Development of the external form up to the end of the embryonic period
The brain significantly increases in volume. The head bends further ventrally. At S14, the maximal bending is achieved. The telencephalon now lies on the umbilicus. At S17, with the development of the cartilaginous vertebral column, the embryo becomes increasingly straightened out. It remains only slightly bent ventrally by the end of the embryonic period. However, the head still constitutes almost half of the embryonic body.
By S11, the development of the face begins, with the formation of the first facial prominences. At the end of the embryonic period, the eyes are already in a frontal position, the auricles of the ears are present, and the nose and the mouth are formed.
From S12, the limbs develop according to a cranio-caudal gradient of maturation: first the buds of the upper limbs, then those of the lower limbs (S13). By the end of the embryonic period, fingers and toes are already differentiated.