Introduction to Psychology/Child and Adolescent Psychology/Prenatal Environment

Prenatal development is the development of an organism before its birth. Stages of Prenatal Development Germinal stage – conception to 2 weeks Begins at conception and ends when the zygote implants itself in the mother's uterine lining. Between 8 and 12 days after conception, implantation occurs. This is when the zygote embeds itself in the inner lining of the mother's uterus. Embryonic stage – 3 to 8 weeks after conception blastocyst differentiates to form three cell layers in the embryo: the ectoderm, mesoderm, and endoderm. The ectoderm is the outer layer of the cell mall, and during the embryonic stage it gives rise to the nervous system, sensory receptors, and outer skin layers. The mesoderm becomes the circulatory system, skeleton, muscles, excretory system, reproductive system, the outer layer of the digestive tract, and the inner layer of the skin. The endoderm will eventually become the respiratory system and the remainder of the digestive system. chronological development following conception 3rd week - vulnerable brain cells and spinal cord form from the neural tube 3rd and 4th week - placenta and umbilical cord form by 4 weeks - eyes begin to form, torso continues to form, heart tissue begins to beat, arm buds appear by 5 weeks - arms are developed and legs buds begin to form during 8th week - organogenesis is complete, signaling the end of the embryonic stage and beginning of the fetal stage Fetal stage - week 9 to birth (38–40 weeks) chronological development following conception 9 through 12 weeks - first arm and leg movements begin, reflexes appear, sex organs develop. 17 through 20 weeks - mother begins to feel movement, heartbeat can be heard with a stethoscope. by 24 weeks - fat forms and rapid weight gain begins 26 through 28 weeks - lungs are mature enough to allow breathing 28 though 40 weeks - major organ systems are functional and brain develops rapidly. Teratogens preterm births occur before 37 weeks of gestation low birth weight is less than five and half pounds (two pounds lighter than average) Fetal Alcohol Syndrom (FAS) overall growth deficiency, head and facial malformations, and dysfunction of the central nervous system effects of alcohol use effects of cocaine use effects of cigarette smoking sexually transmitted diseases effects of stress