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BISC 125 Exocrine Pancreas, Liver, and Gallbladder

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Is the pancreas an exocrine or an endocrine gland?
Both; about 2% of the gland is endocrine, the rest is exocrine.
What is the main unit of endocrine secretion in the pancreas?
the islets of Langerhans
What are the endocrine functions of the pancreas?
To regulate glucose metabolism (by hormones secreted into the bloodstream)
What is unique about the blood supply to the endocrine pancreas?
There is dual blood supply to the islets and the acinar glands; veins come in, pick up the secretory products, and carry them back out through the exocrine portion of the gland
What type of exocrine gland is the pancreas?
A compound tubular-acinar gland (tubes and "bubbles" (like alveoli))
What are the four parts of the tubular-acinar gland of the pancreas and where are they located?
The head (by the duodenum), the neck (in contact with the portal vein), the body (anterior to the aorta), and the tail (by the kidney and hilum of the spleen)
Why is the location of the pancreas so important?
It is near many critical structures, so its secretions can have a large affect
How does the external duct system of the pancreas work?
The (major) pancreatic duct empties into the common bile duct, which empties into the duodenum
How does the internal duct system of the pancreas work?
The lumen of the acinus leads to intralobular ducts which converge to form interlobular ducts, which empty into the main pancreatic duct, which empties into the duodenum
What is unique about the pancreatic acinus?
It is a functional unit with centroacinar cells lining the acinus lumen (only in pancreas)
What epithelium lines the intralobular excretory ducts of the pancreas?
Low columnar epithelium line the nonstraited ducts
What do pancreatic interlobular ducts contain?
Columnar cell epithelium, goblet cells, and occassional enteroendocrine cells
What causes jaundice?
Backflow of bile from the gallbladder to the liver
Why is pancreatic cancer so devastating?
The pancreatic capsule is relatively thin, so cancer cells can easily break out and spread to the crucial organs surrounding the pancreas.
What type of cells line the pancreatic acinus?
Pyramidal cells
What is the structure and function of the apical domain of the pancreatic acinus?
Contains very important junctional complexes, along with Golgi bodies and Zymagin granules (precursor to digestive enzymes). The junctional complexes prevent reflux of secreted products from the ducts into the intercellular spaces.
What is the structure of the basal domain of the pancreatic acinus?
It has epithelial cells, a basement membrane associated with the basal lamina, and a very well developed rough ER
What is acute hemorrhagic pancreatitis?
The premature activation of pancreatic enzymes resulting in the autodigestion of the pancreatic acini; can result from ingestion of heavy metals or excessive alcohol intake
What is cystic fibrosis?
An inherited, autosomal recessive condition that affects the function of mucus-secreting tissues of the respiratory, intestinal, and reproductive systems
Is the liver a gland or an organ?
Both; it is the largest gland
How many lobes does the liver have?
Four, but people typically refer to the right and left hepatic lobes
What is the capsule of Glisson?
The capsule surrounding the liver (made of collagen and elastic fibers) that has almost direct contact with the diaphragm
What two main vessels supply the liver with blood?
The portal vein and the hepatic artery
What does the portal vein do?
It drains blood from the intestinal organs to the liver; it contains about 70% of the liver's blood volume and about 30% of it's oxygen
What do hepatic veins do?
Take blood from the right and left lobes of the liver to the inferior vena cava
How does the bile duct system in the liver work?
The right and left hepatic ducts merge to form the common hepatic duct, which combines with the cystic duct, to form the common bile duct (aka pancreatic duct)
What is the functional unit of the liver?
A hepatic lobule
What is contained in a liver lobule?
Plates of hepatocytes that surround sinusoidal spaces, a central vein, and a portal triad
What does a central vein in a hepatic lobule do?
It is in the center of the lobule, and it collects blood emptied into it from the sinusoidal spaces (blood comes from branches of the portal vein and hepatic artery)
What are the components of a portal triad?
A bile duct, a hepatic arteriole, a portal venule, and lymph vessels and nerves
What are bile canaliculi and where are they located?
They are canaliculi located between adjacent hepatocytes (made of a membrane of hepatocytes); bile secreted by the hepatocytes goes here
Do bile and lymph flow the same way as blood?
No, the opposite way; blood flows to the central vein, away from the portal triad. Bile and lymph go to the triads.
How do bile and lymph get from the canaliculi (or other spaces) to the intrahepatic bile ducts?
They travel from the canaliculi, to the cholangioles (aka intralobular bile ductules), across the canal of Hering (at periphery of the hepatic lobule), to the bile ducts of the portal space, to the intrahepatic bile ducts
What is the structure of the liver lobule according to the classic view?
The lobule is polyhedral (usually a hexagon)with portal triads at the angles and the central venule where blood sinusoids converge
What is the view of the lobule from the portal lobule point of view?
The portal triad is the central axis, draining blood from the surrounding hepatic parenchyma; view is based on bile drainage pathway from adjacent lobules toward same bile duct
What is the view of the liver lobule from the view of the liver acinus?
The boundries of the lobule are two central veins and two triads; there are three zones based on oxygen level (one is richest in oxygen, three is lowest)
What is the space of Disse (aka perisinusoidal space) in a hepatocyte?
The space between adjacent sinusoids (filled with lymph)
What are Kupffer cells?
Macrophages found in hepatocytes.
What are limiting plates?
Plates of hepatocytes that separate the components of the portal triad from the hepatic lobule
What is the space of Mall?
A space that runs continuous with the space of Disse in the hepatocyte; it drains the lymph (then lymphatic vessels pierce the limiting plate and drain lymph)
What are the characteristics of the basolateral domain of the hepatocyte?
It has abundant microvilli, faces the space of Disse, has the space of Mall, and has intercellular gap junctions on lateral surfaces of hepatocytes
What are the characteristics of the apical domain of the hepatocyte?
It borders the bile canaliculus and is sealed by occluding/tight junctions (prevents leakage of bile)
What are the functions of smooth endoplasmic reticulum (extensive in hepatocytes)?
Cholesterol and steroid sythesis, glucose metabolism, turning free fatty acids into triglycerides, removal of iodine from the thyroid, and detox of drugs, lipids, OH
What is the function of the Golgi apparatus in the hepatocyte?
Producing and sorting lysosomal enzymes
What is the function of lysosomes in the hepatocyte?
Storing iron and degrading aged plasma glycoproteins
What do peroxisomes do?
Generate H2O2, then catalase breaks it down into water and oxygen
How do peroxisomes originate?
They self-replicate by budding
What is bile and where is it produced?
Bile is produced by hepatocytes, and it consists of organic components (bile acids, phospholipids, cholesterol, bile pigments, and bilirubin) and inorganic components (mostly Na+ and Cl-)
About how much bile is produced by hepatocytes per day?
2/3 of a liter or 600mL
What is the function of bile?
To help in excretion of cholesterol, phospholipids, bile salts, bilirubin and electrolytes; to help with fat absorption (in intestine); to transport IgA; and to help excrete metabolic products (of drugs and heavy metals)
What is the function of the gallbladder?
Receives dilute bile from the liver via the cystic ducts; stores and concentrates it, then discharges it through the common bile duct to the duodenum
What are the histologic layers of the gallbladder?
The epithelium (simple columnar), lamina propia, muscularis externa and adventitia (NO muscularis mucosa or submucosa)
What are Rokitansky-Aschoff sinuses?
Deep clefts in the mucosa of the gallbladder

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