Bilateral oal thickenings of the surface ectoderm, called nasal placodes, then deelop on each side of the inferior part of the frontonasal prominence.

外胚层表面呈双边增厚鼻板，然后发展为额鼻隆起的下半部分。

The origin of flaps was frontonasal flap in 58 cases, bilobed flap in 67 cases, reforming rhomboid flap in 152 cases, nasolabial flap in 118 cses, forehead falp in 33 cases.

源于额鼻58例，双叶67例，改良菱152例，鼻唇沟118例，额正中33例。