Physiology of urethra
Urethra has two functions
1. For urination
The bladder neck interconnects the bladder with the posterior urethra below. It contains the internal sphincter. The internal sphincter. keeps urine out of the bladder neck and also out of the posterior urethra which leads off from the bladder neck immediately. But its main function is to prevent retrograde ejaculation at sexual intercourse. The urogenital diaphragm contains the sphincter urethrae which is the external sphincter that is under the control of will. It is this sphincter that is opened when there is the need to micturate.
Urethra is an important organ in the male. It is used for both reproductive and urinary functions. It passes semen from its prostatic part into the spongy part. The spongy part is the one that transverses the penis. It is also called penile urethra. When ejaculation is to take place in the male, semen is released from the seminal vesicle or from the tail of epididymis into the prostatic urethra in the first phase of ejaculation. The second phase is controlled by the bulbospongiosus muscle which assists the penile urethra to release forcibly its contained semen to the outside, and in reproductive capacity, into the vagina.
Internal urethral sphincter exists only in the male and it prevents retrograde ejaculation and it contracts when its contained α1 adrenoceptors are stimulated. Urine is stored in the bladder when the detrussor relaxes and the sphincters close.
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Creator: Oluwole Ogunranti