Journal of Anatomy最新文献

Understanding normal structural and functional anatomy is critical for health professionals across various fields such as medicine, veterinary, and dental courses. The landscape of anatomical education has evolved tremendously due to several challenges and advancements in blended learning approaches, which have led to the adoption of the use of high-fidelity 3D digital models in anatomical education. Cost-effective methods such as photogrammetry, which creates digital 3D models from aligning 2D photographs, provide a viable alternative to expensive imaging techniques (i.e. computed tomography and magnetic resonance imaging) whilst maintaining photorealism and serving multiple purposes, including surgical planning and research. This study outlines a comprehensive workflow for producing realistic 3D digital models from embalmed veterinary specimens. The process begins with the preservation of specimens using the modified-WhitWell (WhitWell-Liverpool) embalming protocol, which ensures optimal tissue rigidity and improved colour enhancement, facilitating easier manipulation and better photogrammetry outcomes. Once embalmed, specimens are photographed to create digital 3D models using photogrammetry. Briefly, all images are processed to generate a sparse point cloud, which is then rendered into a 3D mesh. The mesh undergoes decimation and smoothing to reduce computational load, and a texture is applied to create a lifelike model. Additional colour enhancements and adjustments are made using digital tools to restore the natural appearance of the specimens. The 3D models are stored on a cloud repository and integrated into the University of Liverpool's Virtual Learning Environment, providing continuous, remote access to high-quality anatomical resources. The switch to embalmed specimens during the COVID-19 pandemic allowed for longer-term use and detailed dissections, enhancing the quality of digital models. Fresh specimens, though naturally coloured, are less stable for photogrammetry, making embalmed specimens preferable for accurate 3D modelling. Our method ensures embalmed specimens are rigid enough for precise modelling while allowing texture adjustments to enhance digital representation. This approach has improved logistical efficiency, educational delivery, and specimen quality. Innovative embalming techniques and advanced photogrammetry have the power to revolutionise anatomical education with the creation of a vast digital library accessible online to students at any time. This approach paves the way for integrating digital 3D models into immersive environments and assessing their impact on learning outcomes.

Unlike most herbivores, sauropod dinosaurs evolved simple teeth that were replaced rapidly. Sauropod craniodental morphology is conserved relative to that of many archosaur clades, but tooth breadth and replacement rate vary substantially. Two neosauropod clades, Titanosauria and Diplodocoidea, independently evolved both narrow-crowned teeth and high tooth replacement rates among a suite of other convergent features. Brachiosaurids also evolved somewhat narrower-crowned teeth, but the two brachiosaurids whose tooth replacement rate has been examined to date have low replacement rates. Poor and uneven sampling across Sauropoda limits our understanding of the evolution of tooth replacement rate and related ecological inferences. To better understand the evolution of tooth replacement rate and tooth breadth, we integrated histological and tomographic data to nearly double the number of examined sauropod genera, focusing on improved sampling through the Cretaceous. We provide histological descriptions of the dentine and enamel of two Early Cretaceous taxa, Abydosaurus and Moabosaurus. The former has unusually thin daily increments in its dentine, indicating prolonged tooth formation times. The dentine of the latter is typical of what is observed in most sauropods, but it has enigmatic banding in its enamel. We performed ancestral state reconstruction on a time-calibrated phylogeny to show that the earliest macronarians and brachiosaurids retain the ancestral sauropod condition of relatively low tooth replacement rates (2-3 months to replace a tooth in each alveolus), whereas diplodocoids evolved much higher rates (2-5 weeks to replace a tooth in each alveolus). Early diverging somphospondylans had a broad range of tooth replacement rates. Broad-crowned teeth exhibit some correlation with low tooth replacement rates, whereas narrow-crowned teeth display a more variable relationship with replacement rate.

The endosseous labyrinths are associated with several functions, including hearing and spatial orientation. Throughout their evolutionary history, crocodylomorphs have thrived in diverse environments, and the morphology of their endosseous labyrinths has been suggested as a proxy for inferring their lifestyle. However, the relationships between the shape of their endosseous labyrinths and ontogenetic and phylogenetic factors are difficult to interpret and have rarely been investigated in depth previously, particularly in terms of dataset size. Here, we present the most complete dataset to date on the endosseous labyrinths of extant crocodylians, including 111 specimens covering 22 species of different ontogenetic status (from hatchlings to adults). Using 3D geometric morphometrics, we show that allometry constitutes a major contributor of the shape variation of the crocodylian endosseous labyrinths and that the development of this structure is likely linked to the braincase conformation, in all extant genera. We also find a moderate phylogenetic signal, but only without considering the size effect, so it could not be translated into relevant discrete morphological characters. Based on these results, we discuss several remaining problems that prevent the inclusion of fossil forms with highly divergent lifestyles to study how ecological differences shaped the endosseous labyrinths of crocodylomorphs.

Lagosuchus talampayensis is a small-bodied (~0.5 m long) Late Triassic dinosauriform archosaur from Argentina. Lagosuchus long has been a pivotal taxon for reconstructing the evolution of form and function on the dinosaur lineage. This importance is because it has a mix of ancestral archosaurian traits, such as a small pelvis with a mostly closed acetabulum lacking prominences that would restrict hip mobility much, with derived "dinosaurian" traits such as bipedalism, proximally shifted thigh muscle insertions, elongate hindlimbs, "advanced mesotarsal" ankle joints and digitigrade feet. Here, to quantify key functional traits related to the locomotor biomechanics of Lagosuchus, we build a three-dimensional musculoskeletal model, focussing on morphofunctional analysis of the pelvic limb. We survey skeletal material that we have digitised, pointing out hitherto undescribed features and elements, many of which are from taxa other than Lagosuchus. Next, we select ideal elements amongst these to construct a composite model, and articulate adjacent body segments into joints, then estimate body shape including centre of mass, and add muscle paths to create a musculoskeletal model. Finally, we use two methods to quantify the hindlimb muscle parameters ("architecture") in the model. We find that they produce similar estimates of force-generating capacities, and compare these data to the few available data from other archosaurs in an evolutionary context, to reconstruct fundamental patterns of changes in muscle architecture and pelvic limb morphology. Our model forms a valuable basis for future quantitative analyses of locomotor function and its evolution in early archosaurs, and an example of how to navigate decision-making for modelling problematic specimens.

Orofacial morphology in mammals plays a critical role in essential life functions such as feeding and communication, which are influenced by the shapes of these anatomical structures. Bats are known to exhibit highly diversified orofacial morphotypes within their clade, reflecting their varied diets and echolocation behaviors. The presence of bony discontinuities between the premaxilla and maxilla or among the premaxillae is a notable feature of bat orofacial morphology, observed in certain lineages. It is suggested that these unique orofacial morphotypes, not generally found in other mammals, have evolved in relation to dietary adaptations rather than merely for echolocation mode. Until now, the developmental background of the bony discontinuities in the bat orofacial complex has been insufficiently investigated. Here, we present a comparative study of the chondrocranium and epithelial organs in the orofacial complex of three bat species: Cynopterus sphinx, Rhinolophus malayanus, and Vespertilio sinensis. Our observations indicate that the preceding morphogenesis of orofacial cartilage and epithelial structures is remarkably different among these three species. In C. sphinx and V. sinensis, the region forming from the regression of the palatine process of the premaxilla was filled with orofacial cartilage and epithelial structures. We also found that the clefted morphology observed in R. malayanus and V. sinensis was formed via contrastingly divergent developmental processes. Midline clefts among Yangochiroptera have been previously categorized to represent a uniform morphotype, but our study highlights that attributing midline clefts into a singular category should be revisited, advocating for a nuanced categorization of cleft morphology based on their morphogenetic patterns. Further research on the bat orofacial complex may enhance our understanding of bat evolutionary diversification and offer insights into the developmental mechanisms of human cleft palate.

Teratornithidae is an extinct bird family, likely related to Cathartidae, known exclusively from the Americas. They were once thought to be scavengers, but recent theories suggest they were opportunistic or piscivorous birds capable of swallowing prey whole. The most notable species, Argentavis magnificens, had a wingspan of 6 to 8 m and weighed 70 to 80 kg. In order to infer paleobiological aspects of this bird, its endocast (as a proxy for brain morphology), reconstructed from computed tomography scans of the holotype skull, is here described and compared to that of other bird species of zoophagous feeding habits with different flight styles. The brain of Argentavis presents a general appearance similar to that of Cathartidae, being dorsoventrally flattened and anteroposteriorly elongated, with small optic lobes in relation to the total encephalic surface. The estimated volume of the bulbi olfactorii is very similar to that of the Andean Condor Vultur gryphus. The main difference observed with Cathartidae is the marked development of the eminentiae sagittales present in Argentavis (structures closely related to the perception of visual information), which are more similar to those of the Accipitriformes and Falconiformes analyzed. The results obtained here suggest that Argentavis was a scavenger or even maybe a kleptoparasitic bird, relying more on vision than on smell (similar to that observed in the Andean Condor). Furthermore, the inner ear and flocculi exhibit characteristics similar to birds without acrobatic flight, indicating that Argentavis had a soaring flight and inhabited open areas without much vegetation.

The superior gluteal nerve (SGN) is a mixed nerve of the sacral plexus that arises from the posterior divisions of the L4, L5, and S1 nerve roots. Its motor branch plays a crucial role in innervation of hip muscles, which allows for physiological gait or walk-pattern. As for its sensory branch, it provides innervation for the hip joint capsule, especially its superior part. The understanding of this nerve is crucial as it may be injured during many operations involving mostly pelvic surgery, both arthroscopic and open procedures. The risk of injury is especially high during total hip arthroplasty (THA). These lesions often result in the presentation of major walk-pattern abnormalities. The most classical and commonly known would be the Trendelenburg sign, which presents with pelvic instability characterized by having the patient standing on one leg whereby the pelvis on the contralateral side will be dropping, resulting in a positive sign. The aim of this meta-analysis was to obtain all relevant data on SGN and its variations, in order to emphasize its anatomical, physiological, as well as clinical implications. A large-scale search was conducted in all major databases (PubMed, Embase, Science Direct, Google Scholar, and Web of Science) in order to determine and pool all available and relevant SGN data. No restrictions were applied to date or language. The data collection was categorized by prevalence, branching, patterns, course, origin, and distance from anatomical landmarks. A total of 41 studies (n = 869 hemipelves) were included in our analysis. The most common branching pattern of SGN was a spray pattern, 70.4% (95% CI: 54.4-96.8; p < 0.001) of the general population. We found that the closest branch to the greater trochanter of the femur and concurrently the most at risk during surgery was a muscular branch to gluteus minimus muscle. As the trend of pelvic surgeries, especially THA continues to rise, SGN lesions are now more than ever at risk. Yet to the authors' knowledge, this does not seem to be reflected in the current literature thereby making this the first meta-analysis concerning this important anatomical structure. The authors believe it is paramount for surgeons, especially in the orthopedic specialty, to thoroughly understand the SGN with its anatomical variability and clinical tie-ins.

Neural networks are established throughout cortical development, which require the right ratios of glutamatergic and GABAergic neurons. Developmental disturbances in pyramidal neuron number and function can impede the development of GABAergic neurons, which can have long-lasting consequences on inhibitory networks. However, the role of deep-layer pyramidal neurons in instructing the development and distribution of GABAergic neurons is still unclear. To unravel the role of deep-layer pyramidal neuron activity in orchestrating the spatial and laminar distribution of parvalbumin neurons, we selectively manipulated subsets of layer 5 projection neurons. By deleting Snap25 selectively from Rbp4-Cre + pyramidal neurons, we abolished regulated vesicle release from subsets of cortical layer 5 projection neurons. Our findings revealed that chronically silencing subsets of layer 5 projection neurons did not change the number and distribution of parvalbumin neurons in the developing brain. However, it did have a long-term impact on the laminar distribution of parvalbumin neurons and their perineuronal nets in the adult primary motor and somatosensory cortices. The laminar positioning of parvalbumin neurons was altered in layer 4 of the primary somatosensory cortex in the adult Snap25 cKO mice. We discovered that the absence of layer 5 activity only had a transient effect on the soma morphology of striatal PV neurons during the third week of postnatal development. We also showed that the relationship between parvalbumin neurons and the perineuronal nets varied across different cortical layers and regions; therefore, their relationship is far more complex than previously described. The current study will help us better understand the bidirectional interaction between deep-layer pyramidal cells and GABAergic neurons, as well as the long-term impact of interrupting pyramidal neuron activity on inhibitory network formation.

Fossils of embryonic and hatchling individuals can provide invaluable insight into the evolution of prenatal morphologies, heterochronies, and allometric trajectories within Archosauria but are exceptionally rare in the Triassic fossil record, obscuring a critical aspect of archosaurian biology during their evolutionary origins. Microvertebrate sampling at a single bonebed in the Upper Triassic Chinle Formation within Petrified Forest National Park has yielded diminutive archosauriform femora (PEFO 45274, PEFO 45199) with estimated and measured femoral lengths of ~31 mm and ~ 37 mm, respectively. These new specimens provide the unique opportunity to assess the preservation, body size, and growth dynamics of skeletally immature archosauriforms in North America and compare the growth dynamics of archosauromorphs within an evolutionary and ontogenetic context. We assign PEFO 45199 and PEFO 45274 to Phytosauria (Archosauriformes) based on their strongly sigmoidal shape in lateral view, the presence of proximal anterolateral and posteromedial tubera, the absence of an anteromedial tuber of the proximal end, a teardrop-shaped proximal outline, and a fourth trochanter that is not confluent with the proximal head. Osteohistological analyses of PEFO 45274 reveal a cortex comprising low vascularity, parallel-fibered bone composed of primary osteons that lacks a hatching line and any lines of arrested growth. We interpret PEFO 45274 as a slow-growing, post-hatching individual of less than 1 year of age. Surprisingly, osteohistology of some larger phytosaur femora implies faster growth rates in comparison to PEFO 45274 based on the occasional presence of woven bone and overall higher degrees of vascular density, suggesting the ontogenetic shift from rapid-to-slow growth rates might not occur simply or uniformly as expected in Phytosauria and that non-archosaurian archosauriforms may exhibit size-dependent histological characteristics. This study highlights the importance of including osteohistology from multiple body sizes to investigate non-archosaurian archosauriform ancestral growth rates given the phylogenetic position of phytosaurs near the divergence of Archosauria.

As fully aquatic mammals, hearing is arguably the most important sensory component of cetaceans. Increasingly, researchers have been harnessing computed tomography (CT) to investigate the details of the inner ear as they can provide clues to the hearing abilities of whales. We use microCT scans of a broad sampling of the ear bones (periotics) of primarily toothed whales (Odontoceti) to investigate the inner ear bony labyrinth shape and reconstruct hearing sensitivities among these cetaceans, including several taxa about which little is currently known. We find support for sensitivity to the lower frequency spectrum in the archaeocete Zygorhiza kochii and an early toothed mysticete cf. Aetiocetus. Oligocene odontocetes (including one from our novel dataset), stem delphinidans, and two additional species of the long-snouted eurhinodelphinids are found to have been able to hear within the narrow-band high-frequency spectrum (NBHF), which is thought to be a specialized form of hearing that evolved convergently multiple different times in extant groups to avoid predation by macroraptorial predators. Our results thus indicate that NBHF evolved as early as the Oligocene and certainly in stem delphinidans by the early Miocene, and thus may be an ancestral characteristic rather than a more recent innovation in select groups.