Lecture 16 - Liver, Gallbladder, Pancreas Flashcards
Direction of blood in liver
portal vein (70%) and hepatic artery (30%) in portal triad enter into sinusoid and mix. Go to the cetnral vein which exits to hepatic vein and inferior vena cava
Bile and lymph direction in liver
bile ducts and lymphatic vessels flow from central vein towards portal triad
components of portal triad
lymphatic vessel, portal vein (largest in size with no tunica media), bile duct (simple cuboidal), and hepatic arteriole (one or two layers of smooth muscle)
Bile canaliculus
where the bile flows from the central vein to the portal triad. Has no structure of its own, its lumen is a sealed off space between two hepatocytes joined by a zonula occludens (tight junction)
Space of disse
adjacent to hepatocytes and the fenestrated endothelium of the sinusoid.
Kupffer cells
derived from monocytes, have phagocytic properties for foreign materials and old RBCs. take up indian ink during staining. Found in the sinusoid.
ITO cells
(hepatic stellate cells or lipocytes) found in the space of disse and sometimes the sinusoid.
ITO cells and cirrhois
under diseased state, will secrete lots of type I collagen leading to excess CT.
Main cell type found in liver cells
hepatocytes (which can be binucleated). will have lots of RER and mitochondria since making proteins.
Apical side and lateral side of hepatocyte
sinusoid face - microvilli into the space of disse.
lateral face - forms tight junctions with adjacent cells to form bile canaliculi.
4 main functions of hepatocytes
synthesis of plasma proteins (albumin, fibrinogen); storage glycogen; converts amino acids into glucose (gluconeogenesis); detox and conjugation of ingested toxins (goes into bile)
Somatomedins (IGFs)
produced in liver stimulate bone and muscle growth. Stimulate chondroblasts and chondrocytes
Extra-medullary hematopoiesis in the liver
cells with intensely basophilic nuclei (erythroid)
Jaundice
accumulation of bilirubin causing yellowing of skin and eyes. sign of a young or diseased liver.
Bilirubin formation in liver
Hemoglobin is stripped of the heme molecule. Heme is eventually catabolized by heme oxygenase to biliverdin, which is further catabolized by biliverdin reductase to bilirubin.
Bilirubin excretion in liver
glucuronyltransferase conjugates bilirubin with glucuronic acid to make bilirubin glucuronide (water soluble) and excreted into the bile canaliculus.
Gilbert’s syndrome in liver
reduced activity of glucuronyltransferase. Leads to slightly elevated levels of bilirubin.
Crigler-Najjar syndrome in liver
severe deficiency of glucuronidation of bilirubin. Thus lots of bilirubin remains.
Dubin Johnson and Rotor’s syndrome in liver
defect in the ability of hepatocytes to secrete conjugated bilirubin into the bile. Elevated level in blood serum.
Bile acid synthesis of hepatocytes
10% is new, 90% recycled. Cholic acid aids in digestion and excretion and thus are secreted into the bile canaliculus.
Portal/hepatic acinus
zone I is most oxygenated and zone III (closest to the central vein) is least oxygenated
Pit cells
Natural killer cells found in the sinusoid of the liver.
Spinchter of oddi
regulates how much is secreted from the gallbladder, liver, and pancreas into the duodenum.
Common hepatic duct
carries bile from liver to meet up with cystic duct of gallbladder
Cystic duct
from gallbladder and is coiled so it will never be shut close
What type of cells line bile ducts?
(hering’s canals) simple cuboidal cholangiocytes
Secretin in bile ducts
stimulates cholangiocytes to secrete water and bicarbonate into bile. (alkalizes the content of the lumen)
Gallbladder structure and function
epithelium in mucosal folds with lamina propria and smooth muscle underneath. Will store, concentrate (via water reabsorption), and release bile from the liver. No bile synthesis.
Function of bile
promotes reabsorption of fat and carries bilirubin to the duodenum.
type of cells that line the gallbladder
lined by simple columnar cells into folds.
Bile concentration
sodium and water will leave the lumen via a micele, sodium will leave through the basal membrane and water will follow. But the removal of water and sodium concentrates bile in the lumen.
Cholecystokinin (CCK) in gallbaldder
causes the smooth muscle cells in the gallbladder to contract, and relaxes the sphincter of oddi to relax allowing bile to enter the duodenum.
How is the bile returned to the liver?
reabsorbed in the ileum and returned via the portal venous system.
Type of gland in pancreas
compound serous acinar gland (90% - exocrine) and islets of langerhans (10% - endocrine)
Pancreas and liver development
from the primitive foregut
Islets of langerhans in pancreas
produce insulin. lighter staining than the serous acinar gland. endocrine function. contain the alpha, beta, delta, and PP cells
Centroacinar cells of the pancreas
cells at the end of the intercalated ducts.
Secretin in pancreas
coming from duodenum, centroacinar and intercalated duct cells secrete a bicarbonate rich fluid that hydrates, flushes, and alkalinizes the enzymatic secretion of acini.
CCK in pancreas
stimulates pancreatic acinar cells to produce digestive enzymes.
Prevention of autodigestion
enzyme secreted as zymogen (inactive proenzyme) and are membrane bound. Released into dudodenum and vesicles are ruptured, the inhibitors are diluted away, and enterokinase activates.
A cells in pancreas
secrete glucagon (increase blood glucose levels). dark circular appearance
B cells in the pancreas
secrete insulin (decreases blood glucose levels). Have a(n) elongated/striped appearance
Insulin formation in pancreas
made as a promolecule but then portion is cut off. Portions are then layered and held by disulfide bonds.
D cells in the pancreas
secrete somatostatin which inhibits other islet cells. Feedback to inhibit growth hormone in the pituitary-hypothalamus axis.
PP cells in the pancreas
secrete pancreatic polypeptide which may inhibit the exocrine pancreas (but not completely understood)
Are glycogen granules bound or not bound in hepatocytes?
not bound
