Human speech makes possible the expression and communication of thoughts, needs, and emotions through vocalization in the form of words. It is a process whose specialized adaptations differentiate it from the mere making of sounds--a capacity humans share with most animals. In addition to the capacity for laryngeal production of sound (which some animals also possess), speech requires a resonance system for modulation and amplification of that sound and an articulation process for the shaping of that sound into the communally established word-symbols of meaning that constitute the language of a given culture. (Dean Edell) The use of language is made possible by certain cerebral functions: the formation of thoughts; the comprehension, storage, and recall of words; and the selection of words to express the thoughts and the arrangements of these words in a sequence or organization that constitutes (or attempts to constitute) intelligible communication.
             The speech process involves the speech centers of the brain, the respiratory center in the brain stem, the respiratory system, the chest cavity, the structures of the larynx, the pharynx, the nose and nasal cavities, and the structures and parts of the mouth and related facial muscles. There are three identified speech areas. The supplementary motor cortex, on the very top of the left frontal lobe, involves the process of vocalization itself. Broca's area, lower down at the back of the left frontal lobe, appears to involve functions of articulation, vocabulary, inflection, and word sequence. Wernicke's area is mainly the posterior part of the left temporal lobe, with parts of the parietal area; any large destruction of this area results in the loss of the capacity for meaningful speech but not the loss of sound production.
             The speech process starts with an expiration of air, produced by the respiratory mechanisms of lung expansion and contraction: the downward and upward movements of ...