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The female or male external sphincter muscle of urethra (sphincter urethrae): located in the deep perineal pouch, at the bladder's distal inferior end in females, and inferior to the prostate (at the level of the membranous urethra) in males. It is a secondary sphincter to control the flow of urine through the urethra.
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system.The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle.
The pudendal nerve is the main nerve of the perineum. [1]: 274 It is a mixed (motor and sensory) nerve and also conveys sympathetic autonomic fibers.It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or female external urethral sphincter and the external anal sphincter.
Urodynamic testing including Cystometry and Urethral Pressure Profilometry. Women with Fowler's syndrome are often found to have an abnormally elevated urethral pressure profile, increased urethral sphincter volume. [2] [14] The diagnosis is done by testing the Electromyography (EMG) of the external striated urethral sphincter. [citation needed]
A short (1 or 2 cm) portion passing through the external urethral sphincter. This is the narrowest part of the urethra. It is located in the deep perineal pouch. The bulbourethral glands (Cowper's gland) are found posterior to this region but open in the spongy urethra. Pseudostratified columnar: Spongy urethra (or penile urethra)
It is a tendon that is formed at the point where the bulbospongiosus muscle, superficial transverse perineal muscle, [7] and external anal sphincter muscle converge to form this major supportive structure of the pelvis and vagina. [8] [9] [10] Below this, muscles and their fascia converge and become part of the perineal body.
The two Skene's ducts lead from the Skene's glands to the vulvar vestibule, to the left and right of the urethral opening, from which they are structurally capable of secreting fluid. [2] [3] Although there remains debate about the function of the Skene's glands, one purpose is to secrete a fluid that helps lubricate the urethral opening. [2] [3]
Using horseradish peroxidase to stain the neurons, it has been determined that the external anal sphincter motoneurons are located in dorsomedial to the external urethral sphincter motoneuron in the cat, dog, monkey, golden hamster, as well as the man. However, the location of these motoneurons differs in the rat, Mongolian gerbil and domestic pig.