REVIEW OF FOETAL DEVELOPMENT in obstetrics.pptx

FETAL DEVELOPMENT
Prenatal or antenatal development is the process in
which embryo or fetus gestates during pregnancy from
fertilization until birth.
It is also known as fetal development or embryology.

GAMATOGENESIS
 The process of formation and maturation of male and
female gamete is known as gametogenesis.
spermatogenesis oogenesis

SPERMATOGENESIS
It consist of 2 process.
1. Spermatocytosis:
It is the process of development of spermatid from
spermatocyte.
2.Spermiogenesis:
It is the process of conversion of spermatid into spermatozoa.

OOGENESIS
 The process of development and maturation of ovum is
known as oogenesis.
 Egg formation takes place in the ovaries.

FERTILIZATION
 The process by which two gametes fuse to become a
zygote ,which develops into a new organism.
Union of single spermatozoon with ovum at tubule ampulla
occurring 24-48hours after ejaculation in the vagina by sexual
act is called conception.

PROCESS
1.TRANSPORTATION OF GAMATES
-After the ovulation fimbriated end of fallopian tube
sweeps over the ovary, the movement produce in to cilia,
the ovum is sucked in to the fallopian tube with ciliary
movement and reaches the ampulla of the fallopian tube.
-At single ejaculation 200 million sperm deposited only
400-500 reaches the uterine tube.

PROCESS-CTD.
2.APPROXIMATION OF GAMATES.
 CAPACITATION-functional maturation of the
spermatozoa.
 Spermcell membrane changes.
 Hyperactivity of sperm

PROCESS-CTD
ACROSOMAL REACTION
Activation of the acrosomal membrane cause release of
hyaluronidase, hydrolytic enzymes ,helps in removing the corona
radiate ,then zona pellucida of ovum.
PENETRATION OF THE ZONA PELLUCIDA
During Acrosomal reaction the sperm plasma membrane fuses
with outer acrosomal membrane and it binds the zona protein there
is zona reaction.

PROCESS-CTD
3.FUSION OF GAMATES
Once a sperm penetrates the zona pellucida,it
binds to and fuses with the plasma membrane of the
oocyte. Binding occurs at the posterior region of the
sperm head.

DEVELOPMENT OF THE ZYGOTE
 Pre embryonic period : (first 2 weeks after fertilization).
 Embryonic period :(2 weeks to 8 weeks)- It is called as
embryogenesis. Embryogenesis is the process by which an
embryo develops into a foetus
 Foetal period is 8 weeks to birth.-It is called as
organogenesis

PREEMBRYONIC PERIOD
Also known as ovular period or germinal period.
 Embryogenesis start with the fertilization of the egg cell
(ovum) by a sperm cell (spermatozoon). Once fertilized, the
ovum is referred to as zygote, a single diploid cell.

ZYGOTE
 Zygote is a fertilized egg cell that results from the union of
a female gamete (egg or ovum) with a male gamete (sperm).
 During the first week the zygote travels along the uterine
tube towards the uterus, the zona pellucida surrounds the
zygote. It nourished by glycogen secreted by goblet cell of
uterine tube and later the secretory cells of uterus.

MORULA
The two-cell stage is reached approximately 30 hours after
fertilization.
Contains equal cytoplasmic volume and chromosome numbers.
Blastomere continue to divide by binary division.(4,8,16 cell
stage) after that cluster of formed is called morula resembling a
mulberry.
Zona pellucida intact ,morula enters uterine cavity on 4 th day
in the 16-64cell stage.

BLASTOCYST
While the morula remains free in the uterine cavity on
the 4th and 5th day ,it is covered by a film of mucus.
Fluid passes through the canaliculi of the zona
pellucida which separates the cells of the morula called
blastocyst.

IMPLANTATION(NIDATION)
1. APPOSITION-As the zona pellucida surrounding the blastocyst
disappear,Loose connection between blastocyst and endometrium.
2. ADHESION-Blastocyst interacts with the endometrium.
(immunecell,cytokines etc).
3. PENETRATION AND INVASION.(Blastocyst is burrowed more and more
inside the decidua.
4. The process is completed by 10 th or 11th
day.

DEVELOPMENT OF BLASTOCYST
Blastocyst
Outer trophoblast(placenta ,fetal membrane) Inner cell mass
Synctiotrophoblast-outer Cytotrophoblast-inner
◦ Fetus Amnion Umbilical cord

DECIDUA
 The decidua is the endometrium of the pregnant uterus.
 3 layers-
 Decidua basalis-portion contact with the base of blastocyst.
 Decidua capsularis-Thin superficial layer covering blastocyst.
 Decidua vera or parietalis-rest lining uterine cavity outside
implantation.

FUNCTION OF DECIDUA
-Provide place for implantation.
- Supply nutrition-glycogen ,fat
-Deeper penetration(peptides,cytokines,integrins)
-formation of basal plate of the placenta.

CHORION,CHORIONIC VILLI.
CHORION-Trophoblastic cells lined internally -9th
day.
CHORIONIC VILLI- Finger like projection outside of blastocyst.
 Primary villi-12th
day
 Secondary villi-16th
day.
 Tertiary villi-vascularized -21st
day.Villi lying on the side of
uterine cavity degenerate called chorion leave,but those on the
side of uterine wall called chorion frondosum form placenta.

DEVELOPMENT OF INNER CELL MASS-2
WEEK
-Bilaminar germ disc(endoderm,ectododerm)-8th
day
-formation of two cavity(amniotic cavity,yolk salk)
-Formation of Extra Embryonic mesoderm.
-Formation of extra embryonic coelum
-Formation of connecting stalk
- Formation of chorion and amnion

WEEKS 2 to 3
• Embryo is 1.5 to 2 mm in length.
• Lung buds appear
• Blood circulation begins.
• Heart is tubular and begins to beat.
• Neural plate becomes brain and spinal cord

WEEK 5
 Embryo is 4-6mm in length.
 Embryo is 0.4 g weight
 Double heart chambers are visible.
 Heart is beating.
 Limb buds form

WEEK 8
• Embryo is 3 cm in length.
• Embryo is 2 g.
• Eyelids begin to fuse.
• Circulatory system through umbilical
cord is well established.
• Every organ system is present.

WEEK 12
• Fetus is 8 cm in length.
• Fetus is 45gm.
• Face is well formed
• Limbs are long and slender.
• Kidneys begin to form urine.
• Spontaneous movements occur.
• Heartbeat is detected by Doppler transducer
between 10 and 12 weeks.
• Sex is visually recognizable.

WEEK 16
• Fetus is 11.5 to 13.5 cm in length.
• Fetus is 100 g.
• Active movements are present.
• Fetal skin is transparent.
• Lanugo hair begins to develop.
• Skeletal ossification occurs.

WEEK 20
• Fetus is 19cm in length.
• Fetus is 465g.
• Lanugo covers the entire body.
• Fetus has nails.
• Muscles are developed.
• Enamel and dentin are depositing.
• Heartbeat is detected by regular (nonelectronic) fetoscope.

WEEK 24
• Fetus is 780 g.
• Hair on head is well formed.
• Skin is reddish and wrinkled.
• Reflex hand grasp functions.
• Vernix caseosa covers entire body.
• Fetus has ability to hear

WEEK 28
• Fetus is 1200 g.
• Limbs are well flexed.
• Brain is developing rapidly.
• Eyelids open and close.
• Lungs are developed sufficiently to provide gas exchange(lecithin
forming).
• If born, neonate can breathe at this time.

WEEK 32
• Bones are fully developed.
• Subcutaneous fat has collected.

WEEK 36
• Fetus is 42-48 cm in length.
• Skin is pink and body is rounded.
• Skin is less wrinkled.
• Lanugo is disappearing.

WEEK 40
• Fetus is 48-52 cm in length.
• Fetus is more than 3000-3600gm.
• Skin is pinkish and smooth.
• Lanugo is present on upper arms and shoulders.
• Vernix caseosa decreases.
• Fingernails extend beyond fingertips.
• Sole (plantar) creases run down to the heel.
• Testes are in the scrotum.
• Labia majora are well developed.

CTD-
NORMAL SITE FOR CONCEPTION
It is the ampullary part (ampulla) of the fallopian tube which is widest part of
located closed to the ovary.
USUAL TIME FOR CONCEPTION
Conception will takes place about 14 days before the next menstrual cycle.
SEX DETERMINATION
MALE(44+X+Y),FEMALE (44+X+X),The sperm of the father always determines
the child’s sex.

PLACENTA
 Forms from Trophoblast,
 10 weeks after fertilization.
 Round flat mass 20cm in diameter and 2.5cm thik in centre.
 Weighs 1/6 th of the baby’s weight.
 Maternal surface-dark red in colour dure to maternal blood-
20cotlydonsseparated by sulci, decidua dips down to form septa.
 Fetal surface-shiny appearance due to amnion.umbilical vein and
arteries are visible,umbilical cord insertion at centre.

FUNCTIONS
Respiration
Nutrition
Storage
Excretion
Protection
Endocrine

THE MEMBRANES
CHORION-Thick opaque friable membrane from
Trophoblast, continuous with the chorionic plate forms the
base of the placenta.
AMNION- Smooth tough translucent membrane from
inner cell mass, lines the chorion and surface of the
placenta continue over the outer surface of the umbilical
cord.

AMNIOTIC FLUID
Clear alkaline and slightly yellowish liquid contained
within the amniotic sac.
Secreted by the amnion, especially the part covering
placenta and umbilical cord.
Fetal urine, exudate from maternal (decidua)vessels,fetal
(placenta)vessels.
99%water and 1%solid matter.(skin
cell,vernixcaeseosa,lanugo

FUNCTION
 Growth and free movement.

Equalizes pressure and protects from injury.

Maintain intrauterine temperature, protect heat loss, provide small quantities
of nutrients to fetus.

labour-protect placenta and umbilical cord from contractions.

Effacement and dilation of cevix.

UMBILICAL CORD
Formed 5th
week.
Extend from the fetal surface of the placenta to the umbilical cord.
FUNCTION
- Transports oxygen and nutrients and removes waste products.
CORD
- 2 Arteries and 1 vein.
- Blood vessels enclosed and protected by Wharton’s jelly formed from
mesoderm.
MEASUREMENTS
-Diameter 1-2 cm and 40-50cm in length.

TEMPORARY STRUCTURES
1. DUCTUS VENOSUS - Umbilical vein to inferior venacava.
2. FORAMEN OVALE - Opening between the right and left
atria.
3. DUCTUS ARTERIOSUS - Bifurcation of the pulmonary
artery to the descending aorta.
4. HYPOGASTRIC ARTERIES - Branchoff from the internal iliac
arteries and become the umbilical arteries when they enter
the umbilical cord.

ADAPTATION TO EXTRA UTERINE LIFE
UMBILICAL VEIN-ligamentum teres.
DUCTUS VENOSUS-Ligamentum venosum.
DUCTUS ARTERIOSUS-Ligamentum arteriosum
FORAMEN OVALE –Fossa ovalis.
HYPOGASTRIC ARTERIES-Obliterated Hypogastric Arteries

REVIEW OF FOETAL DEVELOPMENT in obstetrics.pptx

REVIEW OF FOETAL DEVELOPMENT in obstetrics.pptx

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REVIEW OF FOETAL DEVELOPMENT in obstetrics.pptx