Final answer:
The body's primary method for maintaining fluid balance is through adjusting urine concentration, regulated by the kidneys with the aid of hormones like ADH and aldosterone, to ensure water homeostasis.
Step-by-step explanation:
The human body requires a balance between water intake and water output to maintain fluid equilibrium - a state known as homeostasis. While water is introduced into the system through consumption, approximately 10% is generated through cellular metabolic processes. The primary system for the regulation of this water balance is the urinary system, particularly the kidneys.
The kidneys adjust the concentration of urine in response to the body's hydration needs. Hormones such as antidiuretic hormone (ADH), also known as vasopressin, play a critical role by increasing water reabsorption in the kidneys when water conservation is needed. Conversely, when there's excess water, urine is made more dilute to allow for its expulsion. Aldosterone and Atrial Natriuretic Hormone (ANH) also affect the fluid balance.
Additionally, the osmolarity and volume of blood are closely monitored and preserved through several mechanisms, including hormonal signals and physiological responses like vasoconstriction, to help maintain the necessary blood pressure for survival. Thus, water balance involves complex interactions between water input, metabolic generation of water, and its excretion through urine, all tightly regulated by hormonal and physiological mechanisms.