K12 Week 4

From Embryology

Week 4

In week four of embryo development organs begin to form within the embryo and surface features begin to form.

This movie of early embryo development from week 3 onward shows the early nervous system forming.

Embryo (right) back view with head to top (left) and tail to bottom (right).

yolk sac (left, large ball shape)

The movie also shows as the embryo grows and folds it increases in size compared to the yolk sac.


K12 Links: Start Here | Week 1 | Week 2 | Week 3 | Week 4 | Week 5 to 8 | Arms and Legs | Heart | Fetus | Brain Growth | Eyes and Ears | Animal Development Times | Humans and Animal Embryology | Comparative Embryology | Thalidomide

Embryo at 4 weeks

Stage13 surface bulges.jpg

(Carnegie stage 13)

Stage13 sem1b.jpg

  • On the embryo surface limb buds can be seen where the future arms and legs will form.


K12 Links: Start Here | Week 1 | Week 2 | Week 3 | Week 4 | Week 5 to 8 | Arms and Legs | Heart | Fetus | Brain Growth | Eyes and Ears | Animal Development Times | Humans and Animal Embryology | Comparative Embryology | Thalidomide

Cite this page: Hill, M.A. (2019, January 19) Embryology K12 Week 4. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_Week_4

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G