Exploring Lifespan Development Chapter 2 Prenatal Development (Part 2)

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 woman’s 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.

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)

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

From Conception to Implantation

Internal Female Organs: Uterus Fallopian Tube Fallopian Tube Ovary Ovary (Via Laparoscopic Surgery)

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

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 woman’s body not to menstruate. Once a Zygote is firmly implanted it is now called an Embryo.

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

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 can’t feel it yet!) Amniotic fluid cradles the embryo and the umbilical cord nourishes it and connects it to the mother’s blood supply. Growth of the head takes precedence over growth of the lower parts of the body

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

The Placenta (In Pictures!) Secretes hormones that preserve the pregnancy, prepare the breast for nursing, and stimulate utermine contractions that prompt childbirth. Placenta passes from the birth canal after the baby.

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. Genital differentiation pics

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

Embryo Development: Weeks 3 through 8: 1 inch long and ½ oz. 3 ½ wks: Neuronal development begins 8 wks: Neurons begin to fire! 6 wks: My heart beats! 1 inch long and ½ oz.

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.

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, < 1 oz. 9 weeks 12 weeks

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

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.

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

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.

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

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.

Critical Periods in Prenatal Development

Teratogens Environmental agents that can harm the developing embryo or fetus. STD’s HIV/AIDS Rubella Toxemia Rh Incompatibility

Teratogens, cont. Drugs taken by the parents Heroin/Methadone Marijuana Cocaine Alcohol Cigarettes

Teratogens, cont. Environmental hazards Parental age

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