Flashcards in Liver, Gallbladder, and Pancreas Deck (66)
What makes up the parenchyma of the liver?
Organized plates of hepatocytes, separated by sinusoids (discontinuous capillaries)
What are the two parts of the stroma of the liver?
1. Fibrous stroma - Dense irregular CT (Type 1 collagen) forming thin capsule around vessels, ducts, and provides some separation into lobules
2. Reticular stroma - Type 3 collagen fibers providing supporting network for hepatocytes and sinusoids.
What is the portal vein's contribution of blood and what type of blood is it?
75% of liver's afferent blood. It is rich in nutrients, but relatively poor in oxygen because it comes from capillary bed in intestines.
What is the hepatic artery's contribution of blood and what type of blood is it?
25% of liver's afferent blood, rich in oxygen, coming from left ventricle of heart
What is blood flow in the liver, from portal vein / hepatic artery to IVC?
1. Portal vein / hepatic artery
2. Interlobular branches
3. Terminal branches
4. Sinusoids / discontinous capillaries
5. Central vein
6. Sublobular vein
7. Hepatic veins
8. Inferior vena cava
What is an anatomic or classic lobule? What is at the center? What is at each corner?
A hexagonal shaped lobule containing a radial array of plates of hepatocytes around a central vein.
At each corner: portal triad + connective tissue
What is a portal triad at the corner of the anatomic lobule?
Hepatic artery branch (interlobular), portal vein (interlobular), and bile ductule
What runs on the sides of anatomic lobules?
Between the hexagons, on the sides, are terminal branches of portal veins and hepatic arteries. They empty blood into the sinusoids, where the blood is mixed
What is the direction of bile flow in the anatomic lobule?
Opposite direction of blood.
1. Intercellular canaliculi
2. Canals of Hering
3. Interlobular bile ducts
What is a portal triad + connective tissue called?
This is at the corner of the anatomic lobules
What is a portal lobule centered around? How many adjacent anatomical lobules?
It is centered around a bile ductule and emphasizes the exocrine function of the liver. This means it is the corner of a hexagonal lobule, and thus pulls from three adjacent anatomic lobules (corners are the central veins)
Triangle - 3 adjacent lobules
What is a liver acinus / functional lobule / Rappaport's lobule centered around?
Delivery of blood to hepatocytes.
It makes a diamond shape from two triangles, with the base of the triangle being a terminal artery, and the apex of each triangle being the central vein of the anatomic lobule
What are the three zones of the liver acinus?
Zone 1: Center of lobule, closest to terminal artery - first to receive oxygen, nutrients, but also toxins
Zone 2: intermediate zone
Zone 3: Cells adjacent to central veins, last to be affected by toxins, but relatively low oxygen levels
What shape are hepatocytes / why are their nuclei weird?
They are large polyhedron cells, with centrally located nuclei. However, sometimes they are binucleate, and may be polyploid (multiple DNA copies)
What is the space between the hepatocytes' plasma membrane and the sinusoid called? What is in it?
Space of Disse - microvilli from cell wall project into it
What are bile canaliculi?
Intercellular canaliculi formed on lateral surface of hepatocytes with adjacent cell's plasma membrane. They transport bile?
What type of junction is used to form a bile canaliculi?
Occludin and claudin - ZO1-3
How can hepatocytes be identified by SEM?
They have well developed rER, sER, Golgi, lysosomes, and peroxisomes. However, their distinguishing characteristics would probably be the large central nucleus, + GLYCOGEN INCLUSIONS
What is the problem with liver cell regeneration?
They can regenerate, but new cells to not establish proper anatomical relationships with one another
What plasma proteins are released by hepatocytes and where are they released?
Albumin, fibrinogen, and coagulation factors all made in sER.
Released into space of Disse and flow into sinusoid from there
How does the liver detoxify lipid-solubel drugs and steroids?
Processes in smooth ER by transforming nonpolar compounds into polar metabolites, making them water-soluble. Thus, they can be excreted in the kidneys
How do chylomicra reach the liver / what do they do en route?
After being released into capillaries by enterocytes, they undergo lipolysis en route, delivering fatty acids to tissues. The remnants are taken up by hepatocytes and metabolized
What happens to chylomicra in the liver?
Fatty acids are esterified to triglycerides by sER. Some of these are stored in fat droplets, most are coated with proteins + cholesterol + phospholipid and are released into blood as VLDL (very low density lipid) particles which are easily used by cells
How is the sER of hepatocytes involved in sugar control?
Glycogen is synthesized and broken down in sER, in the meantime being stored as inclusions in the cytosol
How is iron stored in the liver?
As ferritin or hemosiderin granules in hepatocytes
How is alcohol processed by the liver and why is too much alcohol bad?
Small amounts are metabolized through alcohol dehydrogenase pathway, producing acetaldehyde and acetate.
Large amounts will activate the microsomal ethanol-oxidizing system (MEOS) which produces acetaldehyde and oxygen free radicals which can damage hepatocyte plasma membranes.
Where do hepatocytes synthesize cholesterol, phospholipids, and bile salts? What are the other components of bile?
Smooth ER. Keep in mind that bile salts can sometimes be used from enterocytes which uptook them in the intestines and sent them through the portal vein
Other components: bilirubin + glucuronide, electrolytes, metabolites of drugs, and heavy metals
How is bilirubin, the breakdown product of heme, put in the feces?
Bilirubin is conjugated with glucuronide to make it water-soluble. It is excreted with the bile and is actually the component which makes feces brown
How is bile secreted into intercellular canaliculi?
Via ATP-dependent transports in the canalicular plasma membrane