2 Secretions of the GI Tract and Pancreas Flashcards
The parotid gland contains what types of cells
Serous
What are the main cell types of the submandibular and sublingual glands
Mixed mucous and serous
What are the cells which produce the initial saliva
Acinar
What cells modify the saliva to make it hypotonic
Striated duct (columnar epithelial)
What type of cells contract to eject saliva
Contractile (myoepithelial) cells
What is in saliva
- water
- electrolytes
- α amylase
- lingual lipase
- kallikrein
- mucus
What is kallikrein
Precursor to bradykinin which causes vasodilation
How does saliva compare to plasma
Saliva has more K and HCO3
Saliva has less Na and Cl
What is the overall effect of saliva on ions
Absorption of Na and Cl
Secretion of K and HCO3
What does parasympathetic do at salivary glands
Originates in facial and glossopharyngeal nn and they use mAChR
Where do the sympathetic controls originate
T1-3 and superior cervical region and they wrap around arteries
What do parasympathetic do for salivary glands? Sympathetic?
Both increase secretions
What factors increase saliva
- conditioning
- food
- nausea
- smell
What decreases saliva
- dehydration
- fear
- sleep
- fatigue
What is downstream of the parasympathetic muscarinic receptor in the salivary glands
IP3 and Ca
What is down stream of the sympathetic β receptor on the salivary gland
cAMP
What do parietal cells produce
HCl and IF
Where are parietal cells mainly found
Body of stomach
What do chief cells produce
Pepsinogen
Where are chief cells mainly found
Body of stomach
What do G cells produce
Gastrin
Where are G cells mainly found
Antrum of stomach
Where are mucous cells mainly found
Antrum
Glands of the stomach are divided into what categories
Oxyntic and pyloric
What are the characteristics of oxyntic gland
- located in proximal stomach (body and fundus)
- parietal cells that secrete acid
- D cells, mucous cells, ECF cells, chief cells
What are the characteristics of pyloric glands
- located in distal 20% of stomach
- G cells that secrete and synthesize gastrin
- D cells, mucous cells, ECF cells
What do D cells produce
somatostatin
When the stomach is removed you are at risk for vitamin deficiencies in what vitamins
Fat soluble vitamins
What do parietal cells do
Secrete HCl
Where is HCl formed in parietal cells
Canaliculi
What is the alkaline tide? What cells are responsible
Uptake of HCO3 and secretion of HCl; parietal cells
What does the parasympathetic do to G cells
Stimulates gastrin release through GRP directly and inhibits release of somatostatin
Increased secretion of gastrin increases secretion of what
Somatostatin
What stimulates somatostatin
H in gastric lumen
What cells secrete somatostatin
D cells
Pepsinogen are secreted by what cells
Chief cells
What is the optimal pH for pepsinogen?
1.8-3.5
What is the most important stimulus for pepsinogen
Vagus N
How does omeprazole decrease acid
Inhibits H/K antiporter
How does cimetidine work
Acts on the H2 (histamine) receptor as an antagonist which treats GERD, duodenal and gastric ulcers
What do ECL cells secrete
Histamine
What are stimulators of the H/K ATPase on the parietal cells
M3 receptor (vagus) CCKb receptor (gastrin) H2 receptor (histamine)
What are the main inhibitors for the parietal cells
Somatostatin and prostaglandins
What does atropine do in parietal cells
It is a muscarinic blocker which would function to decrease H secretion in parietal cells
What are the phases of gastric HCl secretion
Cephalic
Gastric
Intestinal
What is the cephalic phase of gastric secretion
- 30% of total HCl secretion
- stimulated by smell, taste, chewing, swallowing, and conditioned reflexes
- works via Vagus N
- Vagus stimulates gastrin which stimulates parietal cells
What is the gastric phase of gastric secretion
- 60% of total HCl
- stimulated by stomach distention and AA
Distention of fundus and body of stomach activates what
Mechanoreceptors in mucosa of oxyntic and pyloric activate direct and indirect vagus stimulation
What does distention of the antrum do
Local (pyloropyloric) reflex stimulates gastrin release
What do AA in the stomach do
Stimulate gastrin release
What is the intestinal phase of gastric secretion
- 10% of total HCl
- stimulated by distention of SI (NS mediated) and presence of digested protein (hormonal regulation)
Gastric juice is made of what components
Non-parietal and parietal
Failure to secrete what and from what cell results in pernicious anemia
IF from parietal cells
Where is Vit B12 absorbed
Ileum
What cells are present in the gastric mucosa
Mucous neck cells and gastric epithelial cells (HCO3)
What are the protective factors of the gastric mucosa
- HCO3 and mucous
- prostaglandins
- blood flow
- gastrin
- GF
What are the damaging factors of the gastric mucosa
- acid
- pepsin
- nsaids
- H. pylori
- EtOH
- bile
- stress
Gastrinomas are associated with what
Zollinger-Ellison syndrome
Under normal conditions, secretin administration _______ gastrin but does the opposite in gastrinomas
Ihibit
Peptic ulcer disease are due to what
Excessive H and pepsin OR loss of protective mucosal membrane
What is the primary cause of ulcers
Defective mucosa caused by H pylori
What allows H pylori to colonize
Urease
What from H pylori causes breakdown of mucosa and underlying cells
Cytotoxin
How does H pylori have an affect on duodenal ulcers
- inhibits somatostatin secretion from D cells
- gastric H pylori infection spreads and inhibits HCO3
H secretion rates are a little higher than normal with what
Duodenal ulcers
What has the highest rate of H secretion
Zollinger ellision syndrome
Where are the gastrinomas often
Pancreas
What are the effects of Zollinger Ellison syndrome
- excessive delivery of H to duodenum
- inactivation of pancreatic lipase due to suboptimal pH
How does the pancreas compare to salivary glands
Isotonic secretions
What comes from pancreatic acinar cells
Enzymatic secretions
What comes from centroacinar and ductal pancreatic cells
Aqueous secretion
What is the net result of the pancreas
Secretion of HCO3 and absorption of H
What are the 3 phases of pancreatic secretion
Cephalic
- initiated via vagus by smell, taste, and conditioning
- produces mainly enzymatic secretions
Gastric
- initiated via vagus by distention of stomach
- produces mainly enzymatic secretions
Intestinal
- 80% of pancreas secretion
- enzymatic and aqueous secretions stimulated
What is the sympathetic innervation of the pancreas
Postganglionic nerves from celiac and superior mesenteric plexuses that are inhibitory
What is the parasympathetic innervation of the pancreas
Vagus which is stimulatory
Preganglionic synapse in ENS and post ganglionic synapse on exocrine pancreas
I cells produce what
CCK
S cells produce
secretin
Acinar cells are stimulated by
ACh and CCK
What stimulates ductal cells of pancreas
ACh, CCK, secretin
Cystic fibrosis transmembrane conductance regulator causes what to fail early
Pancreas, b/c Cl can’t leave cells to come back in and bring HCO3 in
What does motilin do?
Produces migrating motor complexes
Where does GIP get produced? What does it do
K cells (duodenum, jejunum)
Decrease H secretion
Increase insulin release
Where is iron absorbed
duodenum as Fe2
What is pleomorphic adenoma
Most common type of salivary gland cancer
Which bilirubin is water soluble
Direct; it is conjugated with glucuronic acid
Pancreatic insufficiency results in what deficiency
Fat soluble vitamins (ADEK) and B12
How is tropical sprue different than celiac
Responds to antibiotics
What is whipple disease
Infection with type of bacteria
Foamy macrophages in lamina propria
Cardiac symptoms
Arthralgias
Neurologic symptoms
AST and ALT elevated but ALT>AST
Most liver disease
Liver enzymes increased and AST>ALT
Alcoholic liver disease
Alkaline phosphatase is elevated in
Cholestasis (biliary obstruction), infiltrative disorders, bone disease
Gastrin is secreted by what cells
G cells
