Lakhasly

Embryo Stage ?Vernix caseosa, fatty, cheese like secretion of the fetal sebaceous glands, covers the skin to protect it from constant exposure to amniotic fluid.The embryonic disk develops three layers (germ layers): *Ectoderm *Mesoderm *Endoderm 9.Three cell layers .1 Ectoderm= outer .2 Mesoderm= middle .3 Endoderm= inner Ecto= Skin & nervous Meso= Muscles Bones Endo= Digest.E m b r y o g e n e s i s Fertilization Cleavage Oocyte (n) Zygote (2n) 2-cell stage 4-cell stage Sperm cell (n) Morula Blastocyst G a m e t o g e n e s i s Ovary Testis Late week 3 Early week 3 Birth Week 4 Gastrulation Week 8 Week 5 Organogenesis ?S k i n -- Spinal cord Tail e n d A m n i o n - Chorionic villi A m n i o t i c Connecting fluid s t a l k Digestive t r a c t H e a r t C h o r i o n B r a i n Yolk s a c E n d o d e r m E c t o d e r m M e s o d e r m *Endoderm ?The outer cells of the morula secrete fluid, creating a sac of cell (the blastocyst) that has an inner cell mass placed off-center within the sac ?The outer layer of blastocyst cells develops into placenta and fetal membranes.The uterine lining is thick in the upper uterus preventing the placenta from attaching so deeply that it does not easily detach after birth.The upper uterus is richly supplied with blood for optimal fetal gas exchange and nutrition.The morula enters the uterus about 3 to 4 days after conception, it stays in the uterus another 2 to 4 days before beginning implantation.The external genitalia begin to differentiate, but male and female characteristics are not distinct until after the 10th week.Blood formation occurs primarily in the liver during the 9th week but shifts to the spleen by the end of the 12 week.Both vernix and lanugo hair diminish as the fetus reaches term.A sperm penetrates the egg and conception occurs.The zygote divides into 2 cells, then 4, then 8cells while in the fallopian tube.The inner cell mass of the blastocyst develops into the fetus (embryo).Maturation Copyright (C) The McGraw-Hill Companies , Inc.Embryonic structures continue developing during implantation.Formation of the placenta Second week: Implantation is complete by the end of the 2nd week.The most growth occurs in the trophoblast, which eventually become the fetal part of the placenta.Basic structures of all major body organs are completed during the embryonic period.Bladder Copyright (C) The McGraw-Hill Companies, Inc.Lining of gastrointestinal & respiratory tracts.Tonsils, thyroid, parathyroid, liver, pancreas.Lining of urinary bladder and urethra ?The neural tube completes closure during 4th week.The first fetal movement begin but are too slight for the mother to detect.Fetal movement feel like fluttering or butterflies.???????????????????3.????????????

Embryo Stage
 Intrauterine development : Is divided into
three stages:

1. Pre-embryonic Stage


2. Embryonic Stage


3. Fetal Stage


4. Pre-embryonic Stage
    Is the first 2 weeks after
   conception.
    The period from fertilization
   through implantation.
   Egg surrounded
   by sperm. A
   sperm penetrates
   the egg and
   conception
   occurs. It is
   called a zygote
   until it reaches
   the uterus in 3-4
   days.
   Initiation of cell division
    The zygote divides into 2 cells, then 4, then
   8cells while in the fallopian tube.
    Up to the 16 cell stage, the cells become
   smaller with each division, it is called a morula
   Morula:
    The outer cells of the morula secrete fluid,
   creating a sac of cell (the blastocyst) that has
   an inner cell mass placed off-center within the
   sac
    The inner cell mass of the blastocyst
   develops into the fetus (embryo).
    The outer layer of blastocyst cells develops
   into placenta and fetal membranes.
   (trophoblast the feeding layer)
    The morula enters the uterus about 3 to 4
   days after conception, it stays in the
   uterus another 2 to 4 days before
   beginning implantation.
   Maturation
   Copyright © The McGraw-Hill Companies , Inc. Permission required for reproduction or display.
   E m b r y o g e n e s i s
   Fertilization
   Cleavage
   Oocyte (n)
   Zygote
   (2n)
   2-cell stage
   4-cell stage
   Sperm
   cell (n)
   Morula
   Blastocyst
   G a m e t o g e n e s i s
   Ovary Testis
   Late
   week 3
   Early
   week 3
   Birth
   Week 4
   Gastrulation
   Week 8
   Week 5
   Organogenesis
    Complete implantation is a gradually
   process that occurs between the 6 -10 days.
   Embryonic structures continue developing
   during implantation.
    Immediately after implantation the
   endometrium called decidua.
    Normal implantation occurs in the upper
   site of uterus. The upper uterus is the best
   area for implantation and placental
   development for three reasons:
    The upper uterus is richly supplied with
   blood for optimal fetal gas exchange and
   nutrition.
    The uterine lining is thick in the upper
   uterus preventing the placenta from
   attaching so deeply that it does not easily
   detach after birth.
    Implantation in the upper uterus limits
   blood loss after birth because strong fibers
   in this area.
   Function of the decidua
    It is the site of implantation.
    Nutrition of the embryo.
    Formation of the placenta
   Second week: Implantation is complete by
   the end of the 2nd week.
    The most growth occurs in the
   trophoblast, which eventually become the
   fetal part of the placenta.
    The inner cells mass will develop into the
   embryonic disk


5. Embryonic Stage:
    Extends from the beginning of the 3rd
   week through the 8th weeks after
   conception.
    Basic structures of all major body organs
   are completed during the embryonic
   period.
   3rd week
    The embryonic disk develops three
   layers (germ layers):
   *Ectoderm
   *Mesoderm
   *Endoderm
   9.Three cell layers
   .1
   Ectoderm=
   outer
   .2
   Mesoderm=
   middle
   .3
   Endoderm=
   inner
   Ecto=
   Skin &
   nervous
   Meso=
   Muscles
   Bones
   Endo=
   Digest.
   Bladder
   Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
   S k i n — Spinal cord Tail e n d
   A m n i o n - Chorionic villi
   A m n i o t i c Connecting
   fluid s t a l k
   Digestive
   t r a c t
   H e a r t
   C h o r i o n
   B r a i n Yolk
   s a c
   E n d o d e r m
   E c t o d e r m
   M e s o d e r m
   *Endoderm
    Lining of gastrointestinal & respiratory
   tracts.
    Tonsils, thyroid, parathyroid, liver,
   pancreas.
    Lining of urinary bladder and urethra
    Lining of ear canal
    Early heart development begins beating
   at 21 to 22 days.
    The neural tube completes closure during
   4th week.
    Formation of the face and upper
   respiratory tract begins.
    The lower respiratory tract begins growth
   as a branch of the upper digestive tract.
    Gradually the esophagus and trachea
   separate completely.
   8th weeks
    The external genitalia begin to
   differentiate, but male and female
   characteristics are not distinct until
   after the 10th week. 3cm in length
   approximately.
    By the end of the 8th week, all major
   organ systems are in place, and many
   are functioning in a simple way.


6. Fetal Stage
    Is begins 9 weeks after conception and
   ends with birth.
    The first fetal movement begin but are
   too slight for the mother to detect.
    Blood formation occurs primarily in the
   liver during the 9th week but shifts to
   the spleen by the end of the 12 week.
    Fetal movement feel like fluttering or
   butterflies.
    Vernix caseosa, fatty, cheese like
   secretion of the fetal sebaceous glands,
   covers the skin to protect it from constant
   exposure to amniotic fluid.
    Both vernix and lanugo hair diminish as
   the fetus reaches term.
    Lanugo hair cover the fetal body to help
   the vernix adhere to the skin.
    Eyebrows and head hair appear.
    Brown fat is heat producing fat
   deposited on the back of the neck,
   behind the sternum, and around
   kidneys. Brown fat helps the neonate
   maintain temperature stability after
   birth.
   21 – 24 weeks
    Fetus length 26 cm.
    Weight 630 g.
    Skin wrinkled and red, vernix present,
   head and body covered with lanugo.
    The lungs begin to produce surfactant,
   make it easier for the baby to breathe
   after birth.
   25 – 28 weeks
    Fetus length 25-30 cm.
    Weight 1000 g.
    Eyes partially open, eyelashes present.
    Respiratory system immature, but
   fetus may survive if born.
   37 – 40 weeks
    fetus length 36-50 cm.
    Weight 3400 g.
    Pulmonary system matures.
    Lanugo may be present over the
   forehead, upper back and upper arms.
    Vernix may remain in major creases
   such as groin and axillae.