THE COMPARATIVE ANATOMY OF THE THYROID GLAND IN HUMANS AND RATS

Mota O. M., Serkiz S. R

MORPHOLOGY

Scentific article

The comparative anatomy of human organs and organs of experimental animals is of vital importance today, since further development of medical science is not possible without the experiment. Despite the powerful battery of the latest research methods, experiments involving animals continue to be an integral part of solving many up-to-date problems of modern medicine. Laboratory rats are widely used in biomedical research. For this reason, it is necessary to have profound knowledge of the anatomical and physiological characteristics of the experimental animals, because they have certain features. In view of the continuous growth of thyroid pathology, the comparison of morphological features of human and rat thyroid glands is extremely necessary. In the scientific literature we can find only a small quantity of information about the macroanatomical features of the rat thyroid gland. The publications are mainly devoted to the study of the structural changes in the thyroid gland of the animal during a simulation of certain diseases. Dissection and examination of autopsy thyroid glands with the use of methods of descriptive and quantitative anatomy can give the most detailed information on the similarity and difference in the structure of human and rat thyroid glands. There were studied 48 autopsy human thyroid glands (28 male, 20 female), death of whom was not associated with endocrine system damage and with damage of the neck, and 10 thyroid glands of laboratory rats (5 male, 5 female), which weight was 210-250 g. A detailed study of the anatomical structure of the glands, followed by weighing on electronic scales, and the measurement of the thickness and height of the isthmus of human thyroid glands was held. During examination of human thyroid gland preparations, it was found that in 41 cases (85.4%) the glands had a typical form, which consisted of two lateral lobes and an isthmus. In five cases (10.4%) a pyramidal lobe was found and in two cases (4.2%) the absence of an isthmus was recorded. In both cases of the absence of an isthmus, right and the left lobes of the glands adhered tightly to each other, forming an acute angle between their front surfaces. More polymorphic were thyroid glands that belonged to females. In four cases the pyramidal lobe was found in females, and only in one case – in a male. Both glands with absent isthmus belonged to females. Analysis of the average weight of the thyroid gland makes it possible to conclude that this value is higher in the female population. Irrespective of sex, the weight of the right lobe exceeds the weight of the left lobe by an average of 5.5%. Analysis of absolute values of the thyroid gland weight indicates that its minimum value is 18.1 g and was recorded in the male; the maximum weight is 31.2 g and was recorded in the female. The overall weight of the thyroid gland made 0.028 to 0.041% from the weight of the human body. The thyroid gland of the rat has the appearance of two isolated oval lobes of whitish color that adhere to the trachea rings. Considering its topography and external structure, it is very similar to human thyroid gland. However, the lobes of the rat thyroid gland are not connected by an isthmus. Only in one case the lobes of the gland were larger in size, had a specific butterfly shape and were joined by an isthmus. During weighing it is found that the average weight of the gland in female rats slightly prevails over the weight of the gland in male rats. An analysis of the absolute values of the gland weight indicates that its minimum value is 0.0158 g, and the maximum is 0.052 g. The weight of the thyroid gland makes 0.007-0.021% of the weight of the rat body. At the same time, the weight of the right lobe in all cases dominates over the weight of the left lobe, as it was noted in case with human thyroid glands. Thus, after comparing the thyroid gland of a human and a rat, it has been established that there is a significant morphological similarity between them, although there are certain differences. In case of human thyroid gland, a more prominent polymorphism in the number and structure of lobes is typical. An analysis of linear dimensions of the human isthmus indicates that they overtop in males and are quite variable. The thyroid gland of a rat lacks an isthmus, except one case when it was visualized. The weight of the thyroid gland in females somewhat dominates over the weight of the male gland. Similarly, the weight of the thyroid gland of female rats slightly exceeds the corresponding dimension in male rats. As for the thyroid gland of a person and a rat, the asymmetry of lobes is typical: the right lobe dominates over the left lobe.

thyroid gland, human, rat, comparative anatomy.

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«Bulletin of problems biology and medicine» Issue 2 Part 2 (151), 2019 year, 210-213 pages, index UDK 611.441: 599.23]-019

10.29254/2077-4214-2019-2-2-151-210-213