Article

Prostate

The prostate is an accessory gland of the male reproductive system, located below the bladder and surrounding the urethra. It produces a slightly alkaline, milky fluid that forms part of semen. This prostatic fluid helps neutralize the acidity of the vaginal tract, prolonging the lifespan and motility of sperm. The prostate also acts as a mechanical switch between urination and ejaculation.

Typical Size

A healthy adult male prostate typically weighs approximately 15-20 grams (about the size of a walnut) and measures roughly 3 cm in length, 4 cm in width, and 2-3 cm in height Prostate-specific antigen. These dimensions can vary somewhat with age, but generally remain within this range until later life when prostate enlargement becomes more common.

Related Topics

Functions (Expanded)

Prostatic fluid contributes to sperm motility beyond just neutralizing acidity through several mechanisms. While the exact composition and specific contributions are still areas of ongoing research, it contains:

  • Enzymes: Prostate-specific antigen (PSA) is a key enzyme that liquefies seminal coagulum (the gel-like substance that forms when semen initially leaves the body), which has been shown to enhance sperm motility. Other enzymes may also play roles.
  • Hormones and Growth Factors: Components like epidermal growth factor (EGF) have been suggested in some studies to potentially influence sperm function, although evidence is not conclusive [TODO: add citation for specific role].
  • Nutrients: Small amounts of fructose provide energy for sperm movement.
  • Ions and pH Regulation: Maintaining the slightly alkaline pH helps protect sperm from harmful enzymes in cervical mucus and may contribute to membrane integrity or function necessary for motility. The concentration of certain ions, like calcium, can also influence sperm activity.

The precise combination and mechanism by which prostatic fluid boosts sperm motility beyond simple alkalinization are not fully understood but likely involve multiple factors working synergistically [TODO: add citation for the nuanced understanding].

Mechanical Switch Mechanism

The prostate gland acts as a mechanical switch primarily during ejaculation. Smooth muscle contraction within the walls of the urethra, just below where it passes through the bulbourethral glands (which release pre-ejaculate) and above the point where the ejaculatory ducts enter, physically blocks urine flow from reaching the exterior during orgasm.

During an erection preceding ejaculation, muscles surrounding the base of the prostate may relax slightly. However, as orgasm approaches, coordinated contraction of the prostatic smooth muscle, along with contractions in other parts of the male reproductive tract (like the seminal vesicles and bulbourethral glands), forces semen through the urethra.

The specific mechanisms involve:

  1. Urethral Dilation: The prostate gland has a sphincter at its neck that relaxes to allow fluid passage during ejaculation.
  2. Peristalsis/Contraction: Rhythmic contraction of prostatic smooth muscle propels the semen forward, working in concert with contractions elsewhere along the urethra and reproductive ducts.

This coordinated muscular activity effectively reroutes the urinary system's pathway temporarily, ensuring that urine is retained within the bladder while semen is expelled [TODO: add citation for detailed physiology if available].