Table 2:

Summary of embryologic steps of the stapedial and ophthalmic systems

Stapedial SystemEmbryo Size (mm)Ophthalmic System
Regression of the second aortic arch; hyoid artery formation (dorsal remnant of the second aortic arch)4–5Primitive maxillary artery as temporary branch; primitive dorsal OA appearance
Elongation of the hyoid artery; annexation of the mandibular artery (first aortic arch) by the hyoid artery (second aortic arch)5–6Primitive hyaloid artery = plexiform channels; primitive ventral OA appearance
Cranial growing of the hyoid artery (SA) passing into the middle ear (crus of the stapes)7–14Formation of primitive hyaloid and common ciliary arteries
Maximum development of the SA; extension of the 2 branches of the SA, supraorbital and maxillomandibular16–19Migration in origin of the primitive ventral OA; regression of the primitive dorsal OA; formation of the anastomotic ring
Regression of the transosseous (superior orbital fissure) segment of the supraorbital branch20–24Ventral interruption of the anastomotic ring; annexation of the supraorbital branch by the OA