The Sperm Cell: An Overview

The fluid discharged from a man’s urethra during ejaculation, usually at the time of orgasm, is called semen. It can be thin and watery or viscous and almost yellow. About a teaspoon (2-15 Milliliters) of semen comes out of the penis during an ejaculation. Just like blood, semen is made up of two compartments: a cellular one (the spermatozoa) and a non-cellular one.

The non-cellular compartment, also known as the seminal plasma, contains water and small amounts of salt, protein, and fructose. This seminal fluid is produced by the prostate gland and the seminal vesicles, and it also contains substances that cause the ejaculate to coagulate (in which case it is called a coagulum). About 60% of semen comes from the seminal vesicles. The other 40% is mostly produced by the prostate. The bulbourethral glands contribute with a small amount of mucus which gives the jelly-like texture of the ejaculate.

The cellular compartment consists of sperm cells, or spermatozoids. Approximately 200- to 500-million spermatozoids are released during one ejaculation, but this makes up only about 2-3% of the volume of the ejaculate. Given the low volume of sperm cells in semen it is impossible to calculate a man’s sperm count just on the basis of semen quantity.

The testicles are the male reproductive organs. They consist of two oval shaped glands, located in the scrotum, which produce the male hormone, testosterone, and the male sex cell. Every day, one testicle, produces millions of sex cells, which are stored in the epididymis, a sort of reservoir tube. Here, they undergo the process of cell division, resulting in mature spermatozoids. Prior to ejaculation sperm is pumped from the epididymis into the vas deferens where it meets the seminal fluids.

During sexual intercourse, the man’s sperm is released into the woman’s cervix, from which it travels to the fallopian tube, where fertilization occurs. Only one in the millions of sperm cells fertilizes the egg, giving life to a new human being. Half of the sperm cells carry the male Y chromosome, while the other half carry the female X chromosome. If the ovum is fertilized by an Y spermatozoid the new human being will be male. If the ovum is fertilized by a X spermatozoid, it will be female.

Most of the times, semen enters the woman’s cervix through sexual intercourse. For that to happen the man must obviously experience erection, orgasm, and finally, ejaculation. An erection usually occurs when a man is sexually stimulated. When this happens, the brain sends signals to relax the muscles around the arteries that ensure blood flow to the corpora spongiosa, the erectile tissue in the penis. The veins that drain this tissue cannot keep up and they swell. When they reach the limit of the skin, the penis becomes erect. The pressure of the corpora spongiosa on the penile skin closes the veins, thus maintaining the erection.

If the man continues to be sexually stimulated, an orgasm occurs. Also known as the sexual climax, the orgasm is an intense sensation of plesure, accompanied by rhythmic muscle contractions contractions of the urethra, anus, and pelvic floor, followed by release of sexual tensions. The orgasm has two stages: the first one is called ejaculatory inevitability and occurs two to four seconds before ejaculation. At this point the man no longer has control over whether he will ejaculate or not. Once this point is past, the second stage occurs, during which a man will ejaculate, even if sexual stimulation ceases.

Men usually experience only a single orgasm, accompanied by an ejaculation. There are men who can experience multiple orgasms within one sexual intercourse. In this case, ejaculation occurs during the last orgasm.