Histology - Liver, Pancreas, Gallbladder Flashcards
List some of the functions of the liver
- oxidise triglycerides
- synthesise plasma proteins and lipoproteins
- synthesize cholesterol
- convert carbs and proteins into fatty acids and triglycerides
- regulates blood glucose (glycogenesis, glycogenolysis, gluconeogenesis)
- detox metabolic waste
- detox drugs and toxins
- store vitamins and iron
- synthesise and secrete bile
What vessels are present in the portal triad?
- hepatic portal vein
- hepatic artery
- bile duct (common hepatic duct combined with cystic bile duct)
describe the capsule that surrounds the liver
Mesothelium (simple squamous epithelium) --> Collagenous connective tissue --> Liver parenchyma
Describe the lobules of the liver
- Roughly hexagonal in shape
- Centrilobular vein (terminal hepatic vein)
- Portal triads
Describe the portal triads (portal tract) that surround the lobules of the liver
Composed of:
- bile duct
- portal vein
- hepatic artery
and:
- lymphatic vessel
- branch of the vagus nerve
They are supported by collagenous connective tissue
Describe the flow deoxygenated blood through a liver lobule
hepatic portal vein (branch) and hepatic artery --> hepatic sinusoids --> centrilobular vein
Are there distinct connective tissue septa between the liver lobules?
No, but the septa do exist
Describe the lining of a bile ductule
Lined by cholangiocytes
simple cuboidal epithelium
Describe hepatocytes
Epithelial cells
Produce primary bile
Have microvilli:
- project into the perisinusoidal space
- project into the bile canaliculi
Join to form plates of cells, leaving sinusoids between them
Describe a hepatic sinusoid
the space between the plates of hepatocytes
Lined by endothelial cells (as the hepatocytes plates have an endothelial lining)
Supplied by a mix of blood from the hepatic artery and hepatic portal vein
What is a hepatic acinus?
a functional subunit of the liver
an alternate functional rather than structural view (classic hepatic lobule)
Describe the lining of the plates of hepatocytes
The hepatocytes plates are lined by a fenestrated endothelium
They are separated by a thin gap called the the space of Disse (perisinusoidal space)
The microvilli of the hepatocytes project into the perisinusoidal space
Describe the perisinusoidal space (space of Disse)
gap between the hepatocytes and their endothelial lining
the hepatocytic microvilli project into it
Has hepatic stellate cells
Describe the significance of the fenestrated nature of the hepatocytic endothelium
The liquid component of the blood can reach the hepatocytes
But the blood cells can’t as they are too large to fit through the fenestrations
Describe hepatic stellate cells
Modified fibroblasts
Function:
- make connective tissue
- store vitamin A within fat droplets in their cytoplasms
found in the perisinusoidal space
(in cirrhosis they turn into myofibroblasts and produce scar tissue instead)
Describe Kupffer cells
Macrophages in the hepatic sinusoids
Function:
- remove old red blood cells
- remove particulates from the blood
Describe bile
Alkaline solution
Contains:
- water
- ions
- phospholipids
- bilirubin
- bile salts
Describe bile production
Primary bile is produced by hepatocytes
This is then modified by cholangiocytes:
- bicarbonate ions added
- water added
-
Describe cholangiocytes
Simple cuboidal epithelial cells
Lines the biliary tree
Modifies primary bile
Describe the flow of bile through a hepatic lobule and out of the kidneys
Bile produced in hepatocytes --> Flows in bile canaliculi --> bile ducts (portal triad) --> hepatic ducts
Describe the bile canaliculi
Small channels between the membranes of adjacent hepatocytes (joined by tight junctions)
They collect the bile produced by the hepatocytes
The hepatocytes have microvilli that project into the canaliculi, and release the produced bile
Describe the layers of the gallbladder
lumen --> simple columnar epithelium with microvilli --> lamina propria (connective tissue, rich in vasculature) --> smooth muscle --> adventitis (collagenous)
Describe the function of the gallbladder
Stores and modifies bile
Removes 80-90% of bile volume:
- pumps Na and Cl- ions from the bile
- water follows the ions
- water is removed by lymphatics
Delivers bile to duodenum:
- contracts to deliver bile
- controlled by nervous (vagal), and hormonal (cholecystokinin) influences
Describe the epithelium of the gallbladder
Tall simple columnar epithelium with microvilli
Describe cholecystitis
Gallbladder inflammation
Gallstones obstruct cystic duct --> gallbladder pressure increases --> muscular wall hypertrophy and inflammation
Is the pancreas mainly exocrine or endocrine?
Its function in 99% exocrine
Describe the exocrine function of the pancreas
produces digestive juices containing:
- proteases
- lipases
- nucleases
- amylases
- etc.
(^^ all in proenzyme form, are activated in the duodenum)
Juice feeds into the duodenum via the pancreatic duct
Describe the endocrine pancreas
diffuse islands of tissue called islets of Langerhans
makes up 1-2% of the pancreas
Describe the capsule of the pancreas
Thin connective tissue capsule
It is continuous with the septa that divide the pancreas into its lobules
Describe the hepatopancreatic ampulla
Main pancreatic duct joins Common bile duct forming Hepatopancreatic ampulla
It feeds into the duodenum
Describe an pancreatic intercalated duct
The duct extends into the acinus
the duct cells in the acinus are called centroacinar cells
Describe centroacinar cells
the duct cells of intercalated ducts that extend into the acinus
Describe a pancreatic aninus
an acinus of secretory cells surrounding an intercalated duct
