Foundations Practical - Week 9 to 36

From Embryology

The Fetal Period

Growth and organ differentiation.

The fetal period is about continued differentiation of organs and tissues, most importantly this period is about growth both in size and weight.

Fetal growth icon.jpg

Fetal Development - Page with an animation covering the fetal period showing changing proportions, not size, of the fetus.

The cartoon shows changes in the relative proportions of head and body and growth of the limbs, it does not show the overall growth in size.

Many different systems formed in the embryonic period (organogensesis) grow and differentiate further during the fetal period and do so at different times.

For example, the brain continues to grow and develop extensively during this period (and postnatally), the respiratory system differentiates (and completes only just before birth), the urogenital system further differentiates between male/female, endocrine and gastrointestinal tract begins to function.

Finally consider the systems (for example respiratory, cardiac, neural) that will still not have their final organization and function determined until after birth.

Human 12 Week 4D

Ultrasound12wk 3D image.jpg

Fetal Growth

  • First Trimester (1 - 12 weeks) - embryonic and early fetal
  • Second Trimester (13 - 24 weeks) - organ development function and growth
  • Third Trimester (25 - 40 weeks) - organ function and rapid growth


Embryo/Fetus Size Comparison

Size comparison embryo-fetus.jpg

This is an enlarged image of the actual size comparison shown in the introduction of the Embryonic stage 13, 23 and Fetal stage 10 week 40mm.


Fetal size change.jpg


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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 28) Embryology Foundations Practical - Week 9 to 36. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Foundations_Practical_-_Week_9_to_36

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