author(s)
Amer M Hussin and Mustafa AL-Badrani

abstract
This study was designed to focus the light on the histological adaptive changes that occurred in the tissues of adrenal gland of gazelle in response to the mechanism of flight or fight. The study was carried out on 10 adult male gazelle that were collected from Baghdad province in 2017. Immediately after slaughtering, samples of adrenal tissue were collected from these gazelle, fixed with 10% Neutral Buffered formalin and processed for light microscopy. The process of slaughtering represents the fight or flight response. The present study revealed that gazelle had well developed adrenals. The adrenal gland was surrounded by large well developed capsule. The capsule contains ovoid reservoir structures includes primordial undifferentiated cells. These capsular reservoirs replace the exhausted or dead cell in the underlying zones of adrenal with compensatory cells. The capsule was lined by extensive adipose tissue layer. The adrenal gland characterized by a well-developed adrenal cortex. This cortex contains well-developed two zones, the zona glomerulosa and zona fasciculata on account of the small developed zona reticularis. The zona glomerulosa was wide containing two layers: outer dark and inner pale. High mitotic figures and binucleated cells were observed in the first two layers of adrenal cortex. The study concluded that gazelle contains efficient well developed adapted adrenal gland to withstand the predators during fight or flight response. The study declared firstly the presence of undifferentiated primordial cells out and in the lumen of blood vessels. So that, additional way for cellular migration via blood stream was considered for the first time in the present study. The study declared that in gazelle, in spite of the efficient adrenals, its size was adaptively decreased.