L3 DP- Prenatal Development PDF

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Lisa Feigenson...

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Prenatal Development ! • Embryology- the study of prenatal development, starts at conception! ◦ Egg released once/28 days, survive about 1 day (1 egg) ! ◦ If not fertilized, menstruation will occur: sloughing of uterine lining ! ◦ Human egg is largest cell, can be seen by naked eye! • Sperm Production! ◦ 330,000,000-500,000,000 sperm released per ejaculation ! ◦ over 6 hrs will travel through uterus, where it can wait to for conception for up to 6 days ! ◦ only 200-500 will reach the egg, assuming ovulation (some die very soon or go the wrong way)! ◦ just 1 of these will be the winning fertilizer ! • Stages of Prenatal Development/Embryology! ◦ Zygote! ‣ 0-2 weeks, until implantation in uterine wall, after it is an embryo! ‣ single egg with sperm to something more complicated ! ‣ at the end of this phase, it travels down the fallopian tube and implants itself on the uterine wall ! ‣ starts with single fertilized egg cell; rapid cell division continues, creating the blastocyst - a hollow ball of cells ! ‣ structures that feed and protect the developing organism start to form (amnion, placenta, umbilical cord)! ◦ Embryo! ‣ 3-8 weeks until 1 inch long and about 1/2 oz! ‣ most eggs don’t survive and is sloughed off with the uterus lining, and women never knows but if they do survive -> embryonic stage ! ‣ gastrulation occurs- division of blastocyst into 3 layers ! • a portion of the blastocyst will fold in on itself and create an inner layer that is the first important structure! • ectoderm -> skin ! • mesoderm -> muscles and skeletal system and circulatory system and smooth organs! • endoderm -> lungs, urinary tract, and many glands, digestive system ! • continues to have structural differentiation with time ! ‣ at 6 weeks- head and eye spot (no visual capacity), heart, placenta and thick umbilical cord ! ‣ similar structures across species during embryonic stages but very different during fetal stages ! ‣ umbilical cord: tube containing the veins and arteries that connect the developing embryo/fetus to the placenta; delivers nutrients and takes away waste ! ‣ placenta: organ that separates mom & baby’s bloodstream, but permits exchange of nutrients and waste products; needs to be healthy and functioning for the fetus to develop ! ‣ amnion: inner membrane that forms protective covering around developing baby, contains cushioning amniotic fluid ! ‣ chorion: outer membrane, surrounds amnion! ‣ endometrium: lining of the uterus ! ‣ muscle layer of uterine wall ! ‣ in a cesarean birth, ALL of these many layers must be perforated to reach the baby ! ◦ Fetus ! ‣ 9-12 weeks! • Organization and connectivity of organs -> circulatory system, start becoming pseudo functional ! • Lungs expand & contract, not breathing for itself but they are practicing ! • External genitalia form ! • Vigorous motion of arms and legs ! ‣ 13-20 weeks (20 weeks = halfway point)! • Fetus grows much larger! • Mom feels fetal movements! • Responds to light and sounds ! • Covered by vernix- waxy white coating that protects the skin from being submerged for 40 weeks ! ‣ 21-38 weeks! • Fetus enters age of viability - if prematurely born, will the baby survive, age of viability decreases with time ! • Much brain development ! • Eyes can open and move ! • Fetus triples its weight

• Immune system is strengthened via mom’s antibodies ! • Fetus rotates into head-down position in preparation for birth; most positives outcome is when they come out head first ! ◦ butt first = breach, more dangerous ! • Fetal Behavior: Preparing for Life after Birth ! ◦ Much movement in the womb esp, between 12 and 20 weeks ! ◦ Fetal swallowing and breathing ! ◦ Establishes circadian rhythms of activity, REM sleep ! ◦ Receives info from touch, taste, smell, sound, some sight ...! • Even before Birth, Learning Occurs! ◦ Auditory: Infant habituation procedure- got a bunch of pregnant moms with fetuses in last weeks of gestation, put an auditory system onto the outside of the mom’s baby for the fetus to hear, was a sequence of syllables really loud, and they measure the fetus’ response by measuring the change in fetal heart rate, first time it is played there is a big change in the heart rate (told us the could hear) and as it is played over and over, there is a mono tonic steady decline in responsiveness by this stimulus, so then they change it up and reverse the syllable order which causes an increase in responsiveness as the heart rate spikes up again; implicates many psychological process! ‣ fetus remembered auditory stimulus, learned to recognize it, and discriminated a novel phrase - got bored of the stimulus and when it changed the fetus realized it was something new ! ‣ short term fetal memory for auditory stimuli ! high! ! change in heart ! rate! ! ! ! low! ! % % % % "ba-bi"% % % % "bi-ba"! ◦ Auditory: Do fetuses have long term memories, too? ! ‣ Pregnant moms read Cat in the Hat twice/day aloud for last 6 weeks of pregnancy. After birth the baby is brought into the lab. Have a pacifier with a transducer and the rate at which they suck they determine which book they are played out loud. Result, babies adjusted sucking in order to hear familiar story that their pregnant moms had read to them in utero stage. -> Babies have a similarity preference; implicit memories that last in babies at least up through the first week or two; audible book after birth is not in their mother's voice but they have a memory for the rhythm of the words and patterns rather than the voice of the readers -> newborns remember patterns learned in the womb ! ◦ Auditory: Native language ! ‣ Tested french babies. Had pacifier transducer where they could suck to hear russian or a stranger's voice speaking french. Babies adjust sucking patterns to hear their native language. Newborns remember linguistic sounds heard while in the womb and prefer familiar ones to novel ones. In bilingual home no preference between the two but preference against non-native ! ◦ Smell: Amniotic fluid! ‣ Experimenter soaks rag in amniotic fluid during pregnancy. Do newborn babies prefer the cloth soaked in their own mother's amniotic fluid or the stranger next door's amniotic fluid? They prefer a cloth soaked in their own amniotic fluid/from their mother over that of a different baby - this shows that they developed sense of smell in womb ! ◦ Taste: Carrot Juice! ‣ Moms drink carrot juice 4 days/week for 3 weeks and another group of moms drinks an extra glass of water for 4 days/week for 3 weeks. After birth of babies and at 5 months old, baby prefers cereal prepared with the liquid their mother consumed the most. Babies who had been exposed to carrot juice in the womb showed a preference to the carrot juice cereal -> Babies remember a taste/flavor that they encountered in the amniotic fluid 6 months prior ! ◦ Visual: Do fetuses have visual expectations !...