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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 ?
Firstly, defense against peroxidative damage is essential to prevent any reduction in functionally important C20-22 PUFA levels of spermatozoan phospholipids and to maintain the structural integrity of the spermatozoa.
Spermatozeugmata had a mean internal diameter of 76.1 [+ or -] 2.1 [[micro]meter] (range 73.0-79.0 [[micro]meter]) and contained 8000-9000 spermatozoa (based on area of spermatozeugma/area of spermatozoan head).
Sperm motility grades and spermatozoan MDA concentrations from different experimental groups were statistically compared by Student's t-test and Kruskal Wallis test was applied to compare the medians (GraphPad Prism V).
Exposure of C57BL/6 mice to TCDD (0.1-50 [micro]g TCDD/kg) for 24 hr resulted in a decrease in spermatozoan mitochondrial membrane potential compared with vehicle-treated control mice (Fisher et al.
(14)), HIV-1 has also been demonstrated within spermatozoa by electron microscopy, (15) and either HIV-1 DNA or RNA in spermatozoan preparations has also been detected.
The mature spermatozoan nucleus of squids and cuttlefish is a 6-~8-[micro]m long and 1-[micro]m wide cylindrical, fusiform organelle (Maxwell 1975, Fields & Thompson 1976, Healy 1989).
Polymegaly of spermatozoan length and its genetic control in Drosophila species.
In ringed turtle-doves (Streptopelia risoria), testes weights were lower in lead-treated males and spermatozoan numbers tended to be lower (Kendall and Scanlon, 1981).
morphology of the spermatozoan, and biology of fertilization among invertebrates.
The male factor in fertility and infertility: spermatozoan counts in 1000 men of known fertility and in 1000 cases of infertile marriage.
Spermatozoan length in species of the Drosophila affinis subgroup.