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Paper 3
Published in Amanda Rabone, Benedict Thomson, Nicky Dineen, Vincent Helyar, Aidan Shaw, The Final FRCR, 2020
Amanda Rabone, Benedict Thomson, Nicky Dineen, Vincent Helyar, Aidan Shaw
The description of dripping candle wax centred on the diaphysis is typical of melorheostosis. In this condition there is progressive cortical hyperostosis along one side of the affected bone in a ‘sclerotome’, which is a zone supplied by an individual spinal nerve. It is of unknown aetiology and usually asymptomatic initially. It has a slow course in adults and can affect one or more bones of the upper and lower limbs. It may be associated with genu varus, genu valgus and leg length discrepancy.
Embryology of the Spinal Cord, Peripheral Nerves, and Vertebrae
Published in Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand, Pediatric Regional Anesthesia, 2019
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand
The next major developmental feature is the differentiation of somites in three distinguishable areas (Figure 1.7): Two external structures: medially the myotome, and laterally the dermatome (also termed dorsolateral lamella or cutis plate)One internal cell mass, the sclerotome, in which the density of nuclei gradually increases, rostral to caudal
The skeleton and muscles
Published in Frank J. Dye, Human Life Before Birth, 2019
Paraxial mesoderm becomes segmented into paired aggregates of tissue called somites (see Figure 14.3B). The first somites to appear (early in the embryonic period) are in the head region. Subsequently, additional pairs of somites form in a progressively caudal direction. Each somite is organized into two regions: sclerotome and dermatomyotome (see Figure 14.3C). Cells of the sclerotome leave the somites and aggregate around the notochord (the primitive axial skeleton of the embryo) and developing spinal cord. These cells give rise to the vertebrae (by the process of endochondral ossification) and to the intervertebral discs (masses of fibrocartilage between vertebrae). Despite the importance of the notochord to the developing embryo, the notochord's only contribution to the adult is the nucleus pulposus, which occupies the core of each disc. Ossification (bone formation) replaces the original cartilaginous vertebral column with a bony one. This process begins during the embryonic period and continues into about the 25th year of life.
Paracondylar process combined with persistent first intersegmental vertebral artery: an anatomic case report and literature review
Published in British Journal of Neurosurgery, 2023
Haigui Yang, Xiaofei Bai, Xiaoli Huan, Tingzhong Wang
The embryological development of CVJ is different from that of the other vertebra. Normally, hypochordal bow of the fourth occipital sclerotome (S4) never fuses with the first cervical sclerotome (S5). Instead, it partially regresses and only contributes to the foramen magnum, occipital condyles, C1 lateral masses, and posterior arch. The cranial part of S5 contributes to the paracondylar regions of occipital bone and the caudal part of S5 contributes to the C1 transverse processes.21 Therefore, the causes of PCP formation may be as follows. (a) The hypochordal bow of S4 hypertrophies or fails to regress partially, thus contributes lager area to the paracondylar region. (b) Segmentation is disordered between the cranial and the caudal part of S5. Although it is a controversy if PCP is derived from the fourth occipital sclerotome or the first cervical sclerotome,22–24 most researchers agree to the latter.2,15,19
Surgical considerations in posterior C1-2 instrumentation in the presence of vertebral artery anomalies: case illustration and review of literature
Published in British Journal of Neurosurgery, 2019
Lee A. Tan, Manish K. Kasliwal, Carter S. Gerard, Vincent C. Traynelis, Ricardo B.V. Fontes
The incidence of these anomalies range from 0.6 to 4.7% for PFIA, 0.24 to 1.3% for FVA, 0.67 to 1.3% for low-lying PICA, 11.7 to 23% for HRVA, and 5.0 to 52.94% for PP. Furthermore, the incidence of vascular anomalies appears to be much higher in patients with concurrent osseous anomalies at CVJ. This is thought to be due to the fact that re-segmentation of the embryonic sclerotome occurs at similar embryonic stages as vascular rearrangement progresses; therefore, the development of an anomalous VA often coincides with osseous anomalies such as os odontoideum or occipitalization of C1.
Essential role of Mohawk for tenogenic tissue homeostasis including spinal disc and periodontal ligament
Published in Modern Rheumatology, 2018
Ryo Nakamichi, Kensuke Kataoka, Hiroshi Asahara
Scleraxis (Scx) is involved in the early stage of tendon development [30,31]. Analysis of Scx expression in wild-type mouse embryo confirmed expression in tendon progenitor cells at the E9.5, early developmental stage [30,31]. The knockout of Scx causes the development of hypoplastic tendon tissue in the entire body of the mouse. The induction of tendon progenitor cells was intact in Scx−/− mice, but tendon formation was disrupted [32]. As a result, Scx is considered an important early marker in tendon development. In addition, the expression of Scx was observed between the sclerotome and the myotome in the embryonic somite. This area is named the syndetome and is the origin of the axial tendons [33]. The discovery of Scx accelerated the research on tendon development, and there have been reports on the relationship between Scx and growth factors. FGFs induce the expression of Scx in the syndetome and are involved in the differentiation of and interaction between muscle and tendon [33]. The induction of bone morphogenetic protein BMP12 (growth/differentiation factor, GDF 5), which belongs to the TGFβ superfamily, in mesenchymal stem cells (MSCs) resulted in increased expression of Scx and type I collagen. BMP12 plays an important role in tendon development via the TGFβ/Smad pathway [34]. In addition, the expression of Scx was maintained through the TGFβ/Smad 2/3 pathway by adding mechanical stress to tenocytes, and this mechanical stress is important in the maintenance of tendon homeostasis [35]. Tenomodulin (Tnmd), which inhibits VEGF-induced angiogenesis [36], is strongly expressed in mature tenocytes and it is useful as a late marker of tendon development. Furthermore, Scx induces the expression of Tnmd [37]. In Tnmd-knockout mice, the cell proliferative capacity of tenocytes is low, and the collagen fiber bundles in tendons exhibit a non-uniform morphology [38]. TGFβ can induce the expression of Scx and Tnmd. Since TGFβ is expressed only in muscles and chondrocytes at the differentiation stage, it is suggested that interactions between muscle, tendon, and cartilage are important during the differentiation stage [39]. Furthermore, to evaluate the function of Scx about tendon healing, it is reported that Scx-induced MSCs are increased the expression of Col1a1, Dcn, and Tnmd and are lost multipotency [8,40,41]. In addition, several reports indicate Scx positive progenitor cells exist in wound site within tendon healing [42,43]. These reports have indicated that Scx has an important role not only in the tendon development but also tendon regeneration. However, it is known that the expression of Scx is substantially decreased after birth [44]. Therefore, it is not only Scx that regulates the differentiation of stems cells into tenocytes but also other factors that are involved in the homeostasis of post-natal tendons may be critical.