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see spermsperm
or spermatozoon
, in biology, the male gamete (sex cell), corresponding to the female ovum in organisms that reproduce sexually. In higher animals the sperm is produced in the testis of the male; it is much smaller than the ovum and consists primarily of a head,
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the male sexual cell in animals.

In all vertebrates and most invertebrates a flagellum, or tail, enables the spermatozoa to move forward. The spermatozoa of some worms, myriopods, crustaceans, mites, and ticks are tailless and are characterized by a wide variation in structure and by amoeboid movement. Spermatozoa range in length, according to species, from tens to hundreds of micrometers; the spermatozoa of insects may reach several millimeters in length.

Spermatozoa with tails have a comparatively short head that may be spherical, conical, or hooked in shape. A nucleus containing condensed chromatin is found in the head. At the head’s anterior end there is an acrosome containing lysins. Below the head there is a thinner middle piece that ends in a threadlike tail. In most animal species the middle piece is short and encloses a basal granule (centriole) consisting of nine triplets of short microtubules arranged in a ring and surrounded by a halo of four to ten large mitochondria.

Extending from the basal granule is an axial filament, or axo-neme, which by contracting enables the flagellum to beat and the spermatozoon to move. The ultrastructure of the axial filament is virtually the same in all spermatozoa and is similar to that of cilia. A filament consists of fibrils (microtubules 200–250 angstroms in diameter), two of which lie in the center surrounded by a ring of nine peripheral fibril doublets (9 + 2). Sometimes nine additional fibrils are found outside the doublets (9 + 9 + 2). Flagellate peripheral fibrils are transformed directly into microtubules of the basal granule, and the central fibrils remain free. Proteins similar to actin and myosin (found in skeletal muscles) and capable of splitting ATP are found in flagellate axial filaments in fibrils and in structures directly associated with fibrils.

In insects the head of a spermatozoon is very elongated and sometimes spirally coiled, extending almost imperceptibly into a long tail. Much of the tail contains a distinctive structure of mitochondrial origin called a mitochondrial helix.

In many animals several types of spermatozoa are formed in the testes. Most are atypical, resulting from spermatogenic disturbances primarily occurring during meiosis. These spermatozoa apparently cannot fertilize ova.


Wilson, E. Kletka i ee rol’ v razvitii i nasledstvennosti, vol. 1. Moscow-Leningrad, 1936. (Translated from English.)
Rukovodstvo po tsitologii, vol. 2. Moscow-Leningrad, 1966.
Hancock, J. L. “The Ultrastructure of Mammalian Spermatozoa.” In Advances in Reproductive Physiology. London, 1966.



A mature male germ cell. Also known as sperm.


any of the male reproductive cells released in the semen during ejaculation, consisting of a flattened egg-shaped head, a long neck, and a whiplike tail by which it moves to fertilize the female ovum
References in periodicals archive ?
Furthermore, relationship of seminal free L-carnitine with functional spermatozoal characteristics like sperm count, motility and morphology was also examined.
In the light of accumulating evidence that spermatozoal DNA damage may be linked to adverse clinical outcomes, the examination of sperm chromatin integrity emerges as a new, potentially valuable tool in the diagnostic armamentarium of laboratory andrology (33).
The bovine spermatozoal motility characteristics decline with incubation time.
Further evaluation of a simple test for determining the integrity os spermatozoal membrane.
effect of storage temperature, cooling rates and two different semen extenders on canine spermatozoal motility.
Cotton seed oil emulsion also exhibited spermatozoal motility inhibition.
The 2,780 RNAs shared by both samples "are representative of the spermatozoal fingerprint for the normal fertile man," the researchers conclude in the Lancet.
The average percent primary spermatozoal abnormalities was found to be 18 with a standard deviation of 2.
Cladistic study in the Monogenea Platyhelminthes), based upon a parsimony analysis of spermiogenic and spermatozoal ultrastructural characters.
Decline in spermatozoa motility at osmotic pressures less than 270 mOsm/kg may be correlated to the fact that motility depends on ATP contents of spermatozoal mitochondria (Perchek et al.