Into To Liver Flashcards
Describe the anatomy of the liver
The liver has a vascular system, the biliary tree (a system of ducts
that transport bile out of the liver into the small intestine) and an arrangement of liver cells within
these two systems. The liver has a left and right lobe anteriorly with each lobe supplied with its own
blood supply. The two lobes are separated by the falciform ligament. At the bottom of the liver is the
gall bladder (not all species have one).
Describe the quantities of blood supply in the liver
The blood supply of the liver is unique in that around 75% of it is venous blood via the portal vein
coming from the GI tract. This is related to the liver’s function of removing harmful toxins and waste
products before they reach other parts of the body. The remaining 25% of blood supplying the liver
comes from the hepatic artery.
Where does blood from the central veins drain into
Blood from the central veins in the liver lobules drains into the
hepatic vein that then drains into the vena cava.
What are the two types of liver cell
There are two primary cell types of the liver and these are hepatocytes
and Kupffer cells.
What do hepatocytes and kupffer cells do
Hepatocytes account for around 60% of the cells in the
liver and they perform most of the liver’s metabolic functions whilst
Kupffer cells account for around 30% of cells in the liver. Kupffer cells are a
type of tissue macrophage and remove damaged RBCs, bacteria and
viruses.
What are other liver cell types that are present
Other liver cell types include liver endothelial and stellate cells.
Describe the functional unit of the liver
Afunctional unit in the liver is known as the hepatic lobule. It is composed
of hexagonal plates of hepatocytes around a central hepatic vein. At each
6 corners of a lobule is a triad of branches of the portal vein, hepatic
artery and bile duct. Blood from the hepatic arteries and the portal veins
drains into sinusoids that are lined with hepatocytes. These hepatocytes
are then able to access the different nutrients found in the blood passing
through the sinusoids as well as oxygen for respiration. Blood from the sinusoids then drains into
venules that collect in larger veins and then eventually the hepatic vein.
How is bile able to secreted by hepatocytes
The bile duct carries bile and
is lined by hepatocytes that secret bile through a series of channels between cells known as
canaliculi that drain into ducts increasing in size that join up to become the common bile duct. The
flow of bile is in the opposite direction to the flow of blood.
What is the function of Lobule and microstructure structure
The lobules give the liver a very dense
structure. The liver’s microstructure give it a massive surface area for exchange of molecules as well
as a sophisticated way of separating blood from bile. It also allows for specific positioning of different
pumps to achieve specific localisation of materials at the cellular level.
How does the liver act as a protective barrier to the body
The liver acts as a protective barrier to the body mainly mediated through its Kupffer cells. As blood
flows through intestinal capillaries, it picks up many bacteria from the intestine that are almost
always able to colonise. This blood is then filtered at the liver through sinusoids that have Kupffer
cells lining them. These Kupffer cells efficiently remove any bacteria from the blood they come into
contact with (only 0.01s contact time). Less than 1% of bacteria entering portal blood succeeds in
passing through the liver into systemic circulation.
Describe bile and it’s contents
Bile is a complex greenish-yellow liquid consisting of water, electrolytes and organic molecules that
include bile acids, cholesterol, bilirubin and phospholipids. Around 400-800 ml of bile is produced
everyday with hepatocytes initially secreting this bile into canaliculi.
Describe bile before and after modification
This bile that flows into bile
ducts contains large amounts of bile salts, cholesterol and other organic compounds. Its components
are then modified by epithelial ductal cells that secrete bicarbonate-rich secretions as well as water.
Bile is essential for fat digestion, specifically in fat emulsification.
What is the functions of bile
Bile in conjunction with pancreatic
juice, also neutralises gastric juice as it enters the small intestine to provide an environment for
digestive enzymes in the small intestine to work at their optimum.
Bile is also involved in the
elimination of waste products from blood, in particular, bilirubin and cholesterol (approximately 500
mg of cholesterol converted to bile acids daily).
How can bile collected from hepatic ducts be collected
Bile from hepatic ducts can be collected into the
common bile duct where it then enters the duodenum via the sphincter of Odii, or it can be diverted
into the gall bladder via the cystic duct where it is concentrated 5-fold (by removing water and
electrolytes in a process that can lead to gall stones) and stored for future use (30-50 ml).
What compound is excreted into bile
The liver metabolises and excretes many compounds into bile with an important compound being
bilirubin. This is a yellow compound formed from the breakdown of haemoglobin.