Internal urethral sphincter
The internal urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice. It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle, but anatomically and functionally fully independent from it. It is composed of smooth muscle, so it is under the control of the autonomic nervous system, specifically the sympathetic nervous system.
| Internal urethral sphincter | |
|---|---|
The urinary bladder, with the position of the internal urethral sphincter shown as the internal urethral orifice. | |
| Details | |
| Origin | The inferior ramus of the pubic bone |
| Insertion | Perineal raphe |
| Nerve | Sympathetic fibers from T10-L2 through the inferior hypogastric plexus then vesical nervous plexus |
| Actions | Constricts proximal urethra, maintains urinary continence |
| Identifiers | |
| Latin | musculus sphincter urethrae internus |
| TA98 | A09.2.03.009 A09.4.02.013 |
| TA2 | 3444, 3428 |
| FMA | 45769 |
| Anatomical terms of muscle | |
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