Key learning points

1. The kidneys are organs of the excretory system in the human body.
2. Blood passes through the kidneys and is filtered.
3. Urea and excess water and ions move out of the blood plasma into the kidney tubules and are excreted as urine.
4. The kidneys reabsorb as much water as needed from the urine into the blood plasma to maintain water balance in the body.
5. Having too much water in the body leads to dilute urine, and vice versa.

Common misconception

Keywords

• Urea - a waste product created in the process of breaking down excess amino acids

• Blood plasma - the liquid part of the blood which contains dissolved nutrients and waste products

• Kidney - the organ in the excretory system which filters waste products from blood plasma and controls water balance

• Excretory system - the organ system responsible for removing waste from blood plasma

• Urine - a combination of urea, and excess water and ions which is stored in the bladder until urinated