Liver, pancreas and gall bladder Flashcards
Name some functions of the liver.
- Synthesize plasma lipoproteins
- Synthesize cholesterol
- Convert carbohydrates and proteins into fatty acids and triglycerides
what is the liver capsule?
The liver is covered by a collagenous connective tissue capsule, which is in turn covered by a layer of mesothelial cells (simple squamous epithelium) derived from the peritoneum
what segments make up the liver?
lobules
Describe lobules.
Hexagonal and has a branch of the hepatic vein called the centrolobular vein (or central vein) at its centre and portal triads at each corner
what makes up the portal triad?
- hepatic portal vein
- hepatic artery
- bile duct
what do the portal triads also typically include?
lymphatic vessels
what lines the bile duct?
lined by simple cuboidal cells called cholangiocytes
what are the main cells of the liver?
hepatocytes
what are the spaces in-between hepatocytes?
sinusoids that allow blood to flow through
what is the hepatic acinus model of the liver?
the centre is of two joining lobules and not the central vein like it is for the classic lobule
what is the space of Disse?
the narrow space between the endothelial cells that line sinusoids and the hepatocytes
what are the portal tracts accompanied by?
collagenous connective tissue
what are kupffer cells?
resident macrophages scattered within the sinusoids and these cells removes particulate matter from the blood and help remove worn out red blood cells
what is bile?
alkaline solution containing water, ions, phospholipids, bilirubin and bile salts
what produces bile?
hepatocytes
what is the direction of bile flow?
Bile flows via bile canaliculi toward the bile ducts in the portal tracts and thence to the hepatic ducts
How are bile canalculi formed?
formed by tight junctions in the cell membranes of adjacent hepatocytes
what is the structure of the gall bladder?
muscular sac which:
Is lined by simple columnar epithelium backed by a lamina propria of loose connective tissue rich in blood vessels and lymphatic vessels, a coat of smooth muscle and an outer collagenous layer of adventitia
what is the function of the gall bladder?
About 80%-90% of the volume of the bile arriving from the liver is removed by the gall bladder. This is done by actively pumping Na and Cl ions from the bile into the spaces between adjacent epithelial cells. Water then follows due to the increase in osmotic pressure in these spaces, which become distended with fluid when the gall bladder is actively concentrating bile. The water is carried away, largely by the lymphatic vessels of the lamina propria
The gall bladder is stimulated to contract and deliver bile to the duodenum, both under nervous control (chiefly vagal), and via release of the hormone cholecystokinin by endocrine cells of the duodenum when fatty food enters it
what is the gall bladder lined by?
tall columnar epithelial cells with a brush border
what is unusual about the pancreas?
it is both an exocrine and an endocrine gland
Describe the exocrine aspect of the pancreas.
produces about a litre of digestive juices containing proteases to break down proteins, lipases to break down lipids, nucleases to breakdown DNA/RNA, amylase to break down starch, etc, each day. These enter the duodenum via the pancreatic duct
Describe the endocrine aspect of the pancreas.
consists of small, scattered islands of tissue called islets of Langerhans, which produce a number of hormones including insulin and glucagon. Islets make up about 1%-2% of the pancreas
Describe the exocrine pancreas microscopically.
Has numerous serous acini and ducts. The cells are very basophilic because they contain large amounts of RER
