How does the kidney work in homeostasis?

The kidney is involved in osmoregulation (the control of blood water concentration): this is primarily controlled by the hormone ADH which is released from the pituitary gland in the brain when water concentration in the blood is low. ADH works by increasing water re-absorption into the blood. This is by increasing the number of water transporters in the collecting duct in the nephron - the functional unit of the kidney (here, I would explain the structure of the nephron with the aid of a diagram). This means the water levels in the blood will increase and ADH will no longer be released.This is an example of negative feedback (here, I would use a diagram to explain the concept of negative feedback). Water level drops, so ADH is released. The water level rises, so ADH stops being produced.