Pregnancy, Fetal Development,

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Pregnancy, Fetal Development, Genetics

• Chapter 20

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Objectives

• Describe the process of fertilization
• Describe the major events of cleavage
• Distinguish between an embryo and a fetus
• Describe the major events of the fetal stages of
  development

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Development

• Gradual changes of physical and physiological
  characteristics from conception to death

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LIFE

• Life originates from a single cell the size of a
  period at the end of a sentence to trillions of
  cells organized into tissue, organs, and organ
  systems.
• Differentiation is due to genetic instructions

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Fertilization

• Takes dozens of sperm working together to
  penetrate the ova because the ova has a shell
  (corona radiate) that is difficult to get through

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Days 0 - 9
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Zygote
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1st Cleavage
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2 Cell Stage
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4 Cell Stage
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Morula
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Early Blastocyst
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Blastocyst

• The penetration of the blastocyst into the
  uterine wall is referred to as implantation

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Implantation
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1st trimester

• 1st 3 months
• After implantation occurs, a cell mass form an
  Amniotic cavity around the zygote and fills with
  fluids as the zygote develops
• During zygote development, a placenta or tube
  connects the zygote to the uterine wall.
• The rudiments of all major organ systems appear

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4 weeks
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4 Weeks
By the end of the first month, the embryo is
about 1/10 of an inch long. The heart, no larger
than a poppy seed, has begun beating.
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Gastrulation

• 14-16 days after fertilization
• Germ layers are created (p. 546)
• Ectodermal nervous system, portions of special
  sensory organs, epidermis, hair, glands of skin
  and linings of the mount and anal canal
• Mesodermal myo tissue, bone tissue, bone
  marrow, blood, blood vessels, connective tissues,
  internal reproductive organs, kidneys, epithelial
  linings of the body cavities
• Endodermal epithelial linings of the digestive
  tract, respiratory tract, urinary bladder and
  urethra

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8 weeks
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Month 2
The embryo grows to 1 inch long and has distinct,
slightly webbed fingers. Veins are clearly
visible. The placenta is already nourishing the
baby through the umbilical cord. The heart has
divided into right and left chambers.
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12 weeks
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Month 3
Starting at eight weeks, the baby is called a
fetus. By the end of the first trimester, the
fetus is 2 1/2 to 3 inches long and is fully
formed. He has begun swallowing and kicking. All
organs and muscles have formed and are beginning
to function.
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2nd trimester

• Development of organs and organ systems
• Fetus looks distinctly human

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16 weeks
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Month 4
The baby is covered with a layer of thick, downy
hair called lanugo. The heart beat can be heard
clearly. This is when many mothers feel their
baby's first kick.
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20 weeks
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Month 5
 A protective coating called vernix caseosa
begins to form on the baby's skin. If you have an
ultrasound, you might see him sucking his thumb.
By the end of this month, the baby will be 8 to
10 inches long and weigh almost a pound.
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24 weeks
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Month 6
Tiny eyebrows and eyelids are visible. The baby's
lungs are filled with amniotic fluid, and he has
started to practice breathing movements. The baby
can hear sounds, talking and singing, outside the
uterus.
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28 weeks
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Month 7
 By the end of the seventh month, the baby weighs
about 2 1/2 pounds and is about 15 inches long.
His body is well formed. Fingernails cover his
fingertips. He may try to turn toward a source of
bright light.  
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3rd trimester

• Final 3 months!!!
• Rapid fetal development
• Most all of the major organs become fully
  functional
• Usually the largest weight gain

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32 weeks
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Month 8
 By the end of the eighth month, the baby weighs
about 5 1/2 pounds. Hearing is fully developed.
Studies have shown that babies respond better to
high-pitched voices.
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36 weeks
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Month 9
The baby is a around 6 to 9 pounds and measures
somewhere between 19 and 22 inches long. As a
baby becomes more crowded, they move around less.
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40 weeks
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Fetal Circulation

• Fetal hemoglobin has a greater O2-carrying
  capacity than adult hemoglobin
• Umbilical vein carries nutrient rich blood from
  placenta to fetus
• Ductus venosus conducts ½ the blood from
  umbilical vein directly to inferior vena cava,
  bypassing the liver
• Foramen ovale conveys much blood entering the
  R. atrium from inferior vena cava, thru the
  atrial septum and into the L. atrium, bypassing
  the lungs
• Ductus arteriosus conducts some blood from the
  pulmonary trunk to the aorta, bypassing the lungs

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Milk Secretion

• Human milk content
• 4.5 fat
• 1.1 protein
• Cows milk content
• 3.5 fat
• 3.1 protein

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Genetics

• Chromosome (23 pairs)
• Autosomes pairs 1-22
• Sex determination 1 pair
• XX female
• XY male
• X chromosomes carry 750 genes
• Y chromosomes carry 78 genes
• Genes the working subunits of DNA

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Genes

• Alleles variant forms of a gene
• Homozygous an individual who has 2 indentical
  alleles of a gene
• Heterozygous a person with 2 different alleles
  carrier
• Dominant vs. Recessive
• Dominant alleles can mask recessive alleles

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Hereditary

• Punnett Squares uses logic to deduce the
  probabilities of inheriting particular genotypes
  in offspring

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Lifes Greatest Miracle

• Please remember to answer your questions during
  the film, these are participation points!
• The movie