Exploring Lifespan Development

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Exploring Lifespan Development

• Chapter 2
• Prenatal Development
• (Part 2)

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Quick Quiz

• What is the purpose of a menstrual cycle?
• T/F Women are born with all the eggs they will
  ever have.
• Conception happens where in a womans body?
• T/F A woman is pregnant for 10 months.
• The most dramatic changes in our development
  occur when?
• T/F All embryos start out as girls.

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Prenatal Development is Divided into 3 Periods

• Period of the Zygote (1-2 weeks) (Germinal stage)
• Period of the Embryo (3-8 weeks) (Embryonic
  stage)
• Period of the Fetus (9 weeks to birth)
• (stages of pregnancy/fetal development are also
  referred to as trimesters, or 2 month increments)

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1. Period of the Zygote

• Conception Cells Zygote travels
  Implantation
• Occurs ? Divide ? to uterus ? into
  uterine wall
• 0 hours 36 hrs 3-4 days 1 week

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From Conception to Implantation
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Internal Female Organs
Uterus
Fallopian Tube
Fallopian Tube
Ovary
Ovary
(Via Laparoscopic Surgery)
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Know

• The final step in the period of the zygote is
  Implantation to the uterine wall.
• Why?

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Implantation Facts (the answer to Why?)

• The dividing cell or blastocyst will not develop
  if it is not implanted, for it needs nourishment
  from the mother.
• Implantation takes about 1 week to complete.
• Implantation triggers hormonal changes that tell
  the womans body not to menstruate.
• Once a Zygote is firmly implanted it is now
  called an Embryo.

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Cell Division Implantation (what it looks
like)
Blastocyst hatching out of the hard outer shell
before it can begin to implant
Implantation! On to the next phase
Blastocyst
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2. Period of the Embryo

• The embryos body structures and internal organs
  develop.
• Leg, arm buds appear, sensory systems and the
  brain and nervous system have begun to develop.
• The embryo can sense its world, respond to touch
  and is moving. (mom cant feel it yet!)
• Amniotic fluid cradles the embryo and the
  umbilical cord nourishes it and connects it to
  the mothers blood supply.
• Growth of the head takes precedence over growth
  of the lower parts of the body

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Period of the Embryo, cont.

• The heart begins to beat at 6 weeks of pregnancy.
  
• The placenta permits the embryo to exchange
  nutrients with mother
• Placenta filters oxygen/nutrients which pass from
  mother to embryo and permits carbon dioxide/waste
  products to pass to the mother from the embryo.
• Mother and embryo have separate circulatory
  systems

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The Placenta (In Pictures!)
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Guess What Guys?

• You all started out as a female during the embryo
  stage of development!
• At 9 weeks of pregnancy your Y chromosome kicked
  in and here you are, the vagina turned into a
  penis.

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Which Embie is A Human?
Dolphin
Water Buffalo
Komodo Dragon
Whale
Mouse
Human
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Embryo Development

• Weeks
• 3 through 8

3 ½ wks Neuronal development begins 8 wks
Neurons begin to fire!
6 wks My heart beats!
1 inch long and ½ oz.
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3. Period of the Fetus

• The longest prenatal period.
• Further maturation of fetal organ
  systems/dramatic gains in size.
• Gender can be determined via ultrasound.
• Significant increase in brain maturity means new
  behavioral capacities ability to regulate its
  own basic body functions.

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9-12 Weeks of Fetal Development

• The brain signals the fetus to kick, curl its
  toes, open its mouth, and suck its thumb.
• Fingernails, toenails, tooth buds and eyelids
  that open and close are formed.
• 3 inches, lt 1 oz.

9 weeks
12 weeks
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13-24 Weeks of Fetal Development
22 wks
16 wks
20 wks
24-25 wks
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13-24 Weeks of Fetal Development

• Skin thickens and is covered with Vernix-which
  protects it. A soft downy hair develops called
  Lanugo which helps the vernix stick.
• Movements are now strong enough for mom to feel.
• Alternates between periods of sleep/waking.
• Fingers/toes completely formed
• Fetus develops a temperament/activity level
• Fetal hiccoughs common
• Eyebrows, eyelashes and scalp hair emerge.
• 12 inches, 1.8 lbs.

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What is the Age of Viability?

• The point at which a fetus can survive outside
  the womb.
• Usually between
• 23-24 weeks of pregnancy.

22 weeks
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25-38 Weeks of Fetal Development

• Fetus practices breathing by breathing and
  swallowing amniotic fluid
• Heart/lungs capable of sustaining independent
  life.
• Layer of fat is added to aid in temperature
  regulation
• Fetus assumes head down position.
• 19-20 inches, 7.5 lbs.

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Question

• True or false
• Prenatal fetal movement can predict infant
  activity levels after birth.

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Critical Periods in Prenatal Development

• There are specific times during prenatal
  development when certain organs are developing
  rapidly.
• If there is exposure to a Teratogen during these
  Critical Periods there can be harm done to the
  developing embryo/fetus.

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Critical Periods in Prenatal Development
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Teratogens

• Environmental agents that can harm the developing
  embryo or fetus.
• STDs
• HIV/AIDS
• Rubella
• Toxemia
• Rh Incompatibility

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Teratogens, cont.

• Drugs taken by the parents
• Heroin/Methadone
• Marijuana
• Cocaine
• Alcohol
• Cigarettes

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Teratogens, cont.

• Environmental hazards
• Parental age

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Know

• The embryo is generally more vulnerable to
  exposure to teratogens than the fetus.