Banneheka Shyama
Division of Gross Anatomy and Morphogenesis, Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi Dori, Niigata City, Japan.
Anat Sci Int. 2008 Jun;83(2):61-7. doi: 10.1111/j.1447-073X.2007.00202.x.
Ansa cervicalis complex, which innervates the infrahyoid muscles, is formed by the union of two roots derived from the anterior primary rami of the first three or four cervical spinal nerves. According to its relationship with the internal jugular vein, there are three ansa types: medial, lateral, or mixed. Nerve fiber microscopy was carried out in 18 ansa cervicalis complexes after staining with Sudan Black, in order to study composition and structural arrangement in detail. Fibers from both first and second cervical nerves (C1, C2) joined the hypoglossal nerve and later left it partially in the superior root of the ansa, which also contained ascending fibers derived from the inferior root components; usually the second and third cervical nerves. Those ascending fibers, together with the C1 and C2 fibers remaining in the hypoglossal nerve, innervate thyrohyoid and geniohyoid muscles. Cervical nerve fibers could be observed within the hypoglossal nerve even after the ramification of those branches. Further, cervical nerve fibers were continuously issued to the peripheral layers of the hypoglossal nerve where the fibers of the two nerves intermingled, forming a complex structure. The general arrangement of the ansa did not change according to its type or segmental composition. Although the hypoglossal nerve does not make any significant contribution to the formation of the ansa, the close relationship between the two nerves observed in the present study calls for the use of a more descriptive term such as ansa hypoglosso-cervicalis. The pattern of innervation of the infrahyoid muscles is also discussed.
颈袢复合体支配舌骨下肌群，它由来自第1至3或4颈脊髓神经前支的两个神经根结合而成。根据其与颈内静脉的关系，有三种颈袢类型：内侧型、外侧型或混合型。对18个颈袢复合体用苏丹黑染色后进行神经纤维显微镜检查，以便详细研究其组成和结构排列。来自第1和第2颈神经（C1、C2）的纤维加入舌下神经，随后部分纤维从舌下神经离开，进入颈袢的上根，该上根还包含来自下根成分的升支纤维；通常是第2和第3颈神经。这些升支纤维，连同仍留在舌下神经中的C1和C2纤维，支配甲状舌骨肌和颏舌骨肌。即使在这些分支发出后，仍可在舌下神经内观察到颈神经纤维。此外，颈神经纤维持续发出至舌下神经的外周层，在那里两根神经的纤维相互交织，形成一个复杂的结构。颈袢的总体排列并不因其类型或节段组成而改变。虽然舌下神经对颈袢的形成没有显著贡献，但本研究中观察到的两根神经之间的密切关系提示应使用更具描述性的术语，如舌下-颈袢。本文还讨论了舌骨下肌群的神经支配模式。
