Lecture 19 Flashcards
What is the structure of the pancreas that is involved in endocrine function?
Islets of Langerhans
What is the appearance of Islets of Langerhans?
Pale-staining
Clusters
Embedded in exocrine cells
What is the function of Islets of Langerahans?
Production of hormone (insulin)
What is the structure of the pancreas that is involved in exocrine function?
Pancreatic acini
What is the appearance of pancreatic acini?
Dark staining
Zymogen granules - granular appearance
What are the functions of pancreatic acini?
Production of digestive enzymes
Fluid secretion
Electrolyte secretion
Ductal cells of pancreas secrete bicarbonate
Describe the exocrine pancreas
A tubulo-acinar gland with highly branched ducts. Acinar cell has large spherical nucleus in basal position. Mitochondria oriented perpendicular to the basal surface.
Where are protein secretory products synthesised in the acini? Where are they packaged? Where do they accumulate?
Basal rER, packaged in the golgi, and accumulated as zymogen granules in the apical cytoplasm.
Acini produce a small volume of __________-_____ ________. What does this contribute to?
Enzyme-rich fluid
Contributes to pancreatic juice
What do ducts of the pancreas begin with? What do duct cells produce?
The smallest intercalated ducts which are inserted into the acini. Duct cells produce bicarbonate and a large volume of alkaline fluid.
How much alkaline fluid do duct cells produce?
1 litre/day
What are centro-acinar cells?
Intercalated duct cells which penetrate the lumen of the acini
List the sequential ducts that extend from the acini.
Intercalated ducts - intralobular ducts - interlobular ducts -pancreatic duct - hepatopancreatic ampulla of vater - duodenum
What lies in the junction between hexagonal lobules of the liver?
Connective tissue septa containing collagen, blood vessels, nerves, lymphatics
What lies between the hepatocytes of the liver?
Sinusoids
What is each hepatocyte in contact with?
Blood vessels
What is the arrangement of hepatocytes?
Radiating columns of hepatocytes. Columns can branch quite freely but have a radiating pattern
What is the classical/anatomical classification of a portion of the liver?
Hepatic lobule
What type of blood do sinusoids contain? What happens to the blood in the sinusoids?
Mixed blood. Nutrients and O2 diffuse out of sinusoids and into hepatocytes according to gradient. Mixed blood is eventually drained into central vein.
Describe the concentration of Zone 1 and 3
Zone 1: High nutrient and oxygen concentration
Zone 3: Low nutrient and oxygen concentration
Describe the hepatic portal vein
Thin walled, large lumen, low pressure
Carries nutrient rich blood
Contributes 75% blood supply going to liver
Describe the hepatic artery
Thick wall Relatively small lumen High pressure Contributes 25% blood supply going to liver Carries oxygen rich blood
What is the functional way of describing a unit of the liver?
Liver acinus
What does a portal lobule describe?
The flow of bile
What is the usual shape of a hepatocyte?
Polygonal
What are sinusoids?
A special type of capillary
What is another name for sinusoid?
Lumen of sinusoidal capillary
What is the difference between a sinusoid and a normal capillary?
Much wider than capillary. More than one RBC can pass through (up to 10). Leads to increased flow and increased rate of diffusion.
Endothelium has intercellular openings as well as being fenestrated. Leads to leakiness, which is good for substrate diffusion.
What lines the sinusoids?
Endothelium
Where are stellate cells found?
In Space of Disse
What is the Space of Disse?
Lymphatic space between endothelium and microvilli of hepatocytes
What are the functions of the stellate cells?
Fat-storing
Role in vitamin A metabolism
Where are the Kupferr cells found?
In the lumen of the sinusoidal capillary
What are the functions of the Kupffer cells?
Macrophage-like
Prevent obstruction
Antibacterial
What is special about the nucleus of hepatocytes?
Because they undergo a high rate of replacement, there is increased level of cell division and regeneration. It is normal to see binucleate or polypoid nuclei.
What is meant by a polyploid nucleus?
Multiple copies of DNA material contained in a big nucleus
What are bile canaliculi?
Membranous in-foldings that create a channel-like structure. Proteins help form an occluding junction that seals off the bile canaliculus so that it doesn’t leak. Circular structures found between adjacent hepatocytes.
What do canaliculi feed into?
Canaliculi from adjacent hepatocytes all converge and feed into bile ductules, which then feed into the bile duct
