Journal of Anatomy最新文献

Cover image: see A. Griffing et al., ’Diversity and development of the hemibacula of croaking geckos (Sphaerodactylidae: Aristelliger)‘, this issue.

Psittaciformes have a broad distribution across the southern hemisphere, and this wide ecological range is coupled with high levels of morphological diversity, particularly in the skull and beak structure, which has been previously linked to diet and body size. This paper studies how the beak and cranial shape vary in relation to predominant diet across a broad taxonomic range of parrots, using 2D geometric morphometric techniques and regression analyses. The data suggest that whilst there are some levels of significance between diet and beak shape, body mass was a much stronger co-variate. This indicated that skull morphology is more likely explained by parrot body mass and that whilst diet may partially explain beak shape in parrots when compared to other avian groups, it is not determining beak shape within the clade. Further study into other factors related to beak morphology, such as bite force, may prove key in explaining the evolutionary forces shaping the skull in parrots and other birds.

Proximal femoral medullary canal morphology is a key determinant of cementless stem fit, primary stability, and load transfer in total hip arthroplasty (THA), yet population-level three-dimensional characterization remains limited. This study was designed to quantify variability in canal geometry and to capture dominant anatomical modes of variation with statistical shape modeling (SSM). Computed tomography data from 763 candidates for primary THA (389 female, 374 male; 20-92 years) were analyzed. Endosteal contours of the proximal canal were processed to build a point-correspondent SSM by principal component analysis (PCA). Five geometric features were evaluated per specimen: equivalent radius (normalized), roundness, major-axis angle (torsion), flare index, and curvature. Substantial inter-individual variability was observed across all features, with differences by sex and age. The first three principal components accounted for 68.4% of total variance, and each showed interpretable associations with at least one geometric feature. Model behavior was examined by synthetic sampling within ±2 SD (specificity) and by 10-fold cross-validation (generalization), indicating faithful reconstruction of real shapes and stable performance on held-out data. These findings provide a compact description of proximal canal shape variation and its key geometric drivers. The resulting population map is expected to support implant selection and sizing in preoperative planning, inform shape-based classification, and guide design envelopes for standard and personalized stems, with potential efficiencies in manufacturing and material use.

Bone remodeling is the fundamental process of internal turnover through which bone tissue is renewed, repaired, and maintained. Achieved by the spatially and temporally coordinated actions of the basic cellular unit (BMU), this process is intimately linked to age-related increases in cortical porosity, which could be attributed to the imbalance or uncoupling between resorption and formation. Classically, the space carved out by the BMU is depicted to have a cutting cone tunneling through the bone matrix, and a tapering closing cone being filled in with new bone. The morphology of these spaces can reflect the dynamics of the BMU, where excess resorption leads to an enlarged cutting cone, decreased formation results in a shortened closing cone and larger Haversian canal diameter, and the uncoupling or delayed coupling creates a prolonged transition zone between resorption and formation. Using a micro-CT imaging modality that allows for three-dimensional visualization of remodeling events, we hypothesized that with aging, remodeling spaces would exhibit evidence of imbalance and/or uncoupling and this pattern would be more pronounced in women due to the effect of menopause. Micro-CT scans of anterior femoral midshaft specimens from 58 human donors (22 females, 36 males; age range: 20-82 years) were analyzed, yielding a total of 184 remodeling spaces with classically described morphology (a cutting cone followed by a closing cone and then a canal with stable diameter). Lengths and radii representative of the 3D size and shape of the remodeling spaces were measured and analyzed. Results showed that remodeling space morphology exhibits great inter and intraindividual variation, while no differences in the distribution of any measurements were found between sexes. Counter to our hypothesis, remodeling space dimensions decrease with increasing age, and no linear relationship between transition zone length and age was found. Rather, transition zone length was longer in older females but also in younger males, potentially indicating different underlying mechanisms causing prolonged transition zones, with the caveat that this pattern is only significant after removal of outliers. This study was the first to demonstrate the value of 3D analysis at the level of individual remodeling spaces in human cortical bone. Sex and age differences in morphology (or the lack thereof) indicate the intricate interplay of local and systemic controls from different mechanical, hormonal and cell senescence factors on remodeling dynamics, and the potential existence of seemingly normal remodeling events superimposed against the backdrop of overall progressive age-related bone loss. Importantly, our focus on classical remodeling space morphology excludes irregular patterns arising from interconnecting or coalescing pores and trabecularization of the cortex, which is a main limitation to be considered.

The Late Permian Weigeltisauridae are the world's first gliding reptiles, but much remains unknown regarding the anatomy of their patagium (or wing), which, in turn, confounds our understanding of their gliding mechanism and paleobiology. Here, we examine the morphology and osteo-histology of the patagial skeleton of weigeltisaurids using an array of imaging techniques and several thin sections through the wing skeleton of a specimen of Weigeltisaurus from the Late Permian of Germany. We demonstrate that patagials and gastralia share a one-to-one articulation, permitted by the uniquely specialized anatomy of the lateral gastralia. We also show, based on skeletal anatomy, histology, and inferred musculoskeletal relationships, that patagials are likely neomorphic ossifications and are thus not strictly homologous to the gastralia. We provide the first reconstruction of the musculoskeletal anatomy of the weigeltisaurid wing, suggesting that the base of the patagials was likely embedded in the M. obliquus externus group. Similar to the condition in the extant flying lizard Draco, these muscles may have contributed to the unfolding of the patagium, which was likely supported by hooking the manual claws onto the leading edge of the patagium. This would have provided weigeltisaurids with a means to maintain the patagium expanded and under tension while gliding, as well as some measure of control of the dihedral angle of the wing, thereby offering a means to control stability and maneuverability in flight. Wing folding may have been permitted by muscular and tendinous connections between the elements of the patagial skeleton, generating elastic tension toward a folded state, as in Draco. Lastly, the cross sections of the patagials show a bimodal cortical distribution with much thicker cortices along their cross-sectional long axis than short axis. This made the patagials rigid, which likely helped prevent patagial collapse during gliding. This work represents a critical step toward understanding the wing structure and gliding mechanism in weigeltisaurids, paving the way for future morphofunctional or biomechanical studies on the locomotion of the world's first flying vertebrates.

The existence of a striated deep transverse perineal (DTP) muscle remains an ongoing debate. We hypothesize that the DTP is macroscopically and microscopically detectable as a definable striated muscle belly in elderly males, but not in elderly female donors used in the dissection course. Investigations were performed on embalmed human donors of both sexes (n = 10, mean age at death: 82 years). We dissected the ischioanal fossa. After removing all the loose fat and connective tissues, including the arteries and nerves, we exposed the compact transversally running plate-shaped tissue stretched between the ischiopubic rami. Additionally, we removed the ischiocavernosus and bulbospongiosus muscles in the superficial perineal pouch along with the external genitals. The entire tissue plate located in the deep perineal pouch was then detached from the surrounding bony structures and dissected. To verify the musculature and its striation, we analyzed the tissue stereologically using light microscopy. At 40 μm intervals, 4-μm-thick serial sections were made perpendicular to the surface of the dissected tissue block. We determined the volume densities of the connective tissue, smooth muscle cells, and striated muscle fibers in the selected sections relative to the entire tissue in the deep perineal pouch. A relatively thick tissue plate (diameter: 4-5 mm) located superior to a fascia-like structure, the perineal membrane, was observed running transversally to the ischiopubic rami. Macroscopically, a clearly visible transverse running muscle was not observed in both sexes. Histologically, serial sections showed that the samples mainly consisted of connective tissue. In both sexes, the volume densities of the connective tissue were approximately 80%. In females, the volume density of the muscle cells was approximately 20%. In males, about 10% of the tissue was smooth, whereas just over 10% was striated muscle. However, the standard deviation between the donors was remarkable. In females, the proportion of the striated muscle cells was less than 1%. With increasing age, the volume density of the connective tissue increased, whereas those of the smooth muscle cells and/or striated muscle fibers decreased, independent of sex. There was no evidence of the existence of a clearly definable striated DTP muscle, not only in females but also in males. Muscle cells decreased with increasing age.

Facial shape is one of the most widely studied sexually dimorphic traits in humans. Sexually dimorphic facial shape has been linked to processes in neurodevelopment, immunocompetence, social perception, and mate preference. However, research into these associations has produced conflicting results, owing in part to the diverse methods used to quantify sexual dimorphism of the face. Our study compares two commonly used methods for measuring morphological sexual dimorphism: regression scoring and Canonical Variates Analysis (CVA; or linear discriminant analysis). We test both methods on a large sample of adult males (n = 540) and females (n = 540) with three-dimensional (3D) descriptions of the whole face, both with and without prior decomposition of the allometric component. Our results show that CVA outperforms regression scoring, resulting in scores that are more accurate in classifying the sexes and recreating the male-female shape axis (i.e., the difference in shape means based on reported sex). We also find that height is positively associated with regression scores after controlling for sex (p < 0.01), but not with CVA scores. These results suggest the need for a possible reassessment of previous claims that taller males have more male-like facial shapes, as well as a broader re-evaluation of the literature that considers the significance of method selection in shaping research outcomes. We establish a foundation for more accurate comparisons of facial sexual dimorphism and its relationship to various domains of human health and biology.