The Biology of Development I. Pregnancy II. Prenatal Development III. Developmental Hazards
I.Pregnancy How does a person know if she is pregnant?
II.Prenatal Development -280 days, weeks -3 main periods of Prenatal Development -germinal-embryonic-fetal
1.Germinal Period 1st 2 weeks Zygote created, cell division Zygote attaches to wall Cell differentiation Inner cells (blastocyst) grow into embryo Inner cells (blastocyst) grow into embryo Outer cells (trophoblast) provide nutrients/support for embryo Outer cells (trophoblast) provide nutrients/support for embryo
Follicle releasing egg to be fertilzed
Zygote
Blastocyst
Fetal Circulation
Embryos
2.Embryonic Period 2- 8 weeks More cell differentiation Organogenesis 3rd week--neural tube forms, eyes, ears, nose 24 days--heart cells 4th week-arm/leg buds 6 weeks--hands 8 weeks, primitive heart beating
Cell differentiation Inner cells (endoderm) form internal body parts --digestive/respiratory Outer cells Ectoderm (outermost)--on surface Ectoderm (outermost)--on surface Form nervous system, sensory, skin partsForm nervous system, sensory, skin parts Mesoderm (middle)--surrounds internal areas, circulatory system, bones, muscles, excretory and reproductive system Mesoderm (middle)--surrounds internal areas, circulatory system, bones, muscles, excretory and reproductive system
Life Support Of Embryo 1. Placenta 2. Umbilical cord 3. Amnion
Fetal Circulation
3. Fetal Period Last 7 months At 3 mos--3 inches long, weighs 1 oz., 5 mos--lanugo, 11 oz., 10 inches 6 mos inches, 20 oz, 8-9 mos- Proximodistal and cephalocaudal Proximodistal and cephalocaudal
III. Developmental Hazards Teratology…Teratogen 1. Maternal diseases and health AIDS, rubella, syphilis, gonorrhea, polio, diabetes, herpes 2. Age 3. Nutrition 4. RH factor 5. Emotions/Stress 6. Drugs
Drugsharmful to Prenatal Development Thalidomide Barbituates Aspirin Megadoses of vitamins Alcohol Nicotine Caffeine Narcotics LSD Marijuana Cocaine
6. Environmental hazards Radiation Pesticides PCBs Mercury Lead Toxoplasmosis Hot temperatures