7.18B Describe the structure of the urinary system

The idea

The urinary system removes waste and balances water. Blood enters each kidney through the renal artery and leaves through the renal vein; the kidneys filter blood and produce urine. Urine passes down a ureter from each kidney to the bladder, which stores it. Urine then leaves the body through the urethra. So the order is kidney → ureter → bladder → urethra. In multiple-choice questions, match each named structure to its correct position and function: the ureter carries urine from kidney to bladder, the urethra carries urine out of the body, and the renal artery and renal vein connect the kidney to the blood supply. Eliminate options that swap ureter and urethra or place the bladder before the kidney.

What earns the marks

• Identifies the kidneys as the organs that filter blood and produce urine.
• States that each kidney connects to the bladder by a ureter, which carries urine.
• Identifies the bladder as the organ that stores urine.
• States that urine leaves the bladder and body through the urethra.
• Distinguishes the renal artery (blood to the kidney) and renal vein (blood from the kidney) from the urine-carrying tubes.

Common mistakes and how to put them right

• Confusing the ureter with the urethra.

  Put it right: The ureter carries urine from kidney to bladder, while the urethra carries urine out of the body.

• Placing the bladder before the kidney in the sequence.

  Put it right: Kidney → ureter → bladder → urethra.

• Thinking the renal artery carries urine.

  Put it right: The renal artery and renal vein carry blood, not urine.

Exam tips

• Read each option fully and check the direction of flow before choosing.
• Eliminate options that swap ureter and urethra or reverse the order of organs.
• Recall the sequence kidney → ureter → bladder → urethra as a quick check.