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24 Cards in this Set
- Front
- Back
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What tissue do the liver, gallbladder, and pancreas arise from?
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Duodenal epithelium
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Describe the tissue that covers most of the liver.
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Most of the liver (where it faces the peritoneal cavity: visceral and diaphragmatic surfaces) is covered with serosa: serous, single-cell mesothelial lining
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Describe the area of the liver not covered by mesothelium.
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Space bounded by the coronary ligament, containing the caudal vena cava, where the diaphragmatic face of the liver attaches to the diaphragm.
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What lies beneath the mesothelium covering the liver?
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Glisson's capsule:
- thin layer of dense irregular connective tissue - invaginates at the hilus to extend in as the stroma that supports/surrounds vessels/ducts (intrahepatic portal connective tissue) - composed of collagen, fibroblasts, smooth muscle, small blood vessels, lymphatics |
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What are portal triads / portal tracts / portal canals?
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The group of vessels, ducts, and encasing connective tissue that contain branches of the hepatic artery and portal vein, bile duct, lymphatic channel
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Describe composition of hepatic blood supply.
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Dual afferent blood supply: oxygenated blood through hepatic artery (25%) and nutrient-rich/oxygen-poor blood from portal vein (75%)
- the arterial and venous blood mix in the liver sinusoids (like capillary bed) - contains products of gut digestion/absorption and spleen antigen-recognition and RBC breakdown |
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What does the hilus of the liver contain?
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Portal vein, hepatic artery (starts to branch before entering hilus), bile duct
- no blood exits at hilus, just bile |
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Describe efferent blood flow from the liver.
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Blood from hepatic sinusoidal capillary beds flows into larger and larger vessels until it exits each lobe in a hepatic vein.
The hepatic veins merge with the caudal vena cava as it is surrounded by the coronary ligament, just before it passes through the diaphragm. |
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How do hepatocytes differ depending on their orientation?
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Surface specialization:
- microvillous surface faces the perisinusoidal space - canalicular surface borders bile canaliculi - contact surface between adjacent hepatocytes: may have tight junctions, desmosomes |
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Describe how bile leaves the liver.
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- bile is secreted into bile canaliculi (minute spaces between apposed hepatocytes formed by tight junctions)
- bile flows from bile canaliculi into bile ductules (aka cholangioles; lined by low simple cuboidal epithelium, aka cholangiocytes) - ductules connect into interlobar bile ducts lined by simple cuboidal or columnar epithelium - interlobar bile ducts connect into intrahepatic and then hepatic ducts |
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What separated liver sinusoidal endothelial cells from hepatocytes?
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Space of Disse
- interstitial, perisinusoidal, contains reticular fibers (collagen type III) - plasma (but not RBCs) can pass through fenestrations in endothelium into Space of Disse, to be in contact with hepatocytes |
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What are Kupffer cells?
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- resident liver macrophages, located in sinusoids, responsible for phagocytosis, cytokine secretion, antigen-presenting, etc.
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What are stellate cells (Ito cells)?
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- perisinusoidal adipocyte in Space of Disse
- secrete cytokines, produce ECM of Space of Disse, store lipid-soluble vitamins (e.g. Vit A) |
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What are the three zones of the classic hepatic lobule?
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(Hexagon with portal canals at each corner and central vein in the middle)
Periportal zone- closest to portal tract Midzone Centrilobular (aka central) zone- furthest away from portal tract, closest to central vein |
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What are the three zones of the hepatic acinus?
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(Diamond with central vein on two opposite points and portal tracts on the other two)
- zone 1: closest to afferent blood supply; oxygen-rich - zone 2 - zone 3: closest to terminal hepatic vein, oxygen-poor |
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What are portal lobules?
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The unit supplied/drained by a portal canal.
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Describe hepatocytes.
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- arranged in hepatic cords or plates
- large polyhedral cells, round central nuclei (frequently polyploidy, i.e. more than 1 nucleus) |
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Describe shape and function of the gallbladder.
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- pear-shaped organ: blindly-ending fundus, central body, narrow neck
- stores bile (produced in liver) until the bile is needed to emulsify fat in the gut lumen |
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Describe the outside covering of the gallbladder.
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Has serosa over most of it, except for a portion of adventitia that is continuous with Glisson's capsule of the liver
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Describe layers of the gallbladder.
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- tunica mucosa: simple tall-columnar epithelium; no goblet cells or glands
- scanty lamina propria - stringy tunica muscularis - serosa and adventitia (no submucosa or lamina muscularis mucosae) |
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Describe an acinus of the pancreas.
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- secretory cells grouped around a lumen
- eosinophilic apical region of cells contain zymogen granules in vesicles (later released by exocytosis) - basal regions are basophilic because of rough ER |
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Describe the duct system of the pancreas.
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- only gland where duct system begins in acinus
- first portion is intercalated ducts: extends into center of acinus; lined by small centroacinar cells (flattened, cuboidal or low columnar epithelium) - intercalated ducts empty into interlobular ducts, which are lined by columnar epithelium - interlobular ducts empty into the main pancreatic duct, which is lined by a tall columnar epithelium |
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Describe the Islets of Langerhans.
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- lighter staining tissue (compared to exocrine parts)
- demarcated by delicate connective tissue fibrils - well-vascularized (so endocrine products can get into circulation) - 3 major cell types: Beta cells: center of islet (surrounded by rim of alpha and delta cells), most abundant, produce insulin Alpha cells: secrete glucagon Delta cells: secrete somatostatin (Cells of endocrine islet all look the same- cannot tell what they secrete) |
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Describe a hepatopancreas.
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- pancreas combined with liver in lower species (fish, birds)
- islands of pancreatic material scattered throughout liver, surrounded/separated by connective tissue |
