Draw a labelled diagram of the human excretory system. Explain how urine is produced in the nephron.

1. 1 · Define in one line. Excretion is the removal of harmful nitrogenous wastes, such as urea, from the body.
2. 2 · Name the organs. Two kidneys, two ureters, the urinary bladder and the urethra.
3. 3 · Filtration. In the glomerulus inside Bowman's capsule, water, glucose, salts and urea are filtered from the blood.
4. 4 · Reabsorption. Glucose, amino acids, salts and much water are taken back into the blood as the filtrate moves along the tubule.
5. 5 · Urine. The remaining fluid, urine, passes through the ureter to the bladder and out through the urethra.
6. 6 · Draw the excretory system. [Diagram: kidneys, renal artery, renal vein, aorta, vena cava, ureters, urinary bladder, urethra]
7. 7 · Link to daily life. Drinking enough water helps the kidneys; dialysis helps people whose kidneys have failed.
8. 8 · Close in one line. Thus the nephron filters the blood and saves what the body still needs.

Scoring tip: Label the ureter (kidney to bladder) and urethra (bladder to outside) correctly; mixing them up is the most common error.