The thymus has no obvious demarcation into an outer cortex and inner cortex.Lymphocytes and the macrophages are dispersed in the thymus parenchyma equably.

• 牙鲆胸腺没有明显的外区和内区之分，胸腺细胞和巨噬细胞比较均匀地分布于整个组织中，未能观察到胸腺小体。