Flashcards in Liver Deck (23):
Which cells constitute the liver and what is special about these?
- 80% composed of hepatocytes
- Have high regeneration potential - useful for liver transplant.
What are the 5 functions of the liver?
1. Metabolism (anabolism & catabolism)
4. Exocrine function - bile production
5. Endocrine function
The liver is involved in the anabolism (synthesis) of which molecules?
1. Plasma proteins (e.g. Albumin, coagulation factors, Fe and Cu transport proteins)
2. Complement components
4. Haematopoiesis in foetus
The liver is involved in the catabolism (breakdown/toxin degradation) of which molecules?
1. Drugs and poisons (via cytochrome P450)
4. Can take over removal of aged RBCs after splenectomy
What is the role of the liver in storage?
- Storage of carbohydrates and fats as:
- Storage of iron and vitamins A, B12, D and K (liver is very nutritious organ)
Describe the role of the liver in immunity. Why is it an effective immune organ?
- Filtering function: Kupffer cells (type of fixed macrophage) line the sinusoids and play important role in capturing/digesting pathogens and cellular debris.
- Large volume of blood passing through hepatic portal system and liver allows Kupffer cells to clean large volumes of blood very quickly.
What is the exocrine function of the liver?
- Hepatocytes produce bile (1 litre/day) - active role in digestion.
- Bile passes through bile ducts and is stored in the gall bladder. Presence of fat-containing food stimulates duodenum cells to release cholecystokinin - bile secreted to duodenum and emulsifies fat.
How is haem excreted from the body?
1. Kupffer cells destroy old RBCs, but haem cannot be recycled.
2. Hepatocytes convert haem to bilirubin pigment.
3. Bilirubin added to bile to be excreted from the body.
How does the liver act as an endocrine gland?
1. Angiotensinogen (hormone causing vasoconstriction)
2. Thrombopoietin (hormone regulating production of platelets)
3. Insulin-like growth factor 1 (IGF-1) (hormone important in growth and anabolism)
In connection with endocrine function:
1. Modifies vitamin D and thyroxin to active forms
2. Breaks down insulin, glucagon, oestrogen and progesterone
Describe the gross anatomy of the liver.
Consists of 4 distinct lobes:
3. Caudate (posterior side of right lobe, wraps around vena cava)
4. Quadrate (inferior to caudate lobe, wraps around gall bladder)
Where does the peritoneum connect with the liver?
1. Coronary ligament
2. Left triangular ligament
3. Right triangular ligament
4. Falciform ligament
Why is the blood supply to the liver unique?
Has 2 separate blood supplies:
1. Proper hepatic artery supplies O2-rich blood from aorta - 25%.
2. Hepatic portal vein supplies nutrient-rich blood (collects in vein after passing through capillaries of the spleen, stomach, pancreas, gall bladder and intestines) - 75%.
How does blood leave the liver?
Hepatic vein carries nutrient- and O2- poor blood away from the liver to the inferior vena cava and heart.
Which vessel enables bile to leave the liver?
Common hepatic duct.
What is a sinusoid?
Irregular tubular space for passage of blood, taking the place of capillaries and venules in the liver, spleen and bone marrow.
Endothelial cells have large gaps.
What are portal triads?
Hepatic portal vein + proper hepatic artery + common bile duct
Describe a hepatic lobule.
- Hexagonal (or irregular polygonal) arrangement of hepatocytes.
- Surrounded by portal triads, off which branch hepatic sinusoids - allow hepatocytes to extract nutrients for the metabolism or storage of macromolecules and to access oxygen.
- Proper hepatic arterioles and hepatic portal venules drain into a central vein (terminal hepatic venule) when then coalesces into a hepatic vein.
What surrounds portal triads and what arises from this?
- Periportal space of Mall
- Lymphatics arise from this and drain to the liver hilum and then onto the hepatic duct
What is a more pathologically significant structure of hepatocytes units than the liver lobule?
- Liver acinus (between 2 central veins) as it is the cells nearer this acinus that get damaged by toxins.
What structure transports bile into bile ducts?
What is the space of Disse?
- Gap between sinusoids lumen and hepatocytes.
- Allows passage of blood, enabling cells to take up products using large microvilli surface area.
- Contains stellate (Ito) cells.
What are stellate cells?
- Cells full of cytoplasmic vacuoles containing vitamin A.