Pancreas And Liver Flashcards
What is the substance that leaves the stomach into the duodenum?
Chyme
What are some key properties of chyme?
Hypertonic
Acidic
Is partially digested food
Why does chyme need to be modified before it can be effectively processed by the small intestine?
Its hypertonic
Its acidic
What is meant by the chyme is hypertonic?
It has a higher solute concentration than the plasma
What makes the chyme hypertonic compared to the plasma?
The breakdown of food particles increases the number of solutes increasing the number of osmotically active paraticles
How does the body modify chyme to counteract its hypertonicity in the duodenum?
Water gets moved into the chyme from the surrounding circulation to dilute the chyme
How does the body deal with the acidic nature of chyme in the duodenum?
Pancreas releases Bicarbonate ions into the duodenum to increase the pH
Liver also makes bicarb from bile
Where is the pancreas located?
Head is nestled in C shape of duodenum
How does the body help deal with chyme being partially digested?
Produces pancreatic enzymes (exocrine)
What is the basic structure of the pancreas where the enzymes are made?
Acinus makes enzymes
Centroacinar cells makes aqueous component
Duct modifies aqueous secretion
What stimulates pancreatic secretions?
Parasympathetic
Sympathetics inhibit
What enzymes does the pancreas make?
Active:
Amylase + lipase
Inactive:
Trypsinogen
Chymotrypsinogen
Proelastase
Procarboxypeptidase A
Procarboxypeptidase B
What form are protease enzymes like trypsin produced in and way?
Inactive to prevent self digestion
What is the process of producing a pancreatic secretion?
Acinus producing enzyme:
-formed on RER
-moved to Golgi
-concentrated n zymogen granules if inactive
-then released with appropriate stimulus like CCK needs parasympathetic stimulus
What is a zymogen granule?
A membrane bound granule contains an inactive precursor enzyme called zymogen
What does pancreatic enzymes in the blood signify?
Pancreatic damage
What enzyme stimulates the pancreas to secrete bicarbonate ions?
Secretin
What cells produce secretin and when do they produce secretin?
S cells when the duodenal pH is low
What enzyme stimulates the pancreas to release digestive enzymes?
Cholecystokinin
What cell stimulates the release of cholecystokinin?
I cells in duodenum
What are the general functions of the liver?
Energy metabolism
Detoxification (everything absorbed by the gut drains to the liver)
Plasma protein production
What alkaline/bicarbonate rich secretion is produced but the liver?
Bile acids
It excretes bile pigments
What are the main functional cells of the liver?
Hepatocytes
What vessels are located in the portal triads of the liver?
Bile duct
Hepatic artery
Portal vein
What is the blood vessel in the middle of each liver lobule?
Central vein
What 2 blood vessels join together running through the sinusoids to the central vein of the liver lobules?
Hepatic artery and portal vein
What cells form bile in the liver?
Hepatocytes into the bile canaliculi
How are the hepatocytes adapted to being highly metabolically active?
Lots of smooth and rough ER
Stacks of Golgi
Lots of glycogen
What vessel takes most of the blood to the liver where does it get this from?
Portal vein
Drains all the blood from the GI system so it can be detoxified
What blood vessels do the central veins of the liver lobules become?
Merge to hepatic veins which drain to the inferior vena cava
What is the functional unit of the liver called?
Acinus
What is a liver acinus?
Adjoining liver lobules, area between the 2 central veins and the 2 portal triads between them
What are the zones/how are the zones arranged in a liver acinus?
1 = furthest from central vein closest to triads
3 = closest to central vein
What zone would be affected most by toxins flowing into the liver?
What zone would be most affected by ischaemic damage?
Toxins in = zone 1 since its closest to the portal triads where the toxins would flow into the lobule
Ischaemic damage = zone 3 since its furthest away from the inflow fo oxygenated blood which is from the hepatic artery in the triads (portal vein blood not completely deoxygenated tho)
What part of the duodenum does bile produced in the liver drain to after being stored in the gall bladder?
D2
What forms the common bile duct which drains into the duodenum (D2)?
Bile canaliculi join to form bile ducts which join to form the common bile duct
What are the 2 components of bile?
Bile acids and bile pigments (bile acid dependant)
Alkaline solution (bicarbonate and cholesterol) which is bile acid independant
What hormone stimulates the production of the alkaline (bicarbonate) component of bile?
Secretin
What cells produce the alkaline component of bile?
Duct cells
What are bile salts?
Bile acids that have been conjugated with an amino acid
What are the 2 main bile acids?
Cholic acid
Chenodeoxycholic acid
What is the point of bile salts when we have bile acids?
Bile salts are normally soluble at duodenal pHs whereas bile acids aren’t always
Bile salts = amphipathic structure
What is the significance of bile being amphipathic?
Can at the water/oil interface o can emulsify fats since it has a hydrophilic water soluble end and a hydrophobic lipid soluble end
What is the function of bile salts emulsifying fats?
Increases surface area for enzyme digestion
What is the structured called which forms when bile salts emulsify fats and transport them?
Micelles
What is a Micelle?
When a bile acid forms a sphere transporting hydrophobic lipid molecules through an aqueous medium
Where do micelles transport the breakdown products of fat to?
Brush border of enterocyte s
What happens when the Micelle reaches the brush border of enterocyte?
Lipids diffuse into cell down conc gradient
Re esterification of lipids to:
-triglycerides
-cholesterol
-phospholipids
What happens to the resterified lipids in the enterocytes?
Get packed with apoproteins forming Chylomicrons
What happens to the Chylomicrons once they’ve been exocytosed from the enterocyte?
Enter lymphcapillaries travelling to lymphatic system
Renter vascular system reaching the blood stream via the thoracic duct which drains to left subclavian or left internal jugular vein
What happens to bile salts in the body after they’ve done their function?
Remain in gut lumen
Most reabsorbed in terminal ileum so get returned to liver via portal vein so get reused
How can a high fibre diet reduce cholesterol levels?
Cholesterol is a component of bile salts
High fibre diet removes bile salts from body reducing cholesterol
What organ stores bile?
Gall bladder
How does the gall bladder maximise the amount of bile it can store?
Concentrates the bile removing water and ions
Can then be reconcentraed when it needs to released into duodenum
How do gallstones form?
When the bile in gallbladder is concentrated too much
What hormone stimulates the gall bladder to contract to squeeze out bile and relax the sphincter of Oddi?
Cholecystokinin
What is Steatorrhoea?
When fat appears in the faeces
What is Steatorrhoea?
When fat appears in the faeces
What causes steatorrhoea?
When bile acids/salts or pancreatic lipases are not secreted in adequate amounts leadinign to malabsorption of lipids
How does steatorrhoea present?
Fat in faeces:
-pale
-floating
-foul smelling
What is bilirubin?
Breakdown product of Haemoglobin
How is bilirubin excreted from the body?
Conjugated in liver (makes water soluble)
Secreted into bile
Excreted in faces making it brown
what happens if bilirubin accumulates in blood if it cant be excreted?
Jaundice
