They are designed to allow urine to flow past an obstruction in the ureter.

This allows urine to pass through the urethra and out of the body.

The goal of treatment is to relieve the blockage, which will allow urine to drain from the urinary tract.

This muscle tissue must relax to allow urine to flow.

The detrusor contracts and the sphincters relax to allow urine to flow.

The urethra is the tube that allows urine to pass outside the body.

This allows urine to better exit the body and lets the skin pull back when you have an erection (get hard).

This allows urine to flow out of the bladder more easily.

If this support is insufficient, the urethra can move downward at times of increased abdominal pressure, allowing urine to pass.

Other nerves signal the urethra to open, which allows urine to flow.