The myotome is a segmented skeletal muscle developing along the axis and is the first muscle to differentiate in every vertebrate. While fish and tadpole myotomes persist during development, myotomes of amniote embryos disappear during embryogenesis and are replaced by the long and complex epaxial muscles. Whereas the initial development of the myotome has been intensely investigated, very little is known about the fate of the myotome and the morphogenesis of the epaxial muscles in mammals. This study firstly examined epaxial muscle morphogenesis. Myotomal fibres and cell death in muscle fibres were followed by immunohistochemistry during rat embryogenesis. Results showed that the morphogenesis of epaxial muscles occurs through the movement of the differentiated myotomal muscle fibres rather than by de novo fusion of myoblasts after apoptosis of the initial myotomal myofibres. The myotomal muscle masses undergo progressive transformation and segregation that result in the formation of the distinct groups of epaxial muscles. Next, the mechanisms of epaxial muscle morphogenesis were investigated in rat embryos, by following muscle progenitor cells expressing the transcription factors Pax7 and Pax3 during epaxial muscle morphogenesis using immunohistochemistry. This demonstrated that the myoblasts responsible for epaxial muscle growth derive from a population of progenitors mingled within the epaxial muscle masses as they segregate from the myotome. No migration of precursors is involved. Transgenic ScxGFP mouse embryos, carrying a marker green fluorescent protein under the control of scleraxis (a transcription factor specific to tendons and muscle connective tissues), permitted the tracing of the connective tissues during myotome transformation. Results strongly suggest that connective tissues associated with epaxial myofibres could be actively involved in creating the displacement of the myotomal myofibres during the transformation process. Finally, to test whether the mammalian myotome has a function as a neurally-controlled muscle during development, innervation of the myotome was studied using immunohistochemistry in comparison with the innervation of the forelimb muscles of rat embryos. The results were striking, showing that whereas the migratory limb muscles are contacted by nerves from the beginning of their differentiation, the myotome differentiates and then develops over more than two days without nerves. As revealed by the appearance of acetylcholine receptors clusters, functional innervation only occurs in the epaxial muscles when the myotome has started its transformation. The true mammalian myotome is therefore never innervated and seems to have lost its role as a neurally-controlled muscle in contrast to the myotomal muscle of fish and amphibian tadpoles. Overall the results indicate that the development of the epaxial muscles is strikingly different from that of the muscles originating from migratory myoblasts. Contrary to the migratory muscles, the myotome develops in the absence of nerves and its differentiated muscle fibres are transformed in position and orientation to create the epaxial muscles. The development of mammalian epaxial muscles upon a template of embryonic muscle resembles the development of some adult muscles in Drosophila, developing from the larval muscles. This suggests that the mammalian myotome could be of a larval nature but with the loss of innervation.

The role of the anterior neck muscles in cervical dysfunction has become an area of interest in the physiotherapy literature, resulting in the development of new methods for assessing and treating dysfunction of these muscles. However, these methods are based primarily on electromyographic (EMG) and various imaging studies, and lack a detailed anatomical or biomechanical foundation. The purpose of this work was to examine the morphology and basic biomechanics of the sternocleidomastoid (SCM); scalenus anterior, medius, and posterior; longus capitis and colli; rectus capitis anterior and lateralis muscles with a view to better understanding the capabilities of these muscles. This will contribute to our understanding of the mechanisms of cervical disorders and inform more evidence based approaches to treatment. This research was completed in three stages: dissection of the fascicular anatomy of the anterior neck muscles in embalmed cadavers; magnetic resonance imaging (MRI) of these muscles in young volunteers; and biomechanical modelling. Descriptive and morphological data from both the dissection and MRI studies were recorded, and cross-referenced for input into the biomechanical model. The biomechanical study involved calculating the peak force capabilities of each fascicle, and deriving the orientation and distribution of these forces across the cervical motion segments using CT scans. The result was a detailed breakdown of the peak torque, compression and shear forces generated by the anterior neck muscles at a fascicular level, calculated with reference to each cervical motion segment. The dissection study revealed several interesting findings regarding the structure of these muscles, adding considerable detail to anatomical textbook descriptions. Findings are described for each individual muscle. The MRI study found substantially larger muscle volumes than found in the dissection study, due to changes both with age and embalming. Biomechanical modelling demonstrated that in the neutral position the anterior neck muscles are not capable of exerting large forces, and do not act equally on all the cervical motion segments. Moment generating capacity into flexion was dominated by the SCM, and increased at lower levels in the cervical spine. All muscles were capable of producing compression, and total compression capacity remained relatively even at different cervical levels. Shear capacity was minimal, and was only potentially produced by the SCM in the lower cervical spine. The anterior neck muscles are complex and interesting muscles for which textbook descriptions tend to be simplified. These muscles act closely on the cervical motion segments, producing largely compressive forces. The more deeply placed longus and scalene muscles demonstrated a limited capacity for producing flexion moments, especially compared to the SCM. At C2-3 the SCM produced a net extension moment, suggesting that at this level (and above) the longus capitis and colli may proportionally play a greater role in cervical flexion. However, the force capabilities of these muscles remain very small and may be insufficient to produce actions attributed to these muscles in the clinical literature. This research presents data fundamental to understanding the function of these muscles, and which has the potential to contribute towards many different biomechanical applications in future research.

Thesis (Ph. D.)--University of Washington, 1981. / Vita. Bibliography: leaves [233]-251.

Thesis (M.Sc.)--York University, 2006. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR29615

Thèse : Médecine : Paris : 1897. / N° d'ordre : 622.

Thèse d'exercice : Médecine. Chirurgie générale : Université de Nantes : 2004. / Bibliogr. f. 90-96 [63 réf.].

Thèse de doctorat : Médecine. Biologie cellulaire et moléculaire : Université de Nantes : 2006. / Bibliogr.

Thèse de doctorat : Biologie cellulaire et moléculaire : Evry-Val d'Essonne : 2008. / Titre provenant de l'écran-titre.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2007. / Titre provenant de l'écran titre. Bibliogr. p. 217-220.

Thèse d'agrégation de l'enseignement supérieur--Liege. / "Ce travail paraîtra dans les Archives internationales de physiologie et de biochemie, 1955, vol. LXIII." Bibliography: p. 145-151.