The document discusses fertilization, detailing the processes of sperm capacitation and the steps involved from sperm penetration to the formation of the zygote. It also covers implantation, the formation and functions of the placenta, and abnormalities that may arise. Additionally, it explains the role of amniotic fluid in pregnancy, including its sources, composition, and importance for fetal well-being.

1. Fertilization, placenta, cord& AF
BY
Dr. Ahmed Nasef
Assistant lecturer of obstetrics&
gynecology – Benha university

3. Fertilization

4. Participants

5. What is fertilization
It is the act of fusion of male and
female gametes (sperm& ovum) to
form zygote

7. Where does fertilization
happen?
In the ampullary part of the fallopian tube

8. What happens before fertilization

10. Ovulation

11. What happens to sperm to be able for
fertilizing the egg
After insemination sperms pass from vagina into uterus to uterine tubes
Aided by contractions of muscles of uterus& uterine tubes
Only 300-500 sperms reach fertilization site from about 200-300 million sperms
deposited in vagina
These sperms undergo 2 processes to be capable of fertilizing the egg:
1- Capacitation: occur within female genital tract, removal of glycoprotein coat&
seminal plasma proteins
2- Acrosome reaction: secretion of certain substances from acrosomal cap close to 2ry
oocyte which include:
 Hyaluronidase enzyme--- assist in penetration of corona radiata
 Trypsin like substances& acrosin ------- help to penetrate zona pellucida

14. Phases of fertilization
1- penetration of corona radiata:
Only one sperm is required to fertilize the ovum. Others help the fertilizing sperm in penetration
of corona radiata by hyaluronidase enzyme
2- penetration of zona pellucida:
By trypsin like substances& acrosin
3- zona reaction:
Oocyte secrete lysosomal enzymes which make zona impermeable for other sperms
4- fusion of sperm with ovum to form zygote:
After entry of sperm the 2ry oocyte finishes its 2nd meiotic division
The chromosomes of both sperm and ovum become arranged and called male and female
pronuclei which lose their nuclear membranes and fuse forming the zygote

16. Results of fertilization
Formation of the zygote
Determination of sex of the embryo
Initiation of cleavage and differentiation

17. Differentiation
 Z y g o t e rapidly divides by mitosis ------ B l a s t o m e r e (8 cells)
 Then M o r u l a (16 cells)----- reaching uterine cavity after 3 days of
fertilization
 Fluid then accumulate forming B l a s t o c y s t ------ remains free for 3
days in uterine cavity
Then divide into 2 masses of cells:
Inner cell mass---- will form embryo
Outer cell mass (trophoblast)

21. Implantation
Process of embedding of the fertilized ovum into
the endometrium of uterus
Normal site of implantation:
Upper part of posterior or anterior wall of the
uterus
When: it occurs on 6th to 7th day of fertilization
How: apposition --- adhesion then invasion of
trophoblast (chorion) into Decidua

22. Implantation

23. Decidua
Modified secretory endometrium under effect of both
progesterone& estrogen
Functions:
 Site of implantation& nutrition of blastocyst
 Site of formation of placenta
 Protection against invasive power of trophoblast as
invasion stops at a fibrinoid layer called Nitabuch

24. Parts of
Decidua
Decidua basalis
Between chorionic
sac& muscle wall of
uterus
Decidua capsularis
Between chorionic
sac& cavity of uterus
Decidua parietalis
Remaining part of the
decidua

25. Chorionic villi
The chorionic villus is formed of 2 layers of
trophoblast: cytotrophoblast (inner layer)
syncitiotrophoblast (outer layer)
Chorionic villi are 2 types:
Anchoring --- for fixation& attachment
Free --- for food& nutrition
secretion of HCG which maintain CL

27. Chorion parts
Chorion frondosum part of chorion facing
decidua basalis. It will form the fetal part of
placenta
Chorion leave remaining part of chorion facing
decidua capsularis. It will atrophy

29. In vitro fertilization

30. What is IVF
Process in which fertilization is performed
outside the body then transfer of the
developed embryo in the uterus

33. placenta

34. Formation of the placenta
Its formed from 2 parts:
Fetal part Chorion frondosum
Maternal part Decidua basalis
It has 2 surfaces:
Fetal smooth and covered by amnion
Maternal divided into 15-20 cotyledons

35. Normal structure
Shape discoid
Weight 500 gm
Site implantation site (upper uterine segment)
Size 18-20 cm in diameter
Thickness 2.5 cm in center gradually thins
towards periphery
Cord insertion eccentric

37. Functions of placenta
Mechanical attachment
Respiration gas exchange
Nutrition& excretion
Placental barrier making placenta impermeable
to many drugs& organisms
Enzyme production as oxytocinase
Protein production as PAPP
Hormone production sex steroids (E&P)

38. Abnormalities of placenta
Shape
Bipartite placenta 2 equal lobes connected by membrane
Bilobate placenta 2 equal lobes connected by placental tissue
Placenta fenestrata part of placenta is missed
Placenta succenturiata presence of small accessory cotyledons attached to
placenta by membranes
Placenta circumvallate chorionic plate is < basal plate so fetal margin of
placenta shows white ring of decidua
Placenta membranacea chorion leave doesn’t atrophy --- large thin placenta

41. Abnormalities of site
In LUS ---- placenta previa
On uterine septum

42. Abnormalities of size
Small leading to placental insufficiency--- IUGR
Large in cases of syphilis, DM, twins, Rh
incompatibility& placenta membranacea

43. Abnormal adherence
Due to absent Nitabuch layer, may be:
P. Accreta placenta reaches basal layer of
decidua
P. Increta placenta penetrates muscle but
doesn’t reach serosal surface
P. Percreta placenta perforates uterus

44. Umbilical cord

45. Normal structure
Length about 50 cm
Diameter about 2 cm
Contents 2 arteries, 1 vein in a myxomatous
tissue (Wharton's jelly)

46. Abnormalities of the cord
Length
very long lead to coiling around fetus, true knots,
cord presentation& prolapse
Very short lead to failure of engagement& fetal
descent, malpresentation& fetal distress
Knots
True lead to fetal distress
False focal varicosity in collection of Wharton's
jelly

47. Abnormal attachment
Central
Marginal (Battledore)
Velamentous insertion vessels are inserted into
membranes not in placenta

49. Amniotic fluid

50. What is amniotic fluid?
It is the fluid surrounding the fetus
Source
 Maternal transudation through placenta& cord esp. in 1st
trim.
 Fetal urine esp. in 2nd half of pregnancy
 Transudation from fetal skin& umbilical cord
 Amniotic epithelium
 Lungs (bronchial& buccal secretions)

51. Composition of AF
About 99% clear watery
About 1-2% crystalloids& colloids (CHO,
proteins, lipids, hormones& electrolytes)

52. Measurement of AF
Amniotic fluid index (AFI) is a quantitative estimate of
amniotic fluid and an indicator of fetal well-being. It is a
part of the biophysical profile. AFI is the score
(expressed in cm) given to the amount of amniotic fluid
seen on ultrasonography of a pregnant uterus
Single deepest vertical pocket is the deepest longest
vertical pocket between the fetus and uterine wall

54. Functions of AF
During pregnancy
Protection against trauma
Prevents adhesions between fetal skin& amnion
Prevents infection
Thermoregulation
Allow free movement of the fetus so improve muscle
development
Development of alveoli
During labor
Help cervical dilatation
Prevent direct fetal& placental compression by uterine wall
Wash birth canal after ROM

55. Abnormalities of AF
Volume
Polyhydramnios
Oligohydramnios
Meconium staining
Inflammation Chorioamnionitis