Digestive System Lecture #2 W25 PDF

Accessory Digestive Organs, Ruminant Digestion and Hindgut Fermentation Accessory Digestive Organs Liver Pancreas Salivary glands discussed last week Canine liver and pancreas each communicate With the duodenum Functions of the Liver produ...

Accessory Digestive Organs, Ruminant Digestion and Hindgut Fermentation Accessory Digestive Organs Liver Pancreas Salivary glands discussed last week Canine liver and pancreas each communicate With the duodenum Functions of the Liver produces bile (for fat digestion) removes toxins biochemically that come in through GIT has macrophages (Kupffer cells) that scan for and remove foreign germs coming from the GIT stores, metabolizes and releases nutrients when needed  Hepatic circulation About 75% of the blood entering Blood flow the liver is venous blood from the portal vein All venous blood from the small intestine, stomach, pancreas and spleen enters the portal vein The other 25% of blood is arterial blood (hepatic artery) Bile flow Thus, the liver gets "first choice" of everything absorbed in the small intestine Hepatic lobule - organization How is the liver organized? Where is bile made? liver histology, bile formation and t nsportation Hepatic histology – CV = central vein, PC = portal canal (triad), arrows indicate borders of one hepatic lobule What is bile? Bile salts Phospholipids Cholesterol Bile pigments P.S. Horses have no gall bladder and cow livers are all on the right side and have no lobes Canine in dorsal recumbency – looking at the caudal surface of the liver (don’t memorize the lobes ) What does bile do? (see biochem sheet) What is bile? How does the bile get to the duodenum lumen? Canine arrangement Feline arrangement – common bile duct How does the bile get to the duodenum lumen? Connections from pancreas to duodenum – in the cat there is no direct duct from the pancreas to the duodenum – the duct merges with the bile duct, then enters the duodenum. Clinical Applications (aka why do we need to know this???) Recall other hormones involved in digestion Gastrin from the G cells in the pylorus Secretin and CCK from the duodenum (see stomach and duodenum notes from lecture #1) Where does bile go from here? After the lipids are digested and absorbed (more about that in a sec) the bile acids travel along GIT and are re-absorbed 5% in the ileum Go to liver via hepatic portal vein and are recycled by the liver ENTEROHEPATIC CIRCULATION Hepatic Portal Vein – it’s important – first pass effect Liver sits between Canine digestive heart and GIT for a system showing venous reason drainage into portal vein Processes blood leaving GIT before it goes into general circulation  Hepatic Portal Vein Portal vein  percolates through the liver  down through central vein  joins caudal vena cava eventually Portosystemic shunts(PSS) – blood shunted from portal vein to systemic circulation Accessory Digestive Organs: Pancreas Double function as exocrine organ and endocrine organ Exocrine for digestion (the darker pink areas) Acinar cells’ contents go to duodenum Pancreatic secretions (exocrine) Stimulated by duodenum’s release of CCK, secretin and by vagal release of Ach, also by stomach stretching and anticipation of food Sends bicarbonate and enzymes to duodenum Which enzyme s? From where? Exocrine Pancreatic Insufficiency (EPI) What happens to the nutrients after they are broken down? Jejunum – villi plus layers - fats absorbed into lacteal (lymphatic vessel in villus) - sugars and amino acids/small peptides absorbed into capillaries Questions about digestion in monogastric animals?