excretion

• excretion 


  the removal of metabolic waste products and other substances from the body
• homeostasis 


  maintenance of a relatively constant internal environment even if the external environment changes
• what does excretion do?

  it helps keep toxin levels relatively low
• job role of the liver

  breaks down metabolic waste products and harmful substances
• liver structure

  it is made up of liver lobules - cylindrical, and made up of hepatocytes
• deamination 


  the removal of the amine group from an amino acid

  amino acids -> ammonia + organic acids
• ornithine cycle 


  ammonia + carbon dioxide -> urea + water
• urea is less soluble than ammonia, so is less toxic
• what is the protein tested for in a pregnancy test?

  hCG
• how is excretion important in maintaining homeostasis?

  by preventing the accumulation of harmful substances
• bowman's capsule and ultrafiltration

  the filtration barrier consists of the capillary endothelium, the basement membrane, and podocytes, which create small gaps allowing small molecules like water, ions, glucose, and urea to pass through into the glomerular filtrate, while larger molecules such as plasma proteins and blood cells remain in the blood.
• role of the loop of henle

  creates a concentration gradient in the medulla, which is essential for the production of concentrated urine.
• descending limb of loop of henle

  permeable to water
• ascending limb of loop of henle

  impermeable to water

  transports sodium and chloride ions into the medulla through active transport
• what is the main nitrogenous waste product in birds and reptiles

  uric acid
• what is a Kupffer cell

  a specialised type of macrophage that travel within the sinusoids of the liver and breakdown and recycle old red blood cells
• regulating blood glucose concentration

  hepatocytes convert glucose into glycogen
• detoxification of alcohol and drugs
• hepatocytes make bile
• what are sinusoids?


  a type of capillary that connects the hepatic artery and the hepatic portal vein to the central vein