The liver and excretion Flashcards
(13 cards)
What is excretion?
Excretion is the removal of the waste products of metabolism.
-metabolism produces waste products such as Co2 and nitrogenous waste which are toxic and so if they were left to build up they would cause damage in the body e.g by affecting other metabolic reactions.
Why is excretion important?
As it removes waste products from the body, maintaining normal metabolism and homeostasis.
What is one of the functions of the liver?
to break down metabolic waste products and other substances that can be harmful, like drugs and alcohol. they are broken down into less harmful products that can be excreted.
what does the hepatic artery do?
the hepatic artery supplies the liver with oxygenated blood from the heart, so the liver has a good supply of oxygen for respiration, providing plenty of energy.
what does the hepatic vein do?
takes deoxygenated blood away from the liver.
what does the hepatic portal vein do?
the hepatic portal vein brings blood from the duodenum and ileum (parts of the small intestine), so it’s rich in the products of digestion.
this means that any ingested harmful substances are filtered out and broken down straight away.
what’s the role of the bile duct?
the bile duct takes bile (a substance produced by the liver to emulsify fats) to the gall bladder to be stored.
Give a general explanation of the liver histology.
-the liver is made up of liver lobules which are cylindrical structures.
-these structures are made up of cells called hepatocytes, arranged in rows radiating out from the centre.
- each lobule has a central vein in the middle that connects to the hepatic vein.
-many branches of the hepatic artery, hepatic portal vein, and bile duct are also found connected to each lobule.
- the hepatic portal vein and hepatic artery are connected to the central vein by capillaries called sinusoids.
- Blood runs through the sinusoids, past the hepatocytes that remove harmful substances and oxygen from the blood.
-the harmful substances are broken down by the hepatocytes into less harmul substances which then re-enter the blood.
-the blood runs to the central vein, and the central veins from all the lobules connect up to form the hepatic vein.
- cells called kupffer cells are also attached to the walls of the sinusoids.
- they remove the bacteria and break down old red blood cells.
-hepatocytes produce bile and secrete it into tubes called bile canaliculi.
-these tubes drain into the bile ducts.
-the bile ducts from the lobules eventually connect up and leave the liver.
amino acids getting broken down in the liver:
what is deamination?
- first, the nitrogen-containing amino groups
(-NH2) are removed from any excess amino acids, forming ammonia (NH3) and organic acids.
amino acids —-} ammonia + organic acids
- the organic acids can be respired to give ATP or converted to carbohydrate and stored as glycogen.
what is the ornithine cycle?
- ammonia is too toxic for mammals to excrete directly, so it is combined with Co2 in the ornithine cycle to create urea and water.
ammonia + carbon dioxide —–} urea and water. - the urea is released from the liver and into the blood. the kidneys then filter the blood and remove the urea as urine, which is excreted by the body.
what is deoxification?
the process in which the liver breaks down other harmful substances e.g. alcohol, drugs, and unwanted hormones. they are broken down into less harmful compounds that can be excreted from the body.
what are three examples of some harmful products broken down in the liver?
alcohol( ethanol)-
alcohol can damage cells. it is broken down in the liver into ethanal, which is then broken down into a less harmful substance called acetic acid. excess alcohol over a long period can lead to cirrhosis of the liver( when the cells of the liver die and scar tissue blocks blood flow.
paracetamol-
excess paracetamol in the blood can lead to liver and kidney failure.
Insulin-
insulin is also broken down by the liver as excess insulin can cause problems with blood sugar levels.
explain glycogen storage
the liver converts excess glucose in the blood to glycogen in a process called glycogenesis. the glycogen is then stored as granules in the liver cells until the glucose is needed for energy.
