Remove wastes
Cells produce wastes. The excretory system helps remove them and regulate internal conditions. The lungs remove carbon dioxide; the kidneys help remove dissolved wastes from blood.
Excretory system
Investigate how the body removes wastes and balances water.
Class notes
Open PDF →Kidneys filter and regulate
Kidneys filter blood and adjust the amounts of water, salts and other substances returned to it. They produce urine containing excess water and dissolved wastes including urea.
Follow urine
Urine moves from each kidney through a ureter to the bladder. It leaves the body through the urethra. Blood travels to and from the kidneys through blood vessels.
Look inside a kidney
Rotate the kidney and switch from the exterior to its cross-section.
Investigate
Find the renal artery, renal vein and ureter. Follow the blood route separately from the urine route.
Make the connection
Explain why the ureter carries urine while the renal vein carries blood. The model shows kidney anatomy; the microscopic filters are too small to see at this scale.
If the model cannot load on your device, use the illustrated class notes above and the pathway below to trace the same structures.
Explore this idea further
Watch: The excretory system · Crash Course
Investigate how the body removes wastes and balances water.
Open on YouTube →Why do the kidneys need the circulatory system?
Reveal the reasoning
Blood carries dissolved wastes to the kidneys, where filtration and regulation help maintain internal balance.
Try it yourself.
How do the circulatory and urinary systems work together?
Check your thinking
Blood carries dissolved wastes to the kidneys. The kidneys filter and regulate substances in blood and produce urine.
Common question: Are ureters and the urethra the same structure?
No. Ureters carry urine from kidneys to bladder; the urethra carries urine out of the bladder.
Take it further.
A student says urine travels through veins. Explain the difference between blood and urine pathways.
See a possible explanation
Blood reaches the kidneys through blood vessels. Urine leaves kidneys through ureters, collects in the bladder and exits through the urethra.