Journal of Anatomy最新文献

Crocodylians evolved a high variety of rostral morphologies during their evolutionary history, highlighting the strong links between morphological plasticity and environmental and ecological parameters. Two Late Cretaceous alligatoroids, the mesorostrine Leidyosuchus canadensis Lambe, 1907, and the brevirostrine Stangerochampsa mccabei Wu et al., 1996, from Alberta, Canada, preserve a large groove-shaped recess on the posterior part of the maxilla that has not been documented in other alligatoroids. Despite the potential phylogenetic and paleoecological significance of this neurovascular feature, internal and endocranial structures remain under-explored among stem alligatoroids. The endocranial morphology, including the paratympanic sinus system of Leidyosuchus canadensis and Stangerochampsa mccabei, was compared to those of extant crocodylians and of the extinct alligatoroid Diplocynodon ratelii based on computed tomography data. The Cretaceous alligatoroids share endocranial features, such as a posteroventral neurovascular projection of the labiolateral canal that connects to the groove-like recess at the posterior edge of the maxilla and a paratympanic sinus system most similar to those of small-bodied and young extant crocodylians, suggesting that these pedomorphic features may reflect the ancestral crocodylian condition. Future phylogenetic studies should consider internal and endocranial characters alike to improve our understanding on the relationships among crocodylians.

We reasoned that knowledge of the developmental components might provide the basis for clarifying controversial issues regarding atrial anatomy and would provide the background for recent clinical segmentation of the walls. We have revisited the interactive pdf files created by Hikspoors and colleagues to provide a pictorial account of human cardiac development, supplementing this information with the data available in the Human Developmental Biology Resource. We then revisited the multiple dissections of human hearts available in our joint archives. When first identified, the atrial component of the primary heart tube receives the systemic venous tributaries caudally and continues ventrally as the atrioventricular canal. The appendages then balloon laterally and ventrally from the primary component. The systemic venous tributaries are committed to the developing right atrium, with the pulmonary vein initially canalising from a solitary strand before becoming incorporated into the left atrium. The primary component of the atrial septum is reinforced by a second component formed by muscularisation of the mesenchymal cap and vestibular spine. The remaining rims of the oval fossa are interatrial folds. Each definitive atrium possesses a part of the body, a venous component, an appendage, and a vestibule, with the septum separating its cavities. Apart from the nodes of the conduction system, the atrial walls are composed of working myocardium, with the alignment of the myocytes underscoring preferential conduction.

Enamel histology may provide valuable insights into dental growth and life history traits. However, this method presents significant challenges for extinct species, particularly as the periodicity of the increments observed cannot be tested experimentally. Here, we propose a standardized methodological framework to formalize what has been done in the literature and help researchers working with fossil taxa. We applied this framework to a fossil dataset composed of 19 molars belonging to four species of Toxodontia (Notoungulata, Mammalia) - an extinct sub-order of South American notoungulates known for their specialized dental characteristics (crown height increase and change in eruption pattern) - with different crown height and age: the brachyodont species Pleurostylodon modicus from the Casamayor sub-unit of the Sarmiento Formation (Eocene; Argentina), and the three hypsodont species Eurygenium pacegnum from Salla (Late Oligocene; Bolivia), Adinotherium ovinum and Nesodon imbricatus from the Santa Cruz Formation (Middle Miocene; Argentina). Our protocol starts with the identification of Retzius lines as increments reaching the tooth surface and forming perikyma grooves. Retzius lines were often observed in restricted areas of the cervical region and/or outer enamel, as previously reported in the literature and confirmed in Toxodontia. Increments between successive Retzius lines were identified as laminations, corresponding to daily features. Lastly, although rare, sub-daily features in the form of cross-striations or fine laminations were also observed. The daily secretion rate (DSR) ranged from 6 to 22 μm/day, while the enamel extension rate (EER) ranged from 13 to 376 μm/day and the enamel formation front angle (EFFa) varies from 3 to 30°. There were however great disparities, especially depending on species and on crown region. In particular, the EER decreased drastically (and the EFFa increased) between the occlusal and the cervical regions. This decrease was less marked from the middle to the cervical region in more recent toxodonts (Adinotherium and Nesodon), suggesting a cruising speed in tooth growth probably associated with hypsodonty and a longer crown formation time. To investigate interspecific differences, we thus focused on the middle region of the crown. We noted lower values of DSR and EER as well as higher values of EFFa in Pleurostylodon, the smallest, oldest and only brachyodont species of the dataset, compared with the other taxa. However, as our sample is limited taxonomically, we could not clearly distinguish between the relative roles of hypsodonty, body mass, and phylogeny on the histological parameters. This work paves the way for a robust study of a larger dataset of Notoungulata to explore their tooth growth and life history along their repeated evolution of dental specializations.

Planar cell polarity (PCP) provides cells and tissues with a sense of direction in relation to the principal body axes of the embryo. In the developing mouse skin, PCP coordinates cell behaviours within the plane of the epidermal basal monolayer. In this report, evidence is presented for a novel, three-dimensional PCP protein-dependent tissue organising principle(s) operating within the mouse embryonic epidermis which coordinates cell long axis orientation across multiple epidermal layers. Here, the core-PCP protein, Frizzled-6 (Fz6), is found within different layers of developing trunk epidermis. Analysis of fz6 mouse mutant skin suggests Fz6 signalling contributes to several aspects of the novel tissue organising principle. Firstly, the robust coordination of epidermal cell long axis orientation between epidermal layers. Secondly, the timing of the switch in epidermal cell long axis orientation between orthogonal principal body axes, circumferential and longitudinal. Finally, the establishment of robust mirror symmetry of epidermal cell long axis orientation between each mouse embryo mid-flank, when viewed across the ventral midline. Local cell arrays/cell rosette-type arrangements within adjacent epidermal layers are implicated in the underlying mechanism coordinating epidermal cell long axis orientation. A previously unreported morphogenetic event within the superficial layers of the nascent epidermis may also rely on three-dimensional tissue polarity processes.

Cover image: see R. Crompton and colleagues, ‘Bipedalism or bipedalisms: the os coxae of StW 573’, this issue.

Modern trionychids (Testudines, Cryptodira) have a pan-tropical distribution, but their range encompassed Central Europe during the Miocene. However, their true Neogene northernmost limit is uncertain because of limited Miocene exposures in the northern half of Europe, including Poland. Here, we address this problem, describing the first Polish remains from this family, coming from three new Middle Miocene vertebrate localities. The material includes isolated shell fragments and an incomplete skull, studied using computed tomography. Through a detailed review of the variation of cranial characters in extant and extinct trionychids, as well as considering the already existing occurrences of the family in the Miocene of Europe, we propose a tentative assignment for this last specimen to Trionyx cf. vindobonensis. This is somehow unexpected since the geographically closest diagnostic records of the family from the Early Miocene of Czechia belong to Rafetus. These new occurrences hint toward an environment still suitable for thermophilic organisms between the Mid-Miocene Climatic Optimum and Late Miocene "washhouse" climate in the northern part of Central Europe.

Recent advances in the study of cross-sectional geometry have highlighted the value of ontogenetic data for understanding skeletal function, development, and biomechanics. While multiple protocols for extracting bone cross-sections have been validated in limb long bones, the clavicle (despite its unique curvature and developmental trajectory) has received little methodological scrutiny. Critically, two main alignment strategies can be used to extract clavicular midshaft cross-sections from 3D data, yet their comparability remains untested. This lack of standardization compromises the reproducibility and interpretability of clavicular cross-sectional property (CSP) data, particularly in developmental studies. This study evaluates two published alignment protocols for clavicular CSP extraction in non-adults: one that follows the natural curvature of the bone and one based on a standardized transverse plane. We analyzed high-resolution computed tomography scans of 81 individuals (ages 0.5-20 years) from a medieval osteological collection. Midshaft cross-sections were generated using both methods for each clavicle, and CSP variables were calculated. Comparative analysis involved linear regressions, Bland-Altman plots, and percent prediction error (%PE) to assess both systematic bias and the magnitude and direction of error between methods. While total area showed a significant proportional bias and %PE values exceeding the 5% acceptable error threshold, cortical subperiosteal area exhibited a consistent but non-proportional bias, indicating uniform overestimation across specimens. Z_p and J showed the largest directional errors, reflecting greater sensitivity to alignment differences. These discrepancies are not merely numerical but reflect fundamental geometric divergences introduced by the alignment strategy. As a result, CSP values obtained from these two protocols are not directly interchangeable. Together, Bland-Altman and %PE analyses provide a robust framework for evaluating agreement and highlight where pooling data across alignment strategies may be justified and where it is not. Our findings underscore the importance of methodological consistency in clavicular cross-sectional analyses. Given the anatomical complexity of the clavicle and its developmental plasticity, alignment strategy exerts a significant influence on derived CSP values. We recommend that future studies clearly report alignment criteria and avoid direct comparisons between datasets processed with different protocols.

The region of the gastric lesser curvature is reported to differ from other parts of the stomach in lacking rhythmic muscle movement in its proximal part, by fewer enteric nerve cells being present and by differences in distributions of interstitial cells of Cajal (ICC). Because detailed documentation of differences is lacking, we made a thorough investigation of the lesser curvature region. A substantial part of the lesser curvature region had a sparse ganglionated myenteric plexus (about 25% of the density of occurrence of ganglia in other regions). This overlapped with an area lacking longitudinal muscle, in which the enteric ganglia were serosal, at the circular muscle surface. The serosal ganglia lacked associated ICC, unlike other parts of the corpus and antrum, but ICC were numerous in the circular muscle. Close to the oesophagus, enteric ganglia were additionally between the circular and oblique muscle. Immunohistochemical investigation and muscle intracellular recording indicated that there was effective circular muscle innervation throughout the lesser curvature region, although a site of lower effectiveness of inhibitory innervation was found in the proximal part of the lesser curvature region. There was a gradient of reducing excitatory fibre innervation density towards the lesser curvature. Excitatory effects on the muscle were deduced to be indirect, as they are in the adjacent antrum. MRI of gastric movements in vivo revealed large amplitude propulsive waves of contraction at the lesser curvature towards the pylorus, and substantially, fourfold, lower amplitudes closer to the base of the oesophagus. We also describe that the major arterial supplies to the rat stomach radiate from the lesser curvature region and that mucosal specialisation does not correspond with functional or anatomical divisions of the stomach at the lesser curvature or elsewhere. Running parallel and lateral to the line of the lesser curvature were the previously reported esophago-pyloric ligaments that dynamic MRI suggested contract and relax during active antral movements. Thus, there are specialised features that distinguish the region of the lesser curvature from other gastric regions. At the proximal part of the lesser curvature, longitudinal muscle is absent, ganglia are sparse, ICC associated with ganglia are largely absent, and rhythmic circular muscle contractions have substantially lower amplitudes than more distally (in the 5 mm adjacent to the pylorus). The reduced amplitudes of contraction during peristalsis may be protective against mechanical force on the arteries and nerves that enter the stomach at the proximal lesser curvature region.

The ciliary body (CB) represents an immunoregulatory compartment for the ocular system and we questioned whether local immune regulation in the CB in humans could be under neural control. In this study, we explored whether the human CB contains a sympathetic-macrophage neuroimmune link. Seven right eyes from donated cadavers (five male, two female) were enucleated. After removal of the cornea, lens, and vitreous body, each eye was divided into quadrants. One quadrant per eye was processed for light microscopy to assess overall morphology, general and sympathetic nerve presence, varicosities, macrophages, and the proximity of sympathetic nerves to macrophages. Additional quadrants (whole-mount samples) were examined with three-dimensional (3D) confocal microscopy to visualize the spatial relationship between sympathetic nerves and macrophages and to determine whether these macrophages expressed β₂-adrenergic receptors. Our study shows that the human CB contains sympathetic nerves of which a significant amount was spatially associated to β2-adrenergic receptor expressing macrophages. The current study provides morphological evidence for a possible sympathetic-macrophage ocular neuroimmune link in humans which may constitute a novel field for the study of degenerative and inflammatory eye disease. Further understanding of the CB sympathetic nerves and their immunomodulatory capacity is needed for the development of future therapeutics.