The fertilization represents penetration of a spermatozoon into an ovum as a result of which it is restored number of chromosomes and the single-celled embryo a zygote is formed.
The fertilization consists of 3 phases:
1. Distant interaction and coming together of gametes
2. Contact of gametes
3. Infiltration of sperm cell in an ovum and gametic syngamy
In the first distant phase the spermatozoon goes towards to an ovum due to flagella cutting, to a rheotaxis and chemotaxis.
The rheotaxis is spermatozoons locomotion against a current of fluid which is formed as a result of a secretion of an epithelium of female sex organs.
Chemotaxis is ability of spermatozoons to move in a direction of the chemicals secreted by an ovum. The important role in chemotaxis plays gamones. Distinguish ginogamones are produces by ovum and androgamones are produces by a spermatozoons.
In this phase in spermatozoons occurs capacitation -activation of spermatozoons. The proteins of seed fluid leave from its surface. Then the glycoproteins of plasma membrane change. These changes are absolutely essential for fertilization. Capacitation lasts for the man 7 hours.
A lot of spermatozoons surround ovum and the second phase of fertilization (contact of gametes) begins.
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