Excrerion - The Kidneys Flashcards
What are the kidneys?
Excretion organs part or the urinary system
What are the three main roles of the kidney?
- Removal of urea from the blood
- Adjustment of salt levels in the blood
- Adjustment of water content in the blood
Where and why is urea produced?
- In the liver due to excess amino acids
How do the kidneys preform the three roles?
They filter stuff out of the body at high pressure and then reabsorb the useful things - the end product is urine
What are nephrons?
Filtration units in the kidneys - the kidneys contain thousands of nephrons
What three steps take place in the nephron?
- Ultrafiltration
- Réabsorption
- Release of wastes
What happens in ultrafiltration?
- Blood from renal artery flows through the glomerulus
- High pressure is built up which squeezes water, urea, salts and glucose out of the blood into Bowmans Capsule
- Membranes in the glomerulus act like filters so bog molecules like proteins are not squeezed out and say on the blood
What is the filtered liquid in the Bowmans Capsule called?
Glomerular filtrate
What happens in reabsorption?
Useful substances are selectively reabsorbed
Name the three things that are reabsorbed back into the blood?
- All glucose from proximal convoluted tubule by active transport
- Sufficient salt (excess isnt)
- Sufficient water from collecting duct to bloodstream
What happens in the release of wastes?
- Remaining substances (water, salts urea) form urine
- Urine leaves the nephrons through the ureter down to the bladder where it is stored and released via the urethra
