Semen

Sperm Production

Sperm are constantly being produced in the testes in a process called spermatogenesis. During spermatogenesis, sperm stem cells, called spermatozoids, multiply inside the seminiferous tubules of the testes.

After undergoing meiosis, a special division process for gamete cells (e.g. egg and sperm), the cells are called spermatozoa. Spermatozoa have 23 chromosomes; which is half the amount of chromosomes in a normal cell. The spermatozoa are then sent to the epididymis where they are stored allowed to mature. It is in the epididymis that sperm are given the ability to cause fertilization.

During ejaculation sperm are combined with fluids from the seminal vesicles and the prostate to form the ejaculate. Sperm that are not used get old, die and are reabsorbed by the body. The body is constantly replenishing its supply of sperm, and each ejaculation in a healthy man contains around a hundred million sperm, enough to cause a pregnancy.

 

 

Sperm Anatomy

Sperm are specialized male gamete cells that serve as a carrier for genetic material. They contain special features and organelles that help them fertilize an egg and induce pregnancy.

  • The nucleus: Like most cells, the nucleus contains the DNA of the sperm. Unlike most cells, however spermatozoa contain a haploid amount of chromosomes. In humans, this means they have 23 chromosomes instead of the normal 46. When the sperm fuses with the egg in the process called fertilization the resulting in a conceptus. The sperm can be thought of as a transportation device for male's genetic material: The sperm cell's only purpose is to transport genetic material to the egg, so the nucleus is arguably the most important part of the sperm.

  • The Acrosome: This part of the sperm allows the sperm to penetrate the external layers of the egg. The ovum, or egg, has a protective jelly layer that sperm must pass through. Upon meeting the egg's protective layer, the sperm releases digestive enzymes from its acrosome. The sperm's acrosomal enzymes eat through the protective layer, allowing the sperm to reach and fertilize the egg. Only capacitated sperm can produce the acrosomal reaction. Sperm enter the vagina de-capacitated by chemicals in the seminal fluids and slowly become re-capacitated by chemicals in the female's reproductive tract.

  • The Centriole: This is a fibrous structure that is important in the mechanics of flagellar movement. Centrioles are composed of fused microtubules - special proteins important in cellular movement and structure. The centrioles extend out into the flagella as the axial filament.

  • The Axial Filament: This structure is responsible for the whip-like motion of the sperm's tail. The centrioles contain a special arrangement of microtubules in the flagella. The fused microtubules slide past each other, making one microtubule longer than the second. This discrepancy in length curves the sperm tail, as can be seen in the images below. Rapid alterations in microtubule lengths create the vigorous whipping motion observed in activated sperm.

  • The mitochondria: Mitochondria are often called the "powerhouse" of the cell. They convert glucose, a simple sugar, into ATP which cells can use to do all kinds of work. Sperm use ATP to power the movement of their microtubules and propel themselves forward.

  • The Plasma Membrane: Like all cells, sperm have a plasma membrane. The plasma membrane is the cell's "skin" and separates the cell from the external environment and covers the whole sperm. The plasma membrane surrounding the acrosome plays an important role in sperm-egg recognition and in fertilization.

 

The ejaculate (also called semen, cum or the seminal fluids) is a combination of fluids from multiple sex glands inside the male. Semen contains sperm which are produced in the testes and expelled via the vas deferens. The vas deferens begins at the epididymis and winds up past the pubic bone and urinary bladder. There are two vas deferens, one coming from each testicle, and they join at the back of the bladder. When sperm are ejaculated, they are joined by fluids from the prostate and seminal vesicles at the ejaculatory duct in the vas deferens to form the ejaculate, also called the semen. See the male internal anatomy for a detailed diagram showing these organs. The ejaculate is expelled from the penis through the urethra, and is normally accompanied by the pleasurable feelings of an orgasm.

Semen can exit the penis at a variety of speeds and volumes having different consistencies and tastes. Semen is usually a light white or grey color and may have a "clumped" consistency immediately after ejaculation and then turn more liquid later.

 

 

The Composition of Semen

Less than 1% of the semen is actually made up of sperm. This is why men who have undergone a vasectomy have no change in the consistency, look, feel or taste of their semen. Men who have no sperm in their ejaculate, either naturally or artificially, are said to have azoospermia.
Approximately 30% of the seminal fluid comes from the prostate. The prostate releases an alakialine or basic fluid. Sperm survive and function best in a slightly basic environment. Semen's basic nature raises the pH of the vagina's environment if the sperm enters the vagina.
Approximately 70% of the ejaculate comes from the seminal vesicles. The seminal vesicles' secretions add fructose to the ejaculate. Fructose is a sugar which acts as an energy source for the sperm cells. Sperm beat their flagella and propel themselves forward upon receiving fructose (and perhaps other chemical signals). When sperm are motile, they are said to be activated.
Not all sperm are activated all at once. Sperm seem to have an internal clock that dictates when they react to the seminal fluid's activating signals. Sperm activation can be delayed for up to several days, and indeed only 10% of sperm at a given time may be activated. This is how sperm can still penetrate and fertilize an egg for up to 5 days after being ejaculated the vagina. If a sperm had been constantly beating its flagella from the beginning it would have quickly run out of energy.

The seminal fluid also contains chemicals that de-capacitate the sperm. This means that they make the sperm unable to immediately fertilize an egg. This helps keep the sperm intact and ready for fertilization when (or if) they actually reach the egg. Cholesterol may be the main factor that helps stabilize the plasma membrane surrounding the acrosome and preventing the sperm from being able to undergo the acrosomal reaction. De-capacitation helps keep the sperm from reacting too early and missing the chance to fertilize an egg. An unknown chemical (or combination of chemicals) inside the vagina help re-capacitate sperm so that they might be able to react with the egg. Interestingly, scientists do not know how to re-capacitate sperm that are given by sperm donors, but must instead wait awhile for the sperm to become re-capacitated on their own.

 

Semen Difficulties
It is normal for pre-pubescent boys to not produce semen. Boys start producing semen and mature sperm during puberty. There may be a medical problem, however, when adult males do not ejaculate any semen. Except for the experience of a male multiple orgasm, men who do not consistently release ejaculatory fluid during orgasm may be suffering from retrograde ejaculation and should see a doctor.

Average ejaculates can contain around 100 million sperm per ejaculate, but the WHO (World Health Organization) has deemed 20 million sperm per milliliter of semen (roughly 40 million sperm per ejaculate) as normal. Men with a sperm count lower than 20 million sperm per milliliter are said to have oligospermia, which means "few sperm." Men who have no observable amount of sperm in their ejaculate are said to have azoospermia. Men with low sperm counts might have difficulty conceiving and may benefit from various forms of assisted reproductive technology. Keep in mind, however, that men with a lower sperm count still need to use contraceptives if they do not wish to conceive.

 

 

Is it Possible to Make it Taste Better?

After much research, we still have not come across any scientific experiments on ways to make semen taste better. But, there are a lot of personal opinions in the rumor mill coming from people who have experimented on their own. Many people suggest eating or drinking things with high sugar content. The male could eat pineapple or other fruits, or drink fruit juices, in order to sweeten the taste of his semen. Another suggestion is to maintain a vegetarian diet, or simply cut down on meat. Some people suggest cinnamon, lemon or green tea. One could also use a sweetened lube to try to mask the taste of the semen, or wear a flavored condom so there is no contact with the semen at all. Using a condom extra advantages because in addition to escaping the taste of semen it reduces the risk transmitting STIs via oral sex. 

There are also a few products on the market that claim to improve the taste of semen such as Sweeten'd Blow and Semenex.

Our advice is to experiment. Experimenting is the best way to discover personal preferences relating to one's sexuality. Everyone is different, and every couple is different as well. We recommend trying a few of these various techniques to see which one works best for you and your partner. And, if you come to any conclusions, please let us know what you think works best so we can share the information with others who are interested.


 

 

Pre-Ejaculate

Pre-ejaculate, or precum, is the fluid secreted by the Cowper's glands or bulbourethral glands. These glands secrete small drops of alkaline fluid that helps neutralize the acidity of the man's urethra. Most men may notice a few drops of precum on the tip of their penis during sexual arousal. Every man produces precum, even if he does not notice it. The pre-ejaculate can contain sperm from the previous ejaculation or nocturnal emission. This means that pre-cum can cause pregnancy. This is why the pull-out, or withdrawal, method is not an effective method of contraception.

 

 

 

 

References

Crooks, Robert, & Baur, Karla. (2005). Our Sexuality (9th ed.). Belmont: Thomson Wadsworth.

Hardy, Daniel M., ed. Fertilization. Academic Press: London, UK, 2002.

Hyde, Janet Shibley and DeLamater, John D.. Understanding Human Sexuality. McGraw-Hill Companies, Inc., 2006.

Lopez, Laureen M., Grimes, David A., and Schulz, Kenneth F.. "Nonhormonal Drugs of Contraception in Men: A Systematic Review." CME Review Article. Obstetrical and Gynecological Survey, 60.11 (2005): 746 - 758.

Meriggiola, M. Cristina, Bremner, William J., Costantino, Antonietta, Pavani, Anna, Capelli, Maurizio, and Flamigni,Carlo. "An Oral Regimen of Cyproterone Acetate and Testosterone Undecanoate for Spermatogenic Suppression in Men." Fertility and Sterility

"Semen and Sperm Quality". NetDoctor.co.uk. Last updated: April 10, 2005. Viewed: April 11, 2007. http://www.netdoctor.co.uk/menshealth/facts/semenandsperm.htm

Perheentupa, Antti and Huhtaniemi, Ilpo. "Male Contraception - quo vadis?" Denmark: Acta Obstetricia et Gynecologica Scandinavica 83(2004): 131 - 137.

Purves, Sadava, Orians, Heller. Life: the Science of Biology. Courier Companies, Inc., 2003.

Segal, Sheldon J., ed. Gossypol, a Potential Contraceptive for Men. Reproductive biology. New York: Plenum Press, 1985.

 

Last Updated 4 February 2013.

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