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Encyclopedia of Health and Medicine

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356 The Reproductive System<br />

See also ALTERNATIVE METHODS FOR PAIN RELIEF;<br />

ANALGESIC MEDICATIONS; MALDYNIA; SEXUALLY TRANS-<br />

MITTED DISEASE (STD) PREVENTION.<br />

zygote The cell that results when a spermatozoon<br />

(SPERM cell) penetrates an ovum (egg cell)<br />

during fertilization. Each GAMETE (sperm <strong>and</strong><br />

ovum) is a haploid cell; it contains one half the<br />

genetic material necessary to support life. The<br />

zygote is a diploid cell; it contains all the DNA necessary<br />

to create a new life. Fertilization typically<br />

takes place in the fallopian tube. The zygote grows<br />

<strong>and</strong> divides as it makes its way through the fallopian<br />

tube to the UTERUS, a journey <strong>of</strong> about five<br />

days. When it reaches the uterus the zygote<br />

implants into the endometrium, the thick, BLOODrich<br />

lining <strong>of</strong> the uterus. By the time implantation<br />

is complete the zygote has become a two-layered<br />

structure called a blastocyst.<br />

For further discussion <strong>of</strong> the zygote within the<br />

context <strong>of</strong> the structures <strong>and</strong> functions <strong>of</strong> reproduction<br />

<strong>and</strong> sexuality, please see the overview section<br />

“The Reproductive System.”<br />

See also ASSISTED REPRODUCTIVE TECHNOLOGY (ART);<br />

CELL STRUCTURE AND FUNCTION; EMBRYO; FALLOPIAN<br />

TUBE; FETUS; OVA.

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