The thymus that twist around the jugular vein are elongated and begin to divide into the cortex and the medulla in the large lobes from E9 to E10.The rudiments of Hassalls Corpuscles are found at E12.

• 从E9至E10胸腺呈长索状，环绕颈静脉分布，胸腺开始区分出皮质、髓质及大叶，E12出现胸腺小体原基。