The Kidneys (WJEC GCSE Biology)

• Kidney functions include:
  • Regulation of blood water content
    • This maintains blood water concentration
    • Blood volume is maintained, preventing fluctuations in blood pressure
  • Removal of waste products from the blood
    • This includes the removal of urea, which can become toxic at high levels
    • Excess salts are also removed; these can affect blood water concentration

• Note that the removal of waste products is known as excretion; a full definition for this term is:

The removal of metabolic waste from the body

• • Be aware that this is not the same as egestion, which is the removal of undigested food waste; this occurs in the digestive system

Role of the kidneys diagram

The kidneys remove the waste products of metabolism from the body, as well as other substances that are present in excess

• Humans have two kidneys, located at the back of the abdomen
• The regions of the kidney are:
  • Cortex = the outermost region
  • Medulla = the inner section of the kidney
  • Renal pelvis = the tube linking the kidney to the ureter
• The renal artery is a branch of the aorta that carries blood into the kidneys
  • This blood contains waste products of metabolism that will be filtered by the kidneys
• The renal vein carries blood out of the kidney to the vena cava
  • This blood has now been filtered so no longer contains metabolic waste
• The excess water and waste materials filtered out of the blood drain into the renal pelvis 
  • The urine collects in the pelvis before it flows into the ureter 
  • The ureter carries urine to the bladder for storage

Kidney structure diagram

The regions of the kidney include the cortex, medulla and renal pelvis