Fertilization , union of a spermatozoal nucleus , of paternal origin, with an egg nucleus, of maternal origin, to form the primary nucleus of an embryo. In all organisms the essence of fertilization is, in fact, the fusion of the hereditary material of two different sex cells , or gametes , each of which carries half the number of chromosomes typical of the species. The most primitive form of fertilization, found in microorganisms and protozoans, consists of an exchange of genetic material between two cells. The first significant event in fertilization is the fusion of the membranes of the two gametes, resulting in the formation of a channel that allows the passage of material from one cell to the other.
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Fertilization - Embryology
The lucky few sperm who reached the egg in the Fallopian tube surround it and begin competing for entrance. The head of each sperm, the acrosome, releases enzymes that begin to break down the outer, jelly-like layer of the egg's membrane, trying to penetrate the egg. Once a single sperm has penetrated, the cell membrane of the egg changes its electrical characteristics. This electrical signal causes small sacs just beneath the membrane cortical granules to dump their contents into the space surrounding the egg. The contents swell, pushing the other sperm far away from the egg in a process called cortical reaction.
About Translations. Fertilization is the fusion of haploid gametes, egg and sperm, to form the diploid zygote. Note though there can be subtle differences in the fertilization process which occurs naturally within the body or through reproductive technologies outside the body, the overall product in both cases is a diplod zygote. In fertilization research, after humans the mouse is the most studied species followed by domestic and farm animals. The process of fertilization involves components of, and signaling between, both sperm spermatozoa and egg oocyte.
Fertilization occurs when a sperm and an oocyte egg combine and their nuclei fuse. Because each of these reproductive cells is a haploid cell containing half of the genetic material needed to form a human being, their combination forms a diploid cell. This new single cell, called a zygote , contains all of the genetic material needed to form a human—half from the mother and half from the father. Fertilization is a numbers game. During ejaculation, hundreds of millions of sperm spermatozoa are released into the vagina.