Semen

For other uses, see Semen (disambiguation).

Human semen in petri dish.

Semen is an organic fluid, also known as seminal fluid, that usually contains 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 is 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." The process that results in the discharge of semen is called ejaculation.

Physiological aspects

Internal and external fertilization

Depending on the species, spermatozoa can fertilize ova externally or internally. In external fertilization, the spermatozoa fertilize the ova directly, outside of the female's sexual organs. Female fish, for example, spawn ova into their aquatic environment, where they are fertilized by the semen of the male fish.

During internal fertilization, however, fertilization occurs inside the female's sexual organs. Internal fertilization takes place after insemination of a female by a male through copulation. In low vertebrates (amphibians, reptiles, birds and monotreme mammals), copulation is achieved through the physical mating of the cloaca of the male and female. In marsupial and placental mammals, copulation occurs through the vagina.

Composition of human semen

During the process of ejaculation, sperm passes through the ejaculatory ducts and mixes with fluids from the seminal vesicles, the prostate, and the bulbourethral glands to form the semen. The seminal vesicles produce a yellowish viscous fluid rich in fructose and other substances that makes up about 70% of human semen. The prostatic secretion, influenced by dihydrotestosterone, is a whitish (sometimes clear), thin fluid containing proteolytic enzymes, citric acid, acid phosphatase and lipids. The bulbourethral glands secrete a clear secretion into the lumen of the urethra to lubricate it.

Sertoli cells, which nurture and support developing spermatocytes, secrete a fluid into seminiferous tubules that helps transport sperm to the genital ducts. The ductuli efferentes possess cuboidal cells with microvilli and lysosomal granules that modify the semen by reabsorbing some fluid. Once the semen enters the ductus epididymis the principle cells, which contain pinocytotic vessels indicating fluid reabsorption, secrete glycerophosphocholine which most likely inhibits premature capacitation. The accessory genital ducts, the seminal vesicle, prostate glands, and the bulbourethral glands, produce most of the seminal fluid.

Seminal plasma of humans contains a complex range of organic and inorganic constituents.

The seminal plasma provides a nutritive and protective medium for the spermatozoa during their journey through the female reproductive tract. The normal environment of the vagina is a hostile one for sperm cells, as it is very acidic (from the native microflora producing lactic acid), viscous, and patrolled by immune cells. The components in the seminal plasma attempt to compensate for this hostile environment. Basic amines such as putrescine, spermine, spermidine and cadaverine are responsible for the smell and flavor of semen. These alkaline bases counteract the acidic environment of the vaginal canal, and protect DNA inside the sperm from acidic denaturation.

The components and contributions of semen are as follows:

Gland	Approximate %	Description
testes	2-5%	Approximately 200- to 500-million spermatozoa (also called sperm or spermatozoans), produced in the testes, are released per ejaculation.
seminal vesicle	65-75%	amino acids, citrate, enzymes, flavins, fructose (the main energy source of sperm cells, which rely entirely on sugars from the seminal plasma for energy), phosphorylcholine, prostaglandins (involved in suppressing an immune response by the female against the foreign semen), proteins, vitamin C
prostate	25-30%	acid phosphatase, citric acid, fibrinolysin, prostate specific antigen, proteolytic enzymes, zinc (serves to help to stabilize the DNA-containing chromatin in the sperm cells. A zinc deficiency may result in lowered fertility because of increased sperm fragility. Zinc deficiency can also adversely affect spermatogenesis.)
bulbourethral glands	< 1%	galactose, mucus (serve to increase the mobility of sperm cells in the vagina and cervix by creating a less viscous channel for the sperm cells to swim through, and preventing their diffusion out of the semen. Contributes to the cohesive jelly-like texture of semen.), pre-ejaculate, sialic acid

A 1992 World Health Organization report described normal human semen as having a volume of 2 ml or greater, pH of 7.2 to 8.0, sperm concentration of 20x10⁶ spermatozoa/ml or more, sperm count of 40x10⁶ spermatozoa per ejaculate or more and motility of 50% or more with forward progression (categories a and b) of 25% or more with rapid progression (category a) within 60 minutes of ejaculation.

Appearance and consistency of human semen

Human semen.

Most semen is white in colour, but grey or even yellowish semen can be normal as well. Blood in the semen can cause a pink or reddish colour, known as hematospermia, and may indicate a medical problem which should be evaluated by a doctor if it does not readily disappear.

After ejaculation, semen first goes through a clotting process and then becomes more liquid. It is postulated that the initial clotting helps keep the semen in the vaginal canal, but liquefaction frees the sperm to make their long journey to the ova. Immediately after ejaculation semen is typically a sticky, jelly-like liquid often forming globules. Within 5 to 40 minutes it will become more watery and liquid before finally drying.

Semen quality

Main article: Semen quality

Semen quality is a measure of the ability of semen to accomplish fertilization. Thus, it is a measure of fertility in a man. It is the sperm in the semen that is the fertile component, and therefore semen quality involves both sperm quantity and sperm quality.

Semen as an anti-depressant

Research has suggested that semen may have anti-depressant properties. In studies, women who did not use condoms but instead absorbed semen vaginally sustained a better mood. Research has not demonstrated that the semen is the cause or simply correlates with the ultimate cause of the difference in mood between women who use condoms and those that do not.

Semen and transmission of disease

Semen can be the vehicle for many sexually transmitted diseases, including HIV, the virus that causes AIDS.

It is also hypothesized that components of semen, such as the spermatozoa as well as the seminal plasma, can cause immunosuppression in the body when introduced to the bloodstream or lymph. Evidence for this dates back to 1898, when Elie Metchnikoff injected a guinea pig with its own and foreign guinea pig sperm, finding that an antibody was produced in response; however the antibody was inactive, pointing to a suppression response by the immune system.

Further research, such as that by Mathur and Goust, demonstrated that non-preexisting antibodies were produced in humans in response to the sperm. These antibodies mistakenly recognized native T lymphocytes as foreign antigens, and consequently T lymphocytes would fall under attack by the body's B lymphocytes.

Other semen components are shown to spur an immunosuppressive effect are seminal plasma and seminal lymphocytes.

Semen contains proteins with potent bactericidal activity but these proteins are not active against Neisseria gonorrhoeae a common cause of sexually transmitted disease.

Blood in the semen (hematospermia)

Illustration of hematospermia.

The presence of blood in semen or hematospermia may be undetectable (it only can be seen microscopically) or visible in the fluid. Its cause could be the result of inflammation, infection, blockage, or injury of the male reproductive tract or a problem within the urethra, testicles, epididymis and prostate.

It usually clears up without treatment, or with antibiotics, but if persistent further semen analysis and other urogenital system tests might be needed to find out the cause.

Semen allergy

In rare cases, people have been known to experience allergic reactions to seminal fluids, known as human seminal plasma hypersensitivity. Symptoms can be either localized or systemic, and may include vaginal itching, redness, swelling, or blisters within 30 minutes of contact. They may also include generalized itching, hives, and even difficulty breathing.

The best way to test for human seminal plasma sensitivity is to use a condom during intercourse. If symptoms dissipate with the use of a condom, it is possible that a sensitivity to semen is present. Mild cases of semen allergy can often be overcome by repeated exposure to seminal fluid. In more severe cases, it is important to seek the advice of a physician, particularly in the event that a couple is trying to conceive, in which case, artificial insemination may be indicated.

Cultural aspects

Semen and Qigong

Qigong and Chinese medicine place huge emphasis on a form of energy called 精 (pinyin: jīng, also a morpheme denoting "essence" or "spirit") - which one attempts to develop and accumulate. "Jing" is sexual energy and is considered to dissipate with ejaculation so masturbation is considered "energy suicide" amongst those who practice this art. According to Qigong theory, energy from many pathways/meridians becomes diverted and transfers itself to the sexual organs during sexual excitement. The ensuing orgasm and ejaculation will then finally expel the energy from the system completely. The Chinese proverb 一滴精，十滴血 (pinyin: yì dī jīng, shí dī xuè, literally: a drop of semen is equal to ten drops of blood) illustrates this point.

The scientific term for semen in Chinese is 精液 (pinyin: jīng yè, literally: fluid of essence/jing) and the term for sperm is 精子 (pinyin: jīng zǐ, literally: basic element of essence/jing), two modern terms with classical reference.

Cultural views

In some cultures, semen is attributed with special properties of masculinity. For instance, among the Etoro people of Papua New Guinea, it is believed that young boys must fellate their elders and ingest their sperm to achieve proper sexual maturation. This act may also be attributed to the culturally active homosexuality throughout these and other tribes.

Aristotle

In Ancient Greece, Aristotle wrote on the importance of semen:

• "For Aristotle, semen is the residue derived from nourishment, that is of blood, that has been highly concocted to the optimum temperature and substance. This can only be emitted by the male as only the male, by nature of his very being, has the requisite heat to concoct blood into semen."

• "Sperms are the excretion of our food, or to put it more clearly, as the most perfect component of our food."

• "If men start to engage in sexual activity at too early an age... this will affect the growth of their bodies. Nourishment that would otherwise make the body grow is diverted to the production of semen. ... Aristotle is saying that at this stage the body is still growing; it is best for sexual activity to begin when its growth is 'no longer abundant', for when the body is more or less at full height, the transformation of nourishment into semen does not drain the body of needed material."

Sacred semen

In some pre-industrial societies, semen and other body fluids were revered because they were believed to be magical. Blood is an example of such a fluid, but semen was also widely believed to be of supernatural origin and effect and was, as a result, considered holy or sacred.

Semen is currently and has long been revered by Buddhist and Daoist traditions as a very important constituent of human physiology.

Dew was once thought to be a sort of rain that fertilized the earth and, in time, became a metaphor for semen. The Bible employs the term “dew” in this sense in such verses as Song of Solomon 5:2 and Psalm 110:3, declaring, in the latter verse, for example, that the people should follow only a king who was virile enough to be full of the “dew” of youth.

It was widely believed, in ancient times, that gemstones were drops of divine semen which had coagulated after having fertilized the earth. There is an ancient Chinese belief that jade, in particular, was the dried semen of the celestial dragon.

The ancient Celtic tradition of magic regarded semen as a magical element. Celtic belief held that semen was not simply a natural bodily fluid, but a supernatural substance that "appeared" in a man's body during intimate contact with a female. It was often associated with patron spirits of fertility and childbearing.

Based upon the resemblance of dandelion juice to human semen, it was historically believed that the flower magically promoted the flow of sperm. (This belief probably derives from the doctrine of signatures.)

The orchid’s twin bulbs were thought to resemble the testicles, and there was an ancient Roman belief that the flower sprang from the spilled semen of copulating satyrs.

Barbara G. Walker recounts these examples of sacred semen in The Woman’s Dictionary of Symbols and Sacred Objects, the thesis of which is that myth and folklore show a pre-patriarchic rule by women that was later supplanted by masculine culture.

In primitive mythology around the world, semen is very often considered analogous to breast milk in some way. In the traditions of Bali, it is considered to be the returning or refunding of the milk of the mother in an alimentary metaphor. The wife feeds her husband who returns to her his semen, the milk of human kindness, as it were.

In some systems of medical philosophy, such as traditional Russian medicine and the Vital Force theory of Herbert Nowell, semen is regarded as the product of a complex physiological interaction between a man and a woman (rather than merely the product of the male reproductive system).

In the modern St. Priapus Church, consumption of semen in the presence of others is a form of worship.

Semen in popular culture

File:Durex Korea.JPG

The use of spermatozoa in condom marketing campaigns has become socially acceptable on some countries.

Depiction of semen in art and popular culture has, for a long time, been considered a taboo subject.

Japanese artist Takashi Murakami is famous for a manga style piece entitled My Lonesome Cowboy, which features a naked cowboy superhero wielding his own semen as a lasso.

Andres Serrano, whose photos depict bodily fluids such as Blood and Semen II (Semen y sangre II) (1990), became a controversial figure for featuring semen in his work. He was criticized by some for producing offensive art, while others defended him in the name of artistic freedom. His photos were featured on the cover art of two Metallica albums, Load and ReLoad, which feature images made by shining light through a piece of clear plastic on which semen, blood and urine have been splattered and swirled around.

Only recently has semen been depicted (albeit controversially) in movies such as Kika (1993), There's Something About Mary (1998) ("a hard-core staple making its debut in a mainstream Hollywood comedy"), Happiness (1998), American Pie (1999), Scary Movie (2000), Y tu mamá también (2001), Scary Movie 2 (2001), Freddy Got Fingered (2001), National Lampoon's Van Wilder (2002) and Clerks II (2006). Jackass Number Two (2006) features a scene where Chris Pontius drinks horse semen. It has also appeared in the anime movie End of Evangelion.

Semen in espionage

When the British Secret Intelligence Service (SSB) discovered that semen made a good invisible ink, Sir George Mansfield Smith-Cumming noted of his agents that "Every man (is) his own stylo".

Euphemisms

A huge variety of euphemisms and dysphemisms have been invented to describe semen. For a complete list of terms, see sexual slang.

See also

• Sperm
• spermatozoon
• capacitation
• seminophagia
• Spermatogenesis
• Sperm donation
• vasectomy
• Semen extender

External links

• Grizard G, Sion B, Bauchart D, Boucher D (2000). "Separation and quantification of cholesterol and major phospholipid classes in human semen by high-performance liquid chromatography and light-scattering detection". J Chromatogr B Biomed Sci Appl. 740 (1): 101–7. doi:10.1016/S0378-4347(00)00039-6. PMID 10798299.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• "factors that affect spermatogenesis"
• simple article about sperm contents