Foundations Practical - Critical Periods

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We have now had a very quick trip through more than 9 months of development in nearly 2 hours. Before we finish it is worth thinking about times in development when things may go wrong.

Environment Effects

These are developmental times (stages) sensitive to insult, be aware of these times, the causes and the potential effects.

Critical periods of development refer to times when genetic or materal effects can impact upon the developmental process. The timing of these effects will impact on different systems at different times.

Human critical periods of development
Conceptus Embryonic development (weeks) Fetal period (weeks)
1
2
3
4
5
6
7
8
9
16
20-36
38
Early zygote.jpg Week2 001 icon.jpg Stage9 sem4c.jpg Stage13 sem1c.jpg Stage15 bf1c.jpg Stage17 bf1c.jpg Stage19 bf1c.jpg Stage23 bf1c.jpg
Neural
Stage2.jpg Heart
Upper limbs
Lower limbs
Ear
Eye
CSt3.jpg Palate
Teeth
Week2 001 icon.jpg External genitalia
Loss Major abnormalities Functional and Minor abnormalities


Links: Embryonic Development | Timeline human development | Movie - Human Development annotated cartoon | Human - critical periods


Systems with long periods of development or complex developmental origins are more susceptible to developmental abnormalities.

  • Which systems will take a long time to develop?
  • Which systems are complex in origin?

Australian Statistics

Australian abnormalities graph allsystem.png Trisomy21male.jpg

Fetal Origins Hypothesis

The Fetal period is also potentially sensitive to maternal effects that impact upon interuterine growth. Along these lines there is growing evidence that low birth weight, and therefore inhibited fetal growth, has postnatal effects on lifelong health outcomes.




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Foundations Practical: Introduction | Week 1 and 2 | Week 3 and 4 | Week 1 to 8 | Week 9 to 36 | Neonatal | Critical Periods | Additional Resources | Quiz


Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers


Cite this page: Hill, M.A. (2024, March 29) Embryology Foundations Practical - Critical Periods. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Foundations_Practical_-_Critical_Periods

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G