What is the primary function of the ureters in the human body?

The primary function of the ureters is to carry urine from the kidneys to the bladder. The ureters are muscular tubes that extend from each kidney and transport urine, which is produced as a waste product of metabolism, down to the bladder where it is stored until it is ready to be expelled from the body. This function is crucial for the urinary system, as it ensures that waste is efficiently moved from the kidneys, where it is formed, to the bladder, where it can be held until urination occurs.

Considering the other choices, the role of transporting oxygen from the lungs pertains to the respiratory system, specifically involving the trachea and bronchi. Producing hormones is a primary function of the endocrine glands, not the ureters. Additionally, filtering blood is primarily the role of the kidneys and not a function performed by the ureters. Thus, the option about carrying urine aligns perfectly with the anatomical and physiological realities of the ureters in the human body.