The examinations were conducted on five brown bears of both sexes and different age and one polar bear male, 30 years old. Performing a section along the whole limb carried out the investigation of the thickness of the limb arterial walls. Specimens of the arteries were taken at a distance of 10 mm away from each other. This helped to establish the precise thickness of the arterial wall as well as determine what kinds of components are responsible for its structure. The presence of strong thickenings in the bear’s median artery, in the distal part of his antebrachium and in his metacarpus was proved. In the cranial tibial artery and saphenous artery the thickenings in question appear in the distal part of the crus. Inside those thickenings there are large gatherings of the circular muscle cells and across its small part there is a complete lack of the elastic fibres in the middle coat. Such a structure of the arterial wall makes it possible to regulate the degree of closure of the vessel’s lumen and helps to adjust the blood flow in accordance with the requirements and temperature of the environment.

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