glossary of terms
Sphincter: a ring of muscle that when contracted, closes a tube e.g. the internal sphincter closes the urethra at the point where it leaves the bladder. When the muscle is relaxed, the tube is opened.
Urethra: the tube that runs from the bladder to the outside world, down which urine is evacuated.
Voiding: the act of urinating or defecating. i.e. emptying