by the 5th week, right and left mandibular prominences fuse to form the lower jaws and lips by the 6th week, medial nasal prominence merge to give rise to median portion of the nose, middle portion of upper lip, the philtrum---by the 5 th week, right and left mandibular prominences fuse to form the lower jaws and lips ---by the 6 th week, medial nasal prominence merge to give rise to median portion of the nose, middle portion of upper lip, the philtrum