Sexual Dimorphism

Sexual Dimorphism- Various biological studies on the subject of sex differences have been published. The subjects of these studies are not only humans, but also other mammals, birds, amphibians, insects, extending to ostracoda in the Paleozoic era. Moreover, original methods in individual studies have been used. This book provides convincing reasons which explain sex differences. The book also shows that, even if considered that some living things do not have sex differences, in reality they do. The somewhat different data on sex differences in this book will offer new ideas not only to life scientists and biologists, but social and cultural scientists as well

Craniodental Adaptation and Homoplasy in Early Mammals

For the first two-thirds of their over 180-million-year history, mammals left a sparse fossil record. Often the only direct evidence of these early forms are small and unassociated craniodental fragments. Despite these limitations, the three chapters of this thesis support the effectiveness of this type of material for estimating the functional and autecological capacities in Mesozoic mammals, through high resolution imaging and morphometric analysis of the molariform dentition. Each of the three chapters is a self-contained study addressing separate topics relating to the evolution of dental and petrosal morphology. The common thread between all sections is that variation in craniodental structure among Mesozoic lineages is greater than would be expected based only on the disparity seen among extant small mammals. This is a result of both the more “modern” dynamics of dental evolution in more Mesozoic mammalian lineages than historically appreciated (Chapters 1 and 3), and the more “primitive” morphology of the inner ear, even in groups very closely related to extant crown therians (Chapter 2). In both cases, the craniodental morphologies described are outside the range of variation seen in extant species. Chapter 1 describes several new specimens from the herbivorous stem-therian mammal Reigitherium, from the Late Cretaceous of Patagonia. These newly available specimens demonstrate that the herbivorous molar morphology seen in Reigitherium is derived from the more plesiomorphic tuberculosectorial pattern seen in the South American endemic group Meridiolestida. Chapter 2 presents descriptions and analysis of the internal structure of three stem therian petrosal bones from the Late Jurassic of North America, and middle Cretaceous of Mongolia. Within the comparative context of labyrinthine endocast evolution, it can be determined that many of the advanced features of modern therian hearing likely developed only after their divergence from their common ancestor with the fossil groups described here. Finally, Chapter 3 presents a macroevolutionary analysis of lower molariform shape change across a large sample of early mammaliaforms, using high-level morphometric methods. The results of this analysis suggest that the stochastic processes controlling the shape evolution of lower molariforms in crown Mammalia are shared across a wide range of “triconodont”, “symmetrodont”, and “tribosphenic” Mesozoic taxa

Symmetry in Human Evolution, from Biology to Behaviours

Our knowledge of human evolution has made particular progress recently, due to the discovery of new fossils, the use of new methods and multidisciplinary approaches. Moreover, studies on the departure from symmetry, including variations in fluctuating or directional asymmetries, have contributed to the expansion of this knowledge. This Special Issue brings together articles that deal with symmetry and human evolution. The notion of symmetry is addressed, including whether to reconstruct deformed fossil specimens, study biological variations within hominins or compare them with extant primates, address the shape of the brain or seek possible relationships between biological and behavioural data

Comparative anatomy of the mammalian bony cochlea and its ontogenetic development in humans

The cochlea is the organ for sound reception. Mammals place varied functional demands on their sense of hearing to meet the requirements of a broad range of ecological niches and diverse behaviours. However, documenting potentially related adaptations of the cochlea to eco-behavioural traits is difficult due to its complex geometry. The present study aims to determine whether the bony cochlea carries eco-behavioural traits that can be used to contextualize our understanding of the fossil record and evolutionary transitions. This study also includes work on ontogenetic changes since these can yield important insights into evolutionary processes resulting in differences of the adult phenotypes. Advanced techniques in micro-CT imaging, 3D image visualization, geometric morphometrics and statistical methods were used to study morphological variations of the bony cochlea across 45 adult eutherian species. Also, the same set of techniques was used to study 12 human fetal (approximately four to nine months of gestation) cochleae in comparison with five adult cochleae. Results revealed that there was a considerable range of variation in form of the mammalian bony cochlea. Potential links between the bony cochlear morphology and hearing, ecology and behaviour were found. Dimensions of the bony cochlea may be indicative of the eco-behavioural niche that a mammal occupies; e.g., fewer than two spiral turns is associated with obligate marine species. Rodents also showed remarkable variation in the cochlear morphology, more so than any other group of mammals studied, reflecting their diverse eco-behavioural traits. Results from the human developmental study showed that whilst the general coiled shape was achieved at the midgestational age, there was size related morphological change during the postnatal period. The round window size reached mature state prior to birth, by approximately the second trimester, whereas the oval window continued to change in size after birth. The postnatal enlargement may be determined by functional requirements of air-borne hearing, particularly with respect to frequency range and sensitivity

Segmentation d'images IRM du cerveau pour la construction d'un modèle anatomique destiné à la simulation bio-mécanique

Comment obtenir des données anatomiques pendant une neurochirurgie ? a été ce qui a guidé le travail développé dans le cadre de cette thèse. Les IRM sont actuellement utilisées en amont de l'opération pour fournir cette information, que ce soit pour le diagnostique ou pour définir le plan de traitement. De même, ces images pre-opératoires peuvent aussi être utilisées pendant l'opération, pour pallier la difficulté et le coût des images per-opératoires. Pour les rendre utilisables en salle d'opération, un recalage doit être effectué avec la position du patient. Cependant, le cerveau subit des déformations pendant la chirurgie, phénomène appelé Brain Shift, ce qui altère la qualité du recalage. Pour corriger cela, d'autres données per-opératoires peuvent être acquises, comme la localisation de la surface corticale, ou encore des images US localisées en 3D. Ce nouveau recalage permet de compenser ce problème, mais en partie seulement. Ainsi, des modèles mécaniques ont été développés, entre autres pour apporter des solutions à l'amélioration de ce recalage. Ils permettent ainsi d'estimer les déformations du cerveau. De nombreuses méthodes existent pour implémenter ces modèles, selon différentes lois de comportement et différents paramètres physiologiques. Dans tous les cas, cela requiert un modèle anatomique patient-spécifique. Actuellement, ce modèle est obtenu par contourage manuel, ou quelquefois semi-manuel. Le but de ce travail de thèse est donc de proposer une méthode automatique pour obtenir un modèle du cerveau adapté sur l'anatomie du patient, et utilisable pour une simulation mécanique. La méthode implémentée se base sur les modèles déformables pour segmenter les structures anatomiques les plus pertinentes dans une modélisation bio-mécanique. En effet, les membranes internes du cerveau sont intégrées: falx cerebri and tentorium cerebelli. Et bien qu'il ait été démontré que ces structures jouent un rôle primordial, peu d'études les prennent en compte. Par ailleurs, la segmentation résultante de notre travail est validée par comparaison avec des données disponibles en ligne. De plus, nous construisons un modèle 3D, dont les déformations seront simulées en utilisant une méthode de résolution par Éléments Finis. Ainsi, nous vérifions par des expériences l'importance des membranes, ainsi que celle des paramètres physiologiques.The general problem that motivates the work developed in this thesis is: how to obtain anatomical information during a neurosurgery?. Magnetic Resonance (MR) images are usually acquired before the surgery to provide anatomical information for diagnosis and planning. Also, the same images are commonly used during the surgery, because to acquire MRI images in the operating room is complex and expensive. To make these images useful inside the operating room, a registration between them and the patient's position has to be processed. The problem is that the brain suffers deformations during the surgery, in a process called brain shift, degrading the quality of registration. To correct this, intra-operative information may be used, for example, the position of the brain surface or US images localized in 3D. The new registration will compensate this problem, but only to a certain extent. Mechanical models of the brain have been developed as a solution to improve this registration. They allow to estimate brain deformation under certain boundary conditions. In the literature, there are a variety of methods for implementing these models, different equation laws used for continuum mechanic, and different reported mechanical properties of the tissues. However, a patient specific anatomical model is always required. Currently, most mechanical models obtain the associated anatomical model by manual or semi-manual segmentation. The aim of this thesis is to propose and implement an automatic method to obtain a model of the brain fitted to the patient's anatomy and suitable for mechanical modeling. The implemented method uses deformable model techniques to segment the most relevant anatomical structures for mechanical modeling. Indeed, the internal membranes of the brain are included: falx cerebri and tentorium cerebelli. Even though the importance of these structures is stated in the literature, only a few of publications include them in the model. The segmentation obtained by our method is assessed using the most used online databases. In addition, a 3D model is constructed to validate the usability of the anatomical model in a Finite Element Method (FEM). And the importance of the internal membranes and the variation of the mechanical parameters is studied.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF