Oogenesis is the process where an ovum is produced in the ovaries of females. It begins with oogonia that undergo mitosis and become primary oocytes. The primary oocytes then go through two phases of meiotic division to become either secondary oocytes or polar bodies. The secondary oocyte may be fertilized by sperm to form a zygote. This process is regulated by hormones like FSH and LH which stimulate the growth and maturation of ovarian follicles.

1. OOGENESIS

2. Q. Write an essay
on Oogenesis.

3. Total mark = 07
Description = 04
Labeled diagram = 03

4. INTRODUCTION
Human beings are most
evolved with well marked sexual
dimorphism. Puberty is the
maturity age marked by separate
male or female secondary sex
characters due to secretion of
respective sex hormones in gonads
guiding respective gametogeneeis.

5. GAMETOGENESIS
It is the process of
production of male /
female gamete(s) in
respective gonads under
hormonal control.

6. TYPES OF GAMETOGENESIS
It may be of two types :-
Spermatogenesis in male
producing sperms in
seminiferous tubules of testes.
Oogenesis in female
producing ovum in ovary.

7. OOGENESIS
It is the process of production of
OVUM from primary germ cells
in Ovary of female under
stimulation of ESTROGEN
secreted by FOLLICULAR cells
of GRAFFIAN FOLLICLES of
ovary at puberty.

8. OVARIAN FOLLICLE
At puberty, some cells of
ovarian germinal epithelium
detach into cortex. One of them
undergo oogenesis to become
ovum and rest surround it, the
entire structure is called as an
ovarian follicle and graffian
follicle on maturity.

9. STEPS OF SPERMATOGENESIS
 Multiplication Phase
 Growth Phase
 Maturation Phase
→ 1st Maturation Phase
→ 2nd Maturation Phase

10. EXTRA RELATED POINTS
 Hormonal Regulation of
Oogenesis
 Conclusion

11. MULTIPLICATIION PHASE
(Primary Germ Cell to Oogonia)
In this phase deploid (2n)
Primary germ cells of ovary divide
by repeated mitosis to produce
clones called Oogonia (Oogonium –
singular) or Egg mother cells under
stimulation of Estrogen.

12. GEOWTH PHASE
(Oogonium to Primary Oocyte)
In this phase deploid (2n)
Oogonium do not divide but
grow and become large called
Primary Oocyte being nourished
by surrounding follicular cells of
Graffian follicle.

13. 1ST MATURATION PHASE
(Primary Oocyte to Secondary Oocyte)
In this phase, the deploid (2n)
Primary Oocyte divides by meiosis – I
to produce one larger haploid (n)
Secondary Oocytes and one smaller
haploid (n) primary Polar body /
Polocyte. It is a reductional division
of nucleus and unequal cytokinesis.

14. 2ND MATURATION PHASE
(Secondary Oocytes to Ootids)
In this phase :-
Secondary Oocyte divide by meiosis –
II to produce one larger haploid (n)
Ootid and one smaller secondary
polocyte.
Generally primary polocyte dies, but
if survive, divide by meiosis – II to
produce two tertiary polocytes.

15. SIGNIFICANCE OF POLOCYTE
In maturation divisions of
Oogenesis, one daughter cell gets
almost all of organelles and
cytoplasm and become secondary
oocyte and ootid. Other daughter
cells gets almost negligible
organelles and cytoplasm and
become polocyte(s), they generally
die, as they are not needed.

17. HORMONAL
REGULATION

18. HYPOTHALAMUS
(BRAIN)
GONADOTROPIN
RELEASING FACTOR
PITUITARY GLAND

19. PITUITARY GLAND
FSH
(FOLLICLE
STIMULATING
HORMONE)
LH
(LUTEINIZING
HORMONE)

20. FSH LH
STIMULATES
DEVELOPMENT AND
MATURATION OF
OVARIAN FOLLICLES
FINAL MATURATION OF
FOLLICLES, OVULATION,
FORMATION OF CORPUS
LUTEUM
SECRETION OF
ESTROGEN FROM
FOLLICLES
SECRETION OF
PROGESTERON
OOGENESIS & PREGNANCY ON FERTILISATION

21. Oogonia or
Egg mother cell
Primary Oocyte
Multiplication
Phase
Growth Phase

22. Secondary Oocyte
Ootid
1st Maturation
Phase
2ndMaturation
Phase
n n
n n Tertiary Polocytes
Secondary Polocytes
Primary Polocytes

23. Ootid
Ovum

24. SIGNIFICANCE OF SPERMIOGENESIS
It produce haploid Ovum from
deploid germ cells of ovary in
female to be fertilised by
haploid sperm of male forming
deploid zygote in sexual
reproduction.
It restores deploid chromosome
number in offspring.

25. CONCLUSION
Females produce Ovum by
oogenesis. The secondary oocyte is
released from ovary by ovulation phase
on 14th day of menstrual cycle in female
and received by fallopian tube. During
orgasm of coitus, it wait for sperm of
male for probable fertilisation,
pregnancy and child birth for continuity
of race on earth.