In the male reproductive system, one of the important functions is to produce liquid, called seminal fluid, which accompanies sperm when it travels outside of the body during ejaculation. In many mammal bodies, including those of humans, the majority of this fluid is produced in the seminal vesicle, or more accurately, it is made by the two seminal vesicles. These are glands of a couple inches (approximately five centimeters) in length located behind the bladder. Amount of seminal fluid mammalian species derives from each seminal vesicle with each ejaculation varies, but in humans it runs an average of 60% for both vesicles.
The length of each seminal vesicle is rather deceiving. These glands contain much longer tubules that are compactly folded. The tubules connect to the vas deferens, another tube that receives sperm from other parts of the male reproductive system. The combination of sperm and fluid then become the majority of what is ejaculated, should ejaculation occur.
There are several important functions of seminal vesicle fluid, though it is not always necessary for ejaculation or fertility. First, its components blend with seminal fluid produced by the prostate gland, and these two fluids are somewhat opposite on the pH scale. When mixed together, the final result still tends toward higher alkalinity, but provides a closer balance than would be possible if either fluid were present alone.
Second, seminal vesicle fluid has some important nutrients. One of these is fructose, a sugar, which could provide energy to traveling sperm. Yet it’s been noted that more often than not, early sperm reaching the vagina doesn’t necessarily touch seminal vesicle fluid.
Like many parts of the reproductive system, the function of a seminal vesicle is usually determined by presence of male hormones or steroids such as androgens. Especially at younger ages, before middle age, the higher presence of male hormones increases function of the vesicles. This can correspond to a higher amount of fluid ejaculated. When men age and hormones go into natural decline, ejaculate matter may reduce in volume. Provided ejaculation still occurs and no other problems are present this finding may be insignificant.
There are some health conditions that may affect vesicle function. Infection can occur in one or both glands, and this may require antibiotic treatment or more strident measures. Many times infections of the seminal vesicles occur due to infections in the nearby prostate gland. Rarely, one or both vesicles must be removed due to chronic infections, but this scenario is usually one of last resort.