Journal of Anatomy最新文献

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.

The scapula connects the forelimb to the axial skeleton, and its morphology varies among primates, showing similarities across species with comparable locomotor behaviours, particularly forelimb-suspensory locomotion. The serratus anterior (SA), levator scapulae (LS) and rhomboid (Rh), collectively referred to as the LSR, connect the scapula to the trunk. The morphology of the LSR shows interspecific variation among primates, but its diversity and determinants have not been fully elucidated. This study explored the morphological adaptations in primate locomotor evolution by analysing the morphology and innervation of the LSR. We examined 27 limbs of 11 primate species across Catarrhini, Platyrrhini and Strepsirrhini. Based on the LS origin, the LSR were classified as: Type I (Continuous type), where LS is attached to all the cervical vertebrae and continuous with the SA; Type II (Separated type), where LS is attached to the first to fourth cervical vertebrae and separated from the SA; and Type III (Intermediate type), where the demonstrated features are between Types I and II. In all specimens, the LSR were innervated by C3-8, with C4-7 consistently present. In Type II, C5 innervated both the lower LS and the upper SA, whereas in Type I and Type III, C5 innervated the lower LS. Type I was found across all groups, suggesting its representation as the ancestral form. Both Type II and Type III appear to be derived from the Type I. In Type II, separation of LS and SA reflects division of the C5-innervated region rather than loss of the lower LS. Type II occurred only in Hominoidea, suggesting increased functional demands on the upper SA. Type III is considered a subtype of Type I, retaining C5 innervation in the LS despite morphological separation. The occurrence of Type III in small-bodied species of the family Cebidae suggests that it represents a subtype associated with variation in body size. These findings suggest that the morphology of the LSR in primates is shaped not only by phylogenetic background but also by species-specific functional demands.

Shoulder anatomy is complex, varying in shape and pose. Studies have related bone shape and joint function, which can predict each other but not yet in the shoulder. This project aims to investigate bone shape and pose relationships in the healthy shoulder via partial least square regressions (PLSR). Sixty-eight registered humeri, scapulae, and clavicles were segmented (47 males and 15 females, age: 30.7 ± 9.5 years) from medical images (computed tomography and magnetic resonance images) and constituted the shape input (principal component analysis scores). Local bone coordinate systems (three axes and origin) composed the pose information. PLSR analyses were conducted using the shape of one or all three bones to predict the pose and vice versa. The main variation mode explained scaling for shape (38% variation explained) and the three shoulder bones' anteroposterior (AP) and superoinferior translations, and humeral and clavicular AP rotations for pose (8%). There was no difference in explained pose variation whether using the humerus, scapula, or clavicle as predictors. However, pose variations were more intertwined between the scapula and the clavicle when using all three shoulder bones as predictors compared to single-bone models, suggesting a stronger coupling between these bones that likely originates from their shared anatomical constraints with the thoracic cage. The dataset showed a mild to excellent fit to the analysis (R² = 0.4-0.9); however, the findings lacked generalizability (Q² = 0.0-0.1), suggesting that PLSRs require additional information-such as soft tissue contributions-to enhance predictive performance. These findings have potential clinical applications in surgical planning, where individual bone shape could be used to estimate native shoulder poses in trauma patients; however, stronger predictive models incorporating additional anatomical or biomechanical parameters are needed to support such use.

Optical coherence tomography (OCT) is a modern imaging technology crucial for diagnosing retinal diseases by providing high-resolution, non-invasive images of biological tissues. Despite the widespread use of rabbits in ophthalmological research due to their anatomical similarities to the human eye, comprehensive data on normal retinal thickness in rabbits using OCT is limited. This study was conducted with the objective of measuring retinal thickness in rabbits using an OCT device specifically designed for their eyes. The study included 42 rabbits grouped according to age (3-6 and 12 months) and gender, and ethical guidelines for animal research were followed. Using the Envisuu R2310 OCT device, retinal thickness was measured at various distances from the optic disc. The measurements showed that there was no significant difference between genders, but there were significant age-related changes, with thickness peaking at 6 months and thinning at 12 months. The superior retina consistently appeared to be the thinnest region in all age groups. The use of a rabbit-specific OCT device provided accurate, high-resolution images, addressing previous challenges in measurement accuracy. The findings highlight the significance of age in retinal thickness variations, aligning with human studies showing age-related thinning and emphasizing the need for age control in rabbit retinal research. This study provides a valuable reference for future ophthalmological research and advances in developing rabbit disease models, offering insights into age-related retinal changes and enhancing the potential for scientific investigations using the OCT method.

Calcaneal spurs are shown to be increasingly prevalent in modern populations and often contribute to forming heel and foot pain. There are multiple hypotheses for their formation, including exercise, prolonged standing and obesity. The impact of these spurs on foot biomechanics remains unclear; it is suggested that their presence may contribute to enthesial avulsion forces. This study aimed to determine the avulsion properties of the plantar aponeurosis enthesis with and without spurs. Twenty-four feet from 15 cadavers donated to the Department of Anatomy at the University of Otago were used for this study. Tissues were X-rayed to determine the presence of spurs. The donor feet were dissected to isolate the calcanei. These were then mounted in a custom-developed 3D-printed clamping rig to perform tensile testing of the plantar calcaneal enthesis to determine pull-out forces of the central band of the plantar fascia. Biomechanical testing showed no statistically significant differences in avulsion properties between the spur (n = 7) and non-spur (n = 14) samples in any of the avulsion parameters investigated: F_max (1121 ± 358 N vs. 953 ± 283 N, mean ± SD, p = 0.302) and εF_max (53 ± 11% vs. 51 ± 13%, mean ± SD, p = 0.660). Despite this, the avulsion parameters were highly variable. The results of this study indicate that the pull-out force of the central band of the plantar fascia is unrelated to the presence of spurs. Therefore, it is less likely that plantar spurs fulfill a biomechanical function within the plantar fascia complex.

Quantifying strain in the free Achilles tendon (AT_F) is essential for understanding its mechanical function, yet existing in vivo studies report inconsistent strain values, even under comparable loading. These discrepancies are partly due to limitations of conventional two-dimensional (2D) imaging, which cannot fully capture the tendon's complex three-dimensional (3D) geometry. This study presents a novel MRI-based framework for assessing 3D centroid strain of the AT_F under passive ankle rotation. Eighteen healthy adults (10 females, 8 males, age: 24.4 ± 4.0 years) underwent static MRI scans at three joint angles (20° plantar flexion, neutral, and 20° dorsiflexion), from which 3D and 2D AT_F lengths were computed. Results showed that the 2D method failed to detect physiologically relevant strain and even indicated apparent shortening. On the other hand, the 3D method revealed significant but only a small magnitude of elongation of the AT_F (1.2% ± 0.3 from 20° plantar flexion to 20° dorsiflexion). Additionally, an offset simulation demonstrated that small sagittal-plane misalignments (2-4 mm) could introduce substantial variations of the AT_F length in the 2D measurements (2.8-6.3 mm). Such systematic errors can be due to the combined effects of imaging plane misalignment and complex features of distal soleus morphology. Collectively, these findings clearly show the limitations of the conventional 2D approaches when determining AT_F length and its changes upon loading, underscore the superior accuracy of 3D MRI in detecting subtle AT_F deformations, and provide critical insights into the anatomical and methodological sources of error in prior strain assessments.

Ulnar curvature has long been recognized as an indicator of locomotor behavior in mammals, although its relevance has yet to be thoroughly tested in a phylogenetically restricted and functionally diverse group. Extant cercopithecids exhibit a wide range of quadrupedal locomotor behaviors and substrate use, making them an ideal benchmark to test form-function relationships between ulnar curvature and locomotion. While their ulnar curvature has been partly investigated through its anteroposterior curvature, the mediolateral curvature remains largely unexplored. We hypothesized that ulnar curvature covary with habitual substrate use (i.e., terrestrial versus arboreal) and locomotor behaviors (e.g., suspension versus climbing) in both sagittal and coronal planes. In this study, we provide a comprehensive assessment of ulnar curvature in extant cercopithecids, based on an extensive and taxonomically diverse sample of 23 species and 167 individuals, to assess inter- and intraspecific morphological variation. As expected, our analyses confirm previous findings regarding anteroposterior curvature, with terrestrial quadrupeds exhibiting an anteriorly convex ulna, and arboreal taxa showing an anteriorly concave ulna. Regarding mediolateral curvature, arboreal taxa exhibit a lateral convexity, while terrestrial quadrupeds show a more complex sigmoid curvature, possibly reflecting resistance to the various mediolateral constraints generated by hand postures. Although the two curvatures seem to distinguish arboreal and terrestrial locomotor behaviors, their moderate covariation (~55%) suggests that curvature responds to partially distinct biomechanical factors. Suspensory taxa, previously thought to possess relatively straight ulnae, are revealed to have noticeable anteriorly concave bones, consistent with notable brachialis contraction during suspension. Unexpectedly, climbers show intermediate morphologies between arboreal and terrestrial quadrupeds, supporting the idea that ulnar curvature does not allow their distinction, implying that this behavior is difficult to infer through ulnar curvatures.

Chronic low back pain due to intervertebral disc (IVD) degeneration (IVDD) is a major global health burden. Interactions between IVD tissues and surrounding structures are important for spinal health and pathology, yet many studies focus on structures within the IVD and neglect a deeper investigation of adjacent tissues. This study describes a newly identified intervertebral fat pad (IVFP) in rat lumbar spines, its changes following IVD injury, and similar structures in mice and humans. IVFPs were analyzed histologically using naive and injured IVDs from a rat model of IVDD, in which 5-month-old rats underwent a triple-puncture annulus fibrosus (AF) injury of L3-4, L4-5, and L5-6 IVDs. Sagittal and coronal histologic samples were stained with safranin O/fast green and analyzed at 3, 7, 14, and 56 days post-injury. Naive and sham IVDs demonstrated the consistent presence of an IVFP between the anterior AF and anterior longitudinal ligament (ALL) in anterior and anterolateral regions of the IVD, without presence at posterior or postero-lateral IVD regions. The IVFP gradually disappeared in injured IVDs, and became largely absent by 56 days post-injury. Post-injury changes to the IVFP also included adipocyte shrinkage, fibrous tissue infiltration, and gradual IVFP disappearance, together suggesting progressive degeneration. IVFP-like structures were identified histologically in mouse and human IVDs, providing evidence of its presence across species. Fat pads studied in other musculoskeletal joints play roles in health and disease, suggesting a need for further study investigating the potential role of the IVFP in IVDD pathomechanisms and therapeutics.

Cover image: see E. Bruner et al., ‘Morphological variations and cortical atrophy of the precuneus in normal aging andAlzheimer’s disease’, this issue.