The human kidneys are indispensable organs located in the posterior part of the abdominal cavity, functioning as the body's primary filtration system. Structurally composed of millions of nephrons, each kidney contains renal corpuscles and tubules responsible for filtering blood and processing waste into urine. Blood enters the kidneys through renal arteries, where it undergoes glomerular filtration, a process where water and solutes are forced through the glomerular membrane into Bowman’s capsule to form the filtrate.

 

Essential substances like glucose and ions are then reabsorbed into surrounding capillaries through tubular reabsorption, while waste products are actively secreted into the filtrate during tubular secretion. The remaining fluid travels through the renal tubule, where further adjustments to water and solute levels occur before being excreted as urine.

 

The kidneys also play crucial roles in maintaining electrolyte balance, regulating blood pressure, controlling acid-base balance, and producing hormones like erythropoietin, calcitriol, and renin. Various conditions such as chronic kidney disease, acute kidney injury, glomerulonephritis, and kidney stones can impair kidney function, highlighting the importance of understanding kidney operation for maintaining overall health and managing kidney-related diseases.