GI 4- Accessory GI Organs- Pancreas, Liver and Gall Bladder Flashcards
What do the acinar cells of the pancreas do?
synthesize and secrete hydrolases for digestion
What do the duct cells of the pancreas do?
secrete bicarbonate and water
How does the pancreas make the small intestine neutral pH?
Neutralizes gastric H+ by secreting HCO3-
Why Doesn’t the Pancreas Digest Itself?
- Proteolytic enzymes synthesized, stored and secreted as inactive precursors.
- Activated in intestinal lumen
What are the proteolytic enzymes of the pancreas?
enterokinase
trypsin
What are the two stimuli for acini cells in the pancreas?
CCK
ACh/GRP (vasovagal reflux
What does CCK stimulate?
- gallbladder contraction
- sphincter of oddi relaxation
- acinar secretion
- reduced stomach emptying
- reduced HCl secretion
What two substances cause the secreting of CCK through the I cell?
CCK-RP
monitor peptide
What is the main funtion of trypsin?
- breakdown proteins
- if most proteins are broken down then it activates CCK-RP and monitor peptide (causes increased CCK)
What causes an increase in CCK-RP which in turn increases CCK?
fatty acids and peptides in the intestinal lumen
What are the two stimuli for the ductal cells in the pancreas?
secretin
ACh
What do secretin and ACh stimulate the ductal cells to do?
release bicarbonate and neutralize the pH of the small intestine
What is the function of secretin?
➢ cAMP
➢ Phosphorylation of CFTR
➢ increased Cl- conductance
➢ increased HCO3- secretion
Secretin released when pH < ___
4.5
What is secreted more in the presence of HCl: secretin or CCK?
secretin (ductal cells)
What is secreted more in the presence of soap/fats: secretin or CCK?
about equal
What is secreted more in the presence of peptone: secretin or CCK?
CCK (acinar cells)
What mediates the cephalic and gastric phases of pancreatic secretion?
Both phases mediated by vagovagal reflex - low volume, high enzyme secretion (Ach/GRP)
What happens during the intestinal phase of pancreatic secretion?
- acid causes the release of secretin which causes increased HCO3- and H2O
- fats/proteins indirectly cause in increase in CCK through CCK-RP and monitor peptides which then releases enzymes
If the pancreatic secretion rate is low what happens to bicarb and Cl?
− bicarbonate concentration is low
− chloride concentration is high
If the pancreatic secretion rate is high what happens to bicarb and Cl?
− bicarbonate concentration is high
− chloride concentration is low
Pancreatic juice is hypertonic, hypotonic, or isotonic?
isotonic
What does cystic fibrosis do to pancreatic function?
➢ Abnormal sweat composition.
➢ Decreased pulmonary and pancreatic secretion.
➢ Mendelian autosomal recessive
➢ Defective CFTR:
– Sweat Cl- reabsorption
– Pancreatic duct cell function
– Pulmonary mucus clearance
What is pancreatitis?
– Acute and chronic
– Trypsin activation causes pain, inflammation
– Chronic disease destroys acini
– Consequences reflect decreased digestive enzyme production
What can happen without pancreatic enzymes?
− 60% fat not absorbed (steatorrhea)
− 30-40% protein and carbs not absorbed
What is the function of the liver?
➢Cleansing and storage of blood
➢Metabolism of nutrients
➢Synthesis of proteins
➢Metabolism of hormones
➢Storage of energy, vitamins, iron
➢Excretion of lipid-soluble waste products
➢Marked capacity for cellular regeneration
➢Secretion of bile
Cirrhosis increases resistance and produces ____________
portal hypertension
Increased vascular resistance in the liver can cause _______
ascites
What is the role of bile salts (acids)?
- Bile salts (acids) and lecithin required for emulsification and absorption (micelles) of dietary fat.
- Excretion of lipophilic metabolites (bilirubin), excess cholesterol, other waste products, drugs, and toxins
What secretes bile salts,cholesterol,
lecithin, bilirubin, many other lipophilic substances?
hepatocytes
Duct epithelial cells modify primary secretion from pancreas and add…
HCO3-
Where can bile be transported after being secreted from the liver?
- Small intestine for fat digestion
- Gall Bladder for storage
Electrolytes and water reabsorbed or secreted from bile while in Gall Bladder?
reabsorbed
If someone has a cholecystectomy can they still digest fat?
YES
➢ No problems with fat digestion
➢ Bile flow directly into duodenum
What hormone stimulates liver ductal secretion via the blood stream?
secretin
What causes weak contraction of the gallbladder?
vagal stimulation
What causes gallbladder contraction and relaxation of the sphincter of oddi?
CCK
What is the enterohepatic circulation of bile salts?
➢Substance secreted into bile by hepatocytes.
➢ Delivered to lumen of ileum, then reabsorbed.
➢ Transported to hepatocytes via sinusoids
➢ 94% of bile salts recirculated
➢ Bile salts circulate 17x before lost in feces.
What transporter allows for active absorption of bile salts?
Apical sodium-dependent bile salt transporter (ASBT)
What are bile acid reabsorption inhibitors (BARI)?
➢ Drugs that inhibit Bile Recycling
➢ Used to lower LDL levels in blood
What are the different types of bile acid reabsorption inhibitors (BARI)?
- bile acid sequestrants (bined to bile salts in lumen and block transport)
- ASBT inhibitors (new drug that reduces cholesterol levels in ECF)
What is low Apical sodium-dependent bile salt transporter (ASBT) activity associated with?
➢Crohn’s disease
➢Congenital 1° bile acid malabsorption
➢Idiopathic chronic diarrhea
➢Irritable Bowel Syndrome
