MORPHOMETRIC CHARACTERIZATION OF THE STRUCTURAL COMPONENTS OF THE THYROID GLAND UNDER CONDITIONS OF MODELED THERMAL SKIN INJURY

Abstract

The key organ of the peripheral endocrine system, the thyroid gland, shows the ability to adapt and restructure at diff erent levels of structural and cellular organization under the infl uence of various factors. The aim of the study was to determine morphometric changes in the parameters of the structural components of the thyroid gland. The experiment was modeled on 42 male laboratory mature white rats. The burn was modeled with copper plates heated in water at a temperature of 97-100 °C. The size of the aff ected area was 20 % of the animal’s body area, which, according to the current classifi cation, corresponds to a seconddegree burn. Changes in various parameters were studied by morphometric analysis of the obtained histologic sections. Statistical processing of digital data was carried out using the software «Excel» and «STATISTICA» 10.0 using parametric and nonparametric methods of data evaluation. Morphometrically, it was found that the organ contains follicles of three types – large, medium and small, and their quantitative ratio is 1.4: 4,7: 3,9. It was found that the average value of the area of a small follicle is (2342.5498.43) μm2, medium – (3722.53130.44) μm2, large – (5733.77203.67) μm2. The average value of thyrocyte height is (11.430.41) μm. The follicular- colloid index of the thyroid gland of intact animals is the highest for small follicles and is 1.940.08, for medium follicles – 1.81 0.04 and for large follicles – 1.730.05. The average value of the colloid accumulation index for small follicles is the lowest and is 2.600.12, for medium follicles – 4.18 0.19, and for large follicles – 6.270.29. At the light- optical level, on day 7 of the experiment, an increase in the number (1.58 times (p<0.001) compared to the intact index) of large follicles was noted, which are located mainly on the periphery of the lobules and fi lled with a compacted colloid. A decrease in thyrocyte height (1.29 times (p<0.001) compared to the normal value), a signifi cant decrease in the follicular- colloid index and an increase in the colloid accumulation index detected in the early toxemia stage indicate a decrease in functional activity in the organ, disruption of adaptive processes in it and the onset of destructive changes. At the later stages of burn injury (14 and 21 days of the experiment), against the background of a statistically signifi cant (p<0.001) increase in endogenous intoxication, there is a development of deep destructive changes in thyrocytes, organ vessels, proliferation of connective tissue layers, impaired synthesis and secretion of hormones. These conditions are manifested by the dominance of large, overstretched follicles in the parenchyma of the thyroid gland, lined with fl at, degenerating thyrocytes, the height of which at day 21 is 3.31 times signifi cantly (p<0.001) lower than the intact value; a statistically signifi cant decrease in the follicular- colloid index; a signifi cant increase in the colloid accumulation index, as well as a signifi cant deviation from the normal level of pituitary- thyroid system homones, which indicates organ hypofunction.