What is semen?
Semen is the seminal fluid that is expelled from the urethra of the penis during ejaculation. It is a milky-cloudy to yellowish-grey, gelatinous fluid. The seminal fluid has a sweetish odor and is also described as smelling like chestnut blossoms.
The seminal fluid consists of secretions from the prostate, seminal vesicles, Cowper’s glands and sperm.
Prostate secretion
Approximately 20 percent of seminal fluid is a thin, milky secretion secreted by the prostate. This secretion, a salt solution rich in potassium and calcium, contains, among other things, certain enzymes (phosphatases), magnesium, zinc, citrate and spermine – a so-called polyamine that is mainly found in rapidly growing cells. The prostate secretion is slightly acidic (pH value between 6.4 and 6.8) and has a movement-inducing effect on the sperm.
Secretion of the seminal vesicles
The majority of sperm comes from the seminal vesicles (vesicula seminalis). Their secretion makes up about 70 percent of the seminal fluid. It is alkaline and contains fructose as an energy source for sperm movement. It also contains prostaglandins – tissue hormones that promote the contractions of the muscles of the female genital tract.
Secretion of the epididymis
Another ten percent or so of the seminal fluid comes from the epididymis. It contains the sperm.
The pH value of semen
At 7.2 to 7.8, the sperm pH value is in the alkaline range. This allows the seminal fluid to shift the acidic environment in the vagina, which has a pH value of 3.5 to 5.5, into the alkaline range. The sperm need this alkaline environment to be able to move around in the vagina.
The amount of sperm
The volume of an ejaculate is two to six milliliters. Each milliliter contains between 35 and 200 million sperm cells. With very frequent ejaculations, the amount of sperm can be somewhat lower, but it is often higher after prolonged abstinence.
What is the function of sperm?
The seminal fluid serves as a vehicle to transport the sperm to the female egg. The alkaline sperm makes the acidic vaginal environment more alkaline and thus promotes sperm motility.
Where is the sperm located?
What problems can sperm cause?
If there are fewer than 20 million sperm per millilitre in an ejaculate, the probability of fertilization decreases – even if only a single sperm is actually required for fertilization.
A high proportion of malformed sperm in the ejaculate also leads to inability to conceive.
If the amount of sperm is less than two milliliters, this is referred to as hypospermia.
Sexually transmitted diseases such as HIV or hepatitis B can be transmitted via sperm.
