Five primitive tissue lobes grow::a) one from the top of the head down towards the future upper lip; (Frontonasal Prominence):b-c) two from the cheeks, which meet the first lobe to form the upper lip; (Maxillar Prominence):d-e) and just below, two additional lobes grow from each side, which form the chin and lower lip; (Mandibular Prominence)If these tissues fail to meet, a gap appears where the tissues should have joined (fused).