above the vocal tract are typically passive. In dorsal gestures, different parts of the body of the tongue contact different parts of the roof of the mouth, but it cannot be independently controlled so they are all subsumed under the term dorsal. That is unlike coronal gestures involving the front of the tongue, which is more flexible. The epiglottis may be active, contacting the pharynx, or passive, being contacted by the aryepiglottal folds. Distinctions made in these laryngeal areas are very difficult to observe and are the subject of ongoing investigation, and several still-unidentified combinations are thought possible. The glottis acts upon itself. There is a sometimes fuzzy line between glottal, aryepiglottal, and epiglottal consonants and phonation, which uses these same areas. Passive articulators The passive are the more stationary parts of the vocal tract that the active articulator touches or gets close to; they can be anywhere from the lips, upper teeth, gums, or roof of the mouth to the back of the throat. Although it is a continuum, there are several contrastive areas so languages may distinguish consonants by articulating them in different areas, but few languages contrast two sounds within the same area unless there is some other feature which contrasts as well. The following areas are contrastive: The upper lip () The upper teeth, either on the edge of the teeth or inner surface () The alveolar ridge, the gum line just behind the teeth () The back of the alveolar ridge () The hard palate on the roof of the mouth () The soft palate further back on the roof of the mouth () The uvula hanging down at the entrance to the throat () The throat itself, a.k.a. the pharynx () The epiglottis at the entrance to the windpipe, above the voice box () The regions are not strictly separated. For instance, in some sounds in many languages, the surface of the tongue contacts a relatively large area from the back of the upper teeth to the alveolar ridge, which is common enough to have received its own name, . Likewise, the alveolar and post-alveolar regions merge into each other, as do the hard and soft palate, the soft palate and the uvula, and all adjacent regions. Terms like pre-velar (intermediate between palatal and velar), post-velar (between velar and uvular), and upper vs. lower pharyngeal may be used to specify more precisely where an