Session 9: Liver Flashcards
The liver is divided into _____ lobes
Two
The blood that enters the liver comes from where via what?
The GI tract via the hepatic portal vein
How much bile do we produce a day?
1 Litre
When bile is not needed, where is it stored?
In the gall bladder
What is a portal system?
Two capillary systems in series
What are the two examples of portal systems in humans?
- The hepatic portal system (GI to Liver)
- The hypothalamo-hypophyseal portal system (hypothalamus to anterior pituitary)
In general, what happens at the capillary bed of the stomach and intestines?
Nutrients and toxins are absorbed
In general, what happens at the liver sinusoids?
Nutrients and toxins leave
What is the liver made up of?
Hepatic lobules
What travels in the portal vein?
Water, water soluble vitamins, electrolytes (sodium, potassium, chloride, bicarbonate, calcium, magnesium, iron), carbohydrates (glucose, galactose, fructose), proteins (amino acids, dipeptides, tripeptides), intestinal hormones, toxins (including ammonia)
Does ammonia cross the blood brain barrier?
Yes
The liver is the only organ in the body than can complete which cycle?
Urea cycle (Ornithine cycle)
What does the urea (Ornithine cycle) do?
Converts ammonia into urea which can then be excreted in the urine
Toxins can come in the form of what?
Chemicals Bacteris Viruses Protozoa Nematodes Cestodes Termatodes
What does NOT travel in the portal vein?
Lipids
Fat soluble vitamins (ADEK)
Dietary lipids are mostly what three things?
Triglycerides, cholesterol and phospholipids
What are lipids digested by?
Lipases
What is needed to digest lipids?
What do they form?
Bile acids
Micelles
What happens to lipids once they are taken into cells?
They are processed into chylomicrons
What happens to chylomicrons once they have been made?
They are taken up by LACTEALS (part of the lymphatics)
Lacteals contain what?
Chyle
How do lipids eventually end up in the liver if they cannot pass through the hepatic portal vein?
They are processed into chylomicrons and then taken up by lacteals which drain into the abdominal lymphatics which drains into the thoracic duct which joins the venous system at the junction of the left internal jugular vein and subclavian vein. The chylomicrons then enter the liver via the hepatic artery
What are the main functions of the liver?
Metabolism (Catabolism/Anabolism) Storage Filtering Protein--> Bloodstream Detoxification Bile Production
What things are stored in the Liver?
Iron Vitamin A Vitamin B12 Vitamin D Vitamin K Glycogen Carbohydrate Protein
What products are made during anabolism by the Liver?
Albumin Glycogen Numerous coagulation factors Haematopoesis in foetus Complement components of the immune system
What things are broken down during catabolism by the Liver?
Drugs (CYTP450) Hormones Haemoglobin Poisons (CYTP450) (Aged RBCs after spleenectomy)
Which cells aid the Livers filtering function?
What are the cells responsible for?
Kupffer cells
They are responsible for filtering bacteria and small foreign proteins from the blood
Does the Liver have exocrine or endocrine functions?
Both endocrine and exocrine
What is an exocrine function of the Liver?
Secretion of Bile
What are the endocrine functions of the Liver?
Produces: Angiotensin, Thrombopoetin, IGF-1
It modifies Vitamin D and thyroxine to their active forms
It breaks down: Insulin and Glucagon, Oestrogen and Progesterone
What are some features of Hepatocytes?
They renew very well They have lots of mitochondria They have lots of peroxisomes They have lots of free ribosomes They have lots of RER and SER They have lots of Golgi complexes Glycogen deposits
What is a sinusoid?
An irregular tubular space for the passage of blood, taking the place of capillaries and venules in the liver, spleen and bone marrow
What is the portal trid seen throughout the liver?
Portal Venule
Hepatic Artery
Bile duct
Hepatic sinusoids are made up of what cells?
Fenestrated, discontinuous endothelium
Blood from the hepatic artery and the portal venule enter the sinusoid and leave via what?
The central vein
Where do the lymphatics arise from in the Liver?
Periportal space (Space of Mall)
Where do the lymphatics drain to from the liver?
The liver hilum and then onto the hepatic duct
What are the three different perspective of the liver lobules?
Classic lobule
Liver acinus
Portal lobule
What is a bile canaliculus?
Thin tube that collects bile secreted by hepatocytes
What is the space of Disse?
The perisinusoidal space (or space of Disse) is between a hepatocyte and a sinusoid.
What cells can be found in the space of Disse?
Hepatic stellate cells (Ito cells)
What is the role of Stellate cells?
Vitamin A storage
They are full of cytoplasmic vacuoles containing vitamin A
What happens to Stellate cells in liver cirrhosis?
They lose their vitamin A storage ability and differentiate into myofibroblasts that synthesise and deposit collagen resulting in Liver fibrosis
How does liver fibrosis lead to portal hypertension?
What else can this lead to?
The collagen produces by myofibroblasts surround the central vein and constrict it
Vomiting large amounts of blood as the blood tried to find other routes back to the IVC
What are Kupffer cells?
Why are they so important?
Monocyte derived specialist macrophages that form part of the lining of the sinusoids
They are constantly exposed to gut-derived bacteria, microbial debris and bacterial endotoxins
How do the Kupffer cells migrate from the sinusoids into liver tissue at sites of inflammation and damage?
By moving through the perforations in the endothelium
