Final answer:
The urethra is a muscular tube that conveys urine from the bladder to the outside of the body for excretion. It varies in length between males and females and is under voluntary control for the regulation of urination.
Step-by-step explanation:
The muscular tube responsible for conveying urine from the bladder to the exterior of the body is known as the urethra. The urethra's function as part of the urinary excretion system is crucial as it serves as the final pathway for urine to exit the body. In its course, it passes through the urinary sphincter, which is under conscious control, allowing for voluntary regulation of urination. Anatomically, the urethra varies significantly in length between males and females, being longer in males due to its passage through the phallus.
In both males and females, the urethra serves the singular purpose of transporting urine. Although in males, it also conveys semen, whereas, in females, it is solely for the passage of urine. The walls of the urethra consist of longitudinal and circular smooth muscle, which helps in the passage of urine during urination. This muscular tube is an essential component of the urologic system that ensures the safe and efficient elimination of urine from the body.