Which organ is primarily responsible for filtering blood and forming urine?

The kidneys are the organs primarily responsible for filtering blood and forming urine. They perform this crucial function through a complex process that involves several steps, including filtration, reabsorption, and secretion. As blood passes through the kidneys, waste products and excess substances, such as water, salts, and toxins, are filtered out. This process results in the formation of urine, which is then transported to the bladder for storage before being expelled from the body.

The structure of the kidneys—comprised of nephrons, which are the functional units—enables this filtration process to occur effectively. Each nephron has a glomerulus that filters blood and a tubule that processes the filtrate to reabsorb needed substances and secrete unwanted ones, culminating in urine production.

Other anatomical structures, such as the urethra, ureters, and bladder, play supporting roles in the urinary system. The urethra is responsible for transporting urine from the bladder to the outside of the body. The ureters are tubes that carry urine from the kidneys to the bladder, while the bladder serves as a reservoir for urine until it is ready to be excreted. However, none of these organs carry out the function of filtering blood and forming urine, which