What substances are secreted by the seminal vesicles?

Seminal vesicles secrete a fructose-rich, alkaline fluid with proteins, enzymes, prostaglandins, citrate, amino acids, and minerals that together support sperm energy, protection, and transport.

Main secretions and why they matter

• Fructose: The primary sugar fuel for sperm movement and survival.
• Prostaglandins (e.g., PGE, PGF types): Lipid signals that may help sperm move through cervical mucus and the uterus.
• Proteins and enzymes: Contribute to semen coagulation right after ejaculation and later to liquefaction, improving sperm release and forward progression.
• Citrate: Helps maintain pH and binds calcium ions, aiding membrane stability.
• Amino acids and peptides: Provide building blocks and can act as antioxidants or osmoprotectants.
• Minerals and trace elements: Zinc, magnesium, potassium, and others help enzyme activity and membrane function.
• Alkaline fluid: Buffers acidic environments and keeps sperm motility higher.

Typical composition insights

Although exact amounts can vary by individual, diet, hydration, and health, seminal vesicle fluid is usually viscous and contributes 50–70% of total semen volume. The high fructose level is a classic marker. Prostaglandins are present in notable amounts, and the pH tends to be alkaline, which supports fertility.

How each component supports fertility