What is the primary function of the urethra?

The primary function of the urethra is to transport urine from the bladder to the external environment. This role is crucial in the urinary system, where the bladder serves as a reservoir for urine until it is ready to be expelled from the body. The urethra acts as the conduit that facilitates this process, allowing for the elimination of waste products from the body. This function is essential for maintaining fluid and electrolyte balance and for the removal of toxins through urination.

In the context of the other options, the kidneys are connected to the bladder by the ureters, not the urethra, which rules out that choice. The urethra does not play a role in blood circulation, as that function is primarily served by the cardiovascular system, notably through blood vessels such as arteries and veins. Lastly, the development of a fetus occurs in the uterus, not in the urethra, highlighting that this structure does not participate in reproductive functions but is specialized for urinary excretion.