Journal of Anatomy最新文献

The sacroiliac articulation in anurans enables locomotion, including burrowing, swimming, jumping, and walking, by facilitating pelvic rotation and sliding. The hylid tribe Scinaxini comprises 134 Neotropical treefrogs divided into three genera: Julianus, Ololygon, and Scinax. The osteological elements of the sacroiliac articulation are well studied within the tribe, with Julianus having distinctive sacral diapophyses and sesamoids. Notably, the species J. camposseabrai has a medially elongated sesamoid, about three times its width in length, along with a short sacral diapophysis-a unique combination among anurans. However, information on the associated musculature in the tribe remains limited, restricting our understanding of this unique morphology. This knowledge gap prompted a detailed investigation of the musculature of the sacroiliac articulation in this clade of treefrogs. We revisited the osteology of the sacroiliac articulation and described its muscles in nine species of Scinaxini, including J. camposseabrai and J. pinimus. Our results showed that the origin and insertion of the muscles are largely conserved across the tribe, but variations exist in the orientation of the m. coccygeosacralis and the degree of separation between slips of the m. iliolumbaris. The species of Julianus have a unique sacroiliac osteo-muscular configuration, particularly J. camposseabrai, which is distinct from any previously described in anurans.

Some aesthetic medicine procedures, such as hyaluronic acid injections and thread implantations, are performed in the forehead area. Therefore, knowledge of the anatomy of this region is essential to ensure that medical procedures are carried out safely. A cross-sectional analysis of the available literature aims to organize and expand knowledge among specialists. Databases, such as Scopus, Embase, Web of Science, and PubMed were used to conduct a literature review, resulting in 1007 publications. After applying exclusion and inclusion criteria, results from 11 articles were extracted. The supratrochlear vein originates at the medial corner of the eye, where it joins the supraorbital vein to form the angular vein. The supraorbital vein, together with the angular vein, drains into the superior ophthalmic vein, converging at the medial edge of the supraorbital margin. Its main trunk connects medially with the supratrochlear veins and laterally with the superficial temporal veins, forming the transverse supraorbital vein. The superficial temporal veins are located on the temporal fascia and may appear as a single main branch or with three terminal branches, according to different reports. The vascularization of the forehead exhibits significant anatomical variability. Therefore, specialists performing medical procedures in this region should be prepared for diverse anatomy to ensure the safe administration of treatments in the forehead area. It is particularly crucial to recognize that pulmonary embolism may be the most serious venous complication following hyaluronic acid-based procedures, underscoring the need for precise anatomical knowledge and procedural caution.

Full-thickness skin equivalents provide a platform for preclinical screening, streamlining the clinical trial process and reducing the need for animal testing while also providing a tool capable of fundamental insights into skin biology. Understanding the specific role of melanin dynamics across various skin tones is essential not only to better understand its function in photoprotection but is also better representative of a diverse population. Although pigmented skin equivalents (PSEs) have been reported in the literature, they rarely recapitulate the structural location of melanin within native keratinocytes, which is pivotal to its photoprotective role. This is due in part to the reliance of existing technologies on exogenous or animal-derived extracellular matrix (ECM) constituents or the complete lack of a dermal compartment. In this study, we describe the development of novel PSEs representative of skin pigmentation phenotypes in vitro, which comprise fibroblast-secreted endogenous ECM and a differentiated, well-organised epidermis that resembles diverse skin tones. We demonstrate that these skin tones display morphological differences at a gross, histological and ultrastructural level. We then utilised the system to provide fundamental insights into the processes of melanogenesis, melanin transfer from melanocytes to keratinocytes, supranuclear cap formation and melanosome organisation within the epidermis. Quantification of melanosome dynamics allowed for comparison to native tissue and among skin tones, providing a detailed comparison among experimental conditions. This innovative technology enables a wide range of applications, such as studying pigmentation mechanisms in skin responses to external stimuli, disease modelling and drug testing involving the interactions between the epidermis and dermis.

As part of the jaw joint, the quadrate is a key skeletal element of the feeding system in nonmammalian vertebrates, which plays a critical role in resisting joint reaction forces (JRF). Some authors have suggested that the quadrate orientation reflects overall muscle anatomy and, by implication, JRF. Here, we quantitatively test the longstanding hypothesis that quadrate orientation is correlated with JRF orientation using the suchian lineage leading to extant crocodylia. The evolution of the characteristic crocodylian skull is a major transformation in vertebrate evolution in which the quadrate played a crucial role. We use detailed, three-dimensional biomechanical modeling to estimate JRF in a sample of eleven fossil and extant suchians and compare these to the orientation of quadrates. We use the cross-product of orientation vectors to quantify similarity in orientation and show that the angle of the quadrate in the sagittal plane is tightly coupled with JRF in the same. These results demonstrate a coordinated evolution between JRF and quadrate anatomy during suchian evolution and provide a framework with which to analyze evolutionary changes in joint anatomy and biomechanics.

Gustation or taste in elasmobranch fishes (sharks, skates, and rays) is an important sensory modality that dictates the palatability and ultimately the final decision regarding the ingestion of food. However, the surface morphology, size, abundance, and distribution of taste papillae in this group of apex predators has received little attention. This comparative study uses scanning electron microscopy, histology, and quantitative topographic analyses to assess the surface ultrastructure and density of taste papillae within the oropharyngeal cavity of six batoid species from three families and five selachian species from three families, all from a range of habitats and with a variety of diets. Within the batoids, mean taste papilla diameter ranges from 56 to 220 μm (with 0.7–1.6% of the papilla surface covered with sensory microvilli), while papilla diameter ranges from 152 to 360 μm in selachians (with 0.4–1.0% of the papilla surface covered with sensory microvilli). Both batoids and selachians possess two distinct size classes of papillae within the oropharyngeal cavity, where up to five small papillae (56–62 μm in diameter) often surround a large papilla (159–192 μm in diameter). There are significant differences in the total number of taste papillae within the oropharyngeal cavity in both superorders of elasmobranchs with a range of 2,119–20,317 in batoids (papillae occupying up to 3.1% of the oropharyngeal cavity with 0.05% of the cavity occupied by sensory microvilli) and a range of 1,354–11,890 in selachians (papillae occupying up to 1.7% of the oropharyngeal cavity with 0.02% of the cavity occupied by sensory microvilli) with taste papillae generally concentrated in areas used for food mastication. In batoids, papillae concentrate on ridges within the oropharyngeal cavities and in some species also on the oral valves (47–175 cm⁻¹ in the dorsal cavity, 33–160 cm⁻¹ in the ventral cavity). In selachians, the highest concentrations of taste papillae are on the oral valves and anterior regions of the oral cavity (4–215 cm⁻¹ in the dorsal cavity; 5–159 cm⁻¹ in the ventral cavity), which permits taste assessment during biting and manipulation of potential food items. This study is the first to investigate the abundance and distribution of taste papillae in the oropharyngeal cavity of a range of species of elasmobranchs, thereby improving our understanding of the importance of gustation, implications for oral food manipulation, and interpretations of both gustatory resolution and sensitivity.

Certain skeletal muscles are specialized for their functional roles, yet direct comparisons of cellular morphology of distinct muscles beyond fibre type distribution are limited. This study investigated myofibre morphology in predominantly slow, fast and mixed fibre muscles in humans and mice, with the aim of establishing reference values for muscle-specific myofibre size and shape. Nine healthy young men (Age: 26 ± 1 years, BMI: 23 ± 1 kg/m²) had muscle biopsies taken from soleus, triceps brachii and vastus lateralis muscles. Additionally, the soleus and gastrocnemius muscles were harvested from 7 male C57BL/6 mice. Muscle samples were analysed by ATPase (human) or immunofluorescence (mouse) stainings of fibre type specific cross-sectional area, perimeter and Shape Factor Index (SFI; fibre perimeter²/4 × π × fibre cross-sectional area). In humans, type I fibres had 30%–40% larger CSA and 4%–7% higher SFI in soleus (1.54 ± 0.06) compared to triceps brachii (1.47 ± 0.05) and vastus lateralis (1.43 ± 0.04). Type IIa fibres SFI were 10%–11% higher in soleus (1.61 ± 0.08) compared to triceps brachii (1.45 ± 0.04) and vastus lateralis (1.45 ± 0.08). Soleus type I fibres were more heterogeneous in terms of size and shape compared to other muscles. Analyses of mouse muscle showed a similar pattern, in that CSA and SFI were higher in type I and IIa fibres of the soleus compared to the gastrocnemius. These findings suggest a consistent morphological characteristic of soleus fibres across species, with potentially important implications for future biomedical research.

Cover image: see I. Cerda et al., ‘Dental plate histology of †Ischyodus dolloi (Chondrichthyes, Holocephali), from Antarctica’, this issue.

Normal function of the hand and, in particular, the finger joints is fundamental to the activities of daily life. Deterioration of hand and finger function can be detrimental and lead to poor quality of life. There are multiple causes of hand and finger dysfunction that can lead to pain and disability. In this review, we will consider the role of collagen and its organization within the finger joint capsules and adjacent entheses, particularly in the proximal interphalangeal joints, and aim to address three questions: (1) What are the main collagen orientations in the interphalangeal joint capsules of the human hand? (2) Is there a relationship between collagen orientation and joint function? (3) How could altering the orientation of collagen fibers affect the functional performance of the joint following injury or surgical intervention? To answer these questions, we will consider the evidence for the main collagen orientations in the finger joint capsules and entheses and investigate the relationships between structure and function. We will then consider how collagen organization is disrupted following injury and what may be potential modulators. This will provide a better understanding of how common surgical interventions affect collagen orientation in the joint capsules and highlight some implications for post-surgical outcomes.

The life histories of Palaeocene mammals are poorly known, but may have been central to their success in diversifying across terrestrial ecosystems after the end-Cretaceous extinction. Among these mammalian groups, the eutherian Taeniodonta are particularly enigmatic, with few modern analogues and no living descendants, despite being one of the only lineages to apparently traverse the Cretaceous-Palaeogene (K-Pg) boundary. Here, we investigate the life history of an early Palaeocene taeniodont, Conoryctes comma, based on a multi-individual, multi-element sample. Nearly all elements sampled exhibit similar osteohistological architecture, with a small internal zone of compacted coarse cancellous bone surrounded by an internal cortex of periosteally derived fibrolamellar bone of variable thickness, and an outer cortex of lamellar bone. The well-vascularized fibrolamellar complex in the limb bones, lacking cyclical growth marks, is indicative of overall rapid growth to near adult body size. Cyclical growth marks are present in the outer cortex after the transition to slow-growing lamellar bone, but not in the inner cortex, suggesting sexual maturity was reached in 1 year. In some elements, an internal non-cyclical growth mark shares histological similarities with weaning marks in living mammals and other contemporary Palaeocene mammals, and occurred at the body size predicted for this transition in therian mammals. The unusual presence of compacted coarse cancellous bone near the midshafts of multiple limb bones may be related to cortical thickening, and is similar to the arrangement described in some fossorial mammals, supporting previous assertions of this lifestyle in Conoryctes. Altogether, these palaeohistological signals suggest a life history in C. comma similar to living eutherians, despite uncertainty about whether it is within crown Placentalia or a close outgroup. Thus, our data are consistent with an early origin of placental-like reproductive strategies in their eutherian ancestors, although this attribute was likely shared more broadly among Mesozoic mammal lineages prior to the end-Cretaceous extinction.