Early Embryonic Development: Day 1 - 56

By hannah_12334

  • Day 1

    Stage 1, fertilization, the zygote is formed following fertilization

  • Day 2

    Stage 2, the morula is formed

  • Day 3

    Blastocyst is formed
  • Day 4

    Day 4

    Stage 3, the blastocyst hatches (the zona pellucida is lost)

  • Day 5

    Late secretory phase, the blastocyst is free-floating

  • Day 6

    Stage 4, the initial phase of the implantation process
  • Days 7-12

    Days 7-12

    Stage 5, implantation (where the embryo adheres to the wall of the uterus)

  • Days 13-15

    Sage 6, chorionic cavity (help begin the functional units of the placenta)
  • Days 15-17

    Days 15-17

    Stage 7, gastrulation is continuing as the cells migrate from the epiblast, continuing to form the mesoderm

  • Days 17-19

    Stage 8, the neural groove and folds are first seen, neural neurogenesis
  • Days 19-21

    Days 19-21

    Stage 9, somites have begun to form and number between 1 to 3 somite pairs

  • Days 22-23

    Stage 10, neural folds in region developing brain, heart begins to beat
  • Days 23-26

    Days 23-26

    Stage 11, shows key features of heart tube and neural plate, peristaltic flow begins
  • Days 26-30

    Days 26-30

    Stage 12, neural tube continues to close by day 27 neural tube is usually completely closed. Stage 13 starts day 28.

  • Days 28-32

    Stage 13, the embryos CRL is about 4-6 mm, neural tube continues to close
  • Days 31-35

    Days 31-35

    Stage 14, the heart and the circulatory system takes shape ( a bulge indicates where the heart is developing)

  • Days 35-38

    Stage 15, the uterus begins to grow slightly, hormone levels rise rapidly, the neural tube is still under construction
  • Days 37-42

    Days 37-42

    Stage 16, fetuses body takes on C shape, small buds that will eventually become the arms and legs are visible
  • Days 42-44

    Days 42-44

    Stage 17, the arm and leg buds become longer, the facial features start to show such as the eyes, nose, and ears

  • Days 44-48

    Stage 18, heart and brain become more complex during this time, arm and leg joints are starting to form too
  • Days 48-51

    Days 48-51

    Stage 19, eyes, ears, and nose and cheeks are more visible at this time, the baby also is developing a permanent set of kidneys
  • Days 51-53

    Days 51-53

    Stage 20, the tadpole-like form at the bottom of the fetus is now gone, fingers and toes continue to develop as they are still somewhat webbed
  • Days 53-54

    Days 53-54

    Stage 21, fetus taste's buds begin to form as the baby prepares for its first meal

  • Days 54-56

    Stage 22, eyelids develop, an upper lip is forming, the beginnings of a neck of starting