Pancreas and liver microanatomy Flashcards
Desribe the flow of pancreatic juice out of the acini and into the duodenum
Intercalated ducts (go into acini) - Intralobular ducts (go between/within the lobes of acini) - interlobular ducts - pancreatic ducts - combines with the common bile duct to create the swelling known as the ampulla of vater - empties into duodenum
What are the two main cell types found in the pancreas which relate to its dual function?
Exocrine cells and endocrine cells
Describe the structure and function of the exocrine cells
The exocrine cells are arranged in in acini (grape like clusters) around a lumen which empties into a intercalated duct. They are wedge like in shape and appear as dark staining due to zymogen granules (granules that produce enzymes).
The function of these cells is to produce digestive enzymes.
What do the intercalated duct cells produce and why is this important?
Duct cells produce a watery bicarbonate fluid which acts to flush the enzymes through the ducts and plays an important role in neutralizing the acidic chyme entering the duodenum.
What is the structure and function of endocrine cells? (note this is not studied in this course)
Arranged in islets of langerhans. They appear pale staining under the microscope. Their function is to produce insulin and and other hormones and release them directly into the blood stream.
What are the main functions of the liver?
- both exocrine and endocrine functions
- detoxification of toxins and alcohol and also the blood before it re-enters the heart via the IVC
- acts as a storage site for glycogen molecules which are stored in the hepatocytes of the liver
- synthesis of albumin and bile and various other molecules
Describe the structure of the liver lobule. Draw it.
The liver lobes are made up of microscopic units called lobules which are roughly hexagonal in shape.
These lobules comprise of rows of liver cells (hepatocytes) which radiate out from a central point. The hepatic cells are in close contact with blood-filled sinusoids and also lie adjacent to canaliculi into which bile is secreted.
Situated around the perimeter of the lobule are branches of the hepatic artery, hepatic portal vein and bile duct. These cluster together at the “corners” of the lobule forming what is called the portal triad. At the mid-point of the lobule is the central vein. Blood flows out of the sinusoids into the central vein and is transported out of the liver
What is specialised about the endothelial lining of the sinusoids?
It is fenestrated (has little pores) which make them very leaky and allows substrates to diffuse into them.
What are kupffer cells?
A type of macrophage that lines the sinusoids and is responsible for clearing away gut bacteria and other debris in order to keep the sinusoid open to allow for unobstructed flow.
What is the space of disse?
The very small gap/space seperating the hepatocytes from the endothelium of the sinusoids.
What are stellate cells?
Star shaped cells also found in the space of disse that are fat storing cells.
Describe the idea of “zoning” of the hepatocytes
The hepatocytes are zoned depending on how close they are to the arterial supply. The hepatocytes closest to the portal triad are termed zone 1 and has the most oxygenated blood. However they are also potentially exposed to the most nutrient rich blood and the most blood borne toxins coming from the gut.
Note: this zoning can impact on the types of organelles found in the hepatocyte as well as the types of enzymes produced in them.
What fibrous tissue is found surrounding the hepatocytes?
Reticular fibres
