This dissertation examines the phonetic and phonological functioning of the supraglottal part of the larynx, the epilarynx, from an articulatory-physiological perspective. The central thesis is that, through constriction, the epilarynx physically couples the vocal folds to the supralaryngeal vocal tract. This basic principle is important in explaining a wide range of speech phenomena, such as the mechanism of glottal stop, creaky and harsh (“constricted”) phonation, interaction between vocal fold state and lingual state, and the coordination of phonatory and vowel quality as voice quality, which underlies many register-like patterns. Furthermore, oscillation of the epilarynx and (typically) the vocal folds below is the basis for “growl”, which is demonstrated to have numerous expressions in speech, both phonetically and phonologically. The thesis is explored by detailed examination of three functions of the epilarynx: (1) epilaryngeal vibration, (2) epilaryngeal interaction with the vocal folds, and (3) epilaryngeal interaction with the supralaryngeal vocal tract. Phonetic evaluations of these functions include physiological, theoretical, and taxonomic considerations, imaging data (obtained with laryngeal and lingual ultrasound, simultaneous laryngoscopy and laryngeal ultrasound, and videofluoroscopy), and computational modeling. These phonetic evaluations are then taken as the basis for a model of lower vocal tract phonology. Traditional models of such sounds do not accommodate the epilarynx. Rather than positing new distinctive features, an alternative approach is taken. A theoretical model is proposed which is framed in terms of “phonological potentials”, which are the biases associated with physical principles that underlie the formation of phonological systems and patterns. In the context of epilaryngeal function, the phonological potentials are expressed in terms of synergistic relations amongst gross physiological states that either support or hinder epilaryngeal constriction. These biases are argued to exert an articulation-based typological skewing on phonemic systems and patterning, and numerous cases are examined in support of this claim. / Graduate / 0290