its a presentation of introduction of embryology, gametogenesis, fertilization, implantation and 1st wk of development.

1. Embryology;
gametogenesis, fertilization and
implantation
By
Dr Janardan Chaudhary
Asstt. Professor
Department of Anatomy
UCMS

2. Objectives
• Introduction
• Gametogenesis
– Oogenesis
– Spermatogenesis
• Fertilization
• Germinal period
• Implantation

3. Basic Process in Development
• Growth
– Cell division
– By increase in cell size
– By accumulation of intracellular substance

4. Multiplicative growth
• Category 1: nerve cell or neuron
• Category 2: epidermis, intestinal epithelium
• Category 3: liver, kidney
Auxentic growth- oocyte, neurons
Accesory growth- bone and catolage

5. Differentiation
• Histogenesis
• Totipotent – identical twins or uniovular twins
• Plastic phase
• Primitive streak
• Primiary organiser
• Secodary organiser
• Tertiary organiser
• Fixed potentially– specific tissue
• Action of organiser
– Evocator
– Individuation
• Chemo differentiation
• Functional differentiation

6. Female Reproductive system
• Female gonads- a
pair of ovary
• Fallopian tube
• Uterus
• Vagina

7. Female germ cell
Primitive sex cell
– Primordial female
germ cell
– 3rd week of IUL,
endodermal
proliferation
– 5th wk of IUL,
appears in gonads
– 3rd month of IUL,
primary occyte
– 7th month of IUL,

8. Further development

10. Primary oocyte
• Follicular cells
• Primary
ovarian follicle
• At birth, ovary
contains-
2,000,000
• At puberty-
40,000

11. Oogenesis 44
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22
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PRIMITIVE FEMALE SEX CELL
MITOSIS
OOGONIA
PRIMARY OOCYTE
1ST MEIOSIS
SECONDARY OOCYTE
(ovulation)
2nd MEIOSIS
Mature ovum
(maturation only at fertilization)
1st POLAR BODY
2nd POLAR BODY

12. Processes of Maturation
Changes during maturation
• Follicular cell-
proliferation
• Formation of zona
pellucida
• Thecal layer(TL)
– External T L
– Internal TL
• Antrum folliculi

13. Structure of Grafian follicle
• Haploid-22XX
• Polar body

14. Ovulation

15. Structure of secondary oocyte
• Corona radiata
• Zona pellucida
• Perivatelline
membrane
• Occyte- germinal
vesicle
• Cytoplasm-yolk

16. Male Germ Cell
Male reproductive
organs
– two gonads:
testis
– Vas deferens
– Ejaculatory duct-
penis
– Accessory sex
glands: seminal
vesicle, prostate,
bulbo-uthrethral
gland

17. Testis and seminiferous tubules

18. 44
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PRIMITIVE MALE SEX CELL
MITOSISDark type A spermatogonia
2nd MEIOSIS
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XXMITOSISLight type A spermatogonia
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2nd MEIOSIS
Spermatid Spermatid Spermatid Spermatid
MITOSIS
1st MEIOSIS

19. Spermatid
Oval shaped
– Two centriols
– Golgi apparatus
– Mitocondria

20. Spermiogenesis

21. Spermatozoa
• 64 days life days life in man
– 16 days – 1st meosis
– 16 days – 2nd meosis
– 24 days- spermiogenesis
• 24-48 hrs lifespan after
ejaculation
• Normal Count: 200-300
million
• Normal amount: 2-5 ml
Oligospermia- low sperm count
>20 million/ml
Azzoospermia- no sperm count

22. Structure of spermatozoa
• Head
• Neck
• Body
• Tail

23. Sterile /infertility
• infection
• hormonal imbalance
• disease, such as
diabetes
• gene defects
• exposure to radiation

24. Thank you

25. Fertilization
• Fusion of two
mature germ cells in
ampulla.
• Mechanism of
fertilization into the
stages
1. Approximation of
gametes
2. Contact and fusion
of the gametes
3. Effects of
fertilazation

26. 1. Approximation of the gametes
• Involves the transport of
sperm and ova in female
genital tracts to reach the
uterine tube.
• Factors:
A. Male gametes
– Prostaglandins
– Oxytoxin
– Succun effects
B. Female gamets
– Ciliary beats and rhythm
contraction
Anti prostaglandin – regular intake of aspirin by female

27. 2. Contacts and fusion of the gametes
• 200-300 sperm contacts
and disnintegrates the
corona radiata by
hyaluronidase .
• Three barriers
1) Capacitance: final
maturation of sperm
requires 7 hrs
2) Acrosomal reaction:
multiple reaction
involved during
penetration of sperm into
ovum

28. 3) Zona pellucida:
– glycoprotein ZP1
and ZP3
– Induces acrosin
4) Head covered by CM,
later integrated by
peptide integrin
5) Completion of
Meiosis II
6) ZP3 hydrolyses the ZP
plug – to prevent
polygamy

29. • Ooplasm of occyte
contains two
pronuclei- ootids
• DNA undergoes
replication

30. Effects of fertilization
• Complication of meiosis II- extrusion of
secondary polar body
• Restoration of Diploid No of cromosome.
• Determination of chromosomal sex
• Initiation of cleavage division
• Determination of polarity
Parthenogenesis- partial or incomplete development of an embryo

31. Stages of embryology
• Germinal period- 1st – 3rd wks
• Embyonic period – 4th -8th wks
• Foetal period – 3 month to termination of
pregnancy

32. Germinal period
• Changes in the 1st week
After fertilization, zygote undergoes cleavage,
morula and blastula, then subsequently
implantation

33. Cleavage of zygote
(series of mitotic divisions of the zygote)
• Two celled stage: 30
hrs after fertilization
• Four celled stage: 40-
45 hrs
• Twelve celled stage:
about 72 hrs
• Sixteen celled stage-
96 hrs

34. Morula
• Inner cell mass-
gives rise to
embryonic
proper.
• Outer cell mas
– protective
and nutritive
covering

35. Formation of blastocyst
5th day after fertilization
• Blastocoel
• Trophoblast
• Embryonic blast
• embryonic pole
• Abembryonic pole –
mural blast

36. Implantation of blastocyst
• ZP disappears-
proteolyic
enzyme(trypsin)
• Implantation of SC,
SS after 6/7th day.
• Pentasaccharides
lacto-N-
fucopentose-1 on
epithelium and
blasocyst

37. Site of implantation
• On posterior wall
of Junction
between fundus
and body

38. Abnormal implantation
• Extra-uterine
pregnancy
– Ovary, abdominal cavity
or fallopian tube
• Intra uterine abnormal
implantion
– Apart from normal
position

39. In vitro fertilzation of human gamete
• Test tubes
• Embryonic
transfer

40. Thank you