What anatomical feature prevents urinary reflux in healthy individuals?

The anatomical feature that prevents urinary reflux in healthy individuals is the ureterovesical junction. This junction is where the ureters, which carry urine from the kidneys, connect to the bladder. The unique structure and positioning of the ureters at this junction allow for a one-way flow of urine from the kidneys to the bladder.

When the bladder fills, the pressure increases, which also increases the pressure at the ureterovesical junction, effectively closing off the entrance of the ureters. This mechanism helps to prevent the backflow of urine, or reflux, into the ureters and kidneys, which can lead to infections and other complications. The anatomical design of this junction is crucial for maintaining normal urinary function and protecting the upper urinary tract from potential damage and infection resulting from reflux.