Abstract : Volume images of tongue, jaw, velum, nasopharyngeal wall, etc., were acquired by MRI on one French subject uttering a corpus of sustained articulations. Supplementary images of jaw, hard palate, and nasal cavities were acquired by CT. The three-dimensional outlines of these organs are represented by the vertices of triangular surface meshes. Using linear component analysis, the tongue was found to possess five degrees of freedom, including one for jaw movement, and the velum and nasopharyngeal port two degrees of freedom. These parameters can be interpreted in phonetic / biomechanical terms control a linear articulatory model of speech production.