The<unk>  is a collective name for the muscles used to control the flow of urine from the urinary bladder. These muscles surround the urethra, so that when they contract, the urethra is closed.  The muscles originate at the pubic ramus with the insertion point at the median raphe. The function of the<unk>  urethrae is controlled by the Pudendal nerve to constrict the urethra.  There are actually two<unk> s in the human body:
The internal<unk>  muscle of urethra: located at the bladder's proximal inferior end is the junction of the urethra with the urinary bladder. The muscle is made of smooth muscle, so therefore it is under involuntary control. This is the primary muscle for constricting the release of urine.
The external<unk>  muscle of urethra: located at the bladder's distal inferior end is secondary<unk>  to control the flow of urine through the urethra. Unlike the internal<unk>  muscle, the external<unk>  is made of skeletal muscle, so therefore it is under voluntary control. This is the secondary muscle to serve as backup.
Urethral sphincter
Detrusor urinae muscle
Bulbourethral gland
Vas deferens
Urinary bladder
Efferent nerve
Ureter
Excretory duct of seminal gland