Fertilization : easy and brief
explanation
Definition: The process by which male
and female gametes fuse to form zygote
Site of fertilization: the
ampullary region of the uterine tube
Spermatozoa are not able to fertilize
the oocyte immediately upon arrival in the female genital tract but must
undergo a) capacitation b) acrosome
reaction to acquire this capability.
Capacitation : is a period of conditioning in the
female reproductive tract that in the human lasts approximately 7 hours
The acrosome reaction: which occurs after binding
to the zona pellucida, is induced by zona proteins.
The phases of fertilization include
Phase 1: penetration of the corona
radiate.
Phase 2: penetration of the zona
pellucida.
Phase 3: fusion of the oocyte and
sperm cell membranes.
The main results of fertilization are
as follows
·
restoration
of the diploid number of chromosomes
·
determination
of sex
·
initiation
of cleavage
Egg responses in
three ways when the spermatozoon has entered the oocyte
1. cortical and zona reactions:
a) the oocyte membrane becomes impenetrable to other
spermatozoa
b) zona pellucida alters its structure and composition
to prevent sperm binding and penetration
2. Resumption of the second meiotic
division
3. Metabolic activation of the egg
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