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Description:
A spermatozoon (pronounced /ˌspɜrmætəˈzoʊən/, alternate spelling spermatozoön; plural spermatozoa; from Ancient Greek: σπέρμα "seed" and Ancient Greek: ζῷον "living being") is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.)
Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing a Y chromosome will lead to a male (XY) offspring, while one bearing an X chromosome will lead to a female (XX) offspring. Sperm cells were first observed by Anton van Leeuwenhoek in 1677.

The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby decreasing the total sperm quality. Sperm cells come in two types, "female" and "male". Sperm cells that give rise to female (XX) offspring after fertilization differ in that they carry an X-chromosome, while sperm cells that give rise to male (XY) offspring carry a Y-chromosome.
In male humans, sperm cells consists of a flat, disc shaped head 5 µm by 3 µm and a tail 50 µm long. The tail flagellates, which propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone. Semen has an alkaline nature, and they do not reach full motility (hypermotility) until they reach the vagina where the alkaline pH is neutralized by acidic vaginal fluids. This gradual process takes 20–30 minutes. In this time, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Just as they become hypermotile, fibrinolysin from the prostate dissolves the clot, allowing the sperm to progress optimally.
The spermatozoon is characterized by a minimum of cytoplasm and the most densely packed DNA known in eukaryotes. Compared to mitotic chromosomes in somatic cells, sperm DNA is at least sixfold more highly condensed.
The specimen contributes with DNA/chromatin, a centriole and perhaps also an oocyte-activating factor (OAF). It may also contribute with paternal messenger RNA (mRNA), also contributing to embryonic development.

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Sperm Under Microscope Video

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