Development of myodural bridge located within the atlanto‐occipital interspace of rats

Abstract

The myodural bridge (MDB) is a dense connective tissue structure that connects the subocciptal musculature to the spinal dura mater. The purpose of this study was to clarify morphological evolution characteristics and compositional changes in the fibrous structures of MDB during its growth and development in the atlanto-occipital interspace. For this, histological sections from Sprague-Dawley (SD) rats (age, E17 to adulthood) were stained with Masson's Trichrome and Picrosirius Red. The results demonstrated that at age E18, the posterior arch of the atlas was completely closed and MDB fibers had already begun to form. In rat embryos (E18-E21), only few fibers and muscles were present in the suboccipital region, and these were lightly stained. In postnatal rats, an obvious increase in the amount of fibers and muscle tissues was noted. At age P1, MDB fibers originated from the rectus capitis posterior minor muscle and merged into the atlanto-occipital membrane, which was closely attached to the spinal dura mater. As rats matured, MDB fibers gradually became denser and more organized. This study also showed that in postnatal rats, MDB was mainly composed of type I collagen fibers. By observing the development of MDB in SD rats, the function of MDB can be further understood. This study provides a morphological basis for future functional studies involving the MDB.

Development, maturation, and growth of the myodural bridge within the posterior atlanto‐axial interspace in the rat

“…The fibers, observed in the postnatal rats, were primarily composed of type I collagen fibers. This finding is consistent with the findings of Lai et al (2020) who reported on the MDBC within the PAOI of the rat. Type I collagen fibers are known to have high resistance to tension (Franchi et al, 2007).…”

“…Previous studies evidenced that the suboccipital muscles of the rat are immature at birth, with the fibers increasing in number quite markedly after birth (Rayne & Crawford, 1975). Considering that head activity and movement increase in the postnatal rats, this is similar to our previous finding concerning the development of the MDBC within the rat PAOI (Lai et al, 2020).…”

“…In our previous studies, we found that the posterior arch of C1 and C2 begin to germinate at E18 when evaluated utilizing histological sections (Lai et al, 2020). Therefore, the present study began evaluations starting from E18.…”

“…However, there have been few reports on the developmental maturation and growth of the MDB. Our group previously described the developmental growth of the MDB in the PAOI of the rat (Lai et al, 2020). The present study further describes the developmental growth of the MDB in the PAAI of the Sprague Dawley (SD) rat.…”

The morphology of the suboccipital region in snakes, and the anatomical and functional diversity of the myodural bridge

“…Comparative studies have described an MDB in a variety of terrestrial mammals (e.g., Elbrond & Schultz, 2019;Lai et al, 2020;Zhang et al, 2020;Zheng et al, 2017) as well as three species of cetacean (Liu et al, 2017(Liu et al, , 2018Zheng et al, 2017). The number of mammalian taxa examined led Zheng et al (2017) to argue that the MDB was a consistent feature among mammals.…”