Digestive system-4 Flashcards
What are the 3 accessory organs responsible for chemical digestion?
▪ Liver
-digestive function is production of bile (fat emulsifier)
▪ Gallbladder
-chief function is storage of bile
▪ Pancreas
-supplies most of enzymes needed to digest chyme, as well as bicarbonate to neutralize
stomach acid
How much does the liver weigh? what are the four primary lobes? what is the falciform ligament and what does it do? what is the round ligament? what does the lesser omentum do?
▪ Largest gland in body; ~3 lbs
▪ Consists of four primary lobes:
anterior view: larger right & smaller left, caudate & quadrate
Falciform ligament
▪ Separates larger right and smaller left lobes
▪ Suspends liver from diaphragm and anterior abdominal wall
Round ligament (ligamentum teres) o Remnant of fetal umbilical vein along free edge of falciform ligament
Lesser omentum anchors liver to stomach
What are the 3 bile ducts of the liver?
▪ Common hepatic duct leaves liver
▪ Cystic duct connects to gallbladder
▪ Bile duct formed by union of common hepatic and cystic ducts
What are liver lobules? What 3 things do all portal triad contain? what are liver sinusoids?
Liver lobules
▪ Hexagonal structural and functional units
▪ plates of hepatocytes (liver cells) that filter and process nutrient-rich blood
▪ Central vein located in longitudinal axis
Portal triad (see next slide) in each corner of lobule contains:
▪ Branch of hepatic artery, which supplies O2
▪ Branch of hepatic portal vein, which brings nutrient-rich blood from intestine
▪ Bile duct, which receives bile from bile canaliculi
Liver sinusoids
▪ leaky capillaries between hepatic plates
how much bile do hepatocytes produce per day, in mL? what are 6 key functions of hepatocytes? what is the liver’s job in digestion?
▪ Produce ~900 ml bile per day
▪ Process bloodborne nutrients – Example: store glucose as glycogen and make plasma proteins ▪ Synthesis of: - most of the clotting factors - lipoproteins ▪ Store fat-soluble vitamins ▪ Perform detoxification – Example: converting ammonia to urea ▪ Excretion of bilirubin to the bile ▪ Phagocytosis (Stellate macrophages cell) of: - old RBC, leukocytes and some bacteria
The only digestive function of the liver is the production of bile
What are the 2 things that bile contains? What is the 4 step recycling process of bile? how much bile gets recycled?
▪ Bile salts: cholesterol derivatives that function in fat emulsification & absorption
▪ Bilirubin: from heme of hemoglobin
o Bacteria break down in intestine to stercobilin that gives brown color of feces
→ released into duodenum
→ reabsorbed into blood at the ileum
→ returned to the liver by hepatic portal blood
→ secreted from the liver in newly formed bile
▪ About 95% of secreted bile salts recycled, so only 5% is newly synthesized each time
What are 3 examples of homeostatic imbalances in the liver?
1.Hepatitis
▪ Usually viral infection, drug toxicity, wild mushroom poisoning
2.Non-alcoholic fatty liver disease (NAFL)
▪ Most common liver disease in NA
▪ Affects 30% of general population & 70% of obese
3.Cirrhosis
▪ Progressive, chronic inflammation from chronic hepatitis or alcoholism
▪ Liver → fatty, fibrous → portal hypertension
– Liver transplants successful, but livers are scarce
– Liver can regenerate to its full size in 6–12 months after 80% removal
What are 3 key characteristics of the gall bladder? How does it perform muscular contraction?
- Thin-walled muscular sac on the ventral surface of the liver
- Stores and concentrates bile by absorbing its water and ions
- Contains many honeycomb folds that allow it to expand as it fills
• Muscular contraction → releases bile via the cystic duct, which flows into the common bile duct
What causes gallstones? what is the main symptom of obstructive jaundice? What are the 4 ways that gallstones are treated?
Gallstones (biliary calculi): caused by too much cholesterol or too few bile salts
▪ Obstructive jaundice: blockage can cause bile salts and pigments to build up in blood, resulting in jaundiced (yellow) skin
– Gallstone treatment: crystal-dissolving drugs, ultrasound vibrations (lithotripsy), laser vaporization, or surgery
Where is the pancreas located? What is it’s exocrine function? What is it’s endocrine function?
▪ Location: mostly retroperitoneal, deep to greater curvature of stomach; head encircled by duodenum; tail abuts spleen
▪ Exocrine function: produce pancreatic juice
– Acini: clusters of secretory cells that produce zymogen granules containing proenzymes
– Ducts: secrete to duodenum via main pancreatic duct; smaller duct cells produce water and bicarbonate
▪ Endocrine function: secretion of insulin and glucagon by pancreatic islet cells
Where do the bile duct and pancreatic duct unite? Where does it open up into? What does it control? What is the accessory pancreatic duct?
hepatopancreatic ampulla
Hepatopancreatic ampulla open into duodenum via major duodenal papilla
Hepatopancreatic sphincter controls entry of bile & pancreatic juice into duodenum
a smaller duct that empties directly into duodenum
What are the 4 main digestive enzymes produced by the pancreas and what do they break down?
▪ Proteases (for proteins)
▪ Amylase (for carbohydrates)
▪ Lipases (for lipids)
▪ Nucleases (for nucleic acids)
What are the 2 hormonal controls for bile and pancreatic juices? What are 2 things that increase bile secretion?
- Cholecystokinin (CCK)
- Secretin
- large amounts of bile salts in enterohepatic circulation
- Secretin (from intestinal cells exposed to HCl and fatty chime) → gallbladder to release bile
What is the release of CCK and secretin stimulated by?
▪ CCK release stimulated by proteins & fat in chyme
▪ Secretin release stimulated by the acidic chyme
What are 2 things that cause the gallbladder to contract?
▪ CCK causes the GB to contract
▪ Vagus nerve→ weak GB contraction during cephalic & gastric phase
