• Humans have two kidneys
• The kidneys are responsible for carrying out two very important functions:
  • As an osmoregulatory organ – they regulate the water content of the blood (vital for maintaining blood pressure)
  • As an excretory organ – they excrete the toxic waste products of metabolism (such as urea) and substances in excess of requirements (such as salts)

The function of the kidneys & their associated structures table

• The kidney itself is surrounded by a fairly tough outer layer known as the fibrous capsule
• Beneath the fibrous capsule, the kidney has three main areas:
  • The cortex (contains the glomerulus, as well as the Bowman’s capsule, proximal convoluted tubule, and distal convoluted tubule of the nephrons)
  • The medulla (contains the loop of Henle and collecting duct of the nephrons)
  • The renal pelvis (where the ureter joins the kidney)

• Each kidney contains thousands of tiny tubes, known as nephrons
• The nephron is the functional unit of the kidney – the nephrons are responsible for the formation of urine

• There is also a network of blood vessels associated with each nephron:
  • Within the Bowman’s capsule of each nephron is a structure known as the glomerulus
  • Each glomerulus is supplied with blood by an afferent arteriole (which carries blood from the renal artery)
  • The capillaries of the glomerulus rejoin to form an efferent arteriole
  • Blood then flows from the efferent arteriole into a network of capillaries that run closely alongside the rest of the nephron
  • Blood from these capillaries eventually flows into the renal vein