Explains about Fertilization

1. FERTILISATION

2. Learning objectives:
Upon completion of the chapter, the
Students will be able to:
Define fertilization
Describe the process of fertilization and
implantation
Explain the functions of the placenta,
umbilical cord, and amniotic fluid.

3. What is fertilization?
Fertilization is the union of
an ovum and a spermatozoon.
This usually occurs in the outer
third of a fallopian tube, the
ampulla.

4. Fertilization

5. Process of fertilization
 Following ovulation the ovum which is about
0.15 mm in diameter, passes into the uterine
tube and move towards the uterus.
 Ovum having no power of locomotion, it move
by the muscular contraction of the fallopian
tube.
 At intercourse about 300 million sperms are
deposited in the posterior part of the vagina.

6.  These are travels towards the fallopian tube & more
will die on the journey. Only thousands of sperms
reached the “Ampulla” of fallopian tube, where the
fertilization takes place.
 During journey the sperm becomes mature and
release the enzyme Hyaluranidase. Which helps for
the penetration of cell membrane & enter into the
ovum.
 Many sperms are needed for this but only one will
enter into the ovum.

7. ZYGOTE

8.  After this the membrane is sealed to prevent
entry of further sperms.
 The sperm & ovum both contributes 23
chromosomes to make a total of 46
chromosomes.
 The fertilized ovum is called as zygote.

9. Development of fertilized ovum
 When the ovum has been fertilized it
continues its passage & reaches the
uterus 3 or 4 days later.
 During this travel segmentation or cell
division takes place & the fertilized ovum
divides into 2 cells then into 4 then 8,16
and so on, until a cluster of cells formed
known as Morula

11. Morula Blastocele

12.  12 hours later a fluid filled cavity blastocele
appears from the Morula.
 It changes into blastocyst. Around the
outside a layer of cells formed called
Trophoblast. The remaining cells clumped
together and forms Inner cell mass

13.  The blastocyst moves into the uterus for
2 or 3 days, then the innercell mass
forms a finger like projection & it
becomes sticky to adhere into the
endometrium (inner layer of uterus)
 Finally it attached with the endometrium
of uterus, known as implantation.

14. Implantation

15. Decidua
 This is the name given to the endometrium
during pregnancy.
 The increased secretion of estrogen during
pregnancy causes the endometrium to grow
four times than non pregnant time.
 Due to more vascular supply the
endometrium becomes spongy bed in which
the fertilized ovum implants.

16. Layers of decidua
Three layers in
decidua
1. Basal layer
2. Functional layer
3. Compact layer

17. 1. Basal layer
It lies immediately above the
myometrium. It remains unchanged during
pregnancy. But it helps to regenerate after
the delivery
2. Functional layer
This layer consist of rich in nutrients, it
acts like a storage of nutrients for the
development of placenta & fetus.

18. 3. Compact layer:
 This layer contains more blood
supply and also called as spongy
layer.
 In which the placenta attached &
gives nutrients to the developing
fetus.

19. Blastocyst
Trophoblast Innercellmass
Placenta Chorion
Amnion
Fetus Umbilical
cord

20. Trophoblast
It helps for eroding the blood vessels to get
nutrition for the growing fertilized ovum.
It produces a Hormone hCG (Human
Chorionic Gonadotrophin)it is responsible
for informing corpus luteum, that
pregnancy begins. It produces
progesteron to maintain the endometrium
& it suppresses the menstruation.

21. Inner cell mass
It has three different layers:
1. Ectoderm : this layer mainly forms the
skin
2. Mesoderm: this layer forms the bones,
muscles, heart, blood vessels & other
internal organs
3. Endoderm: this layer forms mucous
membrane, & glands

22. Amniotic Fluid

23. Definition
It is a fluid which
is surrounding the
fetus during
intrauterine life.

24. Functions of amniotic fluid
 Allows for the growth & free
movement of fetus
 Equalizes pressure & protect the
fetus from injury
 Maintains temperature for the
fetus
 It gives nutrients
 Protects placenta & membranes
from pressure during labour

25. Origin of Amniotic Fluid
 The source of amniotic fluid is from
both fetal & maternal.
 It is secreted mainly from amnion
(inner covering layer of fetus) & a
part from placenta.
 Fetal urine also contribute some
amount from the 10th week of
gestation.
 The water in the amniotic fluid
exchanges as often as every 3 hours.

26. Volume of amniotic fluid
 The amount of amniotic
fluid increases through out
the pregnancy until 38
weeks of gestation. It is
about 800- 1200 ml.
 After 38 weeks it
diminishes and about
800ml.

27. Abnormal volume of amniotic
fluid
1. Polyhydramnios:
When the total amount
of amniotic fluid exceed
more than 1500 ml is
called as Polyhydramnios.

28. 2.Oligohydramnios:
When the total amount of amniotic fluid
exceed less than 300 ml is called as
Oligohydramnios.

29. Constituents of amniotic fluid
It is a clear pale colour, fluid consist of
99% water and 1% includes nutrients,
vernix caseosa, lanugo like solid
substances

30. Umbilical cord
 It is also called as funis. It extends from
the fetus to the placenta. It transmits the
umbilical blood vessels.
 It is enclosed and protected by wharton’s
jelly a gelatinous substance formed from
mesoderm.

31. Cross section of umbilical cord
 It consist of 2 arteries and one vein.
 Covered by amnion.

32. Length of umbilical cord
 Normal length is about 50 cm
 Long cord : >55 cm, may wrap around the neck
during labour
 Short cord: <40 cm, may cause premature
separation of placenta.

33. The Placenta
What is placenta?
The placenta (also known as
afterbirth) is an organ that connects the
developing fetus to the uterine wall to
allow nutrient uptake, thermo-
regulation, waste elimination, and gas
exchange via the mother's blood supply

34.  The placenta
provides oxygen
and nutrients to
growing fetuses
and removes waste
products from the
fetus's blood.

35. Structure
 The placenta averages 22 cm (9 inch) in length and
2–2.5 cm (0.8–1 inch) in thickness, with the center
being the thickest, and the edges being the
thinnest. It typically weighs approximately 500
grams. It has a dark reddish-blue or crimson color.
 It connects to the fetus by an umbilical cord of
approximately 55–60 cm (22–24 inch) in length,
which contains two umbilical arteries and one
umbilical vein.

36. Development
 The placenta begins to develop upon
implantation of the blastocyst into the
maternal endometrium.
 The placenta grows throughout
pregnancy.
 Development of placenta is complete by
the end of the first trimester of pregnancy
(approximately 12–13 weeks).

37. Functions
Nutrition- The placenta intermediates the
transfer of nutrients between mother and
fetus.
Excretion -Waste products excreted from
the fetus such as urea, uric acid, and
creatinine are transferred to the maternal
blood by diffusion across the placenta.

38.  Storage: Placenta stores some fats,
glycogen and iron.
 Immunity : IgG antibodies can pass
through the human placenta, thereby
providing protection to the fetus in
utero.

39. Endocrine function
 1. HCG:The first hormone released by the placenta is
called the human chorionic gonadotropin hormone. This is
responsible for stopping the process at the end of menses
 2. Progesterone helps the embryo implant by assisting
passage through the fallopian tubes.
 3. Estrogen involves the enlargement of the breasts and
uterus, allowing for growth of the fetus and production of
milk.
 4. Human placental lactogen is a hormone for growth and
development

40. Factors affecting fetal
development

41. Genetic Factors
 Many genes contribute to fetal growth
and birthweight.
 Such studies have shown that both
maternal and paternal influences are
present during fetal development.

42. Maternal Nutrition
 A baby derives the nourishment for its
growth from the mother’s blood.
 Folic acid is needed for the
development of neural tube, calcium
for bones, proteins for muscle growth
and repair etc.

43. Smoking
 Smoking definitely affects the fetal
development.
 Smoking increase the risk of having a low
birth weight baby.
 It also increases the risk for prematurity.
 Smoking reduces the supply of oxygen
received by the baby and increases the risk
of miscarriage

44. Diseases
 Certain diseases cause deformities in
the baby.
 Chicken pox usually causes malformed
limb or sudden labour.
 Viral infections causes developmental
abnormalities in the baby like mental
retardation, blindness etc.

45. Drugs
 Drugs and chemicals can cross into
the fetal blood, affecting its
development.
 Stay clear of addictive drugs like
cocaine, heroine etc.
 This can also lead to addictions in the
baby

46. Maternal Age
 Maternal age does influence the fetal
development.
 There are chances for miscarriages and
still births in mothers below 20 years old.
 There are chances for birth defects, still
births, bleeding etc. in mothers over 35
years

47. Prenatal care
 Prenatal visits to the doctor are
extremely important.
 The doctor monitors the growth of the
baby.
 The doctor recommends supplements or
other vitamins as and when necessary.

48. Videos
 Fertilization
 Fetal Development:
https://www.youtube.com/watch?v=Wt
Dknjng8TA
 Human life in uterus