👉 The term "urena" refers to a collection of tiny tubes or sacs that carry urine from the bladder into the body. These tubes are known as ureters and they play a crucial role in the urinary system, which is responsible for filtering out waste products such as blood and proteins from the kidneys. Urethral sphincters (or sphincters) are muscle-like structures located at the end of each ureter to maintain its integrity. These muscles can be divided into three types