Lobko P I, Denisov S D, Manulik V A, Miranda V
Arkh Anat Gistol Embriol. 1985 Jun;88(6):17-22.
The reason to consider the second thoracic cerebrospinal nerve (Th2) as one of the sources of the brachial plexus is the fact of the intersegmentary connection between Th1 and Th2 by means of a neural branch situating on the internal surface of the thorax near the vertebral column (the intrathoracic or paravertebral branch). However, not all cases of the intersegmentary connection Th1-Th2 should be regarded only as participation of Th2 in the formation of the brachial plexus, this is conditioned by certain peculiarities of its structure and by the character of interconnections with the I intercostal nerve. The macro-microscopic method demonstrates that the intersegmentary connection Th1-Th2 includes somatic and vegetative components, that to the same extent participate both in formation of the brachial plexus and in the I intercostal nerve. The intersegmentary connection Th1-Th2 is considered as a vegetative neural structure, containing somatic conductors and is considered as a homologue of superficial connective branches. It is the way, by which sympathetic fibers can reach the brachial plexus from the segment situating below, without passing through the superior thoracic nodes of the sympathetic trunk.
将第二胸段脊神经（Th2）视为臂丛神经来源之一的原因是，Th1和Th2通过位于胸廓内表面靠近脊柱处的神经分支（胸内或椎旁分支）存在节段间连接这一事实。然而，并非所有Th1 - Th2节段间连接的情况都应仅被视为Th2参与臂丛神经的形成，这取决于其结构的某些特殊性以及与第一肋间神经的连接特征。大体 - 显微镜检查方法表明，Th1 - Th2节段间连接包括躯体和自主神经成分，它们在相同程度上既参与臂丛神经的形成，也参与第一肋间神经的形成。Th1 - Th2节段间连接被视为一种自主神经结构，包含躯体传导纤维，被认为是浅结缔组织分支的同源物。正是通过这种方式，交感神经纤维可以从下方节段到达臂丛神经，而无需经过交感干的胸上神经节。
