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33 Cards in this Set
- Front
- Back
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Describe location/structure of liver
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located immediately inferior to diaphram
largest gland & internal organ of the body 4 lobed structure thin capsule of dense irregular ct (Glisson's capsule) covers surface most of Glisson's capsule covered by simple squamous epithelium (peritoneum) 80% made up of hepatocytes (polyhedral cells) |
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Obj.
Describe histological characteristics of hepatocytes |
-eosinophilic cytoplasm w/ large # of mitochondria
-basophilic RER |
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Obj.
Describe ultrastructural characteristics of hepatocytes |
-large glycogen deposits & lipid droplets
-smooth ER & golgi complexes prevalent -hundreds of scattered peroxisomes in cytoplasm *25% hepatocytes are binucleate |
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What are peroxisomes?
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membrane-limited vesicles, involved in the breakdown of hydrogen peroxide & alcohol metabolism
*converts 50% of consumed alcohol to acetylaldehyde |
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Obj.
Describe functional characteristics of hepatocytes |
-bile formation & secretion
-protein synthesis -storage of metabolites -storage of vitamins (D, B12) -urea synthesis (from ammonia) -detoxification/degradation of hormones, drugs, & toxins |
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What are the major components of bile?
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-water: solute
-bile salts (bile acids): emulsifying agent, digestion of lipids & absorption of LCFA in small intestine (90% of bile acids are recycled, 10% synthesized in SER) -bile pigments: formed from bilirubin |
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Describe formation of bilirubin
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-formed as a result of RBC destruction by Kupfer cell (liver) & spleen
-bilirubin carried to liver bound to albumin, where it is endocytosed by hepatocytes -bilirubin glucuronide (soluble) is formed & secreted into bile canaliculi =detoxification/elimination of bilirubin |
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Hepatocytes synthesize 90% of blood plasma proteins, including (5):
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albumin
coagulation factors (prothrombin, fibrinogen) complement reaction proteins lipoproteins (HDL, LDL) alpha & beta globulins |
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What metabolites are stored in the liver & how are they stored?
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glucose: stored as glycogen, responsible for maintainging normal blood glucose, can also make glucose via gluconeogenesis
lipids: degrades chylomicrons from intestine into FA & glycerol, uses these to make phospholipids & cholesterol or acetyl-CoA. Stores high energy acetyl-CoA as ketone bodies, which may be released to perisinuisoidal space as needed |
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What do microsomal mixed-function oxidases do?
Where are they present? |
inactivate antibiotics & barbituates (toxins & drugs) via methylation, conjugation, or oxidation
present in SER |
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Differentiate btwn lateral and sinusoidal domains of hepatocytes
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Lateral domains:
-4 sides of cube shaped (6 sided) hepatocyte -hepatocyte surfaces are adjacent to other hepatocytes -bile canaliculus btwn adjacent domains is site of bile secretion *1st portion of bile duct system -tight (occluding) jxns immediately lateral to canaliculus, prevent bile leakage -gap jxns along domains, coordinate activities of adjacent cells Sinuisoidal domains: -form 2 of 6 cube surfaces -hepatocyte surfaces adjacent to liver sinusoidal capillaries -surfaces have irregular microvili extending into perisinusoidal space (of Disse) btwn hepatocyte surface & outer surface of sinusoid epithelium -endocrine secretion & metabolite uptake occur at this domain -receptor-mediated endocytosis of hormones -Na+K+ATPase & adenyl cyclase concentrated at domain |
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Obj.
Describe blood flow into liver & vessels involved |
80% of blood enters liver from portal vein & is O2 poor, but nutrient-rich
20% of blood enter from hepatic artery & is O2 rich |
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Describe portal vein system
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*carries blood from abdominal viscera into liver
-portal vein enters inferior liver at hilus & branches, giving rise to veins of portal triad -portal triad veins, portal venule/interlobular vein give rise to distributing veins -distributing veins run in connective tissue along periphery of each classic lobule -small inlet venules carry blood from distributing veins into sinusoidal capillaries -capillaries drain into terminal hepatic venule (central vein) -terminal hepatic venule progresses down lobule, recieving more tributaries & growing in diameter -sublobar vein at base of lobule drains terminal hepatic venule & runs perpendicular to lobules -sublobar veins fuse to form hepatic veins -hepatic veins enter inferior vena cava |
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Describe hepatic artery system
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-hepatic artery enters at hilus of liver
-interlobular arteries/arterioles of portal triad arise from repeated branching of hepatic artery -majority of blood from arterioles flows into capillaries supplying liver's connective tissue stroma -some blood also flows into small inlet arterioles that empty into sinusoids -blood in sunusoid mixes w/ venous blood from portal vein |
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Obj.
Characteristics of liver sinusoids |
-have larger lumens than typical capillaries
-lined w/ discontinuous endothelium possessing large pores/fenestrae & large gaps btwn cells (basal lamina also discontinuous over gaps & pores) |
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What is the perisinuisoidal space (of Disse)?
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small space that serves as site from hepatocyte endocrine secretion
-separates sinusoidal endothelial cells from hepatocyte surface = intermediate compartment btwn bloodstream & hepaocyte |
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what is the function of large fenestrae & discontinuous endothelium?
function of large lumen? |
permit direct contact of most of blood contents w/ sinusoidal domain
results in low resistance, slow blood flow through sinusoids, allowing interaction btwn blood content & hepatocytes |
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Obj.
Describe bile flow in the liver & associated bile duct system |
Bile canaliculi: tubules that receives bile secreted from hepatocytes
Bile ductules (Hering's canals): formed near periphery by union of several canaliculi, ductless, w/i classic lobule Bile duct of portal triad: recieves bile from ductules as they pass out of classic lobule, increase in size to form larger ducts Hepatic duct: single, large duct formed outside liver by fusion of bile ducts *bile from hepatic duct will go to gallbladder |
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T/F
Blood & bile flow together in same direction through liver |
FALSE
blood & bile completely SEPARATE & flow OPPOSITE directions |
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Obj.
What are the 3 diff ways of characterizing liver substructure? |
1. classic liver lobule
- hepatocytes arranged in hexagonal masses -little connective tissue -reticular fibers form stroma -6 outside corners of hexagon are each a portal space w/ portal triad -sinusoids drain from perimeter to center (central vein/terminal hepatic venule) (spoke pattern) -venous/arteriole blood mix in sinusoid -bile drains toward periphery of lobule into bile ducts of portal triads 2. portal lobule -traingle of tissue in which bile drains from periphery to center = bile secreting exocrine gland -center contains bile duct of portal triad -outer boundary made by imaginary lines connecting 3 nearest central vein 3. liver acinus -smallest functional unit of liver, diamond-shaped -short axis of diamond follows border btwn 2 classic lobules, from one portal triad to next -long axis btwn two terminal hepatic venules of adjacent classic lobules -divided into 3 lobes based on patterns of hepatocyte degneration/regeneration following injury |
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What are the components of the portal triad?
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-venule (branch of portal vein)
-arteriole (branch of hepatic artery) -bile duct -lymphatic vessels |
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Differentiate btwn the 3 elliptical zones around the short axis of acinus
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zone 1:
-closest to axis -most oxygen rich -first exposure to nutrients & toxins -last to die & first to regenerate -first affected by bile duct occlusion Zone 2: -intermediate zone Zone 3: -oxygen poor zone -farthest from axis -closest to terminal hepatic venule -first to exhibit necrotic changes & fat accumulation -last to regenerate -last to respond to bile duct occlusion |
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What are the functional differences btwn zone 1 & 3?
Which zone is referred to as "centrilobular" or "perivenous"? |
Zone 1- greatest concentration of glycogen synthesis enzymes, store glucose more readily, produce most of bile & synthesize most of albumin
Zone 3- greatest concentration of enzymes involved in xenbiotic metabolism zone 3 |
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What are Kupfer cells?
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macrophages that reside on sinusoid endothelial lining, extending cytoplasmic processes into pores and gaps
-phagocytize RBC & digest hemoglobin, destroy microorganisms from portal vein, serve as antigen presenting cells |
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What are fat-storing (Ito cells)?
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stellate cells present in perisinusoidal space, occupy shallow depressions btwn hepatocytes w/ some processes extending into endothelial cells
-storage site of vitamin A |
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Obj.
Describe the structure of the gall bladder wall |
hollow organ located at inferior surface of liver, stores bile
-cystic duct extends from gallbladder to join hepatic duct from liver -common bile duct forms from merging of cystic & hepatic duct, empties into duodenum |
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Obj.
Describe histological characteristics of the gall bladder epithelium |
-mucosa is made up of simple columnar epithelium on the lumenal surface & tall columnar cell w/ microvilli on apical surface
-junctional complexes btwn cells -oval nucleus towards basal half -high conentration of mitochondria in basal portion -highly vascularized lamina propria w/ venous sinuses, fenestrated capillaries, & mucous glands (especially near neck) -muscularis externa immediately external to lamina propria, circular orientation -serosa surrounds most of gallbladder except portion attached to liver (adventitia instead), contains adipose & elastic fibers |
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The mucosa is thrown into numerous, deep folds, when the gall bladder is full or empty?
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empty!
(or partially filled) *folds become distended during water resorption, increasing intercellular space |
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Why does the gall bladder contain a high concentration of mitochondria in its basal portion?
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mitochondria provide energy for Na+K+ATPase pumps on basolateral membranes
-pumps used to pump NaCl out, creating osmotic gradient that drives water from gall bladder lumen into intracellular space |
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T/F
Gallbladder does not contain muscularis mucosa or submucosa |
TRUE!
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Obj.
Describe functional characteristics of the gall bladder epithelium |
Mucosa: creates folds or distends when gall bladder is empty or full, contains lamina propria with venous sinuses & fenestrated capillaries, used to carry away reabsorbed fluid
Muscularis externa: smooth muscle, contracts to squeeze contents of bladder into cystic duct |
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Obj.
Gall bladder functions- |
-stores bile received from liver
-concentrates bile -releases concentrated bile into small intestine |
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Obj-
Explain control of gall bladder function |
-openings of common bile duct & pancreatic duct are controlled by a series of sphincter muscles (sphincter closed=bile secreted from liver into gall bladder via backflow)
-cholecystokinin, is released from intestinal enteroendocrine cells, when fat is present in small intestine, controls contraction of smooth muscle in wall of gall bladder - |
