Prenatal Development & Birth Class 5 PDF

6/13/22 Cellular Developmental Processes Cell Division Prenatal...

6/13/22 Cellular Developmental Processes Cell Division Prenatal Zygote = fertilized egg Development First duplication takes 12 to 24 hours. By Day 4, 60-70 cells – hollow, fluid-filled ball (blastocyst) Inner cell mass à embryo Outer ring à protective covering Trillions of cells by birth! Zygote travels down fallopian tube, attaches to uterus (“implantation”), which marks end of zygotic stage at ~2 weeks. Weeks 3-8 = embryonic stage Weeks 9-birth = fetal stage (trillions of cells by birth!) 1 2 3 4 Cellular Developmental Processes Cell Migration Cells move to various destinations. Embryonic disk folds over and forms three layers Cell Differentiation Begin as stem cells in embryo (no fixed function) What happens? Not entirely clear, but location appears to be part of the answer. Cell Death Over-exuberant cell production is followed by cell death. Why? 5 6 1  6/13/22 When things go wrong… Developmental 40-50% of conceptions spontaneously abort in the first few Trends weeks. Cephalocaudal Another 15-20% of embryos / fetuses do so over the next few development: Areas near months. head develop first, top down. Genetic factors are the leading cause of spontaneous abortion or birth defect, although environmental causes also play a Proximodistal role. development: Growth starts at center of body, Teratogens = environmental agents causing developmental moves toward extremities. harm or disruption during prenatal development. 7 8 Prenatal Behavior: Prenatal Experiences: Preparing for the outside world The Development of Senses MOVEMENT: coordinating muscles (patterns of “sendentary” vs. TOUCH - sucks thumb, seeks comfortable position, thrashes if “active” remain quite consistent). hurt or poked Starts moving at 8 weeks but movement not felt by mother until ~20 weeks TASTE & SMELL - amniotic fluid takes on flavors/scents based on maternal diet. Fetus has sweet tooth! SWALLOWING: tongue gets practice for drinking, palate develops, amniotic fluid in digestive system promotes its HEARING - uterus is noisy; fetus hears sounds, learns patterns development Fetal inner ear nearly adult size (wow!) Calories important too…little swallowing = smaller baby. SIGHT - can see, but poorly (very dark); will shield eyes from light BREATHING: moves chest wall in and out (takes in amniotic fluid) Fetal learning apparent after 32 weeks… SLEEPING: develops typical circadian rhythms, REM sleep. 9 10 Early stimulation and Early stimulation sensory and sensory experience: experience: Too much input? Too little input? Rand, K. & Lahav, A. (2013). Im pact of the N IC U environm ent on language deprivation in preterm infants. A cta Paediatrica, 103, 243- 248 D O I: (10.1111/apa.12481) 11 12 2  6/13/22 Birth: We’re born immature! Birth: A good type of bad? Human babies are born earlier and more immature, Orientation of baby in birth canal contributes to ease of developmentally, than many other species’ young. delivery. Some scholars speculate on physiological reasons for Medication for pain: pros and cons. “precocious birth.” For example…? Labor contractions are intense, usually painful – but the Other scholars discuss the results (benefits) of “precocious squeezing triggers multiple beneficial outcomes. birth.” For example…? 13 14 Birth: What if it’s too early, or if the newborn is especially small (under 5.5 lbs)? Premature and low birth weight (LBW) babies are not uncommon. 8% of U.S. births, i.e., 1 in every 12 births. Reasons? As a group, LBW babies face more developmental risks than full-term or normal birth weight peers. Like what? Predicting LBW success: Multiple risk model Initial health status Quality of treatment and postnatal care 15 3