Embryological Development

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Embryological Development

• Ch 38.2
• Page 698 Early Animal Development

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I 1.Development

• Cell division
• Growth
• Differentiation
• From embryonic tissues to
• Specialized tissues organs

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Embryological Development
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Meiosis in the Gonads
Sperm
Meiotic cell division
Egg
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2. Fertilization of egg in fallopian tube by
sperm
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3. Zygote formation

• Fertilized
• Egg
• 2n Chromo-some
• Union of sperm egg

1N Sperm
1N Egg
2N Zygote
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4.Implantation of egg in uterus
Fertilization
Implantation
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5. Cleavage Splitting by mitosis
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3rd Cleavage 8 balls

• cleave
• To cut
• Division of embryonic tissue
• From the zygote to a
• Multi-ball stage

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6.Blastula

• Hallow ball
• After cleavage
• Signals the onset of
• Differentiation of embryo

5th day blastocyst
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Hallow Ball or Blastula
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7. Gastrula

• Infolding of cells
• Follows
• Blastua stage
• Forms ?
• the digestive tract

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7.Differentiation

• differ
• Specialization of embryonic tissue
• Orders cells into tissues organs

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Experimental Studies
Cell Differentiation
Diffe
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Embryonic Development the gray crescent
Diffe
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9.Three cell layers
Ecto Skin nervous

• Ectoderm outer
• Mesoderm middle
• Endoderm inner

Meso Muscles Bones
Endo Digest. Bladder
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Neural Tube Development

• Neural nervous
• tube spinal column

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10-11.Mammal fetus uterus

• Placenta
• uterine lining
• Umbilical cordconnects to uterus
• Amnion sack with fluid
• Fetus baby

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Placenta Umbilical Cord
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Fetal Mothers Blood

• Mothers Blood is
• Separate from the baby!
• What passes across the placenta?
• Food, drugs, wastes, alcohol, oxygen
• What stays behind?
• Red blood cells
• How are wastes removed?
• Diffuse across the placenta (CO2, etc.)

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Marsupial Pouch
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Fetus Development
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4 Week Embryo
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Ultra sound scanning
http//www.pbs.org/wgbh/nova/miracle/windows.html
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Amniocentesis

• Sampling the amnionic fluid
• Check for chromosome abnormalities

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First Trimester
Week 1 Week 12
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Month One

• Limb buds appear.
• Embryo resembles tadpole.
• Heart and lungs begin to form.
• Towards the end of the first month, the heart
  begins to beat.
• Neural tube develops.
• About ½ inch long
• Weighs less than an ounce.

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Month Two

• All major organs and systems are formed, but not
  developed.
• Brain waves
• Placenta begins work
• Ears, ankles, wrists
• Eyelids form (sealed shut)
• Fingers and toes
• About 1 inch long
• Weighs less than an ounce

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Month Three

• Now called a fetus
• Fingers and toes have soft nails
• Mouth has 20 buds which will become teeth
• Can hear babies heartbeat for the first time
  using a Doptone
• Body organs will continue to mature
• 2 ½ inches long
• Weighs a little over an ounce

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Second Trimester
Week 12 Week 24
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Month Four

• External sex organs become distinctly male or
  female.
• Moves, kicks, swallows
• Skin is almost transparent
• Eyebrows eyelashes appear
• 6 to 7 inches long
• Weighs about 5 ounces

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Month Five

• Fetus becomes more active turns from side to
  side and sometimes head over heels
• Activity can be felt by mother
• Sleeps and wakes at regular intervals
• Rapid growth
• 8 to 12 inches long
• Weights ½ to 1 pound

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Month Six

• Skin is red and wrinkled
• Skin is covered with fine, soft hair for
  protection (lanugo)
• Eyelids open
• Finger and toe prints visible
• Active dream states
• 11 to 14 inches long
• Weighs 1 to 1 ½ pounds

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Third Trimester
Week 24 Week 40
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Month Seven

• Fetus can blink and suck its thumb
• Kicks and stretches
• Responds to light and sound
• About 15 inches long
• Weighs about 3 pounds
• Protective waxy substance called Vernix covers
  skin

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Month Eight

• Rapid brain growth continues
• Bones of the head are soft and flexible
• Hair covers the head
• Lungs may still be immature
• Doesnt actually breathe hiccups and makes
  breathing movements
• Sleeps 90-95 of the day
• About 18 inches long
• Weighs about 5 pounds

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Month Nine

• Considered full term
• Lungs are mature and ready to work on their own
• Most lanugo (fine, soft hair covering the skin)
  is gone
• Gains ¼ to ½ a pound a week
• Moves into position to be born
• 19 to 21 inches long
• Weighs 6 to 9 pounds