CELLULAR PHYSIOLOGY OF THE VOCAL FOLDS

The core biologic processes affecting vocal folds are cellular. Although it is rare for a voice professional to understand that vocal health or illness often depends on cellular well-being or dysfunction, the laryngologist must be aware of this relationship. Almost every voice illness can be related either to a tissue change or disorder or to suboptimal or inappropriate functional use of normal or abnormal tissue. A physician must decide whether the tissue is diseased, whether it is being used suboptimally, or both. If the tissue is diseased, treatment should attempt to restore cellular health. Although this article summarizes the information currently available regarding cellular activity, vocal health, and voice disorders, detailed knowledge of these issues is often lacking. The study of vocal health and vocal function has had a decidedly different history than that of many other organ systems. This difference arises in part from the large volume of research performed in this field by speech scientists, speech pathologists, and persons with engineering backgrounds. As these investigators have pioneered research in this field, they have used the tools with which they are most comfortable and experienced. Consequently, there exists a rich foundation in signal processing and acoustical analysis of voice and vocal problems. A substantial foundation is also being developed in other areas of science, such as computer modeling, and in integrated research, as found in the neuromotor field. Voice research at a biologic cellular or molecular level, however, has not been conducted with the same degree of interest. The author hopes that this article will help clinicians understand the biologic and tissue basis for vocal health and vocal pathology and stimulate research in this area. The vocal folds are composed of various tissue types: epithelium, lamina propria, striated muscle, nerves, vascular structures, and cartilage. Although each of these tissue types is important, this article focuses on the epithelium and lamina propria. Pathologic vocal conditions that are related to muscle dysfunction are integrated into the neuromuscular system and often have a neurologic basis for their disorder. Such diseases are beyond the scope of this article. On the other hand, most vocal lesions originate in the lamina propria. The lamina propria is certainly an active and vibrant structure which deserves attention.