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Definition: sperm from Philip's Encyclopedia

(spermatozoon) Motile male sex cell (gamete) in sexually reproducing organisms. It corresponds to the female ovum. Sperm are produced in the testes of male animals. The head of the sperm contains the genetic material of the male parent, while its tail or other motile structure provides the means of moving to the ovum to carry out fertilization. Up to 500 million sperm together may attempt to reach the egg, but only one will fertilize it. See also sexual reproduction


sperm

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
In biology, the male gamete of animals before fertilization in sexual reproduction . Each sperm cell has a head capsule containing a nucleus, a middle portion containing mitochondria (which provide energy), and a long tail (flagellum). In mammals sperm cells are produced in the testes of a male. They are produced by a special kind of cell division called meiosis , which halves the number of chromosomes present. Sperm cells are highly specialized. When they are introduced into the vagina of the female by the penis of the male, they swim up the uterus and oviducts. The swimming is a result of the beating of the tail of the sperm cell. At the other end is the nucleus , but there is little else in the cell, making it fairly small and light. The human sperm is 0.005 mm/0.0002 in long and can survive inside the female for 2–9 days. Sperm counts have fallen by 50% worldwide since 1940, according to a Danish study in 1990. This reduction may be due to increases in pollution – a number of…
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Full text Article sperm

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
In biology, the male gamete of animals before fertilization in sexual reproduction . Each sperm cell has a head capsule containing a nucleus, a middle portion containing mitochondria (which provide energy), and a long tail (flagellum). In mammals sperm cells are produced in the testes of a male. …
| 410 words
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Full text Article sperm

From The Chambers Dictionary
semen; spermatozoa; any generative substance; eggs, spawn, brood, offspring ( obs ); the chalaza of a hen's egg (formerly believed to be contributed by the cock) ( obs ); a sperm whale; sperm oil; a sperm candle; spermaceti. combining form denoting seed. [Gr sperma , - atos seed, semen, from…
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Full text Article sperm autoimmunity

From Library of Health and Living: The Encyclopedia of Autoimmune Diseases
A disorder that can interfere with the normal reproductive process and contribute to infertility but that is not a common cause of complete infertility. Anti-sperm antibodies (ASAs) are immune system cells that mistakenly identify sperm as harmful invaders and attempt to eliminate them. Sperm…
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Full text Article Sperm Competition

From Encyclopedia of Social Insects
Sperm Competition, Fig. 1 Team swimming of sperm...
If a female mates with multiple males resulting in the co-occurrence of ejaculates from multiple males within her sexual tract, sperm often have to compete with each other for limited storage space and/or a defined set of eggs. The resulting processes that bias the reproductive success and fitness…
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Full text Article sperm competition

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Competition between the sperm of rival males within the body of a female. This may involve actual removal of a rival's sperm before mating, for example the penis of a male dragonfly is shaped to scoop out existing sperm; or internal competition between rival sperm cells. In the bug Xylocoris…
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Full text Article sperm whale

From The Columbia Encyclopedia
largest of the toothed whales , Physeter catodon , found in the Atlantic and Pacific oceans. It is also called cachalot. Male sperm whales may grow to more than 70 ft (21 m) long and females to 30 ft (9 m). Most are dark blue-black all over; a few have white undersides. The large squarish head…
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Full text Article Spermatozoa, Sperms

From Black's Veterinary Dictionary
Sperm formation in the testis. (From D. F....
Spermatozoa (sperms) are the motile male sex cells which, having matured in the epididymis, are ejaculated at orgasm and are normally capable of fertilising the ovum or egg. The sperms are derived from non-motile cells in the seminiferous tubules of the testicle. The first-stage cells, …
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Full text Article Sperm Whales

From Princeton Encyclopedia of Mammals
Cutaway drawing of the head of a sperm whale,...
Immortalized in herman melville's novel Moby Dick, sperm whales run to extremes. They are the largest of the toothed whales, have the biggest brains on Earth, are very sexually dimorphic (males weigh three times as much as females), and make possibly the deepest and longest dives of any creature in…
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Full text Article sperm whale

From Britannica Concise Encyclopedia
Thickset, blunt-snouted toothed whale ( Physeter catodon , family Physeteridae) with small, paddlelike flippers and rounded humps on the back. Sperm whales have an enormous head, squarish in profile, and a narrow, underslung lower jaw with large conical teeth that fit into sockets in the toothless…
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Full text Article sperm

From Britannica Concise Encyclopedia
Male reproductive cell . In mammals, sperm are produced in the testes and travel through the reproductive system . At fertilization , one sperm of the roughly 300 million in an average ejaculation ( see semen ) fertilizes an egg ( see ovary ) to produce an offspring. At puberty , immature cells…
| 135 words
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