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

外层表面呈边卵圆形增厚形鼻板，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.

皮瓣来源于额鼻皮瓣58，皮瓣67，改良菱形皮瓣152，鼻唇沟皮瓣118，额正中皮瓣33。