Internal urethral sphincter


This is the involuntary sphincter of the urethra which runs from the bladder neck to the beginning of the preprostatic urethra. It is not found in the female and in the male its main function apart from allowing urine to pass through it in the early stages of micturition, is to disallow retrograde ejaculation during sexual climax in the male. It is contracted during ejaculation so that semen may not enter the bladder. It is open in certain drugs which may cause retrograde ejaculation such as guanethidine. Also in sexual anxiety syndromes it may be open leading to the same retrograde ejaculation. Its contained α1 adrenoceptors which cause contraction of the sphincter may be blacked by α1 adrenergic blockers. In anxiety syndromes blockade may be centrally controlled from the sexual nervous centers in the cortex.


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The Human Anatomy Laboratory
Creator: Oluwole Ogunranti


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DIGITAL LOCATOR OF URETHRA. Layer 1 Skin of pelvis- anterior abdominal wall and perineum). Layer 2- Superficial aspect of pelvis.  Layer 3 - intermediate dissection of male pelvis. Layer  4 - deep dissection of male pelvisLayer 5- deepest layer of male pelvis. Layer 6- layer of pelvic floor of male pelvis. Layer  7 - layer of pelvic bones. Roll over to label;Click to display pages, click the blinking end page to demonstrate urethra page. Layer 5 of male pelvis regional locator





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