
inferior salivatory
What nerve innervates the submandibular ganglion?
facial nerve
What is the innervation to the parotid gland?
Auriculotemporal branch of the trigeminal nerve
Parasympathetic perganglionic fibers to the major salivary glands
Facial and glossopharyngeal nerves
Sympathetic preganglionic nerves originate here that supply the major salivary glands:
the cervical ganglion, postganglionic fibers from this extend to the gland in the periarterial spaces
What aspects of the salivary glands do the parasympathetic and sympathetic mediates regulate?
blood flow, ductular smooth muscle activity, growth, and metabolism (all know salivary gland functions)
From what vertebral level does the superior cervical ganglion arise?
T1-T3
Nervous control of salivary secretions:
psyche, taste, smell, food, chewing, and pain
How do taste, smell, food, chewing, and pain exert nervous control over the CNS?
via oral mechanical and chemical receptors
Which nucleus in the medulla controls salivary secretion?
salivary nucleus
Sympathetic receptors that control salivary secretion:
B-adrenergic receptors and alpha-adrenergic receptors
Parasympathetic receptors controlling salivary secretion:
cholinergic receptors
Where are cholinergic receptors located?
acing cells and duct cells
When is sympathetic innervation to the salivary secretions activated?
fear stimuli, “fight or flight”, scared spit-less
When is parasympathetic innervation to the salivary secretions activated?
meal stimuli
Attributes of salivary content with sympathetic nervous input:
low volume, high viscosity, high protein concentration, and very high mucin concentration
Attributes of salivary content with parasympathetic nervous input:
High volume, low viscosity, low protein concentration, and very low mucin concentration
Sjogren Syndrome:
chronic progressive autoimmune disease, antibodies to salivary and lacrimal gland cells, immunologic injury to acini reduces secretion, expression of Cl-/HCO3- exchanger in ducts is lost, dry mouth, keratoconjunctivitis, can lead to difficulty chewing, caries, difficulty with continuous speech, oral ulcers
True or False? There are significant levels of secretions in the esophagus.
F.
Gastic juices:
H+, water, pepsinogens, intrinsic factor (for B12 absortption)
Functions of acid:
kill bacteria, break chemical bonds in food, activate pepsinogen
Secreted volume of acid:
2-3 L/day
Name of stomach mucosa:
oxyntic gland mucosa
In which stomach chamber are oxyntic gland mucosa:
cardia/ corpus or body
True or False? Gastrin is released into the blood stream.
T
Gastric gland is aka:
Oxyntic gland
Mucous neck cells:
3.0 ml/min when stimulated, isotonic, HCl, KCl, IF
Oxyntic cells are aka:
parietal cells
Functions of duct cells:
modification of secretion s it flows into oral cavity
Why do we need bicarbonate in our saliva?
acid producing bacteria
Exocrine glands release where?
Outside the body, the lumen of ducts
Amount of flow of salivary secretions when maximally stimulated per minute
40 ml/min
F. Concentrations of Na, HCO3-, Cl-, and K+ all increase with stimulation of salivary glands.
K+ decreases
True or False? The osmotic content of saliva is low regardless of stimulation.
T
True or False? Secretions from the endpience are osmotically similar to the interstitial fluid by the end of the duct.
F
Is the change in osmolarity of secretions from the end piece an active or passive process?
passive
Acing cells producew
Interstiial fluid like secretions
The Na/K pump is always located on this side of the cell
basolateral membrane
Which ion is being recycled on the basolateral membrane of the acing cell?
K
Acetylcholine binds this type of receptor on the basolateral membrane of acing cells:
M3 receptors
What can move through the tight junctions in response to Cl- entering the lumen from the acing cells?
Na+ and water
ENac:
distal tubule of kidney and apical side of ductal cells of salivary glands
H/ K exchangers are located on which membrane of the ductal cells of the salivary gland?
apical
When is the H/ K exchanger most effective?
when plasma-like NaCl flow is slow
how to get Cl- out of the lumen and into he interstitial space?
CFTR channels and the Cl- channels on the basolateral side
Duct cells are capable of secretion lots of:
bicarbonate
What channels reduces sodium concentration in the plasma-like NaCl fluid flowing past duct cells of salivary gland?
ENac
As fluid flow rate increases:
bicarbonate concentration increases, M3 receptor is stimulated and Cl- is lost via CFTR (actively pumping bicarbonate into fluid)
True or False? The m3 receptor requires ATP.
F. It is an active process but does not require ATP
Stimulation of what receptor leads to he activation of bicarbonate channels?
M3 receptors on the basolateral membrane of the ductal cell
Sympathetic component to the glands:
norepinephrine release, nothing to do with a meal
Acetylcholine is released onto what cells to control the salivary gland?
duct or acinar cells
Cholinergic receptors are __ receptors.
M3 receptors
Why not to salivate when scared:
you may aspirate saliva and kill you if being chased by a lion
Affect of nonfunctioning Cl-?HCO3- exchanger:
dry mouth and eyes
special tube that carries food and medicine to the stomach through the nose:
nasogastric tube (NG tube)
What can elicit the same gastric juice composition as a meal/
histamine
How is the Na concentration affected when secretory rate increases?
decreases
2 mechanisms for H+ secretion from parietal cells:
increases in surface area and membranes H+ pump activated
The stomach is capable of producing a H+ gradient of ___ times.
1 million
pH range of gastric secretions:
1 to 7
Is the gastrointestinal tract electrically negative or positive in relation o the plasma?
negative
List the stimuli for acid secretion:
Vagal stimulation, G-cells of antrum, in sub-epithelial space
True or False? All methods for stimulating acid secretion increase calcium levels directly.
F. vagal stimulation and G-cells of antrum do,the in sub-epithelials space activates adenylyl cyclase first which converts ATP to cAMP
To what does histamine bind in the stimulation of acid secretion?
unique H2 receptors
Which pump is turned on in the secretion of acid?
gastric hydrogen ion pump
What enzyme stimulates he secretory cells of the stomach folicular be functionally active?
gastrin
2 stage process of food digestion:
initial absorption of digested food hen liberation of gastrin into the circulatory system to stimulate cellular activity
Method to extract gastrin:
trichloroacetic acid in acetone
Pharmacological inhibitors of acid secretion and what they act on:
atropine, vagal stimulation (vagal stimulation), omeprazole ( H+/ K+ exchanger, cimetidine (an H2 receptor blocker)
3 phases of acid secretion:
cephalic phase, gastric phase, intestinal phase
3 chemical stimuli in food digeston:
Gastrin, Acetylcholine, Histamine
Method for studying processes related to cephalic phase
sham feeding: eaten food is diverted by gastric or esophageal catheter so it can’t accumulate, stopping food processing. (In humans: food is tasted by not swallowed)
What, in the lumen of the stomach, inhibits gastrin release?
H+ (pH
How does food affect the pH of the stomach?
raises the pH, stops inhibition of gastrin release by H+
What does distension trigger?
the vast-vagal reflex (check)
Substances in the lumen that stimulate parietal cels or G cells
amino acids, protein, caffeine, calcium, ethanol
Two hours after a meal;
food gone, pH decreases (under 3) H+ inhibits gastrin release, vagal stimulation is gone, enterogastrones released by the duodenum inhibit parietal cells and G cells
3 enterogastronse:
secretin, CCK, and GIP
Symptoms of GERDs:
burning sensation radiating up from the sternum to the throat (commonly referred to heartburn)
Treatment of GERDs:
Antacids (mild symptoms), h2 receptor blockers, Na+/K+ ATPase blockers
3 basic salts used in the treatment of GERDs:
magnesium, calcium, and aluminum - with hydroxide or bicarbonate ions
Examples of H2 blockers:
cimetidine, Zantac (ranitidine)
What is a gastric (peptide) ulcer?
sore in the wall of the stomach
This bacterium is responsible for most gastric ulcers:
helicobacter pylori
How do you treat Helicobcater pylori:
antibiotics
Where in the stomach does Helicobcater pylori?
Where bicarbonate is released from surface cells in the stomach.
True or False? Smooth muscle pushes food to the back of the oral cavity.
F. skeletal muscle
What happens in the complex reflex involving the nerve coordination of skeletal muscle?
close the epiglottis, opens the upper esophageal sphincter, and propels food into the esophagus
What is the last voluntary act in processing food until the analysis end of the gastrointestinal tract?
swallowing
Where is the junction of smooth and striated muscle?
just below the upper sphincter of esophagus
True or False? The peristaltic wave is due to spontaneous muscle activity.
F
What activates a reflex stimulation via the vagus for the secondary peristaltic wave?
stretch receptors in the esophagus
To where do the stretch receptors in the esophagus feed back to?
vagal nuclei in the brain stem
What relaxes to let food pass into the stomach?
the lower sphincter of the esophagus
Neurotransmitter for the relaxation of LES:
VIP and NO (inhibitory motor neurons)
Functions of the stomach:
secretes acid, intrinsic factor, pepsinogen, store food and mix food
True or False? The storage of food is involved in motility/
T
Factors that can relax LEX:
alcohol, coffee, chocolate
Factors that can open the LES:
large meal or pregnancy (baby pushing on stomach?)
stomach resting volume:
100 ml
What controls receptive relaxation:
Purigenic reflex and CCK: fats in the small intestines triggers CCK which triggers relaxation
vagotomy:
surgery to cut one or more branches of vagus, typically to reduce the rate of gastric secretion (e.g., in treating peptic ulcers).
Origin of basal secretion:
surface cells
Origin of stimulates secretions:
parietal cells
Composition of basal secretions:
NaCl, NaHCO3-, KCl, Isotonic H2O
Composition of stimulated secretions:
HCl, NaCl, KCl, Isotonic H20
What stops inhibition of gastrin release by H+?
food raising the pH of stomach
gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve coordinate responses to gut stimuli via the dorsal vagal complex in the brain:
Vagovagal reflex
Which complex in the brain coordinates responses to gut stimuli?
dorsal vagal complex
On which cells does Acetylcholine act in the stomach?
parietal and G cells (probably more)
A hormone released from intestinal endocrine cells which stimulates gastric acid secretion in the stomach, hypothesised to exist in humans:
Entero-oxyntin
Intestinal endocrine cells activate:
“entero-oxytonin”
2 stimuli that can lead to the release of acid from parietal cells:
gastrin and absorbed amino acids
Stimulus for the gastric phase:
distention
Stimulus for the intestinal phase:
digested protein
Stimulus for all phases:
gastrin and Acetylcholine
Distention triggers:
local reflexes and vagus nerve
Vagus nerve triggers the release of:
GRP or Ach
Examples of H +/K+ ATPase blockers:
Prilosec (omeprazole), Nexium (esomeprazole)
H. pylori can live at what pH level?
7
reflex where gastric fundus dilates when food passes down pharynx and esophagus:
Receptive relaxation
The opening of this can lead to heartburn:
LES (lower esophageal sphincter
At what stomach volumes does the pressure increase sharply?
about 1500 ml
At what stomach volume does the intraluminal pressure really start to increase?
800 ml
In what type of muscle are the pacemaker cells found?
longitudinal
In which portion of the stomach does spontaneous muscle activity start?
mid-stomach
Is there peristalsis in the actual stomach?
yes
True or False? The peristaltic wave decreases in speed as it moves down the stomach.
F. accelerates
Main functions of gastric peristalsis:
mix food with a little food pushed out
What controls gastic peristalsis?
Vagal stiulation via Acetylcholine and gastrin
Percent of test meal remaining in stomach, greatest to least:
oleate meal, acid meal, saline meal
How does deviation from isotonicity effect vagal stimulation?
lowers it
True or False? Fats increase CCK activity.
F. decrease
Does acid inhibit or increase purigenic stimulation?
inhibit
Vomiting is aka:
emesis
Where is the vomiting center in the brain?
pons-medulla junction
How are the proximal GI organs involved in vomiting innervated?
cranial nerves
How are the diaphragm and abdominal muscles involved in vomiting innervated?
spinal cord
Physiological changes during vomiting:
hypersalivation, larynx and hyoid bone are drawn forward, soft palate rises, glottis closes, esophagus dilates, cardiac sphincter releases, fundus becomes flaccid, diaphragm contracts sharply, abdominal muscles and incisor anglers contract, gastric contents forced into esophagus and expelled
Which organ describe most of the work of digestion?
pancreas
How long does it take for food to be propelled to the stomach?
8 seconds
How long does food stay in the stomach?
about 2 hrs
Why do we need B12?
red blood cell formation intrinsic factor to bind to it
What type of bacterial does not get killed in the stomach?
H. pylori
Total body water:
about 40L
Gastric glands are located?
bottom of stomach/ antrum
Surface epithelial cells secrete this in h unstimulated state:
sodium chloride and bicarbonate
How can you increase the HCl secretion of the parietal cells?
histamine or food
True or False? Surface cells change their rate of production when stimulated by histamine.
F.
How do both Cl- and K+ concentrations change with histamine concentration?
they don’t change much
Secretions from these cells dominate in the basal state:
surface cells
What are secretion in the stimulated state dominated by?
H+
True or False? Secretion of H+ is an active process.
T. 1 million times gradient
The stomach is the only site of this active transporter:
K+/ H+ pump, always in the same place on the cell (luminal/ apical side)
Source of acid in the parietal cell to create HCl
CO2, metaboolic byproduct
What enzyme is used to make HCl out of CO2 in the parietal cells?
carbonic anhydrase
Overall reaction in parietal cells
H and some K through tight junctions, lumen inalways negative, leak some K down its gardent, HCl solution and lots of water goes with it
True or False? Equal parts of bicarbonate and hydrogen are produced in the parietal cell.
T
Why does the large increase in bicarbonate in from parietal cells not change overall body pH?
movement of hydrogen from the pancreas
True or False? Vagal stimulation initiates the actions of both Acetylcholine and G-cells of the antrum to lead to acid secretion.
T
What happens at the molecular level to turn on the Gastric Hydrogen ion pump?
phosphorylation
What receptors are blocked with atropine?
M3
True or False? There are M3 receptors in the salivary gland.
T, in the eyes as well (they will jitter)
How does atropine help with ulcers?
reduces acid secretion, but effected other systems
True or False? Histamine is always there so you will always have acid secretion.
T. just a little of the other two will produce a lot of secretion
Antihistamine affect on acid secretions in the stomach.
Nothing, because this is the only place that H2 receptors are found
pylorus:
mucosa of the antrum of the stomach
True or False? Blocking the H2 receptor will have a minimal effect on overall acid secretion.
F. Big effect
Na/K blocker:
Oubain
True or False? Omeprazole will block all acid secretion.
T
True or False? Many digestive enzymes don’t like an acidic environment.
T
What nerve produces acid in the stomach?
vagus, anything that stimulates the vagal nuclei (the stimulates the enteric plexus)
_ of the 3 agonists are released by the vagus.
2
Which food source is especially basic?
protein
What neurotransmitter is involved on both sides of the vago-vagal reflex?
Acetylcholine
3 stimuli of the parietal cells:
gastrin, entero-oxyntin and amino acids
3 hormones are released to inhibit acid secretion from this part of the GI tract:
duodenum
True or False? Increased calcium consumption can lead to the formation of acid.
T
GERD can lead to:
ulcers
True or False? Ulcers can be caused by stress.
F. (not directly at least)
True or False? H. pylori will die in the lumen of the stomach.
T
True or False? The pH at the level of the mucus secreting cells in the stomach is neutral.
T
What cells release pepsinogen?
chief cells
When, in swallowing, does the lower sphincter of the esophagus open?
right after food is pushed form the pharynx and past the upper sphincter of the esophagus
Pressure in the stomach does not raise significantly until:
1,500 ml of volume filled
How is the intraluminal pressure altered with a vagotmoy?
pressure begins to rise at a much lower stomach volume, almost linearly
What prevents food from entering the small intestines too quickly?
greater concentration of GAP junctions need the antrum of the stomach which speed contraction ahead of the wave. This prevents the forward progression of the bolus.
Function of hyper salivation before vomiting:
neutralize the acidic pH of the gastric contents…?
