Lecture 15 Flashcards
Accessory organs to GI tract?
Pancreas, liver, gallbladder
Function of pancreas?
Exocrine (99%): secretes enzymes into duodenum to break down food
Endocrine (1%): releases hormones (insulin/glucagon/somatostatin) into bloodstream affecting carb metabolism
Role of acinar cells?
Secrete enzymes/fluid into duct system of pancreas
Structure of duct system?
Pancreatic duct fuses with bile duct on entry to duodenum
Pancreatic juice (aqueous component)?
200-800ml secreted each day, rich in bicarbonate (pH~8) -> helps to neutralise acidic chyme as it enters duodenum, secretion stimulated by secretin
Pancreatic juice (enzymatic component)?
Proteolytic enzymes, pancreatic amylase, lipolytic enzymes
Proteolytic enzymes?
Split peptides, secreted in inactive form (activated by enterokinase) e.g. trypsin
Pancreatic amylase?
breaks down starch, secreted in active form
Lipolytic enzymes?
Lipase secreted in active form (activated by trypsin in duodenum) e.g. colipase/cholesterol esterase
Control of pancreatic secretions?
Cephalic phase: nervous reflex
Gastric phase: gastrin released in response to stomach digestion
Intestinal phase: secretin and Cholecystokinin released by mucosa in response to chyme in duodenum
Pancreatitis?
Pancreatic enzymes activated withing pancreases (organ attacks itself)
Causes of pancreatitis?
Gallstones, alcohol abuse, unknown cause (idiopathic)
Treatment for pancreatitis?
Pain management, electrolyte therapy (nutrients/salts balanced)
Some functions of liver (has many)?
Process digested food from intestine, manufacture bile, convert excess monosaccharides to glycogen, stores iron/vitamins, metabolise drugs/break down poisons
Kupffer cells?
Phagocytic cell - eat/surround toxic substance
Structure of liver?
Hepatic (liver) cells around central vein, hepatocytes make up functional units lobules, lobules form two main lobes of liver
Role of hepatic cells?
Extract oxygen/most nutrients, detoxify/store poisons + drugs, secrete products into hepatic vein (except bile)
Hepatic blood supply?
Receives double blood supply (oxygenated from hepatic artery, deoxygenated (nutrient rich) from portal vein)
Bile?
Excretory product of liver metabolism/digestive secretion
Where can bile go?
Go straight to duodenum or stored in gallbladder - determined by presence of fat
Bile salts?
Emulsify fat into small droplets (as fat is in aqueous environment)
Bile cholesterol?
Made soluble by salts
Bile pigments (bilirubin)?
Are yellow/brown - gives urine/faeces their colour, absorbed from blood
Where are bile salts, cholesterol, pigments secreted from?
Liver cells - hepatocytes
What is secreted from epithelial cells lining bile ducts?
Bicarbonate ions - neutralise acidic chyme
Circulation of bile salts?
Travel down bile duct: if stomach empty then stored, if fat in duodenum then used to emulsify in digestion (then reabsorbed/recirculated)
Function of gallbladder?
Stores/concentrates bile by extracting water/ions - can lead to increased insoluble cholesterol levels (gallstones)
Entry of bile into gallbladder?
Enters by cystic duct when small intestine is empty
Ejection of bile from gallbaldder to duodenum?
Occurs when protein/fat-rich chyme enters duodenum (causes CCK release)
Role of CCK (cholecystokinin) in gallbladder?
Causes it to contract + sphincter of Oddi to relax allowing bile to enter duodenum
Gallstones?
Crystalline deposits, accumulate when too much cholesterol + not enough bile salts
Treatment for gallstones?
Small: can be dissolved
Severe: gallbladder can be removed (cholecystectomy)
Why jaundice symptom of gallstones?
Stones block common bile duct so increased bilirubin (pigment) in blood plasma
