5.1.2 Excretion Flashcards
excretion
define excretion
excretion is the removal of the waste products of metabolism from the body. it helps to maintain metabolism and homeostasis.
and example of a metabolic product we remove from the body.
carbon dioxide from respiration. it is expelled from the lungs in mammals and gills in fish.
what is the function of the hepatic artery
supplies the liver with oxygenated blood from the heart so the liver has a good supply of oxygen for respiration.
what is the function of the hepatic vein
takes deoxygenated blood away from the liver
what is the function of the hepatic portal vein
brings blood from the duodenum and ileum (small intestine) so it is rich in products from digestion so harmful products can be filtered out and broken down immediately
what units is the liver made up from
liver lobules
what is a sinusoid
where blood from the hepatic artery and hepatic portal vein mix
what do hepatocytes do
remove harmful substances from the blood and break them down into less harmful substances that then re-enter the blood
what is a bile canaliculus
tubes which bile is secreted into from hepatocytes which connect up to the bile ducts
what is the function of a kupffer cell
removes bacteria and breaks down old red blood cells
what is in the centre of each lobule
central vein leading to hepatic vein
what are excess amino acids broken down into
ammonia and keto acids
what are the keto acids used for
enter the Krebs cycle and respired to give atp or stored as glycogen
what cycle does ammonia enter
ornithine cycle
what is the purpose of the ornithine cycle
to convert ammonia to urea
what is the removal of amine groups from amino acids called
deamination
what is the first step in the ornithine cycle
ammonia is combined with carbon dioxide which reacts with ornithine to get citrulline
what is the second step of the ornithine cycle
ammonia is added to citrulline to make arginine. water is lost
what is the third step of the ornithine cycle
water is added to arginine to regenerate ornithine and produce urea
how does the liver remove alcohol
breaks it down into ethanal and then acetic acid which is less harmful
name 2 substances that the liver breaks down
alcohol, paracetamol and insulin
what does excess alcohol do to the liver
cirrhosis of the liver (ells die leaving scar tissue blocking blood flow)
what does the liver store
glycogen
what blood vessel does blood enter the kidney through
renal artery
which is the darker thick layer of the kidney
medulla
what is the outer light layer of the kidney
cortex
what tube does urea leave kidney via
ureter
what is the pelvis of the kidney
area at the centre of the kidney where urine collects to be filtered into ureter
where does ultrafiltration take pace
glomerulus and bowman’s capsule
what causes liquid and small molecules to filter out of capillaries.
the afferent capillary has a wider lumen then the efferent which causes there to be a high pressure pushing out the liquids and small molecules.
what is the basement membrane
stops larger molecules leaving the capillaries
what are podocytes
cells that are wrapped around the bowman’s capsule and allow filtration
what is selective reabsorption
when useful substances are reabsorbed back into the blood
where does selective reabsorption take place
proximal convoluted tubule
how does selective reabsorption take place
- sodium ions are co transported into cells of the PCT wall with glucose and amino acids
- glucose and amino acids can enter blood via diffusion down a concentration gradient, sodium ions are actively transported into blood
- water moves by osmosis to the blood from the PCT
what mechanism is used to reabsorb water in the loop of Henle
counter current multiplier
how is water reabsorbed in the loop of henle
- sodium and chloride ions are actively transported out of the ascending limb which decreases the water potential in the medulla
- water diffuses out the descending limb via osmosis
3some ions are reabsorbed into the descending limb to create a cycle
which limb of the loop of Henle is impermeable to water
ascending limb
what hormone controls water reabsorption
ADH (antidiuretic hormone)
what gland releases ADH
posterior pituitary gland
what detects changes in water potential
osmoreceptors in the hypothalamus
what happens when ADH binds to receptors on collecting duct membrane
- stimulates CAMP production which stimulates vesicles containing aquaporins to bind with membrane
2 water can filter out of the aquaporin channels
is there more or less concentrated urine when more ADH is produced
more concentrated
how can we detect kidney failure
glomerular filtration rate is low
what can cause kidney failure
high blood pressure and infections
what problems does kidney failure cause
build up of waste, fluid accumulation, imbalance of electrolytes and anaemia
what is haemodialysis
patients blood is passed through a dialysis machine. waste filters out into dialysis fluid. anti clotting agents are added
advantages of haemodialysis
only need to do it a few times a week
what is peritoneal dialysis
dialysis fluid enters abdominal cavity and waste diffuses across peritoneum.
advantages of peritoneal dialysis
can be done at home
what is a kidney transplant
a new kidney is implanted to replace the damaged one
advantages of transplant
cheaper than continual dialysis and more convenient
disadvantages of transplant
can be rejected by immune system and risks of infection during surgery
how is urine used in pregnancy tests
- monoclonal antibodies attached to a dye bind to hCG in urine of pregnant woman.
- urine moves up to test strip where immobilised antibodies are fixed. hCG binds to them and dye is concentrated showing a positive result
what is the other method of chemical testing of urine
gas chromatography and mass spectrometry
what animals would have a longer loop of henle
ones living in dry environments because they will need to reabsorb more water
