Removal of Waste (WJEC GCSE Biology): Revision Note

Removal of Urine

• After selective reabsorption, the remaining filtrate travels down the collecting duct to the renal pelvis 

• The liquid exits the kidneys and travels via the ureters to the bladder

• This waste solution is called urine; it is stored in the bladder before being released from the body via the urethra

• Urine produced by the kidneys contains:

  • Urea

  • Excess salts

  • Excess water

Urine composition and health

• Glucose in the urine can be a sign of diabetes

  • In a person with normal blood glucose levels, we would expect all of the glucose to be reabsorbed from the filtrate back into the blood

  • People with diabetes often have unusually high blood glucose concentrations, meaning that not all of the glucose is reabsorbed

  • The glucose in the filtrate ends up in the urine, so the presence of glucose in the urine can indicate diabetes

• The presence of blood, cells, or proteins in the urine can indicate disease in the kidney

  • Kidney disease can cause damage to the lining of the capillaries in the capillary knot

  • Large molecules, such as proteins, as well as whole cells, can be forced out of the blood during the process of filtration under pressure

  • These substances end up in the urine, where their presence indicates kidney damage