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43 Cards in this Set
- Front
- Back
- 3rd side (hint)
What is the largest gland associated w/ the digestive system?
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liver
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What type of gland is the liver?
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endocrine and exocrine
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Describe the liver's morphology.
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-subdivided into lobes
-invested in a CT CAPSULE, composed of fine elastic CT; this layer is covered by serosa |
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The inferior of the liver is subdivided into hepatic lobules, what do these represent?
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The STRUCTURAL UNITS of the liver
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The hepatic lobules are centered around the smallest branches of the hepatic vein; hence their name
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What separates the lobules from one another?
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SEPTAE
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not clearly defined in man
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What are the two main consituents of the lobules?
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Hepatocytes and sinusoids
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What is the bulk of the liver's lobule composed of?
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a parenchyma of epithelial cells called HEPATOCYTES
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What performs most of the functions of the liver?
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hepatocytes
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How are hepatocytes arranged?
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In plates that are one cell thick
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Describe the plate configuration of hepatocytes?
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Have the appearance of spokes in a wheel; they radiate out from the center of the lobule.
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How many nuclei do hepatocytes have?
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usually 2
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What lies at the center of the lobule?
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central vein
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What is the central vein?
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The smallest tributary of the hepatic vein lying in the center of the lobule.
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What is the second cell type contributing to the lobule?
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Sinusoids
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A system of blood channels
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What provides blood to the liver?
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Hepatic portal system
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The liver is the terminus of the hepatic portal system
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What vessel does the liver derive its ability to perform most of its functions?
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portal vein
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Where does this vessel enter the lobule?
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porta hepatis
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The portal vein carries blood to the liver from where?
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spleen and digestive tract
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What vessel accompanies the portal vein?
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proper hepatic artery
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What key substance does the proper hepatic artery provide the cells of the liver?
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oxygen
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Describe the branching of the liver's two main vessels.
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They divide into INTERLOBAR branches which follow the ct between the lobes and then into INTERLOBULAR which follow the sparse ct between the lobules.
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What comprises the hepatic triad?
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Hepatic a, portal v, bile duct
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What other type of vessel associate with the hepatic triad?
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lymphatic vessels
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carry foluminous lymph produced in the liver to the general circulation
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What do the triad, lymphatic vessels and surrounding ct form?
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porta canal
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Describe each component of the porta canal.
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-portal vein - a large, thin-walled vessel engorged with blood
- the hepatic a - smaller with a thicker wall - bile duct - cuboidal epithelium - lymphatic vessels - irrecular clear spaces lined by endothelial cells |
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Describe what a terminal vessel is and how blood flows from the terminal vessel to the sinusoids.
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Terminal vessels of the portal vein and hepatic artery (terminals of the interlobular vessels) branch at right angles to the portal canal and course in the margins between adjacent lobules. Blood flows from these branches into the sinusoids.
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What type of epithelium are the hepatic sinusoids lined with?
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discontinuous epithelium
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How are the sinusoids distinguished?
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Large FENESTRATIONS and large GAPS between neighboring cells. Incomplete basal lamina and absent in some locations.
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What are the fixed macrophages considered part of the sinusoid lining?
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Kupffer cells
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What system do Kupffer cells belong to?
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Mononuclear phagocyte system
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What is the function of Kupffer cells?
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To remove old rbcs from the circulation
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What separates the sinusoidal lining from the plates of hepatocytes?
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space of Disse
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How is the exchange of substances between the hepatocytes and plasma improved?
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Microvilli extend from hepatocytes into the space of Disse providing an expanded surface area
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What is the specialized cell located in the space of Disse? What's its function?
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Hepatic stellate cell; stores vitamin A in cytoplasmic lipid droplets.
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What is the direction of blood flow in the lobule? Is it oxygenated or not?
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Blood flows in the sinusoids is from the periphery to the center of the hepatic lobule. Since blood branches from both the hepatic artery and portal vein, blood is oxygenated and venous.
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Where do all the sinusoids drain in the lobule?
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central vein
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first tributary of the hepatic veins draining the liver
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Describe the formation of hepatic veins.
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Central veins form sublobular veins which unite to form hepatic veins
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Does the venous drainage course through the triad?
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No, it's independent of the triad; therefore hepatic veins are seen in sections of solitary vessels
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What constitues the exocrine secretion of the liver?
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Bile
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What type of cells make bile?
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hepatocytes
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What is the bile secreted into?
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small canals, bile canaliculi
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they do not have walls of their own; are formed by the plasma membranes of adjacent hepatocytes
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What borders the canaliculi?
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microvilli (project into the lumen)
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In what direction does bile flow?
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toward the portal triads (opposite of the sinusoidal blood flow)
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