Embryogenesis is the process by which the embryo forms and develops. In mammals, the term refers chiefly to early stages of prenatal development from conception to 8 weeks of pregnancy .Later it is referred to as fetogenesis

1. FROM
CONCEPTION TO
CHILDBIRTH
UTSHA CHAKRABORTHY
EMBRYOLOGIST
FEMELIFE FERTILITY FOUNDATION
www.femelife.com
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2. PROCESSES INCLUDED IN CHILD
BIRTH
• OOGENESIS
• SPERMATOGENESIS
• FERTILIZATION
• CLEVAGE
• CELL DIVISION
• CELLULAR DIFFERENTIATION:
*GASTRULATION
*NEURULATION
*ORGANOGENESIS

3. EMBRYO :

4. FIRST STEP IS OOGENESIS
Process: Formation of ova from the
Primary oocyte is oogenesis.
*oocytogenesis is formation of primary
Oocyte, which is completed in 20
Weeks of foetal age.
*400,000 primary ova are present
At the time of birth, which
Remain dormant till ovulation.
*CELL DIVISION gives rise to
Secondary oocyte capable of
fertilization on maturation.

5. DETAILS OF OOGENESIS
• FEMALE GAMETOGENESIS:
• Development of female germ cells into a
new INDIVIDUAL.
• DIPLOID precursor cells undergo cell
division and differentiation to form
mature HAPLOID gamete.
• Female gametes are ova produced in
the ovaries.
• ONLY 1 diploid OVUM and 3 haploid
polar bodies are formed in this process(
which may degenerate later).

6. CHROMOSOMAL DIVISION
• OOGONIA:DIPLOID(2N) WITH 46
CHROMOSOMES
• PRIMARY OOCYTE:DIPLOID(2N)
WITH 46 CHROMOSOMES
COMPLETE FIRST MEIOTIC
DIVISION TO FORM
HAPLOID(N)SECONDARY
OOCYTE WITH 23
CHROMOSOMES
• HAPLOID(N) MATURE OVUM
WITH 23 CHROMOSOMES
FORMED AFTER SECOND
MEIOTIC DIVISION

7. CELL DIVISION • MITOSIS is equal division in which
daughter cells are genetically
identical to the parent cell.
• MEIOSIS is reduction division in
which daughter nuclei are
genetically non-identical to the
parent cell.
• MEIOSIS is the central feature of
gametogenesis
• Its responsible for genetic
diversity and repair of damage in
DNA TO BE PASSED to progeny.

8. SPERMATOGENESIS
• SPERMS OR SPERMATOZOA are the
male gametes which fertilize an
egg.
• SPERMATOGONIUM:DIPLOID(2N)/4
6 chromosomes*1
• PRIMARY
SPERMATOCYTE:DIPLOID(2N)/46
chromosomes*2
• SECONDARY
SPERMATOCYTE:HAPLOID(N)/23chr
omosomes*2
• SPERMATIDS:HAPLOID(N)/23chrom
osomes*4
• SPERMATOZOA:HAPLOID
(N)/23chromosomes*4
GENETICS RELATED TO SPERMATOGENESIS IN MAN

9. DETAILS OF SPERMATOGENESIS
*SPERMATOGENESIS is the process of
production of spermatozoa from
spermatogonial stem cells.
*SPERMATOGONIA yield PRIMARY
SPERMATOCYTES by mitotic division.
*EACH primary spermatocyte give rise to
2 SECONDARY SPERMATOCYTES BY
FIRST meiotic division.
*EACH secondary spermatocyte divides
into 2 SPERMATIDS BY MEIOSISǁ
*EACH spermatid differentiates into
SPERMATOZOA OR SPERMS.
*THE PROCESS TAKES 74 DAYS IN
HUMANS(minimum)
*TESTES produces 200-300million
sperms daily .

10. CHROMOSOMAL DISTRIBUTION
• C
• O
• M
• P
• A
• R
• I
• S
• I
• O
• N

11. FERTILIZATION IN HUMAN BEINGS
• FERTILIZATION is the process involving
FUSION of sperm nucleus with an egg to
form a DIPLOID cell, called ZYGOTE.
• SPERM binds through the CORONA
RADIATA.
• On encountering a SECONDARY OOCYTE,
the ACROSOME of the sperm bursts to
produce enzymes
which help it burrow through the ZONA
PELUCIDA.

12. POINTS ON FERTILIZATION
• THE SPERM PLASMA FUSES
WITH THE EGG PLASMA
MEMBRANE
• THE SPERM HEAD
DISCONNECTS WITH ITS
FLAGELLUM AND EGG
REACHES THE UTERUS DOWN
THE FALLOPIAN TUBE.
• THE GENETIC MATERIALOF
SPERM AND EGG COMBINES.

13. GROWTH AND IMPLANTATION
• THE DEVELOPMENT OF THE EARLY
EMBRYO UNTIL IMPLANTATION IS
COMPLETED IN THE UTERUS.
• CELL DIVISION AND CELLULAR
DIFFERENTIATION TAKES PLACE.
• EMBRYOGENESIS COVERS FIRST 8
WEEKS OF DEVELOPMENT.
• THE BLASTOCYST GETS IMPLANTED.
• THIS STUDY IS CALLED EMBRYOLOGY.

15. FOETAL DEVELOPMENT • THE GESTATION PERIOD IS 38 WEEKS
OR 9 MONTHS(mo)
• AT THE BEGINNING OF 9th WEEK ,THE
EMBRYO IS CALLED FOETUS.
• THE GERMINAL STSGE TAKES AROUD
10 DAYS DURING WHICH ZYGOTE
BEGINS TO DIVIDE BY CLEAVAGE.
• GASTRULATION DURING WHICH
3GERM LAYERS OF THEEMBRYO FORM
IN A PROCESS CALLED HISTOGENESIS.
• THEN COMES NEURULATION.
• THE PROCESS ENDS WITH
ORGANOGENESIS.
• HEART BEAT COMES AT AROUND
20WEEKS.