What is the purpose of the urethra?

The urethra serves the essential purpose of excreting urine from the bladder to the outside of the body. When urine is stored in the bladder, it is eventually expelled through the urethra during the process of urination. This is a critical function in the urinary system, as it allows for the removal of waste products and excess fluids from the body. The urethra also plays a role in controlling the flow of urine, aided by the sphincters that regulate its release.

Other choices represent different aspects of the urinary system but do not accurately describe the function of the urethra. For instance, transporting urine from the kidney pertains to the ureters, which are the tubes that carry urine from the kidneys to the bladder. Draining urine from the renal pelvis relates to the same ureters and not to the urethra. Filtering blood in the nephron describes the primary function of the nephron units in the kidneys, where blood is processed to form urine, but it does not involve the urethra itself. Each of these functions is essential to the urinary system, but they take place in different structures.