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2.9.4Structure & Functions in Living Organisms

Structure of the Urinary System — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions

5 min read 4 parts Lesson 18 of 21 Unit quiz

📚 Edexcel International GCSE Biology 4BI1 Hub / Topical Revision
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Part 1 of 4Organs of the Urinary System

2.9.4 Structure of the Urinary System

Urine is made in the kidneys and leaves the body through a series of tubes and a storage organ.

Kidney
  • A compact, bean-shaped organ that filters the blood to remove urea and excess ions and to regulate the water content of the blood.
Ureter
  • One tube leaves each kidney and carries urine to the bladder, moved along by waves of muscle contraction.
Bladder
  • A muscular, stretchy sac that stores urine until it is convenient to release it from the body.
Urethra
  • A single tube that carries urine from the bladder to the outside of the body.
StructureNumberFunction
Kidney2Filters blood, forms urine
Ureter2Kidney to bladder
Bladder1Stores urine
Urethra1Bladder to outside

Part 2 of 4Blood Supply to the Kidneys

Blood Supply to the Kidneys
Renal artery
  • This vessel carries blood from the aorta into each kidney, and the blood contains urea that needs to be filtered out.
Renal vein
  • This vessel carries filtered blood with much less urea away from each kidney towards the vena cava.
High flow
  • The kidneys receive a large flow of blood because filtering the blood is a continuous task.
Position
  • The kidneys sit at the back of the abdominal cavity, one on each side of the spine.

Part 3 of 4Path of Urine

Follow a molecule of urea from the blood to the outside.

1
Urea travels in the blood through the renal artery into the kidney.
2
Inside the kidney, nephrons filter the blood and form urine from the filtrate.
3
Urine collects in the renal pelvis and leaves the kidney through the ureter.
4
The ureter carries urine to the bladder, where it is stored and the bladder wall stretches as it fills.
5
When the bladder empties, urine passes through the urethra and out of the body.

Part 4 of 4Exam Checklist & Tips

2.9.4 – Key Points for the Exam

  • Ureter The tube that carries urine from a kidney to the bladder.
  • Urethra The tube that carries urine from the bladder out of the body.
  • Renal artery The blood vessel that brings blood to the kidney.
  • Renal vein The blood vessel that takes filtered blood away from the kidney.
  • Bladder The organ that stores urine.

Common Mistakes

  • Swapping ureter and urethra; the ureter joins the kidney to the bladder and the urethra leaves the bladder.
  • Saying the bladder makes urine; it only stores it, as urine is made in the kidneys.
  • Saying urine travels in the renal vein; blood travels in renal vessels and urine in the ureter.
  • Stating that the renal vein carries blood to the kidney; it carries blood away.

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