Assessment of the Morphological Development of the Thymus in Turkey (Meleagris gallopavo)

The post hatch (PH) development of the thymus gland in turkey (Meleagris gallopavo) was studied from day (D) 1 post hatch to day 140. The thymus gland composed a bilateral chain of 5-8 irregular elliptical lobes that varied in size from cranial to caudal lobes, and from pale red to pink in color. Histologically, in all ages the thymus was enclosed by a connective tissue capsule from which septa penetrated and divided the stroma into incomplete lobules. Each lobe consisted of a central medulla surrounded by a lobulated cortex. At D 1 PH, lymphocytes and few granulocytes dominated the parenchyma with classical Hassall’s corpuscle in the medulla. By D 14, reticular structures were observed in the medulla, and many vacuoles were associated with it by D 28. At D 42, several pink cells and highly basophilic cells dominated the medulla. From D 56, strands of connective tissue fibers formed network in the parenchyma. Encapsulated nodules dominate by lymphocytes with some plasma cells were observed at D 112. At D 140, there was marked depletion of thymic cells, and the distinction of the cortex from the medulla was in apparent.