Lecture 49- Gastric, Pancreatic And Bile Secretions Flashcards
How do most bile salts return to the liver?
Via enterohepatic circulation
How are bile salts transported from SI lumen into portal blood?
Na/bile salt co-transporter
What does the liver extract? What does it add to?
Extracts bile salts
Adds to hepatic bile salt/bile acid pool
When does the ejection of bile occur?
30 minutes after meal is ingested
What contracts the gallbladder and relaxes the sphincter?
CCK
What cells in the gallbladder absorb ions and water?
Epithelial cells
Bile is provided _________ and stored.
Continuously
What are the functions of gallbladder?
Stores, concentration and ejects of bile
What is bilirubin?
Product of hemoglobin degradation
What are the products of lipid digestion?
Bile salts bind products to form micelles and assist in absorption of lipid products
How are the two primary bile acids made?
Made by hepatocytes
What are the two primary bile acids
Colic acid, chenodeoxycholic acids
What properties do bile salts have?
Amphipathic
Emulsify lipids so digestion can occur
What is the composition of bile?
50% are bile salts, 40% phospholipids, 2% bile pigments, 4% cholesterol
What charge do bile salts have?
Negative
Causes charges to repel each other
Liver conjugates ______ ______ with _______ to form bile salts
Bile acids
AA
Why is bile secretion needed?
Digestion
Absorption of lipids
What is the binary system made of?
Liver, gallbladder, bile duct, duodenum, ileum, portal circulation
What synthesize components of bile, flow out of bile ducts into gallbladder?
Hepatocytes
What stimulates contraction of gallbladder and relaxes sphincter of Oddi?
CCK
After lipid absorption, bile salts recirculated to the _______ via reabsoprtion in the ______.
Liver
Ileum
What is aqueous stimulated by?
Hydrogen in duodenum
What is the cephalic phase initiated by? Which nerve?
Initiated by smell, taste, conditioning -> vagus nerve
What is the gastric phase initiated by? The nerve?
Gastric phase-initiated by distinction of stomach->vagus nerve
What is the most important phase in the regulation of pancreatic secretion?
Intestinal phase
(80% of secretions)
Which cells are receptors for CCK and Ach?
Acinar cells
What does CCK stimulus?
AA, peptides, FA
What potentialem the action of CCK?
Ach
What are receptors for CCK, Ach, secretin?
Ductal cells
Aqueous and enzymatic portions are regulated ________.
Separately
Which two flow rates remain consistent?
Na
K
Which concentration rate increases and which decreases at high flow rates
HCO3- concentration increases
Cl- concentration decreases
At low flow rates, what does the solution mainly contain?
Na Cl and water
At high flow rates, what does the solution mainly contain?
Na
HCO3-
Water
What are the two components of pancreatic secretions?
- Enzymatic component
- Aqueous component
What does the aqueous component of pancreatic secretions contain?
Na Cl K HCO3
Juice is isotonic
Aqueous component
What makes initial secretion? And what is it modified by?
Centroacinar and ductal cells make initial secretion, then modified by transport process in ductal cells
Aqueous component
What does the luminal membrane contain?
What does the basolateral membrane contain
Luminal membrane: HCO3-/Cl- exchanger
Basolateral membrane: Na/K ATPAse & Na/H exchanger
Enzymatic component of pancreatic secretion
What are secreted as active enzymes?
Amylase and lipases
Enzymatic component of pancreatic secretion
What are proteases secreted in?
Inactive forms
Enzymatic component of pancreatic secretion
Where are enzymes synthesized on?
Rough ER of acinar cells
What comprises 90% of the pancreas?
Pancreatic secretions
Aqueous + enzymatic components
What is the structure of exocrine glands?
Acinus lined with acinar cells
Ducts lined with ductal cells
Centroacinar cells
In the exocrine glands, what secretes aqueous portions?
Ducts lined with ductal cells
Centroacinar cells
What is the inner action of exocrine pancreas?
SNS -> celiac and superior mesenteric plexuses (inhibit)
PNS -> vagus nerve (stimulate
When do duodenal ulcers occur?
H+ secretory rate higher than normal
Overhwelming buffering capacity of pancreas
What is Zollinger-Ellison syndrome (Gastrinoma)?
High rates of H secretion due to high gastrin
Delivery of high H to dudeonum
Causes steatorrhea
What happens if there is low pH in SI?
Inactivates lipases
So no fat digestion
What form gastric ulcers?
Form because mucosal barrier is defective
What is the one cause of gastric ulcers?
H. Pylori
What is peptic ulcer disease?
Ulcerative lesion of gastric or duodenal mucosa
Caused by loss of mucus, have excessive H+ and pepsin secretion or combination of both factors
What are the barriers to acid and pepsin damage to gastric mucosa?
Bicarbonate
Mucus
When is HCl secretion inhibited?
When no longer needed for conservation of Pepsinogen to pepsin
**need pH for conversion
What are three things that inhibit HCl secretion?
- Decreased pH of gastric contents
- Somatostatin
- Prostaglandins antagonize histamine by reducing cAMP
How does somatostatin inhibit HCl secretion?
Binds parietal cells and antagonizes histamine pathway by decreasing cAMP
Inhibits both histamine and gastrin release
During the cephalopods phase what % is HCl secretion
30
During the gastric phase what % is HCl secretion?
60
What are the stimuli of cephalic phase?
Smelling, tasing, chewing, swallowing, conditioned reflexes
What are the stimuli of gastric phase?
Distension of stomach and presence of AA and peptides
What are the stimuli of intestinal phase?
Products of protein digestion
What are the four mechanisms to promote HCl secretion during gastric phase?
Distension -> vagal stimulation
-indirect via gastrin
-distension of Antron -> local reflexes -> gastrin
-AA + peptides -> Gastrin
What is the direct path of vagal stimulation?
Vagus nerve -> Ach -> parietal cells -> HCl
Vagus nerve -> GRP -> G cells
What is the indirect path of vagal stimulation (rest of G cell path)
Gastrin from G cells -> systemic circulation -> HCL from parietal cells
Why will atropine not block HCl secretion completely?
Using GRP in G cell pathway
