Pancreas And Liver Flashcards
How does the chyme become isotonic?
Hypotonic as enters duodenum as stomach is impermeable to water.
But, duodenum is permeable to water so it draws water in so is isotonic as leaves duodenum.
What does secretin do?
Acts on pancreas to stimulate an aqueous bicarbonate (HCO3-) component of the pancreatic secretion
What does CCK do?
Acts on pancreas to stimulate release of enzymatic component of pancreatic secretions to help digest proteins and fats.
CCK also acts on gallbladder (contracts) and relaxes sphincter of oddi.
What stimulates the release of CCK and secretin?
Chyme
What does CCK stimulate the release of?
CCK and vagus stimulate acini to produce enzymes.
-Amylases and lipases (active)
-Proteases (inactive) - so not digest pancreas —Trypsin —Chymotrypsin —Elastase —Carboxypeptidase
What are zymogen granules?
Granules that store the concentrated protease enzymes (inactive) that are produced within acinar cells.
The zymogen granules contain zymogen (inactive proteases) which is converted to active proteases in intestinal lumen.
What do duct cells of the pancreas release?
Aqueous component (isotonic) Bicarbonate
They act to neutralise the acidic chyme
What does the liver secrete in response to chyme?
Bile (stored in gall bladder) into duodenum.
What does bile consist of?
Bile acids and bile pigments
Alkaline solutions
What does bile do?
Emulsifying fats (lipids) in duodenum so they can be readily digested by lipases secreted by pancreas
Where does all blood from the gut go?
Into the liver via the portal vein
What are the lobes of the liver?
Left
Right (bigger)
Caudate
Quadrate
What is the micronatomy of the liver?
Lobules - Hexagonal arrangement of hepatocytes, bile ducts and blood vessels.
Sheets of hepatocytes arranged towards a central hepatic venule.
Describe the structure of a liver lobule
Hexagonal arrangement
Triad of structures at each corner
- Portal vein
- Hepatic artery
- Bile duct
Central vein in the middle.
Blood enters a lobule via hepatic artery and portal vein.
What flows in apposing directions of the liver lobule?
Blood flows in towards the central vein via sinusoids -(Portal vein and hepatic artery)
Bile flows out -along canaliculi, then into the bile duct and into the duodenum.
What is the functional area of a lobule called?
Acinus
Describe anatomy of acinus
Can be divided into three zones.
1 is closer to middle (to the arterial supply) and 3 on outside.
So, if problem with oxygenation, zone 3 more likely to get ischaemic first whereas if something toxic, zone 1 will be affected first.
What stimulates contraction of gallbladder?
CCK
What is bile mostly made from?
Bile salts
Bile is created by hepatocytes duct cells in the liver.
What are bile salts?
Bile salts are conjugated bile acids. (Conjugated to amino acids)
This is good as bile salts are more soluble at duodenal pH than bile acids.
Bile salts = amphipathic
What do bile salts do?
Lipids form large globules by the time they have reached the duodenum.
Bile salts then emulsify fat into smaller units. -Disperse droplets increasing surface area, allowing for lipases to act.
Bile salts then create micelles with products of lipid breakdown
Micelles act as a ‘vehicle’ for transporting hydrophobic molecule (products of lipid digestion) towards enterocytes.
Where and how do lipids move?
Micelle transports digested lipids to luminal membrane of enterocytes.
Lipids diffuse into intestinal epithelial cell (cytosol of enterocyte) but bile salts do not.
How do bile slats get recycled?
Bile salts remain in the gut (do not enter enterocyte)
But, are reabsorbed in the terminal ileum.
They are then returned to the liver in port blood.
The liver recycles the bile salts they do not have to re-synthesise large volumes.
What are chylomicrons and what do they do?
Chylomicrons are formed in enterocytes to carry digested fats into lymphatic system to then reach blood circulation.
Inside enterocyte, lipid molecules are built back up again to triglycerides, phospholipids and cholesterol.
Packed with apoproteins within enterocytes (chylomicrons)
Chylomicrons are then exocytosed from the basolateral membrane of the enterocyte as they are too large to enter capillaries. This means then enter the lymphatic capillaries into the thoracic duct.
