Week 1- Flashcards
what is the anatomy of the liver? size, segments
-can have hepatic diseases
-it is the largest organ in the body
-has a left and right lobe which are divided into 8 segments called lobules
-capillaries will join to form veins
-bile ducts join to form common bile duct which drains
bile into duodenum after storage and concentration in
the gallbladder
how is each lobule described as containing?
-they each have a central vein, radiating sinusoids (type of blood capillary), bile ducts, hepatocytes and other cells
what is the blood supply like for the liver?
- it has an aorta that carries blood from the heart and branches to the hepatic arteries in the left and right lobe
- has the hepatic vein that carries deoxygenated blood from liver to heart through the inferior vena cava
- hepatic portal vein which carries nutrient rich blood coming from the gastrointestinal tract
- bile ducts that gather and form the common bile duct which then has the gall bladder off it which stores the bile
what is the vascular structure of the liver?
-25% of resting cardiac output
-Hepatic artery –
25% of blood to
liver – oxygen rich
-Hepatic portal vein
– 75% of blood to
liver – nutrient rich coming from the gut
-Leaves by hepatic
vein to vena cava
what is the hepatic lobules described as looking like?
- hexagonal structures and in the middle there is a central vein
- outside there is a portal triad, a branch of the hepatic artery, portal vein and bile duct
how does blood get into the liver?
from the outside through the hepatic artery and portal vein which turn into sinusoidal capillaries then eventually they will join to get the central vein taking deoxygenated blood away
what is the main component of the liver?
hepatocytes its the cells and make and store everything in the liver
what are bile canaliculi? where are they found?
found between hepatocytes they are small branches of the bile ducts that will then take the bile made from the hepatocytes away
what is the portal triad?
portal vein, bile duct and hepatic artery
what is the structure of the hepatic lobule?
- in the centre there is the central vein
- on the outside of the hexagon theres the bile duct, the portal vein and hepatic artery
- between this both there are hepatocytes and bile canaliculus that gathers the bile made by the hepatocytes
what are the important cells that are present in the hepatic lobule?
-hepatocytes
-macrophages
resident macrophages (Kupffer cells) involved with phagocytosis of foreign stuff, can also become inflammatory cells
-fibrocytes- support hepatocytes and are responsible for fibrosis during liver disease.
-hepatic stellate cells, support hepatocytes and are responsible for fibrosis during liver disease.
what are the funcions of the liver?
Metabolism Immunity Storage Detoxification of drugs Synthesis Catabolism Activation Transport Excretion
how is the liver involved with metabolism?
-liver involved with breaking down and storing nutrients
-Carbohydrate
Stores glucose as glycogen
Glycogenolysis in fasting
Gluconeogenesis in fasting
-Lipid
Synthesis of cholesterol cholesterol is carried around in the body by Lipoproteins – VLDL, LDL,
HDL
- Protein
Amino acid synthesis
Breakdown of amino acids to ammonia and then
urea for excretion
in the liver harmful ammonia is converted into what ?
urea
what does the liver detoxify? how does it occur?
- drugs and xenobiotics (contaminants etc)
- Phase I reactions by cytochrome P450 enzymes
- Phase II reactions – conjugation with other compounds to become more hydrophyllic eg gluconosyltransferases
what affects our ability to detoxify stuff in the liver?
-Age, nutrition and genetics influence drug metabolism
how and what does the liver modify?
hormones
-vitamin D3 converted to 25-OH vitamin D3 in the liver then travels to the kidney to become 125-OH vit D3
how and what does the liver degrade?
hormones
- Insulin and glucagon
-Oestrogens, glucocorticoids, growth hormone, PTH
-Gastrin and other GI hormones (although kidney
degrades more of these)
what is stored in the liver?
Fats Glycogen Trace elements – Copper, Iron Vitamins Vitamin A Vitamin D Vitamin K Some water-soluble B vitamins for shorter periods
what is a fatty liver and what is it and indication and early sign of what disease?
when the liver is taken up and storing fats
early signs of liver disease but is reversible
what hormones are synthesised in the liver?
- Insulin-like growth factor
- Thrombopoietin – stimulates platelets
what plasma proteins are synthesised in the liver?
- Coagulation factors
- Transport for cholesterol (lipoproteins)
- Transport for steroid and thyroid hormones
- Angiotensinogen – important in salt conservation
what iron transport and metabolism proteins are synthesised in the liver?
Transferrin= transports iron in the blood haptaglobin= binds free haemoglobin in the blood hemopexin= bings free haem in the blood hepcidin= inhibits uptake of iron in the gut
why is it important to not have free iron in the blood?
- it is a prooxidant so can cause damage to vascular cells could lead to CVD
- during infection pathogens will take in iron as its one of the key nutrients
what other acute phase proteins are synthesised in the liver?
-complement proteins
what are the 2 different types of bile salts that are synthesised in the liver?
Primary – cholic acid and chenodeoxycholic acid
Secondary – deoxycholic acid and lithocholic acid
what does bile consist of?
Aqueous alkaline fluid containing: Bile salts Cholesterol Lecithin Bilirubin
what is bile’s pathway through the body?
Actively secreted by liver and actively diverted to gallbladder between meals then moves into duodenum after a meal
what are the main facts about bile salts?
-Derivatives of cholesterol
-Convert large fat
globules into a liquid
emulsion as micelles which therefore increases the SA for lipase to work on
-After participation in
fat digestion and
absorption, most are
reabsorbed into the
blood
what is the structure of a micelle?
in the middle there’s the lipid and the outside there’s the aqueous layer
how are bile salts excreted?
95% of them will be rearbsorded in the terminal ileum and recycled
- 5% will be lost in faeces
- one of the components is bilirubin which is a breakdown product of haem
what is the pathway for removal of RBC and Heme breakdown?
- when RBC have done their job they’ll be broken down and the heme will be broken down to bilirubin by macrophages sing an enzyme called heme oxygenase-1
- the unconjugated bilirubin thats formed is all complexed in the liver and conjugated to glucuronic acid
- this conjugated bilirubin is then secreted into the bile and travels to the intestine
- in the intestine in the colon part the glucuronic acid is removed by the bacteria
- the bilirubin that is now free is converted to urobilinogen some of this is reabsorbed into the blood and then transported to the kidney
- the rest will stay in the colon and be excreted and the urobilinogen left in the colon is the oxidised by intestinal bacteria and goes to stercoblin some is reabsorbed then excreted again.
what is the immune function in the liver?
- Carried out by the Reticuloendothelial system
- Macrophages (Kupffer cells attached to endothelium)
phagocytose and degrade bacterial/other antigens
carried from the gastrointestinal system in the portal
vein
-Hepatic stellate cells
Perisinusoidal
Antigen-presenting role
Major cell involved in liver fibrosis - Other immune cells
Role in inflammatory response
