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Conception & Period of Conception & Period of the Zygotethe Zygote
ReproductionReproduction
Begins when female gamete (ovum) Begins when female gamete (ovum) fertilized by male gamete (sperm)fertilized by male gamete (sperm)
ZygoteZygote
Single cell formed through Single cell formed through fertilizationfertilization
23 pairs of chromosomes23 pairs of chromosomes
Conception & Period of Conception & Period of the Zygotethe Zygote ZygoteZygote
Egg & a sperm fuseEgg & a sperm fuse Create single cellCreate single cell
23 unpaired chromosomes from egg & 23 unpaired chromosomes from egg & sperm combine to formsperm combine to form 1 set of 23 paired chromosomes1 set of 23 paired chromosomes
1 chromosome of each pair is from1 chromosome of each pair is from Mother’s eggMother’s egg Father’s sperm Father’s sperm
Each parent contributes 1/2 of Each parent contributes 1/2 of offspring’s genetic materialoffspring’s genetic material
PrenatalPrenatalDevelopmentDevelopment
3 prenatal periods3 prenatal periods 1. 1. GGerminal Perioderminal Period 2. 2. EEmbryonic Periodmbryonic Period 3. 3. FFetal Periodetal Period
((GGabby abby EEats ats FFrogs)rogs)
1. The 1. The GerminalGerminal Period Period
Takes place in 1Takes place in 1stst 2 weeks after 2 weeks after conception. conception.
1. Creation of zygote 1. Creation of zygote
2. Cell division2. Cell division
3. Attachment of zygote to uterine 3. Attachment of zygote to uterine wall wall
The Course of Prenatal Development
The Germinal PeriodThe Germinal PeriodEgg goes from ovary through fallopian tube (uterine tube)Egg goes from ovary through fallopian tube (uterine tube)
Creation of zygote (fertilized egg)Creation of zygote (fertilized egg) Mature human eggMature human egg
23 chromosomes23 chromosomes
Mature human spermMature human sperm 23 chromosomes23 chromosomes
Egg fertilized by spermEgg fertilized by sperm Creates zygoteCreates zygote
46 chromosomes46 chromosomes
The Germinal PeriodThe Germinal Period
Many sperm race to eggMany sperm race to egg 1 wins…usually.1 wins…usually.
Makes way to egg by smellMakes way to egg by smell Once a sperm penetratesOnce a sperm penetrates
Chemical is releasedChemical is released Prevents other sperm from enteringPrevents other sperm from entering
2 penetrate2 penetrate Possible miscarriagePossible miscarriage
The Germinal PeriodThe Germinal Period
Zygote Zygote
The Germinal PeriodThe Germinal Period
2. The 2. The EmbryonicEmbryonic Period Period
2. The 2. The EmbryonicEmbryonic Period Period
Occurs 2 - 8 weeksOccurs 2 - 8 weeks after conceptionafter conception
Cell differentiation intensifiesCell differentiation intensifies
Support systems for cells formSupport systems for cells form
Organs appearOrgans appear Heart firstHeart first
The Course of Prenatal Development
Umbilical cord
Umbilical arteries
Umbilical vein
Uterus
Maternal portion of placenta
Placenta
Fetal portion of placenta
The Placenta and the Umbilical Cord
Fig. 3.2
The Course of Prenatal Development
PlacentaPlacenta
Attaches to inside of uterus Attaches to inside of uterus Connected to fetus by umbilical cordConnected to fetus by umbilical cord Produces pregnancy-related Produces pregnancy-related
hormoneshormones Small blood vessels carrying fetal Small blood vessels carrying fetal
blood run through placenta, which is blood run through placenta, which is full of maternal blood. full of maternal blood.
Embryo’s Life-Support Embryo’s Life-Support SystemSystem
PlacentaPlacenta Intertwines Intertwines
Does not join mother & babyDoes not join mother & baby
Umbilical cordUmbilical cord Connects baby to placentaConnects baby to placenta
The Course of Prenatal Development
Amnion & amniotic fluidAmnion & amniotic fluid Provides baby’s environmentProvides baby’s environment
Drinks itDrinks it
OrganogenesisOrganogenesis Organ formationOrgan formation
Especially vulnerable to Especially vulnerable to environmental changes environmental changes
Embryo’s Life-Support Embryo’s Life-Support SystemSystem
3. The 3. The Fetal Fetal PeriodPeriod
Begins 2 mo’s after conceptionBegins 2 mo’s after conception
Lasts @ 7 mo’s - birthLasts @ 7 mo’s - birth
Largest prenatal size & weight gainsLargest prenatal size & weight gains
Development:Development: FingersFingers toestoes lungslungs
Skin Skin featuresfeatures reflexesreflexes
The Course of Prenatal Development
Trimester 2: Week 21 - 27Trimester 2: Week 21 - 27
The BrainThe Brain
At birth – 100 billion neuronsAt birth – 100 billion neurons
Basic architecture assembledBasic architecture assembled 11stst 2 trimesters 2 trimesters
Neural tube: first 18–24 daysNeural tube: first 18–24 days Forms the spinal cordForms the spinal cord
Neural Tube Defects Effect so severe, won’t show youEffect so severe, won’t show you
Defect tied to nutritionDefect tied to nutrition
The Course of Prenatal Development
Neural Tube DefectsNeural Tube Defects
The BrainThe Brain NeurogenesisNeurogenesis: :
55thth prenatal week: prenatal week: Proliferation of new immature neuronsProliferation of new immature neurons
Continues through prenatal periodContinues through prenatal period
33rdrd trimester trimester Connectivity Connectivity
Functioning of neuronsFunctioning of neurons
Fetal LearningFetal Learning 33rdrd Trimester Trimester Increased responsiveness:Increased responsiveness:
Familiar voicesFamiliar voices Differences in heart rate Differences in heart rate
ExperimentExperiment Cat in the Hat Cat in the Hat read to fetus read to fetus 2x’s a day2x’s a day
Preference for book & voice after birthPreference for book & voice after birth
Any help to development?Any help to development? None detectedNone detected
THREATS TO PRENATAL THREATS TO PRENATAL DEVELOPMENTDEVELOPMENT
Threats to prenatal Threats to prenatal developmentdevelopment
Teratogen Teratogen Any agent that causes a birth Any agent that causes a birth
defectdefect Severity & type of defect affected Severity & type of defect affected
byby DoseDose Genetic susceptibilityGenetic susceptibility Time of exposureTime of exposure
Hazards to Prenatal Development
All drugs (prescribed, illegal) can have All drugs (prescribed, illegal) can have effects on unborn fetuseffects on unborn fetus Antibiotics, analgesics, asthma Antibiotics, analgesics, asthma
medicationsmedications
X-raysX-rays
PollutionPollution
Large doses Vitamin ALarge doses Vitamin A
1961: thalidomide tragedy1961: thalidomide tragedy
Threats to prenatal Threats to prenatal developmentdevelopment
Fetal Alcohol SyndromeFetal Alcohol Syndrome
Zygote Embryonic period (wks) Fetal Period (wks)
Period of susceptibility to functional defects
Fig. 3.7 (modified)
11 22 33 44 55 66 77 88 99 1616 3232 3838
Teratogens and Timing of Their Effects on Prenatal Development
Most serious damage
from teratogens in first 2–8
weeks
Period of susceptibility to structural defects
Central nervous system Heart
ArmsEyes
Legs Ears
TeethPalate
External genitalia
Psychoactive DrugsPsychoactive Drugs
Psychoactive drugs Psychoactive drugs Act on nervous system & change Act on nervous system & change
moodsmoods
Alter states of conscious, modify Alter states of conscious, modify perceptionsperceptions
Extent of risk & harm variesExtent of risk & harm varies
Hazards to Prenatal Development
Your Doctor Wants You to Smoke Your Doctor Wants You to Smoke 19511951
Nicotine (March of Dimes Nicotine (March of Dimes longitudinal study, 2011)longitudinal study, 2011)
– – Heart defectsHeart defects– Absence or severe underdevelopment of – Absence or severe underdevelopment of hands, feet, radius, tibia, ulna or fibulahands, feet, radius, tibia, ulna or fibula– Missing fused or extra fingers or toes– Missing fused or extra fingers or toes– Clubfoot– Clubfoot– Cleft lip or palate– Cleft lip or palate– Eye defects– Eye defects– Gastrointestinal defects– Gastrointestinal defects
Baby more likelyBaby more likely 2 or more defects2 or more defects
Dangers of second-hand smokeDangers of second-hand smoke http://thechart.blogs.cnn.com/2011/0
3/07/pregnant-women-secondhand-smoke-can-harm-your-unborn-baby/
Extent of risk & harm variesExtent of risk & harm varies
Psychoactive DrugsPsychoactive Drugs
Environmental HazardsEnvironmental Hazards
Father’s exposure to lead, radiationFather’s exposure to lead, radiation
X-ray radiationX-ray radiation
Pollutants & toxin wastesPollutants & toxin wastes
Fertilizers & pesticidesFertilizers & pesticides
Lead-based paints Lead-based paints
PetrochemicalsPetrochemicals Why father’s exposure causes harm?Why father’s exposure causes harm?
Hazards to Prenatal Development
Weight GainWeight Gain 25 - 35 lbs. best reproductive 25 - 35 lbs. best reproductive
outcomesoutcomes
Inadequate & excessive weight gainInadequate & excessive weight gain May affect May affect
Baby birth weightBaby birth weight
Mother’s healthMother’s health
Gestational DiabetesGestational Diabetes
Maternal NutritionMaternal Nutrition
Maternal NutritionMaternal Nutrition
NutritionNutrition Increased need for all nutrientsIncreased need for all nutrients 50% increased need for:50% increased need for:
ProteinProtein IronIron Vitamin DVitamin D CalciumCalcium PhosphorusPhosphorus MagnesiumMagnesium
Water essential Water essential
Strategies for Expectant Mothers
Maternal NutritionMaternal Nutrition
Maternal diet, nutrition, & weightMaternal diet, nutrition, & weight Folic acid & ironFolic acid & iron
Fish: PCBs & mercury levelsFish: PCBs & mercury levels
Maternal ageMaternal age Highest risks: adolescents, over 35 yearsHighest risks: adolescents, over 35 years
Down syndromeDown syndrome
Maternal emotional statesMaternal emotional states
Hazards to Prenatal Development
Exercise During Exercise During PregnancyPregnancy
Decrease duration & intensity as Decrease duration & intensity as pregnancy progressespregnancy progresses
Avoid high-risk activitiesAvoid high-risk activities Warm up, stretch, cool downWarm up, stretch, cool down
Reduce exercise significantly in last 4 Reduce exercise significantly in last 4 weeksweeks
Exercise Exercise notnot linked to preterm birth linked to preterm birth
Strategies for Expectant Mothers
Parental FactorsParental Factors
Paternal factorsPaternal factors Father’s diet & low vitamin CFather’s diet & low vitamin C
Drug use effects on spermDrug use effects on sperm
Smoking – effects of second-hand smokeSmoking – effects of second-hand smoke
Father’s age at conceptionFather’s age at conception Birth defects: dwarfism, Marfan’s SyndromeBirth defects: dwarfism, Marfan’s Syndrome
Hazards to Prenatal Development
PRENATAL TESTSPRENATAL TESTS
Chorionic Villas SamplingChorionic Villas Sampling
INFERTILITY & INFERTILITY & REPRODUCTIVE CHOICEREPRODUCTIVE CHOICE
2.32.3