Prenatal Development
Conception
Stages
•
(NOT Trimesters)
Germinal/Blastocyst/Zygote Stage
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Begins with Conception and ends with implantation
0-(8-14) days-first two weeks
Egg and sperm meet (Zygote)
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travel down the fallopian tube to the uterus and implants
~ 3-4 days after conception
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Differentiation of cells begins
eventually becoming the blastocyst: embryonic disk and
trophoblast
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Amnion, Chorion, & Placenta
30-50% of all conceptions end
Death??
12-17 conceptions are male to 1 female-WHY?
Conception
Stages
•
(NOT Trimesters)
Embryonic Period
–
Begins with implantation and ends with
ossification (calcification) of the bones.
2-8th week
First two (or so) weeks: Embryonic disk
forms 3 layers:
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Ectoderm-Nervous system & skin
Mesoderm-Muscles, skeleton, circulatory system
Endoderm-digestive system, lungs, urinary tract,
glands
Second month: systems become more
complex & defined
Stages
•
(NOT Trimesters)
Embryonic Period (cont)
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Organogenesis complete (heart beat)
Skeleton complete
Sexual differentiation between 7-10 weeks
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Female unless presence of presence of Gene,
SRY, is present on the short arm of the Y
chromosome
Differentiation of gonads into testes
25-50% of all pregnancies terminate
spontaneously
•
Death?
Stages
•
Fetal Period
–
•
(NOT Trimesters)
Begins with ossification of the bones and ends with
birth
– Purpose is for growth (in size and complexity) and
connections
– 9-38 weeks +/- 2 weeks
– 5% born on due date
– Less than ¼ conceptions make it to delivery
– From last menstrual period→40 weeks
– At Birth 106 males to 100 females
– But, at 1 year 96 males to 100 females
Page 88-92 of your text- pics BUT
DON’T FOCUS ON TRIMESTERS.
FOCUS ON PERIODS
Sonograms
Critical Period
• What is it?
• Embryonic Period??
Critical Period
• Embryonic Period
– Cell differentiation is occurring,
organogenesis, skeleton forming, timing is all
genetically programmed.
Development and Growth
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Cephalocaudal- Head to toe
Proximal-Distal- Inside to out
At birth approximately 19-21 inches
At birth approximately 6-8 ½ lbs
7 ½ white> Af Am>Native Americans &
Latino Americans
Group Exercise
Group Exercise
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The mother can feel movement
Implantation occurs
The groundwork for all body structures is laid.
The placenta is connected to the developing organism
by the umbilical chord
The baby has reached the age of viability
A mass of cells drifts down and out of the fallopian tubes
and attaches itself to the wall of the uterus
The ectoderm, mesoderm, and endoderm are formed
Organs, muscles, and nervous system start to become
organized and connected
The embryonic disk (blastocyst) is formed
The developing organism is sensitive to sound and light
Group Exercise
• The mother can feel movement (fetal)
• Implantation occurs (germinal)
• The groundwork for all body structures is laid
(embryonic).
• The placenta is connected to the developing organism
by the umbilical chord (germinal)
• The baby has reached the age of viability (fetal)
• A mass of cells drifts down and out of the fallopian tubes
and attaches itself to the wall of the uterus (germinal)
• The ectoderm, mesoderm, and endoderm are formed
(embryonic)
• Organs, muscles, and nervous system start to become
organized and connected (fetal)
• The embryonic disk (blastocyst) is formed (germinal)
• The developing organism is sensitive to sound and light
(fetal)