child chapter 2 prenatal 2.2

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


Zygote Zygote

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


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


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


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


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


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


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?


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


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 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


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


PRENATAL TESTSPRENATAL TESTS

Chorionic Villas SamplingChorionic Villas Sampling

INFERTILITY & INFERTILITY & REPRODUCTIVE CHOICEREPRODUCTIVE CHOICE

2.32.3

child chapter 2 prenatal 2.2

Health & Medicine

prenatal development

conception period

prenatal week

prenatal developmentthreats

prenatal periods

prenatal development

zygote zygote

egg sperm