目的　明确胸腰骶部不同节段脊神经根鞘的解剖学和组织学结构及其分布特点，探讨其临床意义。  方法　取7例成人脊柱标本，解剖观察胸腰骶部不同节段神经根鞘的硬脊膜囊开口方式，并制成组织切片后显微镜下观察神经根鞘的结构。  结果　胸腰段神经根鞘存在单孔和双孔两种硬脊膜囊开口方式，而骶段神经根鞘只存在单孔开口方式；单孔根鞘又根据前、后根之间有无双层袖套结构分为Ⅰ型和Ⅱ型。较之神经根其他部位，神经节处硬脊膜袖套的胶原纤维层少且结合疏松。腰4/5和骶1~5节段神经节处的硬脊膜袖套的厚度比其他节段更薄（F=37.31，P<0.01）。神经根袖套下腔隙终止于神经节。  结论　Ⅰ型和Ⅱ型神经根鞘在各节段的分布规律，解释了腰骶部神经根受压时多表现为感觉和运动功能同时受累的现象；而神经节处的硬脊膜袖套在下腰骶节段最薄的特点，也和腰腿痛高发的现象相关系。脊神经节是脊神经根开始转化为脊神经的标志。

Objective　To investigate the anatomical and histological structure of the sheath of thoracic, lumbar and sacral nerve roots as well as their distribution, and to explore the clinical significance.  Methods　Seven adult cadaveric spine specimens were dissected to observe the way out of the dural sac of the nerve root sheath of different segments, and to prepare sections to observe the structure of the nerve root sheath under the light microscope.　Results　There were one-hole and two-hole nerve root sheaths both in thoracic and lumbar segments, while there was only one-hole nerve root sheath in sacral segments; the one-hole nerve root sheath could be classified intoⅠtype and Ⅱ type because of the different structures inside. Compared with the other sites of the nerve root, there were only several layers of collagenous fibers being loosely connected with each other in the ganglion. The dural sleeve of ganglion at lumbar 4/5 and sacral 1~5 segments is the thinnest (F=37.31，P<0.01). And the space under the sleeve does not disappear until the ganglion.　Conclusion　The distribution ofⅠtype and Ⅱ type nerve root sheath accounts for the phenomenon of patients presenting early sensory and motor dysfunction at the same time when compressed. And the dural sleeve of ganglion at lower lumbar and sacral segments is the thinnest, which is related with the high incidence of the lumbocrural pain. The nerve root transforms into the peripheral nerve from the ganglion.