Liver and Pancreas Flashcards
Functions of the Liver
Stores and processes nutrients absorbed from the GIT.
Neutralises and eliminates toxic wastes
Poduces Bile
Produces plasma proteins
Explain the Liver’s dual blood supply
The hepative portal vein brings nutrient rich, but oxygen poor blood from the GIT and the hepatic artery brings oxygen rich blood from the aorta
These two bloods mix in the portal regions and then flow in the sinusoidal calpillaries past the hepatocytes of the liver. The blood is then collected in the central veins and eventually back to the heart via the IVC
The liver is arranged into lobules
around the central veins.
The hepatocytes are arranged into sheets or cords separated by liver sinusoids. Around the periphery of the liver lobules are found in the portal areas- where the branches of the hepatic portal vein, hepatic artery and bile ducts are found.
Explain the structure of the liver
Cells are arranged in columns or cords of cells radiating out from a central vein
the liver cords are separated by sinusoids through which blood flows to the central vein
This arrangement creates hexagonal lobules with a central vein and a series of portal regions at the periphery of the lobule
What are the sinusoids lined by?
Specialised endothelium consisting of DISCONTINUOUS simple squamous epithelium and macrophages (KUPFFER CELLS)
What extends into the space of disse
Cuboidal cells
ITO cells (hepatic stellate cells- HSC) which are thought to produce vitamin A- and are involved in liver fibrosis.
it is thought that lymph originates from the Space of Disse. It’s flow in the space is opposite that of blood flow!
What organells indicate that the hepatocyte is a secretory cell
Numerous golgi, rER, sER, mitochondria and glycogen granules
Portal Region- what is in it?
The portal regions contain a
- hepatic artery
- hepatic portal vein
- bile duct
- lymphatic channel
Each portal region services more than one lobule
Each lobule has a number of portal regions
List the bile flow from the liver to the duodenum
Hepatocytes -> bile capillaries -> small bile ducts -> right and left hepatic ducts -> common hepatic duct -> common bile duct (or cystic duct for storage in gall bladder) -> hepatopancreatic ampulla (of vater)
The Gallbladder- histology?
Like the liver is an outgrowth of the duodenum
Lined by simple columnar epithelium with a brush border. Mucosa is very folded and when actively reabsorbing water shows evidence of intercellular speces in the basal regions of the epithelium
Note there is characteristic ‘tunelling’ of the epithelium.
A band of smooth muscle completes the structure of the wall. There is NO submucosa in the gall bladder.
Explain hormonal control of exocrine liver function
- Parasympathetic impulses along vagus (X) nerves stimulate production of bile by the liver
- Fatty acids and amino acids in chyme entering the duodenum stimulate the secretion of cholecystokinin (CCK) into the blood -> CCK causes contraction of the gall bladder
- Acidic chyme entering the duodenum stimulates the secretion of secretin into the blood –> secretin enhances the flow of bile rich in HCO3- from the liver.
Light micrograph of the pancreas: what would the exocrine and endocrine components of the pancreas look liuke?
Endocrine : Islets of Langerhans: lighter, alpha, beta, delta: secrete glucagon, insulin
Exocrine: basophilic.
Dont have striated ducts = different from parotid gland
In the pancreas each acinus (group of secretory cells) h as a basophilic basal region and an eosinophilic apical region. Why?
This is the typical appearance of an active protein secreting cell. The basophilia is caused by rER and the eosinophilia by zymogen granules
Explain the structure of the pancreatic acinus
The centroacinar cells of the intercalated duct extend into the lumen of the acinus. (this is not seen in salivary glands).
The zymogenic cells secrete the digestive enzymes The Duct cells secrete bicarbonate rich fluid.
These secretions are under the control of CCK (enzymes) and secretin (bicarbonate) from enteroendocrine cells of the duodenum).
