What is meant by osmoregulation? How is it maintained in human body? (AS1)

Osmoregulation is the maintenance of osmotic pressure of the blood. During the removal of wastes, like urea, from our body the blood also regulates its composition, that is, the percentage of water and salts in the blood. For example in the summer we urinate fewer times and the urine that passes is thicker than that in winter. This is because; in summer we lose a considerable amount of water through perspiration and thus the kidney has to reabsorb more water from the urine thus making the urine thick and more concentrated.