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UD - HDFS 220 - Week 5 Notes - Class Notes

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UD - HDFS 220 - Week 5 Notes - Class Notes

School: University of Delaware
Department: Human Development
Course: CHILD DEVELOPMENT I: PRENATAL TO AGE 3
Professor: Jennifer Carrano
Term: Fall 2017
Tags:
Name: Week 5 Notes
Description: Chapter 4 (cont)
Uploaded: 12/10/2017
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background image Lecture Notes  Thursday, September 28, 2017
11:01 AM
Chapter 4: Prenatal Development: Birth and 
Newborn 
Prenatal Development  Historically, we have largely ignored the prenatal period, thinking it didn’t  matter all that much for development. We now know that this time is crucial!  
The Process of Conception 
An ovum (unfertilized egg) is released by the female’s ovaries during  ovulation (the release of a mature egg from the ovaries). During intercourse, the male releases approximately 300 million sperm  during ejaculation. o Only healthiest sperm make it to egg o Only around 200 actually make it  If just one of these sperm penetrates the outer layer of the ovum, this results  in its fertilization, beginning the prenatal journey of the child. Usually, only one egg is released and fertilized, but sometimes women  release more than one egg during a cycle Twins occur either when a fertilized egg splits early in prenatal development  (resulting in monozygotic twins) or when two eggs are released and fertilized 
by two different sperm cells (dizygotic twins)
o Genetically identical because same egg fertilized by same sperm  (because egg is split in half)  o About 70% of twins are DZ The likelihood of having DZ twins is influenced by both genetics and the  mother’s age   o As women get older more likely to release 2 eggs  More males are conceived than females  o Between 107 and 170 males are conceived for every 100 females But fewer males survive to birth o Males may be more susceptible to toxins during prenatal development o More likely to have X-linked chromosomal/genetic disorders  o If disorders are serious enough (like at chromosome level) the  babies may not survive until birth o Do not have second X to compensate 
background image o Grow more rapidly than females, so more difficult for mothers to  provide them with appropriate nutrients o All of these things increase the risk that males won’t survive and their risk for developing diseases  
Three Stages of Development 
Germinal  Embryonic  Fetal   
The Germinal Stage
Lasts from conception to two weeks Once the egg is fertilized it’s known as a zygote The zygote walls thicken immediately after fertilization, preventing other  sperm from entering the egg The zygote starts as a single cell, and in about 15 hours, splits to become two o Continues splitting to 4 cells, then 8, then 16, etc. After 4-5 days, there are 32 cells that are ready to implant into the wall of the uterus Only about 40% of zygotes ever implant; the rest simply pass out of the  woman’s body and don’t survive o Majority of fertilization no baby ever comes of it -- evolutionary --  healthiest sperm, egg, zygote make it to birth  As the cells continue splitting, the once solid ball becomes hollow (called a  blastocyst) The blastocyst has:
o
An inner cell mass: solid clump of cells that become an embryo o Becomes baby's body o Trophoblast: an outer ring of cells that become the life support  system for the embryo (the placenta and & chorion) Extensions from the trophoblast grow  into the uterine wall, allowing the  blastocyst to take in nutrients from the mother and grow  
The Embryonic Stage 
2 weeks to 2 months Baby is known as an embryo
background image Trophoblast develops into the support system: o Chorion – The outer wall that gives rise to the placenta o Amnion - The inner wall that surrounds the fetus o Membrane, holds in amniotic fluid-- protective mechanism  Placenta: brings nutrients and oxygen to the embryo and carries away waste o Although mothers and embryos have separate blood systems, some  substances are small enough to pass through the placenta and enter the 
baby’s blood
o Placenta keeps blood separate !  o Example: alcohol passes through easily and circulates in babies  blood  Inner Cell Mass Splits into 3 layers 
o
Ectoderm o Mesoderm o Endoderm o WHAT TO TURN OFF AND WHAT TO TURN ON  o DIFFERENTIATE INTO DIFFERENT BODY PARTS  Humans develop in a cephalocaudal way: from the head down o So, brain develops first! Organogenesis: the process by which all of the body’s major organ systems  begin to form o Laying down of different organ systems  o Entire process ends by about 8 weeks Really quickly -- absolutely critical time in development (can  have huge implications on whether or not child will be healthy)  Organogenesis is a critical period in development o Embryo is developing so rapidly that anything disrupting the process  can cause severe and irreversible damage o High risk of miscarriage (50-80% are due to chromosomal disorders) o Women can get to this stage without even knowing their pregnant (so  they may still be drinking, etc.) By the end of the embryonic phase, embryo is about 1 inch long, weighing  less 1/30 th  of an ounce o But, all organ systems are formed Many women have their first ultrasound between 6 and 10 weeks o Depends on when they figure out that they are pregnant

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School: University of Delaware
Department: Human Development
Course: CHILD DEVELOPMENT I: PRENATAL TO AGE 3
Professor: Jennifer Carrano
Term: Fall 2017
Tags:
Name: Week 5 Notes
Description: Chapter 4 (cont)
Uploaded: 12/10/2017
11 Pages 16 Views 12 Unlocks
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  • Notes, Study Guides, Flashcards + More!
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