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Edexcel GCSE Biology · 1BI0
Edexcel 1BI0 · 7.18B Check the specification (PDF) (opens in a new tab)
The urinary system has two , two , a and a . Its arrangement makes more sense if you follow two separate routes: blood travels to and from the kidneys in blood vessels, while urine travels away from the kidneys in tubes. The kidneys remove wastes and excess water and mineral ions from the blood, producing urine.
Blood enters and leaves each kidney through renal blood vessels; urine passes through each continuous ureter into the bladder, then leaves through the urethra.
Each kidney receives blood through a renal artery. Blood leaves through a renal vein after passing through the kidney. These are blood vessels: urine does not travel through them.
Each kidney has its own ureter, a tube that carries urine down to the bladder. The bladder is a muscular sac that stores urine. When urine is released, it leaves the bladder through the urethra and passes out of the body. So the route for urine is kidney → ureter → bladder → urethra. The similar-sounding ureter and urethra have different positions and jobs.
A kidney has an outer cortex and an inner medulla. Urine produced within the kidney drains into a collecting space called the renal pelvis, which leads into the ureter. The tiny filtering structures that produce urine are called nephrons; how they filter blood is covered separately. For this lesson, the important structural link is that blood enters and leaves each kidney through vessels, while urine collects inside the kidney before flowing into its ureter.
Two kidneys produce urine. Each receives blood through a renal artery and blood leaves through a renal vein.
Kidney → ureter → bladder → urethra → outside the body. There is one ureter from each kidney; the bladder stores urine. Inside each kidney, urine drains into the renal pelvis before entering the ureter.
On a diagram, trace urine from a kidney through a ureter to the bladder, then through the urethra to outside the body.
Do not confuse a ureter, which carries urine to the bladder, with the urethra, which carries it out of the body. Renal arteries and veins carry blood, not urine.
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Urinary system
The organs and tubes that produce, carry, store and release urine.
Kidney
One of two organs that filter blood and produce urine.
Renal artery
A blood vessel that carries blood into a kidney.
Renal vein
A blood vessel that carries blood away from a kidney.
Ureter
One of two tubes that carry urine from the kidneys to the bladder.
Bladder
A muscular organ that stores urine before it leaves the body.
Urethra
The tube that carries urine from the bladder to outside the body.
Put your knowledge into practice — try past paper questions for Biology
Urinary system
The organs and tubes that produce, carry, store and release urine.
Kidney
One of two organs that filter blood and produce urine.
Renal artery
A blood vessel that carries blood into a kidney.
Renal vein
A blood vessel that carries blood away from a kidney.
Ureter
One of two tubes that carry urine from the kidneys to the bladder.
Bladder
A muscular organ that stores urine before it leaves the body.
Urethra
The tube that carries urine from the bladder to outside the body.