3 Secretions Of The GI Tract And Pancreas Flashcards
Parotid glands are what type of glands?
Submaxillary/submandibular glands?
Sublingual glands?
Serous
Serous and mucous cells; fluid and mucin glycoprotein
Serous and mucous cells; fluid and mucin glycoprotein
Structure of salivary glands:
_____ produces initial saliva.
____modifies saliva.
_____ contracts to eject saliva as stimulated by neuron I put
Acinus
Striated duct
Contractile (myoepithelial cells)
Initial digestion of starches, lipids, and dilution of food, lubrication with mucus for swallowing
Saliva
Kallikrein secreted in saliva used to make _____.
Bradykinin for vasodilation
Composition of saliva
Water, electrolytes, alpha amylase (ptyalin), lingual lipase, kallikrein, mucus
Saliva is ______ compared to plasma.
Higher levels of _____.
Lower levels of _____.
Hypotonic
K, HCO3
Na, Cl
What cells modify the saliva?
How?
Ductal cells
Saliva was isotonic and plasma like; ductal cells modified the plasma solution to make it hypotonic (saliva)
There is a net absorption of solutes because ductal cells are impermeable to water and not absorbed with the solute->solution becomes hypotonic
What pumps are on the luminal membrane (apical) of a ductal cell?
Basolateral membrane (blood)?
IN/OUT
Na/H
Cl/HCO3
H/K
K/Na
——/CL
HCO3,Na/——
Why are there multiple channels moving H and HCO3?
Allow the enzymes to work because they work optimally at different pH levels
Parasympathetic innervation of salivary glands
Sympathetic innervation
Fx?
Facial and glossopharyngeal N
Originate from T1-T3 and superior cervical ganglion
Increase salivary secretions
Sympathetic postsynaptic nerve fibers extend to glands by _____.
Periarterial spaces
Salivary gland parasympathetics stimulated by _____.
Inhibited by ______.
Conditioning, food, nausea, smell
Dehydration, fear, sleep
Stimuli->parasympathetic response though _____ nerves-> release ______ binding to ______ receptors in the tissue->secrete _____ in the acinar/ductal cell.
CNVII, CNIX (facial and glossopharyngeal)
ACh
Muscarinic
Ca, IP3
Stimuli->sympathetic response through _____ nerves->release _____ binding to _____ receptors in the tissue -> secrete ______ in the acinar/ductal cell
T1-T3
NE
Beta
cAMP
Main components of gastric juice and fx
HCl: initiates protein digestion; converts pepsinogen to pepsin; kills bacteria
Pepsinogen: inactive precursor to pepsin
Intrinsic factor: secretes vitamin B12
Mucus: lines the stomach and protects, lubricates, neutralize acids
Water
Cells and location of the oxyntic gland
In gastric mucosa of proximal stomach, little in body and fundus
Parietal cells D cells Mucous cells ECF cells Chief cells
Cells and location of pyloric gland
Distal stomach (antrum)
G cells
D cells
Mucous cells
ECF cells
Location and fx of parietal cells
Body (oxyntic glands)
Secrete HCl (pepsinogen->pepsin) Increase secretion of H ions (HCl) so more acidic->increase absorption of HCO3
Intrinsic factor
Alkaline tide
Venous blood has a higher pH than arterial blood
Because net secretion of HCl and absorption of HCO3 in parietal cells
Location and fx of G cells
Antrum (pyloric gland)
Secrete gastrin
Parasympathetic stimulation of G cells by _____ nerve-> release ______-> directly stimulate release of gastrin
Vagus N
GRP
Parasympathetic stimulation of _____ nerve -> releases ______ binding to muscarinic receptors on D cells -> stimulating D cells to secrete somatostatin-> indirectly _____ gastrin release.
Vagus N
ACh
Inhibits
Somatostatin is secreted from _____. Act on G cells by _____ gastrin release.
Negative feedback: gastrin ____ somatostatin secretion
H in lumen stimulates _____ secretion.
D cells
Inhibiting
Increases
Somatostatin
Location and fx of chief cells
What stimulates chief cells?
Body of stomach in oxyntic glands
Secrete pepsinogen
Vagus N
Pepsinogen needs a ____ pH.
Why?
inactivated at a _____ pH.
Low
Pepsinogen is converted to pepsin (breaks down peptides/proteolytic enzyme) at the optimal pH of 1.8-3.5 (LOW)
Therefore needs parietal cells to secrete HCl (H+) and decrease pH
High
Vagus N -> releases ACh -> binds to M3 receptors on parietal cells-> stimulate H+ secretion-> triggers _____ reflexes-> stimulates chief cells to secrete _____.
Cholinergic
Pepsinogen
Secretion and CCK come from ______ and affect what contents of stomach
Duodenum
Location and fx of gastric mucous cells
Antrum of stomach
Mucus and pepsinogen
K/H pump on the _____ membrane of parietal cells.
Cl/HCO3 pump on the _____ membrane of parietal cells.
Fx?
Powered by _____.
Apical/lumen
Basolateral/blood
How H+ is secreted because Cl follows into lumen
HCO3 absorbed into blood
ALKALINE TIDE
Na/K ATPase pump
K/H pump on parietal cells is inhibited by what?
How?
Omeprazole (prilosec, zegerid)
Reduces HCl secretion
Inhibitors of ECL
Activators of ECL
ECL secretes _____ that binds to a _____ receptor.
Prostaglandins and Somatostatin
ACh and gastrin
Histamine which binds to an H2 receptor -> G protein -> cAMP -> K/H pump -> H+ secretion
Inhibitor of prostaglandin
What effect does it cause?
NSAIDS—allow gastric secretions
Inhibit prostaglandins therefore preventing the inhibition of H+ secretion from parietal cells
What inhibits the ACh M3 (muscarinic) receptors on parietal cells?
Atropine
Combined response of two stimulants that exceeds their summed response
Require a separate receptor for each stimulant
Potentiation
Histamine potentiates ____ and _____.
ACh potentiates _______ and ______.
Effects of Cimetidine and Atropine??
ACh and gastrin
Histamine and gastrin
Cimetidine blocks direct action of histamine, therefore blocks potentiated effects of ACh and gastrin
Atropine blocks direct action of ACh, therefore blocks potentiated effects of histamine and gastrin
Three phases of gastric HCl secretion
Cephalic, gastric, intestinal
Stimuli of cephalic phase of gastric secretion
Smell, taste, chewing, swallowing, conditioned reflexes
Mechanism of cephalic phase of gastric secretion
Vagus N DIRECTLY stimulates parietal cells by releasing ACh
Vagus N INDIRECTLY stimulates G cells to release gastrin
Vagus N releases GRP-> activates G cells -> release gastrin-> stimulates parietal cells to secrete HCl
Stimuli of gastric phase of gastric secretion
Distention of stomach, amino acids, small peptides
All stimulate gastrin release leading to HCl release from parietal cells
Activates direct and indirect vagus N stimulation of parietal cells
Distention of stomach
Pyloropyloric reflex
Local reflex in the antrum of stomach that stimulates gastrin release—> H+ release from parietal cells
Stimuli of intestinal phase of gastric secretion
Distention of SI, and presence of digested protein
Gastric juice is a mixture of what two secretions?
Non parietal and parietal
______ secrete intrinsic factor which is required for vitamin _____ absorption in the _____.
Lack of intrinsic factor will cause what?
Parietal cells
B12
Ileum ***
Pernicious anemia
Gastric mucosal defense includes ____.
Types of cells
Mucous neck cells (mucous)
Gastric epithelial cells (HCO3)
Protects against HCl and pepsin
Protective factors of gastric mucosa
HCO3 Mucus Prostaglandins Blood flow Gastrin Growth factors
Damaging factors of gastric mucosa
Acid Pepsin NSAID/aspirin H. Pylori Alcohol Bile Stress
_____ is used in the diagnosing of gastrin-secreting tumors (gastrinoma).
Why?
In gastrinomas, injection of secretion causes a paradoxical increase in gastrin release
Normally secretin inhibits gastrin release
Peptic ulcer disease caused by what?
Loss of protective mucosal barrier
Excessive secretion of H and pepsin
H. Pylori infection and use of NSAIDS
Gastric ulcers caused by _____ bacteria that secretes _____.
H. Pylori
Urease: allows the bacteria to colonize
Converts urea to NH3 (decrease H+) therefore increase in gastrin
Releases cytotoxins that breakdown the mucosal barrier
Duodenal ulcers ____ secretion higher.
H. Pylori inhibits _____ from D cells.
H+ secretion
Inhibits somatostatin (nothing to control gastrin)
Increase gastrin levels
Gastric H. Pylori infection can spread to the _____ and inhibit HCO3 secretion
Duodenum
H+ secretion is the highest
Pancreatic tumor secretes LARGE amounts of gastrin
Trophic effect on parietal cell (mass increases)
Zollinger-Ellison Syndrome
Effect of trophic parietal cell from Zollinger-Ellison Syndrome
Treatment
Excessive delivery of H+ to duodenum
Inactivated pancreatic lipases therefore fat in stool (steatorrhea)
Treat with cimetidine, omeprazole, surgery
Two main components of pancreatic secretions
Aqueous solution (ISOTONIC) with HCO3, Na, K, and Cl (to neutralize H+ from stomach)
Enzymatic secretion of pancreatic amylase and lipase, and pancreatic proteases (to digest CHO, protein, lipids)
What secretes HCO3 from pancreas?
What secretes enzymes?
Ductal epithelial cells secrete aqueous solution with HCO3
Acinar cells secrete pancreatic enzymes
Ductal cells of the pancreas cause a net reaction
Secrete HCO3 and absorb H+ in the blood
Modify initial isotonic solution
Three phases of pancreatic secretions
Cephalic, gastrin, and intestinal
Pancreas sympathetic innervation (INHIBITORY) includes _____ nerves from _____ and ______ plexuses.
Pancreas parasympathetic innervation (STIMULATORY) includes the _____ nerve; preganglionic fibers synapse in _____ and postganglionic fibers synapse on _____.
Postganglionic
Celiac and superior mesenteric plexues
Vagus
ENS
Exocrine pancreas
Pancreatic phases:
Cephalic is initiated by ______ nerve by _____ and produces _____.
Gastric is initiated by ____ nerve by _____ and produces _____.
Intestinal phase contains _____ of pancreatic secretions and stimulates _____.
Vagus N
Smell, taste, and conditioning
Enzymatic secretions
Vagus N
Distention of the stomach
Enzymatic secretions
80%
Enzymatic and aqueous secretions
Duodenal i cells secrete ___ and S cells secrete ____ that help regulate pancreatic secretions during the intestinal phase.
CCK and secretin
Regulated Cl channel on the apical surface of ductal cells in pancreas
Cystic fibrosis transmembrane conductance regulator (CFTR)
In a CFTR mutation, the Cl channel does not work -> can’t regulate/secrete HCO3–> build up of H+
Pancreas will fail early in this disease t
Cystic fibrosis
A carbonic anhydrase inhibitor causes what?
Decrease formation of HCO3 therefore decrease secretion of HCO3 secretion into salivary ducts
