Flashcards in Unit 6 - Liver and Gallbladder Deck (25)
what is liver enclosed in?
Glisson's capsule (fibrous connective tissue)
how is liver used for storage?
vitamins ADK and Fe
how does liver have endocrine-like functions?
liver modifies action of hormones released by other organs, including vit D and thyroxine conversion, and production of GHRF (growth hormone releasing factor)
what is the dual blood supply of liver?
75% from hepatic portal vein (depleted of O2, but rich in nutrients, toxins, and hormones)
25% from hepatic artery (carries O2ated blood)
blood mixed before entering hepatic sinusoids
what are the components of the portal triad?
all present in CT of Glisson's capsule in portal canal with lymphatic vessels and nerves
what is the central vein?
terminal hepatic venule
-sinusoids are radially arranged around it
-CV gets larger as it progresses along lobule, and empties into sublobule veins, which form hepatic veins to IVC
do the sublobular, hepatic, portal, and central veins travel together?
no, they travel separately so the portal veins are distinguished as part of portal triad
blood from where is in contact with hepatocytes?
blood from hepatic sinusoids
what are the 4 structural components of the liver?
1. parenchyma - one cell thick plates of hepatocytes separated by sinusoidal capillaries
2. CT stroma - continuous with Glisson's capsule and branches into smallest portal canals
3. Sinusoidal capillaries (sinusoids) - separate plates of hepatocytes
4. Perisinusoidal spaces (spaces of Disse) - lie between sinusoidal endothelium and hepatocytes
what is the "classic liver lobule"? how is it visualized?
hexagonal cylinder of tissue of 0.7 x 2 mm
-central vein is at center of lobule
-visualized by connecting portal canals around a central vein
what is the portal lobule?
emphasizes exocrine functions of liver
-major for bile secretion, so portal lobule has portal canal at center
-drains bile from hepatocytes into bile duct
-triangle is formed by connecting lines between 3 closest central veins
what is the liver acinus? what does it do? what are its zones?
lozenge/football shape whose long axis is a line drawn between 2 central veins, and short axis between adjacent portal canals between central veins
-blood perfusion, metabolic activity, and liver pathology
-zone I: hepatocytes that are the first to get O2, nutrients, and toxins from sinusoidal blood
--die last when circulation is impaired, first to regenerate
-zone II: intermediate
zone III: first to show ischemic necrosis, and first to show fat accumulation
what are hepatic sinusoids?
discontinuous sinusoidal capillaries with large fenestrae and gaps between neighboring cells
-part of wall is filled by Kupffer cells that extend into lumen
what are Kupffer cells? where are they?
members of mononuclear phagocytic system that destroy aged RBC with spleen, digest Hb, and destroy bacteria
-make up 15% of liver cell population in hepatic sinusoids
what is the perisinusoidal space (of Disse)?
site of exchange of materials between blood and liver cells
-hepatocytes have many microvilli that project into space and increase SA up to 6x
-Ito (hepatic stellate) cells in space store vit A
what happens to Ito cells if there's chronic inflammation or cirrhosis?
Ito cells lost storage ability of vit A, and transform into myofibroblasts that make collagen for liver fibrosis
what percentage of the liver is hepatocytes? how are its nuclei?
-large, spherical, central nuclei with prominent nucleoli
--have binucleate and polyploid nuclei, mostly tetraploid in adult liver
have long life span of 5 months
-after injury, disease, or surgery, some can be replaced by regeneration
-aging reduces this capacity
what are cytoplasmic components of the hepatocyte?
reflect diversity of cell's functions
-Golgi is elaborate, and each cell may have up to 50 units
-both RER and SER are highly developed
how can SER vary with metabolic activity?
-ethanol - hypertrophy
-neonatal hyperbilirubinemia - underdeveloped
--treat with blue fluorescent light
how does bile flow? what do its pathways contain?
outward from center of classic liver lobule
-bile canaliculi are 0.5 microns in diameter, and formed by adjacent hepatocytes, isolated by tight junctions
--small microvilli rich in ATPase and other alkaline phosphatases project into lumen
-BC empty into intrahepatic ductules (canals of Hering) w/in lobule close to portal canal
-ID join with interlobular bile ducts of portal triad
how much liver bile is secreted and its makeup, and how much is recycled
1 L of bile/day
-water, phospholipids, cholesterol, bile salts/pigments, electrolytes
-90% of bile salts are recycled by gut reabosorbtion, portal vein transport, and hepatocyte resecretion
--cholesterol, lecithin, electrolytes, and water also recycled
what is bilirubin glucuronide?
bile pigment from Hb breakdown
-excreted with feces to provide color
-not broken down if neonatal hyperbilirubinemia (underdeveloped SER)
mucosa of gallbladder
made of simple columnar epithelial cells with apical microvilli, complex lateral placations, and concentrations of mitochondria
-lamina propria, but no muscularis mucosa
-if empty, has rugae (flatten out when full)
-invaginations of mucosa form diverticula that extend into muscularis, and increase with age