This critical interplay between rapid cell growth and cell death in taste buds and olfactory epithelial cells is critical to maintain normal taste and smell function. SALIVA is the active source of these factors for the taste bud, while NASAL MUCUS in the active source of these factors for the olfactory epithelium. Taste and smell functions are critical to maintain a homeostatic balance: Taste acts as the guardian of what we eat before entering the gastrointestinal tract; smell acts as the guardian of what we breathe into our lungs and respiratory tract. These senses allow us to eat foods and to drink beverages that are both non-toxic and nourishing, and to breathe air that is free from pollutants and contaminants.
Taste buds and olfactory receptor cells are the fastest growing and most rapidly regenerating cells in the body. Taste buds regenerate completely in a 24 hour period. The entire bud is replaced by new cells on a daily basis. This process depends upon stimulation of the basal cells or stem cells of the taste bud by several families of growth factors (carbonic anhydrase VI, adenylyl cyclases,etc), hormones (thyroxine, carbohydrate-active steroids,etc.), trace metals (zinc, copper, magnesium, etc), and many other proteins and substances present IN SALIVA.
There is also rapid control of the regeneration that takes the form of programmed cell death or apoptosis. This process is controlled by several families of “death factors” IN SALIVA including tumor necrosis factor alpha (TNFAlpha), TRAIL, and other cytokines which inhibit growth. This push-pull function is carefully orchestrated by a process which preserves taste function despite other processes which act to inhibit growth or activate cell death, not unlike putting hot pizza into the mouth which burns the tongue or palate. Other factors include oral diseases such as gingivitis, fungal infections, and other processes which inhibit cell growth or activate cell death.
Olfactory epithelial cells are also among the fastest growing and regenerating cells in the body. Olfactory epithelial cells, unlike taste bud cells, regenerate in a variety of time frames, from every 24 hours to days and weeks. This process, as in the taste bud, depends upon stimulation of basal cells or stem cells of the olfactory epithelium by growth factors, hormones, trace metals and other proteins and substances present in the NASAL MUCUS which stimulate growth.
By contrast, there is also rapid control of cell growth through secretion of “death factors” such as TNF alpha, TRAIL, and other cytosine which inhibit growth. As in the taste bud, there is a delicate balance between cell growth and cell death so that olfactory receptor cells can function normally and preserve smell function. As in the mouth, there are many processes which are both physiological and pathological which can either inhibit growth or activate cell death. These processes include inhalation of smoke or toxic gases, catching a cold or some viral illness which produces inflammation and infection in the nasal cavity and other such processes.
The interplay between cell growth and cell death and the roles of saliva and nasal mucus in establishing and preserving this interplay help to explain the importance of these fluids in the taste and smell systems and how important these fluids are in maintaining our normal eating and breathing.
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