What is the function of the urethra?

The urethra plays a critical role in the excretory system by transporting urine from the bladder out of the body. This tubular structure connects the bladder, where urine is stored, to the external environment, allowing for the controlled and voluntary expulsion of urine during urination.

The urethra is lined with smooth muscle, which can contract or relax to facilitate the movement of urine. It is also equipped with sphincters that provide the ability to control when urine is released. This function is essential for maintaining bladder control and ensuring proper waste elimination.

Other options, while related to the urinary system, describe functions performed by different components. The filtration of blood into urine is primarily the role of the kidneys, while the storage of urine is the function of the bladder. Regulating hydration levels involves various systems in the body, including antidiuretic hormone action in the kidneys, but this is not a primary function of the urethra specifically.