5.1.2 - excretion - the liver Flashcards
excretion
removal of the waste products of metabolism from the body
how is carbon dioxide excreted
excreted from the lungs as one of the waste products of cellular respiration
how are bile pigments excreted
excreted in the bile from the liver into the small intenstine via the gall bladder and bile duct
how are bile pigments formed
formed in the breakdown of haemoglobin from old red blood cells in the liver
why is the release of faeces called egestion, not excretion?
not involved in metabolic reactions in cells, just undigested food which have never entered the bloodstream.
why do we get rid of metabolic waste products
they can alter the pH interfering with cell processes so the normal metabolism is affected, they may also inhibit enzymes
why must we excrete nitrogenous compounds?
amino acids cant be stored because they have a toxic animo group that needs removing
hepatic artery
supplies the liver with oxygenated blood from the heart so the liver gas a good supply of oxygen for respiration, providing plenty of energy
hepatic vein
takes deoxygenated blood away from the liver
hepatic portal vein
brings blood from the small intestine so its rich in the products of digestion; means any harmful substances are filtered out and broken down straight away
bile duct
duct that carries the bile secreted in the liver from the liver to the gall bladder
why is it important that the blood flows from the stomach and intestines to the liver before it enters general circulation?
so that any toxins which entered blood can be removed from blood before general circulation (preventing potential harm)
lobules
cylinderical structures made up of rows of individual liver cells called hepatocytes
in what vessel does blood from the vein and arteries mix
sinusoids
role of the hepatocytes
remove oxygen, release carbon dioxide and detoxify the blood as it flows past
what is the purpose of blood passing through sinusoids
put the blood in close contant with liver cells that alter the concentrations of substances in it
canaliculi
little channeks that collect the bile made by the hepatocytes
kupffer cells
deal with any pathogens entering the liver
how do hepatocytes store glycogen
in granules in the cytoplasm
how does bile help with digestion
bile emulsifies lipids (fats), it breaks them down into smaller droplets which have a high surface area so they can be acted on more efficiently by lipase enzymes
how is alcohol broken down by detoxification
ethanol is broken down by ethanol dehydrogenase to ethanal which is then converted to ethanoate.
this is converted into fatty acids, then into acetyl co-A which can be used in respiration
what is deamination?
the removal of the amino group from an amino acid producing ammonia and a keto acid
what is the ornithine cycle?
ammonia is converted to urea by combining it with co2 and the amino acid ornithine
why do we convert ammonia into urea for excretion rather than just excreting the ammonia?
urea is less toxic and less soluble than ammonia
less water is needed to excrete it from the body (reduces water loss)
function of the liver - carbohydrate metablism
when blood glucose levels rise, insulin levsls rise and stimulate hepatocytes to convert glucose to glycogen
