Sperma

Spermatozoidi, u ovom slučaju ljudski, su primarna komponenta normalnog semena i agensi oplodnje ženskih jajnih ćelija.

Ćelija sperme prodire u jajnu ćeliju za vreme oplodnje.

Sperma (od grčke reči σπέρμα, spérma, što znači seme) ili ejakulat (od latinske reči eicěre: izbaciti, odnosno eiaculatum: ono što je izbačeno) mutna je mlečnobela do bledožuta tečnost koja se pod određenim uslovima izbacuje iz semenih puteva, a sastoji se od spermatozoida, sekreta polnih žlezda i sekreta epididimisa. U pravilu se izbacuje kroz spoljni otvor mokraćne cevi, a ređe u mokraćni mehur. Izbacuje se najčešće za vreme polnoga odnosa ili za vreme samozadovoljavanja. Čak i u snu može doći do izbacivanja sperme. To je tzv. noćna polucija i dešava se obično kada snovi imaju seksualni sadržaj.

Fiziologija

Oplodnja

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 most vertebrates, including 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.

Ljudi

Kompozicija

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 ductal fluid by reabsorbing some fluid. Once the semen enters the ductus epididymis the principal 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 (c.f. sexual conflict) 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 and buffer 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(s)	Approximate fraction	Description
testes	2–5%	Approximately 200 million – 500 million spermatozoa (also called sperm or spermatozoans), produced in the testes, are released per ejaculation. If a man has undergone a vasectomy, he will have no sperm in the ejaculate.
seminal vesicles	65–75%	Amino acids, citrate, enzymes, flavins, fructose (2–5 mg per mL semen, 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. (The zinc level is about 6999135000000000000♠135±40 µg/mL for healthy men. 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 20×10⁶ spermatozoa/mL or more, sperm count of 40×10⁶ 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.

A 2005 review of the literature found that the average reported physical and chemical properties of human semen were as follows:

Property	Per 100 mL	In average volume (3.4 mL)
Calcium (mg)	27.6	0.938
Chloride (mg)	142	4.83
Citrate (mg)	528	18.0
Fructose (mg)	272	9.25
Glucose (mg)	102	3.47
Lactic acid (mg)	62	2.11
Magnesium (mg)	11	0.374
Potassium (mg)	109	3.71
Protein (mg)	5,040	171
Sodium (mg)	300	10.2
Urea (mg)	45	1.53
Zinc (mg)	16.5	0.561
Buffering capacity (β)	25
Osmolarity (mOsm)	354
pH	7.7
Viscosity (cP)	3–7
Volume (mL)	3.4
Values for average volume have been calculated and rounded to three significant figures. All other values are those given in the review.

Opis

Neposredno nakon izlivanja, sperma je lepljiva zgrušana tečnost nalik na žele, moguća je pojava i sitnih grudvica. Specifičnog je mirisa (najbliže je mirisu cveta kestena) i lužnatog je okusa. Delovanjem enzima likvefakcija tj. razgradnja ugruška (razvodnjavanje) obično je završena nakon 30 minuta. Ukupna je zapremina ljudskoga ejakulata vrlo promjenjiva, uglavnom od 1,5 do 6 ml (prosečno od pola do jedne čajne kašike), u njemu se nalazi oko 50 miliona spermatozoida, a pH-vrednost ejakulata kreće se u opsegu od 7,2 do 8,2.

Veći deo sperme čine izlučevine semenih mjehurića (60%), prostate (20%) te Cowperovih i Littreovih žlezda, koje štite spermatozoide od štetnih uticaja i omogućavaju im kretanje i oplodnju jajne ćelije. Pre semena iz mokraćne cevi izlazi sekret tih žlezda (0,1-0,2 ml), nakon toga prostatički sekret (0,5 ml), a spermatozoidi čine samo jedan procenat ejakulata.

Izgled i konzistentnost

Ljudsko seme u Petrijevoj posudi

Semen is typically translucent with white, grey or even yellowish tint. 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 the symptom persists.

After ejaculation, the latter part of the ejaculated semen coagulates immediately, forming globules, while the earlier part of the ejaculate typically does not. After a period typically ranging from 15 to 30 minutes, prostate-specific antigen present in the semen causes the decoagulation of the seminal coagulum. It is postulated that the initial clotting helps keep the semen in the vagina, while liquefaction frees the sperm to make their journey to the ova.

A 2005 review found that the average reported viscosity of human semen in the literature was 3–7 centipoises (cP), or, equivalently, millipascal-seconds (mPa·s).

Vidi još

• Vaginalno podmazivanje
• Spermatozoid

Literatura

• Vilard, Huntington F.; Robert L. Nasbom; Tomson, Margaret V.; Tomson, Džejms Klej; Mekins, Rodrik R. (2001). Thompson & Thompson genetics in medicine. Filadelfija: V. B. Saunders. ISBN 978-0-7216-6902-1. 
• Grizard, G; Sion, B; Bauchart, D; Boucher, D (31. 3. 2000). „Separation and quantification of cholesterol and major phospholipid classes in human semen by high-performance liquid chromatography and light-scattering detection”. Journal of Chromatography B: Biomedical Sciences and Applications. 740 (1): 101—7. PMID 10798299. doi:10.1016/S0378-4347(00)00039-6. CS1 одржавање: Формат датума (веза)

Spoljašnje veze

• SUNY Podcast – Semen study results
• Hyena, Hank (21. 8. 2000). „The quest for sweet semen”. Salon. CS1 одржавање: Формат датума (веза)