Image Caption : Semen Volume Break Down by Producing Glands: Image of a test tube with the components of semen separated by volume from various glands. The majority of semen is seminal plasma, which accounts for 95% with secretions from the seminal vesicles, prostate gland, and bulbourethral (Cowper's) gland; sperm produced in the testicles make up the remaining 5% of semen volume. The seminal vesicles contribute most of the volume of ejaculate (60%) in the form of seminal fluid; one of the most important components of the seminal fluid is fructose, a sweet-tasting natural sugar which provides energy for the sperm on their long journey to the fallopian tubes. The secretions from the prostate make up the next largest portion of the ejaculate (30%) and include prostaglandin and other supportive compounds such as immunoglobins; prostaglandin actually causes uterine contraction-which may aid in the uptake of sperm. The bulbourethral glands contribute the remaining volume of the ejaculate (5%) which includes mucin, a potent basic buffer designed to counter the hostile acidic environment of the vagina.

Seminal Fluid

Seminal fluid, or semen, is a slightly alkaline mixture of sperm cells and secretions from the accessory glands. Secretions from the seminal vesicles make up about 60 percent of the volume of the semen, with most of the remainder coming from the prostate gland. The sperm and secretions from the bulbourethral gland contribute only a small volume.

The volume of semen in a single ejaculation may vary from 1.5 to 6.0 ml. There are usually between 50 to 150 million sperm per milliliter of semen. Sperm counts below 10 to 20 million per milliliter usually present fertility problems. Although only one sperm actually penetrates and fertilizes the ovum, it takes several million sperm in an ejaculation to ensure that fertilization will take place.

Illustration of the male reproductive system

National Cancer Institute / NIH

Semen, also known as seminal fluid, is an organic fluid that may contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize female ova. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa, and provide a medium through which they can move or "swim".

Semen is produced and originates from the seminal vesicle, which is located in the pelvis. The process that results in the discharge of semen is called ejaculation.

Semen is also a form of genetic material. In animals, semen has been collected for cryoconservation. Cryoconservation of animal genetic resources is a practice that calls for the collection of genetic material in efforts for conservation of a particular breed.

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