External: 4-12 pairs of somites; fusion of neural folds is imminent or in progress; the opic sulcus may have appeared; pharyngeal arch 1 begins to be visible on the surface.
Internal: The cardiac loop is appearing; the laryngeotracheal sulcus develops; the intermediate meso-derm becomes visible.
Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.
Published by Carnegie Institution of Washington, Publication 637. 1987.
Stage 10 (PDF 582 KB)
QUESTION: What is the state of the neural folds?