AP PSYCH - CH 11 -"Development" PART I: Prenatal Development

Human Development: Sequence of age-related changes that occur as a person progresses from conception to death.

Early Development: ★ Baby’s beginnings ★ Child development physically, cognitively, socially, & emotionally ★ Influences of friends & family Development: Study of how people change over their lifespan. Forms of Development: Physical, Cognitive, Social, & Emotional Development occurs throughout the lifespan. Psych is focused mostly on child development.

IMPLANTATION: Many sperm will try, but only one will fertilize the egg. Once that happens... Mass of dividing cells slowly migrates along mother’s oviduct to uterine cavity About 6th-7th day: Cell mass begins to attach itself to uterine wall Implantation takes about 1 week

Good News: In the Womb: Produce ¼ million brain cells/min. Bad News: Basically all you are ever going to develop. Although the brain does not develop many new cells, the existing cells begin to work more efficiently- forming more complex neural networks. After birth: PRUNING

Germinal Stage: 1st phase of prenatal development: 1st two weeks after conception Zygote: Created through fertilization. Within 36 hours, rapid cell division begins. Becomes a microscopic mass of multiplying cells. Mass of cells slowly migrates along the mother’s fallopian tube to the uterine cavity. About the 7th day: Cell mass begins to implant itself in the uterine wall. Process takes about a week & is far from automatic.

Germinal Stage: Many zygotes are rejected at this point. As many as 1 in 5 pregnancies end with the woman never being aware that conception has occurred. Placenta: Structure that allows oxygen & nutrients to pass into the fetus from the mother’s bloodstream & bodily wastes to pass out to the mother. Critical exchange takes place across thin membranes that block passage of blood cells, keeping the fetal & maternal bloodstreams separate.

GERMINAL STAGE (weeks 1- 2): 30 HOURS: Fertilization & formation of zygote DAY 4: Formation of blastocyst DAY 5-8: Attachment of blastocyst DAY 8: Appearance of amniotic cavity

First few weeks of embryogenesis

EMBRYONIC STAGE (Week 3-8): Week 3: Development of neural tube (day 18), Beginning of blood circulation (day 24) Possible abnormal events: Twins, Teratogens (foreign substances: influence developing fetus) very damaging from wk 3-8. Weeks 4-8: Formation of head, tail, lateral folds, primitive gut. Heart moves to normal position. Appearances of brain, limbs, eyes, ears, & nose. Development of human-like 8 6 Wks Virtually all the basic physiological structures are being formed. If anything interferes with normal development during this phase: Effects can be devastating. Most miscarriages occur during this period. Most major structural birth defects are also due to problems that occur during the embryonic stage.

No, this is NOT photoshopped. All humans have a tail in the embryo stage. It is reabsorbed as we develop. VERY Few babies are born with a tail. And in those rare cases, they are typically removed. The human tail upon birth is caused by a lack of cell destruction of the distal end of the embryonic tail. Atavism: Trait of distant ancestors that reappears in modern day.

Why Some Humans Are Born With Tails

FETAL STAGE (weeks 9-36): Weeks 9-12: Fetal head = ½ of fetal body. Eyelids fused. Upper Limbs develop to normal proportions. Male & female genitalia recognizable by 12 weeks. Weeks 13-16: Rapid fetal growth. Fetus doubles in size. Kidneys secrete urine. Fetus appears human. Placenta is fully formed. Weeks 17-23: Fetal growth slows. Lower limbs formed. Fetal movement at 20 weeks. Fetal heartbeat begins.

FETAL STAGE (weeks 9-36): Weeks 24-27: Skin growth is rapid. Eyes open. Fetus is viable at 27 weeks. Weeks 28-36: Weight gain is steady. Fetus has a good chance of survival. 23 weeks: 10%–20% chance of survival Probability still slim, but climbs rapidly over the next month 26 weeks: 75% survival rate at 26 weeks Premature infants born near the threshold of viability go on to experience a wide range of developmental problems.

FULL TERM (weeks 37-40): Fingernails & toenails grow. Skull is fully developed. Fetus is ready for birth. Brain development occurs during the entire time. Brain starts to develop early (~ 4 weeks) & continues to develop both neurons & connections for entire gestation period. However, once birth occurs, neural development slows down (some argue that it stops) Pruning occurs: Connections are made among cells & connections that are redundant are “trimmed.”

Why Can’t We Remember Being Babies?