Fetal Development and Genetics

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Chapter 10

• Fetal Development and Genetics

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Fertilization

• Haploid number of chromosomes unite
• Ova viable for 24 hrs- Sperm 72 hrs
• Fertilization takes place in ampulla
• Male determines sex

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Preembryonic

• Zygote-moving toward uterine cavity
• Morula- 16 cells-to uterus 72 hrs after
  fertilization
  
• Blastocysts
• Trophoblast-implantation occurs, cells
  differentiate into embryo and membranes.
  
• Does she know she is pregnant?

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Embryonic

• Day 15 after conception to 8th week
• Basic structures completed
• Umbilical cord- 2 arteries one vein -Whartons
  jelly
  
• Amniotic fluid-movement- trauma-temp.
• Medium to practice.
• Alterations in volume

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Function of the Placenta

• Materials for growth, energy and removal of
  waste
  
• Maternal and fetal blood do not mix
• Some viruses can pass through the placenta
• Produces hormones- hCGpregnancy test
• hPL-causes insulin resistance
• Progesterone- maintains pregnancy
• Relaxin- maintains pregnancy- relaxes ligaments
  and cervix
  

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Fetal Circulation

• O2 carried by vein to vital organs
• Hepatic capillaries to ductus venosus to inferior
  vena cava to foramen ovale to left atrium left
  ventricle and ascending aorta.
  
• Blood with most O2 to brain.
• Deoxygentated blood from superior vena cava to
  rt. atrium rt ventricle to pulmonary artery

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Changes after Birth

• Foramen Ovale-closes with first gasp
• Ductus Venosus- closes with clamping of cord
• Ductus arteriosis closes due to increase in
  arterial O2 levels
  
• Adult circulation-rt atrium to pulmonary artery
  to lt atrium to lt. ventricle to body

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Genetics

• Humane Genome Project
• Ethics vs. Science
• Mutation- any change in gene structure
• Karotype- analysis of individuals genes
• Homozygous-identical
• Heterozygous-different

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Chromosomal Abnormalities

• Problem with number of genes
• Trisomies- Down 3 copies of gene 21
• Common features- cardiac condition
• Kleinfelter Syndrome- effects males extra X
• Trisomies 13 and 18 have very poor prognosis
• Monosomies- Turners Syndrome

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Structural Abnormalities

• Deletion or translocation
• Cry of the Cat- missing piece of 5
• Fragile X- Mother is carrier
• Affects more males
• Most common cause of mental retardation.

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Autosomal Dominant

• Abnormal gene pair causes disease
• Dominates normal gene
• 50 chance of being affected
• Having mutation does not mean you will have
  disease
  
• ExamplesHuntington disease, BRCA,
  hypercholesterolemia

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Autosomal Recessive

• Mutation of two genes (homozygous)
• Seen among ethnic groups
• Single gene abnormal may not have disease
• Effects males and females
• 25 risk of transmission to newborn
• 50 risk of becoming carrier
• ExampleSickle cell, thalasemia, phenylketonuria

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X Linked

• Gene mutation on X chromosome
• Usually only men effected
• Daughters of affected males are usually carriers.
  
  
• Females 50 chance of passing to sons.
• Examplehemophilia, muscular dystrophy, color
  blindness

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Nursing Management and Genetics

• Obtain genetic history
• Importance of preconceptual counseling
• Does client need referral
• Genetic counselors help couple make decision.
  Give accurate information regarding risks.
  
• Relationship of trust and respect