Light and electron microscopic study of thyroid gland in the African giant rat,cricetomys gambianus,waterhouse

The morphology of thyroid gland of african giant rat (cricetomys gambianus),a wild cricetid rodent has been described. histologically,the morphological components of the thyroid (follicular cells,c-cells,colloid and interstitial tissue) were similar to that of some rodents like mice,rats,hamsters and guinea pig. however,peripheral vacuoles were rare in the colloid. most of the follicular epithelia were predominantly lined by cuboidal and columnar cells,while squamous cells were uncommon. the mean internal follicular diameter of the small,medium and large round follicles were 62.4±0.7μm,130.5±08μm and 176.6±0.6μm,respectively. the follicular epithelial height was 3.8±0.06μm in flat cells,6.5±0.04 μm in cuboidal and 8.3±0.08 μm in columnar cells. ultrstucturally,apical pseudopods and microvilli were commonly observed. large intraepithelial capillaries were also encountered. parafollicular were located basally in cluster of 2 or 3 cells. they contained abundant electron dense granules within highly elongated cytoplasmic processes. the morphological features suggest that the thyroid gland is very active in response to the feral habit of the rat and the harsh tropical environment. © 2014 zoological society of pakistan.