The elastic pharynx

Abstract

In doing a preliminary histologic study of equine pharynx tissue to determine the underlying cause of dorsal displacement of the soft palate (DDSP), I became aware of the role of elastic fibers in this tissue. The study led me to an hypothesis that some cases of DDSP may originate due to a deficiency of elastic fibers in the pharynx. Elastic connective tissue is generally found in organs being acted upon by fluctuating internal pressures. 1 The major sites of elastic tissue in the body are the respiratory and cardiovascular systems. Elastic fibers are composed of elastin which is laid down on a microfibril skeleton. They are synthesized by fibroblasts and smooth muscle cells. 2 These fibers can be stretched up to two and a half times their normal length before recoiling when external pressures are released. 2 The half-life of elastic tissue is thought to exceed the life of the individual. However, enzymal degradation is possible through the action of certain types of proteases, referred to as elastases. 3.4 Elastases are produced by activated neutrophils, monocytes, macrophages and some species of bacteria. 3 In a normal physiological situation, the proteolytic action of these agents is kept in check by deactivating