How do seminal vesicles interact with the prostate gland?

Seminal vesicles and the prostate mix their fluids during ejaculation, using shared ducts, timing, and chemistry to form semen that protects, energizes, and frees sperm to move.

Anatomy and pathway

Each seminal vesicle joins a vas deferens to form an ejaculatory duct that passes through the prostate and opens into the urethra. This close placement allows precise mixing of fluids from the vesicles and the prostate at the right moment. The prostate surrounds the first part of the urethra under the bladder, so its secretions join late in the pathway, shaping semen properties at the end of the journey.

Functional teamwork

• Volume and fuel (vesicles): Seminal vesicles contribute most of the semen volume and provide fructose for energy.
• Enzyme power (prostate): The prostate adds proteolytic enzymes (like PSA) that break down the semen clot, speeding liquefaction so sperm can move freely.
• pH balancing act: Both fluids are generally alkaline, which helps counter vaginal acidity and maintains motility.
• Signal support: Vesicle prostaglandins and prostate factors together influence mucus penetration and sperm transport.
• Ion and protein balance: Citrate, zinc, and other components from both glands stabilize membranes and enzyme systems needed for motility and capacitation.

Timing matters

Ejaculation occurs in phases. Prostatic fluid often appears early, and vesicular fluid adds bulk and sugars. Rapid coagulation may occur first, protecting sperm briefly. Then, within minutes, prostatic enzymes promote liquefaction, freeing sperm to progress. This timing ensures sperm are protected during transfer but released to swim soon after.

When interaction goes wrong

• Blockage: Ejaculatory duct obstruction prevents mixing, leading to low semen volume and poor sperm delivery.
• Infection or inflammation: Prostatitis or vesiculitis can change pH and protein balance, reducing motility.
• Surgical or congenital issues: Anomalies can disrupt the ducts and alter semen composition.