Life-span development chap 4 notes

Essay by upenncheatCollege, Undergraduate September 2002

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Prenatal Development


Germinal Period - Conception to 2 weeks

1. Creation of the zygote

2. Continued cell division

3. Implantation - attachment of the zygote to the uterine wall (10 days after conception)

* Blastocyst - inner cells (embryo)

* Trophoblast - outer layer (placenta/umbilical cord - life supports systems)


Embryonic Period - 2 to 8 weeks after conception

1. Cell differentiation intensifies, support systems for cells form and organs appears

2. Attached zygote becomes embryo

* Endoderm (digestive/respiratory systems)

* Mesoderm (circulatory system, bones, muscles, excretory system, reproduction system)

* Ectoderm (nervous system sensory receptors, skin parts such as hair and nails)


Fetal Period - 8 weeks after conception until birth

1. Fetal size increases and organs start functioning

2. Reflexes appear and there is sexual differentiation


Miscarriage and Abortion

1. Most occur within 1st trimester (chromosomal abnormalities)

2. 15-20% pregnancies end in miscarriage


male fetuses more likely to miscarry

3. Abortions legal in U.S. until end of 2nd semester

* 1 abortion for every 2 births

* Unwanted pregnancies stressful for woman regardless of how it is resolved

* Psychological effects of abortion include relief and guilt (usually mild and disappears)

* Women with previous psychiatric problems more likely to experience adverse effects


Teratology and Hazards to Prenatal Development


Teratogen - any agent that causes birth defects


Environmental Hazards

* Radiation (chromosomal abnormalities)

* Pollutants & toxic wastes (lead, pesticides, carbon dioxide, mercury dangerous to fetus)

* Drugs

Thalidomide - prescribed in 1960's for morning sickness (deformed babies)

Cocaine/heroin (addiction/withdrawal symptoms/neurological defects)

Alcohol (fetal alcohol syndrome)

Smoking (low birth weight, ADHD, premature births, SIDS)

Marijuana, antibiotics, excessive vitamins, antihistamines, aspirin, diet pills harmful


Maternal diseases can cross the placenta barrier and cause birth defects

- Rubella (German measles)...