Internal sphincter muscle of urethra
| internal sphincter muscle of urethra |
|
| Coronal section of anterior part of pelvis, through the pubic arch. Seen from in front. (Region visible, but muscle not labeled.) |
|
| Urinary bladder (Region visible, but muscle not labeled.) |
| Latin |
musculus sphincter urethrae internus |
| Origin |
Pubis ramus |
| Insertion |
Median raphe |
| Artery |
|
| Nerve |
Sympathetics from L1-L2 through lumbar splanchnic and hypogastric/pelvic plexus |
| Actions |
Sympathetic contracts; parasympathetic relaxes |
The internal sphincter muscle of urethra is a urethral sphincter muscle which constricts the internal urethral orifice. It is the junction of the urethra with the urinary bladder. The muscle is made of smooth muscle, so therefore it is under involuntary control. It is kept tonically contracted by lumbar splanchnic nerves (L1-L2) of the sympathetic nervous system. During micturition it is relaxed via the parasympathetic nervous system. This is the primary muscle for preventing the release of urine.
|
|
|
| Abdomen |
|
|
| Pelvis |
|
|
|
|
|
noco/acba/cong/tumr, sysi/epon, urte
|
proc/itvp, drug (G4B), blte, urte
|
|
|
|