Editor’s Choice Articles

The mental eminence (chin) is a uniquely human anatomical feature with critical relevance across multiple domains of biomedical and anthropological research. This transdisciplinary review aims to synthesize current knowledge regarding its morphology, population variability, evolutionary origin, and surgical relevance. A comprehensive scoping review aims to map how the mental eminence has been defined and evaluated in anthropological, forensic research, identifying the main methodological approaches, anatomical landmarks, and sources of morphological variability, as well as the reliability and applicability of current assessment methods in clinical–forensic contexts. The search strategy was performed in October 2025. The authors initially identified 3125 records, and 26 studies were finally included and assessed for qualitative analysis. Moreover, the analysis integrates data from osteological collections, radiographic imaging, and modern morphometric studies. The mental eminence exhibits significant variability across human populations, with pronounced sexual dimorphism and evolutionary distinction from non-human primates. Its emergence in Homo sapiens is a key taxonomic trait. Clinically, the chin serves as a landmark in surgical procedures involving genioplasty, trauma reconstruction, and dental implantology. Recent advances in imaging and biometrics have refined its analysis in both anthropological and diagnostic contexts. Though often overlooked, mental eminence plays a vital role in craniofacial morphology and human evolution. Its study bridges osteology, anthropology, and surgery, offering insight into both phylogenetic development and applied anatomical practice. A multidisciplinary understanding of this structure enhances its diagnostic and therapeutic utility. Full article

Background: Larger brains are believed to rely more heavily on intra-hemispheric than inter-hemispheric processing, which may lead to a proportionally reduced callosal size. Methods: To test this hypothesis, we used T1-weighted magnetic resonance images from a large population sample (n = 38,034). The sample was drawn from the UK Biobank and included 19,947 females and 18,087 males, aged between 44 and 83 years (mean ± SD: 64 ± 7.72 years). Linear modelling was used to assess the relationship between proportional callosal volume and total intracranial volume, with sex, age, and handedness included as covariates and interaction terms. Results: We observed a significant negative relationship between proportional callosal volume and total brain volume, such that larger brains had proportionally smaller corpora callosa. Conclusion: These findings support the hypothesis that increasing brain size is associated with reduced inter-hemispheric connectivity, potentially due to conduction constraints that promote greater intra-hemispheric processing in larger brains. Full article

Background: Lower phylogenetic species are known to rebuild cut-off caudal parts with regeneration of the central nervous system (CNS). In contrast, CNS regeneration in higher vertebrates is often attributed to immaturity, although this has never been conclusively demonstrated. The emergence of stem cells and their effective medical applications has intensified research into spinal cord regeneration. However, despite these advances, the impact of clinical trials involving spinal cord-injured (SCI) patients remains disappointingly low. Long-distance regeneration has yet to be proven. Methods: Our study involved a microsurgical dorsal myelotomy in fetal rats. The development of pioneering long primary afferent axons during early gestation was examined long after birth. Results: A single cut triggered the intrinsic ability of the dorsal root ganglion (DRG) neurons to reprogram. Susceptibility to hypoxia caused the axons to stop developing. However, the residual axonal outgrowth sheds light on the intriguing temporal and spatial events that reveal long-distance CNS regeneration. The altered phenotypes displayed axons of varying lengths and different features, which remained visible throughout life. The previously designed developmental blueprint was crucial for interpreting these enigmatic features. Conclusions: This research into immaturity enabled the exploration of the previously impenetrable domain of early life and the identification of a potential missing link in CNS regeneration research. Central axon regeneration appeared to occur much faster than is generally believed. The paradigm provides a challenging approach for exhaustive intrauterine reprogramming. When the results demonstrate pre-clinical effectiveness in CNS regeneration research, the transformational impact may ultimately lead to improved outcomes for patients with spinal cord injuries. Full article

Peripheral nerve injuries (PNIs) commonly result from trauma, compression, or iatrogenic causes, leading to functional deficits. Despite the peripheral nervous system’s regenerative capacity, current treatments yield inconsistent outcomes. Basic science and translational research supporting nerve repair remain underdeveloped, partly due to the absence of standardized protocols, limiting reproducibility. Animal models are essential for studying injury mechanisms, repair strategies, and therapeutic development. This review examines commonly used animal models in PNI research, from non-mammalian species to rodents and large mammals. We discuss the relevance of injury types, experimental variables (i.e., age, sex, nerve type), and study design elements (i.e., nerve gap size, injury induction methods). Assessing these models’ strengths and limitations, this review aims to guide researchers in selecting appropriate models that enhance preclinical relevance. It also addresses the need for standardized protocols and future directions for improving PNI research and patient outcomes. Various PNI treatments—including microsurgery, nerve grafts, scaffolds, stem cells, immunomodulators, nerve augmentation strategies, and polyethylene glycol-mediated fusion—have been developed using animal models. These models are essential for driving innovation and translating emerging therapies to improve outcomes across a broad range of peripheral nerve injuries. Full article

Background/Objectives: The hypoglossal nerve plays a crucial role in cervical surgery, requiring precise anatomical knowledge to prevent iatrogenic injury. This study examined its position relative to key structures using cadaveric dissections and assessed ChatGPT-4’s reliability in providing anatomical insights. Methods: Ten cadavers were dissected to identify the hypoglossal nerve’s course in relation to the internal jugular vein, carotid arteries, thyro-linguo-facial trunk, hyoid bone, and digastric muscle. Measurements were taken, and ChatGPT was queried for anatomical guidance and surgical recommendations. Results: The hypoglossal nerve was consistently medial to the internal jugular vein and lateral to the carotid arteries. The measured distances to the surrounding structures showed notable variability, particularly with the thyro-linguo-facial trunk. ChatGPT accurately described major landmarks but overlooked lesser-known anatomical triangles and provided no additional dissection guidance. It primarily suggested intraoperative monitoring and preoperative imaging. Conclusions: The carotid and submandibular triangles serve as reliable landmarks for identifying the hypoglossal nerve. This study highlights an unreported variability in its relationship with the thyro-linguo-facial trunk. ChatGPT, while informative, lacked detailed surgical applicability for dissection. Full article

This article explores the continuation of the pathological morphology research program at neuroscience-related institutes from the Kaiser Wilhelm Society after World War II. It covers the research tradition in the brain sciences, which can be described by an emphasis on gross anatomy, the functional implications of morphological substrates, and the analysis of neurohistological research paths of the human brain in comparative contexts. To enable examination of the assimilation processes of the Kaiser Wilhelm Society’s legacy, the decisions and developments of the newly created Max Planck Society in Germany and its early brain science facilities will be assessed for the time period from 1948 to 2002. Pertaining to these overall developments in the Max Planck Society, a persistence of the “morphological paradigm” (microanatomy, pathology, comparative anatomy, etc.) can be identified as lasting until the 1960s. The newer “functional paradigm” (neurophysiology, electroencephalography, cybernetics, and behavioral studies) only became more visible when the first generations of the scientific leaders left their positions in this national research society. It is of note that many directors and scientific members, including Detlev Ploog (1920–2005), Dieter Lux (1924–1995), Georg W. Kreutzberg (1932–2019), Otto Detlev Creutzfeldt (1927–1992), Hans Thönen (1928–2012), Manfred Eigen (1927–2019), Erwin Neher (b. 1944), Hartmut Wekerle (b. 1944), Albert Hertz (1921–2018), Bert Sakmann (b. 1942), and Wolf Singer (b. 1943) were part of the American Neuroscience Research Program as associates, members, conference chairs, or trainees. Likewise, they joined the Society for Neuroscience early on, after it had emerged from the Neuroscience Research Program’s steering committee in 1969. This article seeks to clarify the context of the reorganization of the brain research-related Max Planck Institutes during the postwar period after World War II. Its trajectory includes the location of the institutes, their previous involvement in applied research, and personal continuities in scientific leadership positions, contributing to debates during the first decades of the Max Planck Society. The lens of pathological brain research emerges here as an important viewpoint to aid the understanding of the continued impact and concerns over the dominant morphological approaches in postwar West German neurology and psychiatry. Full article

The rhesus monkey (Macaca mulatta) is a non-human primate with a genome that is 93.5% identical to that of humans. Both species, therefore, have numerous phenotypical similarities in common. Consequently, this non-human primate is regularly studied in biomedical research. Not only does the rhesus monkey play an important role as an animal model for studying human disease, but it is also often featured in zoos, and there are substantial feral populations that live in Asia. Since they are exploited as research subjects, their appropriate housing and husbandry and the validation of obtained research data benefit from the comprehension of the rhesus monkey anatomy. Unexpectedly, the number of anatomical documents on the rhesus monkey are largely outnumbered by publications on the anatomy of domestic animals. In addition, the limited number of available anatomical books and atlases are, unfortunately, outdated, e.g., by presenting black-and-white photographs and using archaic nomenclature, or failing to cover the in-depth anatomy of various anatomical systems. Since state-of-the-art data on the rhesus monkey anatomy are requested by biomedical researchers and veterinarians responsible for the daily care of these captive animals, the present study describes the musculature of the foot of the rhesus monkey. It builds on a recently published manuscript on the topographical anatomy of the pelvic limb of this non-human primate. Full-color anatomical (stereomicroscopic) photographs are taken during layer-by-layer dissections of the feet of three rhesus monkeys. All the muscles, from the superficial to the deepest layer, are described using veterinary anatomical nomenclature and annotated on multipaneled figures. Although the foot musculature of the rhesus monkey largely parallels that of its human counterparts, the small number of dissimilarities should be recognized when extrapolating these research data. In addition, a solid understanding of the rhesus monkey anatomy by veterinarians can be valuable during medical interventions, such as surgery for foot injuries. Full article

During anatomical dissection of a female body donor at the Howard University College of Medicine, a rare renal anomaly was discovered. Detailed anatomical and histological analyses on this anomaly were compared to a normal kidney from another donor and previously published reports from a comprehensive literature review. Anatomical assessment confirmed the condition of pancake kidney, a rare form of completely fused, ectopic kidneys without an isthmus. Due to the lack of symptoms in patients with this condition and the limited number of published case reports, very little information is available regarding the anatomy, development, and histology of pancake kidneys, making it difficult to determine an accurate estimate of the number of individuals who are affected. In the case presented here, a single kidney was located in the pelvis, below the bifurcation of the abdominal aorta into the common iliac arteries. The histological analysis of the pancake kidney revealed focal segmental glomerulosclerosis, dilated renal tubules, and increased interstitial fluid, all common characteristics of renal disease and not present in the normal kidney of the other donor. Future studies are needed to compare the histology of pancake kidneys and typical kidneys in order to help determine potential pathologies. Full article

The pancreas is a vital organ nestled deep within the abdomen, playing a crucial role in both endocrine and exocrine functions. It is elongated and tadpole-shaped, with a head, body, and tail. The intricate connections to adjacent structures through a network of blood vessels, ducts, and supportive tissue transform pancreatic cancer into one of the most fatal malignancies globally as a result of a typically late diagnosis and metastatic form of the disease. Lymph node metastasis (LNM) is prevalent in the majority of individuals diagnosed with pancreatic cancer, signifying a critical factor influencing prognostic outcomes. The para-aortic lymph nodes (PALN) play an important role in the lymphatic drainage of various organs, including the kidneys, pancreas, and parts of the gastrointestinal tract. In pancreatic cancer, the risk of PALN metastasis holds considerable clinical significance, and diagnosing your involvement is primordial to therapeutic decisions and to increase the survival expectations of these patients. Full article

Bone remodeling is essential for maintaining bone health. The imbalance between bone formation and bone resorption leads to bone diseases such as osteoporosis. Connexin43 (Cx43) is a gap junction molecule that plays an important role in bone homeostasis. The present study investigates the morphological characteristics of bone trabeculae and the distribution of Cx43 in bone cells using osteoporotic rat models to explore the relationship between osteoporosis and bone remodeling. Female Sprague–Dawley rats were divided into three groups: sham, ovarectomy with food deprivation (OVX+diet), and ovarectomy with steroid administration (OVX+steroid) for 3 and 12 months to induce osteoporosis. The lumbar vertebrae were processed for histomorphometric and immunohistochemical evaluation of the trabeculae and the distribution of Cx43 in bone cells. The data showed a significant reduction in trabecular bone in both osteoporotic groups. After 12 months, the OVX+diet treatment resulted in reduced mineralization and an increase in unmineralized bone. The percentage of alkaline phosphatase-positive areas in the OVX+diet vertebrae was lower at 12 months compared to the sham group. A significant increase in tartrate-resistant acid phosphatase (TRAP) positive osteoclasts was observed in the OVX+diet group. Both osteoporotic groups showed a decrease in Cx43-positive osteoblasts areas. An increase in the number of osteoclasts positive for Cx43 was detected in the OVX+diet group. The changes in Cx43 distribution in bone cells, together with trabecular mineralization, suggest that Cx43 may play a role in the progression of osteoporosis and could be a valuable target to improve bone remodeling. Full article

The mesial piriform region plays a central role in olfaction. Its small size and complex geometry, however, make it a difficult target in functional neuroimaging studies, while histological maps often represent schematic drawings, which are not compatible with requirements for modern imaging. To bridge this gap, cytoarchitectonic analysis and mapping of the region was performed in serial histological sections over their full extent in 10 postmortem brains. The temporobasal areas PirTBd and PirTBv and temporal areas PirTu and PirTit were identified and analyzed. Probabilistic cytoarchitectonic maps of the piriform areas in MNI reference space and high-resolution maps of the amygdala-piriform region on the BigBrain model were calculated as part of the Julich-Brain. Differences in the cytoarchitectonic “texture” of the region were quantified based on the Gray Level Co-Occurrence Matrix. Results showed that allocortical areas were not consistently associated with the rostral Limen insulae, although it was often suggested as a landmark in neuroimaging protocols. PirTu was associated with the uncal tip. PirTit was the largest area, reaching to the temporal pole, with a “temporal” (caudal) and a “temporopolar” (rostral) part having complex neighborhood relationships. The probabilistic maps reflect interindividual variability; they are openly available via the digital EBRAINS platform to serve as an anatomical reference for studies related to olfaction. Full article

This article delves into the life and accomplishments of Juan Valverde de Amusco (c. 1525–c. 1587), a Spanish anatomist. Specifically, it focuses on his book titled HISTORIA de la composición del cuerpo humano. The book was the first anatomy opus published after Andreas Vesalius’ De humani corporis fabrica libri septem, written in a Romance language, the Castilian Spanish language, making it the most renowned post-Vesalian anatomy book in Europe and beyond during the 16th and 17th centuries. Compiling complete editions and reproductions of figures, it had 19 editions and several translations. One of its principal contributions was the initial graphical representation of the stapes ossicle. It provided the first accurate description of the pulmonary circulation, vomer bone, and four extraocular rectus muscles. Throughout the book, Valverde corrected numerous of Vesalius’ anatomical observations. HISTORIA de la composición del cuerpo humano was the first anatomy book to use chalcographic illustrations, which are of superior anatomical quality than those printed from engraved wood in Andreas Vesalius’ book. Next, many anatomy textbooks of that time incorporated Valverde’s book illustrations. Valverde’s book was practical, timely, and well referenced, making it a valuable resource for scholars and non-scholars. The conclusion is that Juan Valverde de Amusco merits a place as a pioneer in scientific knowledge transfer. Full article

This review addresses the role of chemical communication in mammals, giving special attention to the vomeronasal system in pheromone-mediated interactions. The vomeronasal system influences many social and sexual behaviors, from reproduction to species recognition. Interestingly, this system shows greater evolutionary variability compared to the olfactory system, emphasizing its complex nature and the need for thorough research. The discussion starts with foundational concepts of chemocommunication, progressing to a detailed exploration of olfactory systems. The neuroanatomy of the vomeronasal system stands in contrast with that of the olfactory system. Further, the sensory part of the vomeronasal system, known as the vomeronasal organ, and the integration center of this information, called the accessory olfactory bulb, receive comprehensive coverage. Secondary projections of both the olfactory and vomeronasal systems receive attention, especially in relation to the dual olfactory hypothesis. The review concludes by examining the organization of the vomeronasal system in four distinct mammalian groups: rodents, marsupials, herpestids, and bovids. The aim is to highlight the unique morphofunctional differences resulting from the adaptive changes each group experienced. Full article

Tissue engineering is a powerful tool with which to systematically identify the determinants of biological functions. Applied to the design and fabrication of biomimetic brains, tissue engineering serves to disentangle the complex anatomy of neural circuits and pathways by recapitulating structure-function relationships in simplified model systems. The complex neuroanatomy of the cerebral cortex, with its enigmatic columnar and stratified cytoarchitectonic organization, represents a major challenge toward isolating the minimal set of elements that are required to assemble neural tissues with cognitive functions. Whereas considerable efforts have highlighted important genetic and physical correlates of early cortical tissue patterning, no substantive attempt to identify the determinants of how the cortices acquire their relatively conserved, narrow range of numbered layers is evident in the literature. Similarly, it is not yet clear whether cortical columns and laminae are functionally relevant or epiphenomena of embryonic neurodevelopment. Here, we demonstrate that spatial frequencies (m⁻¹) derived from the width-to-height ratios of cerebral cortical columns predict sinusoids with a narrow range of spatial cycles over the average cortical thickness. The resulting periodicities, denoted by theoretical wavenumbers, reflect the number of observed cortical layers among humans and across several other species as revealed by a comparative anatomy approach. We present a hypothesis that cortical columns and their periodic layers are emergent of the intrinsic spatial dimensions of neurons and their nested, self-similar aggregate structures including minicolumns. Finally, we discuss the implications of periodic tissue patterns in the context of neural tissue engineering. Full article

Computed tomography (CT) angiography is the main method for the initial evaluation of cerebral circulation in acute stroke. A comprehensive CT examination that includes a review of the three-dimensional and maximum-intensity projection images of the main intra and extracranial arteries allows the identification of most abnormalities and normal variants. Anatomical knowledge of the presence of any normal variants, such as fenestration, duplications, and persistent fetal arteries, plays a crucial role in the diagnosis and therapeutic management of acute stroke. However, the opposite is also true. In fact, sometimes it is the clinical picture that allows weighing how relevant or not the alteration found is. Therefore, in this review, a concise representation of the clinical picture attributable to a given arterial vessel will be included. Full article

(1) Background: The anatomical variations of neurovascular canals that are encountered in oral surgery are often overlooked by anatomy textbooks or provided with insufficient information. The aim of this study is to analyze the most common variations, describing their morphology, prevalence and clinical implications. (2) Methods: A review of published literature from the 20th century onwards was performed using the PubMed electronic database as well as anatomical textbooks. The variations being investigated were: retromolar canal (RMC) and foramen (RMF), accessory mental foramen (AMF), midline (MLF) and lateral (MLF) lingual foramina and canalis sinuosus (CS). (3) Results: Anatomical variants of neurovascular canals and foramina have a significant incidence and important clinical implications in the most common oral surgery procedures such as third molar extraction, bone harvesting and implantology. (4) Conclusions: Knowledge of these variables is highly important both for students to have a more accurate anatomical awareness and for professional surgeons to be able to provide better diagnoses and prevent complications during oral surgery techniques. Full article

Although the presence of an arrector pili smooth muscle is documented in many monkey species, its regional peculiarities are hitherto not well documented. We aimed to study this aspect in the face of rhesus monkeys with different areas of hair coat. Eight different regions of six monkeys (male and female) were studied using light microscopy and immunohistochemistry (antibody against smooth muscle alpha actin). We identified two regions (lips and eyelids) with vellus hairs that did not show an arrector pili muscle. In the eyelids, the hairs are rather small and short; in the lips, the vellus hairs were surrounded by striated muscle fibers from the orbicularis oris muscle. In all other regions (frontal region, forehead, cheek, chin), the vellus hairs contained an arrector pili muscle with comparable morphology. Only in the chin region, where additional striated muscles from the face muscles were present, the arrector pili muscles were thinner. All vibrissae showed a close relation to striated muscle fiber bundles of the facial muscles. They never developed smooth muscle bundles assigned as arrector pili equivalent. Full article

Development of effective in vitro human lip models, specific to the vermilion epithelium, has not progressed as much as that of skin and oral mucosa/gingiva models in vitro. Our histologic examination demonstrated that a Japanese macaque (male, 7 years and 9 months old) had vermilion in the lip distinct from adjacent skin and oral mucosa, resembling histological characteristics of the human lip. Therefore, in this study, we examined the gene expression profile of the three distinct epithelia (skin/vermilion/oral mucosa) within the lip of a Japanese macaque to explore a single potential marker of human vermilion epithelium. Six pairwise comparisons in the skin/vermilion/oral mucosa epithelium in vitro and in vivo revealed 69 differentially up-regulated genes in vermilion epithelium in vivo, in which a few unique genes were highly expressed when compared with both skin and oral mucosa epithelium in vivo using clustering analysis. However, we could not detect a single marker specific to vermilion epithelium supported by the gene expression profile of a Japanese macaque. Instead, the pair of keratin 10 and small proline-rich protein 3 resulted in a potential marker of vermilion epithelium in the human lip (female, 53-year-old) via a double-immunostaining technique. Nonetheless, our result may provide further clues leading to other potential markers of the vermilion epithelium. Full article