The document provides a detailed overview of oogenesis and spermatogenesis, the processes of gamete formation in females and males, respectively. Oogenesis begins in the fetal stage and involves several stages including pre-natal, antral, and pre-ovulatory phases, resulting in one functional ovum per cycle. In contrast, spermatogenesis is a continuous process that begins at puberty and produces millions of sperm daily, with distinct stages such as spermatocytogenesis, spermatidogenesis, and spermiogenesis.

1. MRS.P.CHRISTEN,RNM
M.SC-N-OBG
ASSISTANT PROFESSOR

2.  At the beginning of embryonic development, the
primordial germ cells lie along the wall of the yolk sac.
 In the 4th week, they pass the hindgut to reach the
differentiating gonads.
 These cells are referred to as oogonia or spermatogonia
if they develop into ovaries or testicles, respectively.
 Gametes are peculiar in that they have a haploid set of
chromosomes. So, they contain only 23 chromosomes
with mixed maternal and paternal attributes.
 Later in the fertilization of the egg cell by the sperm,
a diploid set of chromosomes is formed.
 Meiosis is responsible for halving the set of
chromosomes.

3.  Oogenesis is the process
of formation of female
gamete or ovum through
a series of mitotic and
meiotic divisions
occurring in the female
reproductive system.
 Oogenesis starts in the
fetal period but then
pauses.
 It is continued during
puberty at the age of 12–
15 years.

4. Oogenesis is the process of formation of
female gametes.
This process begins inside the fetus
before birth.
The steps in oogenesis up to the
production of primary oocytes occur
before birth.
Primary oocytes do not divide further.
They either become secondary oocytes
or degenerate.

5. Oogenesis occurs in the outermost layers
of the ovaries.
Oogenesis starts with a germ cell called
oogonium and undergoes mitosis to
increase in number.
The process of oogenesis takes place in the
following three stages:
 Pre-natal
 Antral
 Pre-ovulatory

6. Pre-natal
Stage
• The primary oocyte grows while being arrested in meiosis-I.
• The follicular cells proliferate and form a stratified cuboidal epithelium. Such
cells are known as granulosa cells.
• These cells secrete glycoproteins to form zona pellucida around the primary
oocyte.
Antral Stage
• The fluid-filled area, present between granulosa cells, combines to form a
central fluid-filled space called the antrum. These are known as secondary
follicles.
• In every month cycle, these secondary follicles develop under the influence of
follicle-stimulating hormone and luteinizing hormone.
Pre-
Ovulatory
Stage
• This stage is induced by LH surge, and meiosis-I completes here.
• Two haploid cells of unequal sizes are formed within the follicle.
• One of the daughter cells that receive less cytoplasm forms a polar body. This
cell does not participate in ovum formation.
• The other daughter cell is known as the secondary oocyte. The two daughter
cells undergo meiosis-II. The polar body replicates to form two polar bodies,
while the secondary oocyte arrests in the metaphase stage of meiosis-II.

9.  Spermatogenesis is the
process of formation of
mature sperm cells
through a series of
mitotic and meiotic
divisions along with
metamorphic changes in
the immature sperm cell.
 In contrast to oogenesis,
male germ cells are able
not only to develop before
birth but also to replicate
after birth.

10. Prenatal
maturation of
male germ cells
• Prenatally, Sertoli cells stop the male germ cells in their maturation process
after their immigration into the testicle. As mainly undifferentiated cells, they
remain in the testicle whose tubules are not yet canalized. With the onset of
puberty, the seminiferous tubules develop and the maturation of the
spermatogonia to sperms begins.
Postnatal
maturation of
male germ cells
• When puberty begins, the spermatogonia significantly proliferate. Two types
of spermatogonia can be recognized: the first type always provides new
spermatogonia; the second type begins with maturation.
• In the first step, the primary spermatocyte or spermatocyte of the first
order develops out of the second type when the spermatogonia enter the
prophase of meiosis. They have a diploid set of chromosomes (2n2c). This
phase lasts roughly 3 weeks.
• Further phases of the first meiotic division follow the long prophase. At the
end of it, there are 2 spermatocytes. These are referred to as secondary
spermatocytes or spermatocytes of the second order. They undergo the
second meiotic division, resulting in 4 haploid spermatids.
• With each division, the size of the cells is halved so that the spermatids
amount to about a quarter of the size of the spermatocytes.

13. Basis for
comparison
Spermatogenesis Oogenesis
Definition
Spermatogenesis is the
process of formation of
mature sperm cells through
a series of mitotic and
meiotic divisions along with
metamorphic changes in the
immature sperm cell.
Oogenesis is the process of
formation of female
gamete or ovum through a
series of mitotic and
meiotic divisions
occurring in the female
reproductive system.
Nature of the
process
It is the male version of
gametogenesis which results
in the formation of mature
male gametes.
It is the female version of
gametogenesis which
results in the formation of
mature male gametes.

14. Basis for
comparison
Spermatogenesis Oogenesis
Stages
The process of spermatogenesis is
completed through the following
three stages;
spermatocytogenesis,
spermatidogenesis, and
spermiogenesis.
The overall process of
oogenesis is divided into
three stages; the follicular
phase, the ovulation phase,
and the luteal phase.
Occurs in
The overall process of
spermatogenesis occurs in the
testes until the sperm moves to
the epididymis and gains
motility.
The overall process of
oogenesis occurs in the ovary
until the mature ovum
moves to the fallopian tube.
Continuity of the
process
Spermatogenesis is a continuous
process that begins with puberty
and continuous until death.
The early stages of oogenesis
begin in the fetal stage while
the rest continue after
puberty till menopause.

15. Basis for
comparison
Spermatogenesis Oogenesis
Occurrence
Spermatogenesis occurs
continuously, and all
spermatogonia undergo meiosis,
producing sperms all the time.
Oogenesis occurs for one egg
cell at a time, and some cells
might require many years to
reach maturation.
Rate of production
Spermatogenesis forms millions
of sperms every day.
Oogenesis releases one ovum
per month.
Develops from
The male gamete develops from
the germinal epithelium of the
seminiferous tubules of the
testes.
The female gamete develops
from the germinal
epithelium lining the ovary.
Starting cell
The starting cell during
spermatogenesis is the primary
spermatocyte.
The starting cell during
oogenesis is the primary
oocyte.

16. Basis for
comparison
Spermatogenesis Oogenesis
Functional cell
produced from
division
The meiotic division of primary
spermatocyte results in four
spermatids, each of which
develops into a sperm cell.
The meiotic division of
primary oocyte only forms a
single functional secondary
oocyte.
Cytogenesis
Cytogenesis in spermatogenesis
forms two equal cells.
Cytogenesis in oogenesis
forms two unequal cells;
larger secondary oocyte and
a smaller polar body.
Sertoli cells
Sertoli cells are found in the
testes that provide nourishment
to the developing male gamete.
Sertoli cells are not found in
the ovary, and the
nourishment to the female
gamete is provided by the
yolk present around the
ovum.

17. Basis for
comparison
Spermatogenesis Oogenesis
Growth phase
The growth phase during
spermatogenesis is shorter than
in oogenesis.
The growth phase during
oogenesis is longer than in
spermatogenesis.
Resting phase
There is no resting phase during
the spermatogenesis process.
The resting phase occurs
during oogenesis from the
embryonic stage till puberty.
Size of the gametes
The male gametes formed after
spermatogenesis are smaller in
size than the female gametes.
The female gametes formed
after oogenesis are larger in
size than the male gametes.

18. Basis for
comparison
Spermatogenesis Oogenesis
Motility of the
gamete
The male gamete formed is
motile.
The female gamete formed is
non-motile.
Nuclear condensation
Nuclear condensation can be
seen in a male gamete.
Nuclear condensation
doesn’t take place in the
ovum.
Food preservation
The male gamete stores less
amount of food within itself.
The female gamete stores a
lot more food within itself.

21. https://youtu.be/6fBa8UqEano
https://youtu.be/63hFfJOJg9w

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