OOGENESIS, SPERMATOGENESIS,FERTILIZATION,IMPLANTATION,OVULATION,DENELOPMANT OF INNER CELL MASS, DECIDUA

1. EMBRYOLOGY & FETAL
DEVELOMENT
KHUSHBU PATEL
GCS NURSING
COLLEGE

2. GAMETOGENESIS
• The process involved in maturation of
spermatozoon in male and ovum in
female is called gametogenesis.
• Oogenesis:- the process involved in
development of mature ovum in ovary
is called oogenesis
• Spermatogenesis:- the process
involved in the development of
spermatozoa in testis is called
spermatogenesis.

3. OOGENESIS

4. OOGENESIS

6. • SPERMATOGENESIS

7. SPERMATOGENESIS

11. OVULATION
• It is the process of discharge of
secondary oocytes from the mature
graffian follicle in the ovary.
• -hormone responsible for ovulation LH
from anterior pituitary gland.
• -after ovulation,the follicle changes in to
corpus luteum.

14. Fertilization is the process of fusion of a
single spermatozoon with a single
mature ovum in the tubal ampulla to
from a zygote.

16. Fertilization
• Divided into 4 steps:
• 1. Contact and recognition
(“Casual Introductions”)
• Sperm undergo capacitation (further maturation)
within the female reproductive tract
• Recall that sperm were produced in the testes
and matured in the epididymus until ejaculation
• Sperm reach the egg in the oviduct where
fertilization will occur

17. • 2. Sperm Entry
• Only ONE sperm is allowed to enter
• Fast block - electrical charge in egg
plasma membrane prevents polyspermy
• Slow block - depolarization of egg
plasma membrane due to Ca++ release

18. • 3. Egg Activation
• The release of calcium ions in egg
plasma membrane also triggers protein
synthesis
• 4. Fusion
• The sperm nucleus is propelled to the
egg nucleus by microtubules

19. Week 1 post conception
• Zygote divides repeatedly moving
down tube toward uterus
(cleavage)
• The daughter cells are called
blastomeres
• Morula: the solid cluster of 12-16
blastomeres at about 72
hours(mulberry like ball of cell)
• Day 4: late 60 cell morula enters
uterus, taking up fluid becoming
blastocyst

21. DEVELPOMENT AFTER FERTILIZATION

22. DEVELPOMENT AFTER FERTILIZATION

23. Blastocyst stage
• Two distinct types of cells
– Inner cell mass: forms the embryo
– Trophoblast: layer of cells surrounding the cavity
which helps form the placenta
• Floats for about 3 days
• Implantation on about day 6 post conception
– Trophoblast erodes uterine wall
– Takes 1 week to complete
• If inner cell mass of a single blastocyst divides:
monozygotic (identical) twins
_____inner cell mass
______trophoblast

24. IMPLANTATION(NIDATION)
• On 6th day IMPLANTATION occurs in the endometrium of the anterior
or posterior wall of the body near the fundus

25. IMPLANTATION: 4 stages
1.Apposition
2.Adhesion
3.Penetration
4.Invasion

28. DEVELOPMENT
OF
INNER
CELL
MASS

29. • Ectoderm: central and peripheral nervous system, epidermis
of skin, pituitary glands, salivary glands, mucous lining of
nasal cavity, Para nasal sinuses, roof of mouth etc.
• Mesoderm: bones, cartilage, muscles, cardiovascular
systems, kidney, gonads, spleen, most of genital tract,
pleural and peritoneal cavity etc.
• Endoderm: epithelial lining of GI tract, liver, gall bladder,
pancreas, epithelial lining of respiratory tract and most of
mucous membrane of urinary bladder and urethra etc.

31. MAJOR DERIVATIVES OF THE EMBRYONIC GERM LAYERS

32. Extraembryonic Membranes
• These membranes develop from the germ
layers, but are NOT part of the embryo (they
are lost at birth)
• They lie outside of the embryo & provide
protection and nourishment
• Four exist in terrestrial vertebrates:
• Chorion, amnion, allantois (stores
nitrogenous waste in reptiles), & yolk sac
(not found in humans, but yolk aids in
formation of RBC

33. DECIDUA:IS THE ENDOMENTRIUM
OF THE PREGNANT UTERUS

34. FUNCTIONS OF DECIDUA
• Nourishment of early implanted ovum
• Formation of placenta by decidua
basalis
• To control deeper penetration of the
trophoblast
• Provide site for implantation of the
blastocyst

36. FETAL DEVELOPMENT