How does seminal vesicle fluid support sperm motility?

The seminal vesicles are two small glands behind the bladder. They make a thick, yellowish fluid that forms most of the semen volume. This fluid mixes with sperm from the testes in the ejaculatory ducts. Together, they create the right environment for sperm to move (motility), survive longer, and reach the egg. Good motility is key for fertility, and seminal vesicle fluid directly supports it.

Key ways the fluid boosts motility

• Energy supply: Fructose and other sugars act as fuel so sperm can keep swimming. Without steady energy, sperm slow down and may not reach the egg.
• pH buffering: The fluid is slightly alkaline. It helps neutralize the natural acidity of the vagina, which would otherwise reduce sperm movement and survival.
• Osmotic balance: Proper salt and fluid levels protect the sperm membrane and tail function, keeping the swimming motion stable.
• Liquefaction support: Proteins and enzymes help semen change from sticky to more fluid after ejaculation. This frees sperm to swim forward.
• Coating and protection: Seminal proteins form a protective coat that reduces oxidative stress and mechanical damage, preserving tail motion.
• Signaling molecules: Prostaglandins can influence the female tract and may aid sperm transport by affecting muscle contractions and mucus properties.

What happens step by step-

1. Sperm leave the epididymis with limited fluid support.
2. During ejaculation, seminal vesicle fluid mixes in and bathes the sperm.
3. Alkaline pH and buffers protect sperm as they enter the vagina.
4. Fructose fuels mitochondria in the sperm midpiece to power the tail.
5. Liquefaction over 15–30 minutes reduces semen thickness so sperm can move freely.