Abstract
<jats:p>The main aspects of the morphological changes of the mesenteric arteries in COVID-19 are qualitative reactions in the tissue of the blood vessel wall, which proceed with the accumulation of the following intermediate products. In particular, COVID-19 infection is manifested by the accumulation of acidic mucopolysaccharides, which belong to the family of hydrophilic glycosaminoglycans, which create an acidic environment in the wall of the mesenteric arteries. It is precisely to determine this qualitative reaction that the SHIFF reagent is used. As a result of the action of iodide acid contained in the SHIFF reagent, it is manifested by the staining of acidic mucopolysaccharides in a blue color. It is in the anatomical layers of the mesenteric arteries that the largest concentration of SHIFF-positive structures is found along the subendothelial and medial layers (muscular and fibrous structures) with uneven borders. This is one of the morphological markers indicating the development of metabolic dysfunction in the vascular walls against the background of COVID-19 and the lack of the hyaluronidase enzyme, which normally breaks down mucopolysaccharides.</jats:p>