Topic 9 - Detoxification: Liver Flashcards
Learning objectives
- Descibe external and microscopic anatomy of the liver, including the portal vein, hapatic arteries, bile ducts, liver lobules and portal triads
- Describe the livers role on maintaining blood cholestrole levels
- Describe how albumin helps maintain blood volume
- Describe the control of iron balance in the body, including the role of transferrin, ferroportin and hepcidin
Hepatic = Liver
Ferrous = Iron
Liver location
- Under ribcage
- Mostly on RHS of body
- Ontop of gall bladder
Liver blood supply
Hepatic Portal vein
- Gut to liver (food broken down, high in nutrients, low in O2)
Hepatic Vein
- Liver to heart (Low in O2)
Hepatic artery
- Heart to liver (High in O2)
Liver Internal Anatomy
- Main liver cells are called hepatocytes (They are responsible for most functions of the liver) (80% cells are hepatocytes)
Portal triad
- Group of 3 vessels (2 deliver blood, 1 takes away, creating high pressue)
Central Vein
- Takes blood away from liver tissue
Cholesterol balance
Cholesterol is in cell membranes helping maintain flexibility of the membrane
The liver helps maintain cholesterol levels in the body with LDL & HDL.
* too much cholesterol is dangeous as it builds up in blood vessels causing blockages
- Triglycerides can create cholesterol in the liver
- Cholesterol can be taken from the liver to the gut by bile
Low density lipoproteins (LDL)
Moves cholesterol from the liver to deposit in blood vessels
- Often persieved as bad
High Density Lipoproteins (HDL)
Moves cholesterol from deposits back into the liver
- Often persieved as good
Albumin and H2O in blood
- Albumin is a blood protein responsible for maintaining blood osmolarity
- Albumin proteins increase the osmolarity of blood, preventing water loss into the interstitual fluid
- Albumin sits in blood vessels
Iron Balance
- Iron helps red blood cells carry oxygen
- Free iron ions are toxic, but is safely carried in tranferrin
- Transferrin is a glycoprotein that carries 2 iron atoms at once
- RBC are made in bone marrow
Factors increasing iron in the body
- Absorption from the gut (food)
- Recycling RBC
- Release of stores in the liver (from ferritin)
Factors decreasing iron in blood
- Making more RBC
- Blood loss (menstruation/ injury)
- Cells lost from lining of gut and skin
- There is no mechanism to get rid of excess iron
Iron in and out of cells
Into cells:
- Transferrin binds to a receptor on the cell surface, then moves inside to release the iron
Out of a cell:
- Can only leave cells through ferroportin
Ferroportin
The exit pathway for iron to leave a cell
Found in 3 places:
Gut cells
* Absorption from food, then into circulation via ferroportin
White Blood Cells
* Phagocytose of old RBC and release iron into circulation via ferroportin
Liver
* Release stored iron from ferritin via ferroportin transporters
Control of iron levels in the blood stream
Controlled by a Negative feedback loop
- Usual transferrin levels are 250-300mg/dl
Hepcidin is the controller hormone
- Ferroportin acts like a trap, releasing iron into the blood stream
Hepcidin role
The hormone that controls ferroportin
- Hepcidin turns off the ferroportin transporters
- Hepcidin binds to ferroportin transporters, removing it from the membrane breaking it down. Preventing the release of iron from cells into the blood stream
