HISTOLOGICAL AND MICROMETRIC ANALYSIS OF MYOID CELLS IN THE THYMUS OF ASEEL BIRD

The present study was conducted to investigate the age-related histomorphology and micrometry of thymic myoid cells in healthy TANUVAS Aseel birds. Birds belonging to five age groups (day-old, 4, 8, 18, and 32 weeks) were obtained from the Poultry Research Station, Madhavaram Milk Colony, Chennai. Thymic tissues were fixed in 10% neutral buffered formalin, processed routinely, sectioned at 5–6 µm, and stained using routine histological and special staining techniques. Myoid cells were observed in both the cortex and medulla of the thymus in all age groups. Two morphological types, namely spindle-shaped and oval-shaped myoid cells, were identified, with both exhibiting cytoplasmic striations and centrally placed round nuclei. In day-old birds the spindle shaped myoid cells were noticed, whereas spindle and oval cell types were observed in older age groups. Spindle-shaped myoid cells predominated in younger birds, while oval-shaped cells were more numerous in adult birds. Masson’s trichrome stained myoid cells red, whereas phosphotungstic acid haematoxylin (PTAH) stained them bluish, confirming their identity. Myoid cells were frequently located near Hassall’s corpuscles and showed a characteristic circular arrangement in adult birds. Micrometric analysis demonstrated an age-related increase in the size of both oval- and spindle-shaped myoid cells, with the largest cells recorded in 32-week-old birds. The increased number and size of myoid cells with advancing age suggest their possible association with thymic involution and age-dependent functional changes.