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The membranous urethra or intermediate part of male urethra is the shortest, least dilatable, and, with the exception of the urinary meatus, the narrowest part of the urethra. [citation needed] It extends from the apex of the prostate proximally to the bulb of urethra distally. It measures some 12 mm in length. It traverses the pelvic floor.
The prostatic urethra, the widest and most dilatable part of the urethra canal, is about 3 cm long.. It runs almost vertically through the prostate from its base to its apex, lying nearer its anterior than its posterior surface; the form of the canal is spindle-shaped, being wider in the middle than at either extremity, and narrowest below, where it joins the membranous portion.
Membranous urethra: 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 ...
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.
Ejaculation occurs in two stages, the emission stage and the expulsion stage. [4] The emission stage involves the workings of several structures of the ejaculatory duct; contractions of the prostate gland, the seminal vesicles, the bulbourethral gland and the vas deferens push fluids into the prostatic urethra. [3]
In males, the urethra begins at the internal urethral orifice in the trigone of the bladder, continues through the external urethral orifice, and then becomes the prostatic, membranous, bulbar, and penile urethra. Urine exits the male urethra through the urinary meatus in the glans penis.
The part of the urethra passing through it is called the prostatic urethra, which joins with the two ejaculatory ducts. [2] The prostate is covered in a surface called the prostatic capsule or prostatic fascia. [4] The internal structure of the prostate has been described using both lobes and zones.
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.