Theme 1: The Hepatic System Flashcards
What are the three learning outcomes for the hepatic system?
- Describe the key anatomy and physiology of the hepatic system, including the liver and portal hepatic system.
- Understand different functions of the liver and gallbladder.
- Understand how bilirubin is metabolised for safe excretion out of the body.
What is the livers two major function
It helps with nutrition, growth and repair
It helps with elimination
What are the two lobes of the liver?
The right and left lobe
The right lobe is 6 times larger than the left lobe.
(2 more smaller lobes called the caudate lobe and quadrate lobe)
What is the hepatic lobules?
Is the functional unit of the liver, it is shaped in a heaxagon shape (can be split into 6 sections)
Each section has working cells called ** hepatocytes** these are impressive cells as they do all the functions of the liver they also regenerate when damaged.
Each section has a 1. Bile duct 2. Portal vein and 3. Hepatic artery
> this is called the portal triad,
> each section is then connected to a dedicated sinusoids which drain processed blood into a hepatic vein which collectively drains blood to inferior vena cava.
What are the 7 roles and responsibilities of the liver?
Metabolism of macro-nutrients
Bile Production
Bilirubin metabolism
Detoxification
Blood storage
Mineral and nutrient storage
Hormone metabolism
What are the two major blood supplies to the liver>
Hepatic artery > provides the liver with o2 to function.
Hepatic portal vein > network called hepatic portal system
What is the hepatic portal system?
It supplies blood from a variet of organs
The contents of the blood will be different, for example as explored earlier the blood from the small intestines will have absorbed nutrients ready to be processed, whilst blood from the pancreas may have excess hormones that need metabolising.
What is the gall bladder?
The gallbladder stores bile produced by the liver and it can release bile in response to eating a meal. When we consume a meal, the gallbladder contracts and empties it’s bile contents into the common bile duct which mixes with enzymes produced by the pancreas.
This in turn breaks down fats from large globules into free fatty acids and glycerol which will be turned into mixed micelles ready for further production and absorption in the small intestines
Metabolism of macronutrients?
The liver can convert glucose into glycogen, the only polysaccharide that is stored in the body. Glucose is converted to glycogen through a process called glycogenesis. In response to insulin, the liver can release glycogen and convert glycogen into glucose via glycogenolysis which will increase blood glucose levels in response to hypoglycaemia. The liver can also generate glycogen from certain amino acids, lactate and glycerol. This is called gluconeogenesis.
What protiens are produced by liver?
Proteins are synthesised by the liver to create the majority of plasma proteins such as albumin, as well as the synthesis of amino acids.
All clotting factors are also synthesised from proteins in the liver, as is thrombopoietin which is the hormone that triggers bone marrow to produce platelets. This means that the liver contributes greatly to the body’s healing abilities.
What is formed by protein sythesis?
Waste products are formed by protein synthesis, including urea and ammonia. Ammonia needs to be converted in urea before it is excreted in urine. Urea is toxic so any build up of urea can be dangerous for the body. Thus another vital function of the liver is to detoxify ammonia into urea.
Lipids are used by the liver to synthesise cholesterol, as well as using fatty acids and glycerol to generate fat. This can then be used for body functions such as cell membrane integrity or be stored in adipose tissue.
What does the liver do with blood?
Because the liver is an expandable organ, it means it can collect and pool blood in all the blood vessels. This means that the liver is a very effective blood reservoir, which is useful in case there is excessive blood flow.
How does the liver produce bile?
Bile is produced by the liver and released via bile ducts. It can directly drain into the duodenum where is can emulsify fats, or it can be stored in the gall bladder ready for another tim
What is bilirubin?
It is the toxin produced in the production of red blood cells, it is toxic and results in yellow pigmentation of the skin (JAUNDICE)
- When the spleen first produces bilirubin, it is insoluble to water, meaning it will not be excreted > called unconjucted bilirubin
- When bilirubin is transported to the liver via plasma proteins, enzymes in the liver breakdown into water soluble which turns it to conjugated bilirubin (now can be excreted into fences and why is brown)
How is hormones metabolised in the hepatic system?
The pancreas sends blood to the portal system if excessive hormones such as insulin needs to be metabolised. This prevents dangerous build up of hormones that can cause more problems than good. The liver also produces hormones such as angiotensinogen which helps the renin angiotensin-aldosterone system (RAAS).
