Murphy Kelly A., Ryan Nicholas, Fakoya Adegbenro O.
Naval Medical Center San Diego
Lousiana State University, HSC, Shreveport
The nerves supplying the upper limb originate from the brachial plexus, which is formed by the anterior rami of spinal nerves C5 to T1. The roots combine to form the superior (C5-C6), middle (C7), and inferior (C8-T1) trunks. Each trunk divides into anterior and posterior divisions that reorganize into the lateral, medial, and posterior cords. The median nerve, 1 of the 5 terminal branches of the brachial plexus, is formed by the union of the lateral and medial cords. The combined fibers from C5 to T1 contribute to the entire cervical enlargement, resulting in a mixed nerve with a broad segmental origin. The median nerve innervates most forearm flexors and several intrinsic hand muscles. Knowledge of median nerve anatomy and physiology is essential for diagnosing neuropathies such as carpal tunnel syndrome (CTS), localizing lesions after trauma, and interpreting electrodiagnostic studies. Surgical planning for nerve repair, tendon transfers, or decompression procedures relies on the precise understanding of the nerve's course, branches, and motor distribution. Awareness of anatomic variations prevents iatrogenic injury during procedures involving the axilla, arm, or wrist and guides rehabilitation strategies that restore function and preserve fine motor control.
上肢的神经支配分为前（腹侧）支，这些分支支配前侧肌肉（如肱二头肌、肱肌、旋前圆肌、桡侧腕屈肌、掌长肌、指浅屈肌和指深屈肌以及旋前方肌）。这些肌肉由C5 - T1脊髓神经支配。脊髓分为白质柱（有髓轴突）和灰质角（运动神经元的细胞体）。感觉神经元的细胞体位于后（背）根神经节。它们有一个外周突，支配皮肤中的感觉器官，还有一个中枢突，将后根神经节与脊髓后（背）柱相连以实现感觉功能。运动功能的细胞体位于前（腹侧）灰质角。后根负责感觉。前根具有运动功能。后根和前根会合形成混合性脊髓神经。支配上肢的神经源自脊髓节段C5 - T1。整个脊髓发出八对颈神经、十二对胸神经、五对腰神经、五对骶神经和一对尾神经。这些混合性脊髓神经会合形成臂丛神经（拉丁语brachium意为手臂）。混合性脊髓神经发出后支和前支。来自C5 - T1的前支称为臂丛神经的根。来自C5和C6的分支会合形成上干。来自C7的分支形成中干。来自C8和T1的分支形成下干。后支参与椎旁肌的神经支配。然后每个干又分为前支和后支。来自C5、C6和C7的前支会合形成外侧束。来自C8和T1前支的分支形成内侧束。来自C5 - T1的后支会合形成后束。正中神经是臂丛神经的五个终末分支之一。外侧束和内侧束的会合形成该神经，它接受C5 - T1所有前支的分支。
