How do kidneys regulate blood volume and pressure

 

The kidneys keep blood volume and pressure balanced by controlling how much water and salt the body keeps or removes. When blood pressure drops, sensors in the kidneys release renin, an enzyme that triggers the renin–angiotensin–aldosterone system (RAAS). 

This system causes blood vessels to tighten (raising pressure) and signals the adrenal glands to release aldosterone, which tells the kidneys to reabsorb sodium and water. More water in the bloodstream means higher blood volume and pressure. If blood pressure is too high, the kidneys excrete extra sodium and water, reducing fluid volume and easing pressure. 

They also produce urine to remove excess water and maintain electrolyte balance. Additionally, a hormone called antidiuretic hormone (ADH) from the brain tells the kidneys to conserve or release water depending on hydration levels. 

Together, these mechanisms keep the body’s fluids stable, ensuring that organs get the right blood flow without overloading the circulatory system. Essentially, the kidneys act as precise regulators filtering the blood, balancing salt and water levels, and fine-tuning pressure with every heartbeat.