top of page

DEVELOPMENT WEEK 4

3D Models

Each embryo model below shows one day of development. These models are an approximation of what an embryo should look like at each day. The models are interactive and can be viewed full screen to see details more clearly.

Rotate: click + drag

Zoom: scroll

Move: shift + click + drag

Click on the annotations to learn more about specific structures

Day 22
Day 23

Main External Characteristics of Day 22-23

  • Carnegie stage 10

  • 4-12 somites

  • Length: 2.0-3.5mm

  • Embryo is straight or slightly curved

  • Neural tube is forming or has formed opposite somites, but is widely open at the rostral and
    caudal neuropores

  • First and second pairs of pharyngeal arches
    are visible

​

Day 24
Day 25

Main External Characteristics of Day 24-25

  • Carnegie stage 11

  • 13-20 somites

  • Length: 2.5-4.5mm

  • Embryo is curved owing to head and tail folds

  • Rostral neuropore is closing

  • Otic placodes are present

  • Optic vesicles have formed

​

Day 26
Day 27

Main External Characteristics of Day 26-27

  • Carnegie stage 12

  • 21-29 somites

  • Length: 3.0-5.0mm

  • Upper limb buds appear

  • Rostral neuropore is closed

  • Caudal neuropore is closing

  • Three pairs of pharyngeal arches are visible

  • Heart prominence is distinct

  • Otic pits are present

​

Day 28

Main External Characteristics of Day 28-30

  • Carnegie stage 13

  • 30-35 somites

  • Length: 4.0-6.0mm

  • Embryo has C-shapes curve

  • Caudal neuropore is closed

  • Four pairs of pharyngeal arches are visible

  • Lower limb buds appear

  • Otic vesicles are present

  • Lens placodes are distinct

​

bottom of page