Semen

Semen is the main male sexual fluid that carries sperm.  Semen is is composed of sperm from the ampulla as well as fluids and other compounds made in the seminal vesicles and prostate.  Semen is a thick, white fluid that thins shortly after ejaculation. 

When semen is ejaculated, the contents of semen are not always consistent, because the glands that produce the various fluids empty their contents in a sequence rather than all at once.  For example, the first wave of semen has a higher volume of secretions from the bulbourethral glands and periurathral glands due pre-ejaculate left in the urethra as well as some secretions at the beginning of ejaculation.  Pre-ejaculate often only accounts for a few drops of less than 5% of semen volume. 

 

The prostate is the next gland to empty fluid followed by the ampulla which contain the sperm.  This occurs during emission.  Thus earlier waves of semen are higher prostate fluid, accounting for 20-40% of semen.  The sperm rich ampulla contribute only small amounts of fluid, amounting to only 5% of semen volume. 

The seminal vesicles often release fluids last, so later waves of semen during ejaculation are rich in seminal vesicle fluids that contain nutrients.  Seminal vesicles secretions make up the bulk of semen volume, accounting for 50-70% of the volume. 

The normal volume of semen can vary but is usually 3-5ml (½-1 teaspoon) and contain around 200 million sperm.  The graph shown here shows the timing of when those fluids are released prior to and during ejaculation as well as the relative volumes released by each gland/structure. 

Semen Components.jpg

Since torsion is most often caught at birth, most of these surgeries are performed in babies.  When a curvature is also present, the erect penis often has a corkscrew appearance.

[i] Bhat A, Correlation of severity of penile torsion with type of hypospadias & ventral penile curvature and their management. African J of Uro 21(2), 2015, 111-8.

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