The seminal vesicles are paired accessory reproductive glands situated above the prostate and on the lateral sides of the ampulla of ductus deferens.

They are located extraperitoneally on both sides of the bladder and between the rectum and urinary bladder.

The seminal vesicles are elongated, flattened, and twisted tubes in the wall of the ductus deferens. Each gland is approximately 2 inches (5 cm) long, 0.8 - 1.6 inches (2 - 4 cm) wide, and 0.4 inches (1 cm) thick.

The wall of the seminal vesicles is formed by mucous membrane, smooth muscle and connective tissue layers.

The seminal vesicles produce mucous, transparent, slightly yellow secretion, which mixes with sperm during ejaculation.

The fluid contains fructose, which is used as an energy source by the sperm, and prostaglandins, which stimulate the contractions of smooth muscle in the male and female reproductive tracts to accelerate the movement of sperm.

These secretions make up most of the volume of the ejaculate, in total around 60%.

The seminal vesicles have three parts:

Base (pointed upwards)
Body
Excretory duct

The excretory duct of each seminal vesicle joins with the ampulla of the ductus deferens and forms the ejaculatory duct, which opens into the prostatic urethra on each side.

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Seminal vesicles