Oogenesis
Process of formation of femal gametes. Oogenesis is initiated in embryonic stage.
Oogonia form primordial follicle and development into primary oocyte (at birth oogonia replaced by primary oocyte).
Primary oocyte maximum development at 20 week of gestational age, million primary oocyte created.
At birth ovary contains around 400,000 primordial follicle which contain primary oocyte.
At puberty ovary has about 60,000 primary follicles.
Only 400 mature oocyte to ovulate during entire reproductive age.
Process of Oogenesis
Germ cells
I mitosis
Oogonia
I
Primary oocyte
I (46, XX)
Maturation of graafian Follicle
I Completion of 1st meiotic (meiosis) division.
Unequal sharing distribution of cytoplasm
I produce one large cell and one small cell
Secondary oocyte 1st polar body
(Ovum) (23, X), Haploid (23,X ), can’t under go fertilization
I Ovulation
Not fertilized; degenerates within 24 hours.
Fertilized; completion of 2nd meiotic (meiosis) division.
I
Female pronucleus Second polar body (23,X), can’t undergo fertilization
After process of fertilization, egg and sperm fuse to make a cell with 46 chromosomes (23 pairs), called a zygote.
