M. V. Shayhelislamova - Dr.Sc. (Biol.), Professor, Department of Anatomy, Physiology and Human Health, Kazan Federal University (Volga region). E-mail: bettydn@mail.ru N. B. Dikopolskaya - Ph.D. (Biol.), Associate Professor, Department of Anatomy, Physiology and Human Health, Kazan Federal University (Volga region). E-mail: bettydn@mail.ru G. G. Kayumova - Post-graduate Student, Department of anatomy, physiology and human health, Kazan Federal University (Volga region). E-mail: guzelka1003@yandex.ru