ABSTRACT
Objective The dense fibrous connective tissue that connects sub-occipital muscles which consist of the rectus capitis posterior minor muscle (RCPmi), rectus capitis posterior major muscle (RCPma), obliquus capitis inferior muscle (OCI) and nuchal ligament (NL) to the spinal dura mater (SDM), is described as the myodural bridge (MDB) in humans. The MDB is perceived as an essential anatomical structure and has been a subject of interest for clinicians. Studies have revealed that MDB may be related to the dynamic circulation of the cerebrospinal fluid (CSF) and a chronic cervicogenic headache. To date, the MDB is identified as a universal, existing structure in mammals and it exists in other vertebrates as well, such as Gallus domesticus and Rock pigeons in Avifauna, Siamese crocodile and Trachemys scripta elegans in Reptile. The current study is to further analyze different structures features of the MDB in sundry classes and provide the anatomical basis for functional studies. The JapaLura Splendida is the most common species in Lacertiformes, Reptilia. So we chose it as the experimental object to supply the morphological study of the MDB in Reptilia. Methods The study was based on gross anatomical dissection, thick sheet section, histological staining to observe the structural characteristics of the post-occipital area of twenty JapaLura Splendidas and the existence of the MDB. Results The deep post-occipital muscles were composed of the rectus capitis dorsal muscle (RCD) and the obliquus capital posterior (OCP) muscle. The RCD was merged by the rectus capitis dorsal major muscle (RCDma), the rectus capitis dorsal minor muscle (RCDmi) and the obliquus capitis anterior muscle (OCA). In the atlanto-occipital space, the dense fibrous bundles were found to originate from the ventral aspect of the RCD and run ventral, closely inserting into the SDM. In the atlanto-axial space, the dense fibrous bundles were found to originate from the ventral aspect of the OCP and run ventral, closely contacted with the SDM. These dense fibrous bundles were the collagen type I fibers with strong double refraction. Conclusion The result of this study indicates that the MDB is located between the post-occipital muscles and the SDM in JapaLura Splendida. The MDB of Japalura splendida may be related to the activities of the head and neck, and exert a physiological function similar to the MDB in humans.