Micro-mechanical properties of different sites on woodpecker’s skull

The uneven distributed microstructure featured with plate-like spongy bone in woodpecker’s skull has been found to further help reduce the impact during woodpecker’s pecking behavior. Therefore, this work was to investigate the micro-mechanical properties and composition on different sites of Great Spotted woodpecker’s (GSW) skull. Different sites were selected on forehead, tempus and occiput, which were also compared with those of Eurasian Hoopoe (EH) and Lark birds (LB). Micro structural parameters assessed from micro computed tomography (μCT) occurred significantly difference between GSW, EH and LB. The micro finite element (micro-FE) models were developed and the simulation was performed as a compression process. The maximal stresses of GSW’s micro-FE models were all lower than those of EH and LB respectively and few concentrated stresses were noticed on GSW’s trabecular bone. Fourier transform infrared mapping suggesting a greater organic content in the occiput of GSW’s cranial bone compared with others. The nano-hardness of the GSW’s occiput was decreasing from forehead to occiput. The mechanical properties, site-dependent hardness distribution and special material composition of GSW’s skull bone are newly found in this study. These factors may lead to a new design of bulk material mimicking these characteristics.     

Comparative study of the mechanical properties,micro-structure,and composition of the cranial and beak bones of the great spotted woodpecker and the lark bird

Woodpeckers are well able to resist head injury during repeated high speed impacts at 6–7 m s⁻¹ with decelerations up to 1000 g. This study was designed to compare the mechanical properties, microstructures and compositions of cranial bone and beak bone of great spotted woodpecker (Dendrocopos major) and the Mongolian sky lark (Melanocorypha mongolica). Microstructures were observed using micro-computed tomography and scanning electron microscopy and their compositions were characterized by X-ray powder diffraction and Fourier-transform infrared spectroscopy. Under high stress, the cranial bone and the beak of the woodpecker exhibited distinctive mechanical features, which were associated with differences in micro-structure and composition, compared with those of the lark. Evolutionary optimization of bone micro-structure has enabled functional adaptation to the woodpecker’s specific lifestyle. Its characteristic micro-structure efficiently avoids head impact injury and may provide potential clues to the prevention of brain injury using bio-inspired designs of shock-absorbing materials.     

Response of Woodpecker's Head during Pecking Process Simulated by Material Point Method

Prevention of brain injury in woodpeckers under high deceleration during the pecking process has been an intriguing biomechanical problem for a long time. Several studies have provided different explanations, but the function of the hyoid bone, one of the more interesting skeletal features of a woodpecker, still has not been fully explored. This paper studies the relationship between a woodpecker head’s response to impact and the hyoid bone. Based on micro-CT scanning images, the material point method (MPM) is employed to simulate woodpecker’s pecking process. The maximum shear stress in the brainstem (SSS) is adopted as an indicator of brain injury. The motion and deformation of the first cervical vertebra is found to be the main reason of the shear stress of the brain. Our study found that the existence of the hyoid bone reduces the SSS level, enhances the rigidity of the head, and suppresses the oscillation of the endoskeleton after impact. The mechanism is explained by a brief mechanical analysis while the influence of the material properties of the muscle is also discussed.     

Early development of the cephalic skeleton of Barbus barbus (Teleostei, Cyprinidae)

The inception, and development of the cephalic skeleton of Barbus barbus from hatching to 24 days passes through periods of fast and slow growth; these rates are not the same in different parts of the skull. Trabeculae, parachordal plates, Meckelian cartilages and hyposymplectics are present at hatching. Then the cartilaginous floor of the neurocranium develops, the pars quadrata, the hyoid bars and branchial arches elements appear shortly before the first movable dermal bones, the dentaries, maxillae and opercles. The first bone of the braincase to appear is the parasphenoid; other bones develop subsequently and at the same time: the angular, quadrate, interopercle and fifth ceratobranchial. Later the splanchnocranium continues to develop at a relatively fast rate while the neurocranium shows little growth. The braincase does not begin to close before the 24th day, nor do the first bones of the skull roof appear, while the bucco-pharyngeal apparatus is complete, having the adult shape. The early constitution of the latter structures seems to be linked with the mechanical demands of biological functions such as breathing and feeding.     

Ontogeny of the osteocranium in the African catfish,Clarias gariepinus Burchell (1822) (Siluriformes: Clariidae): Ossification sequence as a response to functional demands

The ontogeny of the bony skull of the African catfish, Clarias gariepinus, is studied from initial ossification until a complete skull is formed. The ossification sequence in C. gariepinus seems to be related to the functional demands that arise in a developing larva. Early ossification of the opercular bone coincides with the initiation of opercular skin movements. Early ossifications involve several dentulous bones, formed shortly before the transition phase from endogenous to exogenous feeding. The enlarging branchiostegal membrane becomes supported by the gradual adding of branchiostegal rays. Parasphenoid ossification may be related to protection of the brain during prey transport, whereas the several hyoid bones, including the parurohyal, are formed in relation to the increasing loads exerted onto the tendons of the sternohyoideus and consequently onto the hyoid bar. Overall skull reinforcement occurs almost simultaneously, with a whole set of perichondral bones arising especially at places of high mechanical load. The suspensorium becomes protected against dislocation in an anteroposterior direction through a ligamentous connection, which even becomes partially ossified, forming the sesamoid entopterygoid. Later, the cranial lateral-line system becomes enclosed by a set of gutters, which close, frequently becoming plate-like later in ontogeny. The brain also becomes covered dorsally. Additional dentition (prevomeral tooth plates) formation seems to coincide with formation of the opercular four-bar system, as well as with the time the digestive system becomes completely functional. Eventually, unossified regions between the bones become closed off, fortifying and completely covering the skull. J. Morphol. 235:183–237, 1998. © 1998 Wiley-Liss, Inc.     

Comparative anatomy and evolutionary history of suction feeding in cetaceans

Some odontocetes possess unique features of the hyolingual apparatus that are involved in suction feeding. The hyoid bone and associated musculature generates rapid, piston‐like retraction, and depression of the hyoid and tongue. “Capture” suction feeders (e.g., Globicephala) use suction for capturing and swallowing prey. “Combination” feeders (i.e., Lagenorhynchus) use both raptorial feeding (to capture prey) and suction (to ingest prey). In “capture” suction feeders, features of the hyoid and skull have been attributed to creating suction (i.e., large surface area and mandibular bluntness). In addition to odontocetes, a mysticete, the gray whale (Eschrichtius robustus), is considered a benthic suction feeder. However, anatomical studies of purported suction‐feeding structures of the gray whale are lacking. In addition, few studies have utilized evolutionary approaches to understand the history of suction feeding in cetaceans. This study incorporates quantitative and qualitative hyoid and cranial data from 35 extant and 14 extinct cetacean species into a multivariate principal component analysis and comparative phylogenetic analyses. Conclusions from these analyses are that some commonly attributed features (i.e., ventral throat grooves and mandibular bluntness) and one principal component are significantly correlated with suction feeding. Finally, ancestral state reconstructions indicate that suction feeding likely evolved once, early in cetacean evolutionary history.     

Sagittal plane kinematics of the adult hyoid bone

The hyoid bone is a unique bone in the skeleton not articulated to any other bone. The hyoid muscles, which attach to the hyoid bone, may play a role in neck mechanics, but analysis of their function requires quantifying hyoid bone mechanics. The goal of this study was to obtain the detailed kinematics of the hyoid bone over a large range of flexion-extension motion using radiographs at 5 postures. The position of the hyoid bone in the sagittal plane was characterized with respect to head, jaw, and vertebral movements. Sex differences in hyoid kinematics were also investigated. We hypothesized that (1) the position of the hyoid bone in the sagittal plane is linearly correlated with motion of the head, jaw, and vertebrae, and (2) the hyoid position, size, and kinematics are sex-specific. We found that the hyoid bone X, Y, and angular position generally had strong linear correlations with the positions of the head, jaw, and the cervical vertebrae C1-C4. Hyoid X and angular position was also correlated to C5. Sex differences were found in some regressions of the hyoid bone with respect to C1-C5. The angular and linear measurements of the hyoid bone showed sex differences in absolute values, which were not evident after normalization by posture or neck size. Incorporating these results to neck models would enable accurate modeling of the hyoid muscles. This may have implications for analyzing the mechanics of the cervical spine, including loads on neck structures and implants.     

Infant skull and suture properties: measurements and implications for mechanisms of pediatric brain injury

The mechanical properties of the adult human skull are well documented, but little information is available for the infant skull. To determine the age-dependent changes in skull properties, we tested human and porcine infant cranial bone in three-point bending. The measurement of elastic modulus in the human and porcine infant cranial bone agrees with and extends previous published data [McPherson, G. K., and Kriewall, T. J. (1980), J. Biomech., 13, pp. 9-16] for human infant cranial bone. After confirming that the porcine and human cranial bone properties were comparable, additional tensile and three-point bending studies were conducted on porcine cranial bone and suture. Comparisons of the porcine infant data with previously published adult human data demonstrate that the elastic modulus, ultimate stress, and energy absorbed to failure increase, and the ultimate strain decreases with age for cranial bone. Likewise, we conclude that the elastic modulus, ultimate stress, and energy absorbed to failure increase with age for sutures. We constructed two finite element models of an idealized one-month old infant head, one with pediatric and the other adult skull properties, and subjected them to impact loading to investigate the contribution of the cranial bone properties on the intracranial tissue deformation pattern. The computational simulations demonstrate that the comparatively compliant skull and membranous suture properties of the infant brain case are associated with large cranial shape changes, and a more diffuse pattern of brain distortion than when the skull takes on adult properties. These studies are a fundamental initial step in predicting the unique mechanical response of the pediatric skull to traumatic loads associated with head injury and, thus, for defining head injury thresholds for children.     

Why do woodpeckers resist head impact injury: a biomechanical investigation

Head injury is a leading cause of morbidity and death in both industrialized and developing countries. It is estimated that brain injuries account for 15% of the burden of fatalities and disabilities, and represent the leading cause of death in young adults. Brain injury may be caused by an impact or a sudden change in the linear and/or angular velocity of the head. However, the woodpecker does not experience any head injury at the high speed of 6-7 m/s with a deceleration of 1000 g when it drums a tree trunk. It is still not known how woodpeckers protect their brain from impact injury. In order to investigate this, two synchronous high-speed video systems were used to observe the pecking process, and the force sensor was used to measure the peck force. The mechanical properties and macro/micro morphological structure in woodpecker's head were investigated using a mechanical testing system and micro-CT scanning. Finite element (FE) models of the woodpecker's head were established to study the dynamic intracranial responses. The result showed that macro/micro morphology of cranial bone and beak can be recognized as a major contributor to non-impact-injuries. This biomechanical analysis makes it possible to visualize events during woodpecker pecking and may inspire new approaches to prevention and treatment of human head injury.     

Quantitative evaluation of the degree of bone tissue deposition in sponge-like skeletal segments experimentally subjected to mechanical stress

A 12-month old dog was sacrificed 4 months after fixation of the left anterior limb, in a cutaneous pouch, to the thoracic wall, and division of the ipsilateral brachial plexus; 27 and 7 days before sacrifice, Alizarin red (20 mg/Kg) was injected intravenously. Rarefaction of spongy bone and increase in the rate of osteogenic activity were recorded from the sections of the distal end of the unloaded left radius compared to the corresponding part of the control bone. The events mentioned appeared more marked in the "tubular" than in the "lamellar" spongiosa. These findings seem to offer new evidence supporting the suggestion that in adult life bone tissue reconstruction rate is relatively higher in the areas of spongy bone comparatively less involved in the mechanical resistance.     

Micromachined interfaces: new approaches in cell immunoisolation and biomolecular separation

As a novel therapeutic application of microfabrication technology, a micromachined membrane-based biocapsule is described for the transplantation of protein-secreting cells without the need for immunosuppression. This new approach to cell encapsulation is based on microfabrication technology whereby immunoisolation membranes are bulk and surface micromachined to present uniform and well-controlled pore sizes as small as 10 nm, tailored surface chemistries, and precise microarchitecture. Through its ability to achieve highly controlled microarchitectures on size scales relevant to living systems (from microm to nm), microfabrication technology offers unique opportunities to more precisely engineer biocapsules that allow free exchange of the nutrients, waste products, and secreted therapeutic proteins between the host (patient) and implanted cells, but exclude lymphocytes and antibodies that may attack foreign cells. Microfabricated inorganic encapsulation devices may provide biocompatibility, in vivo chemical and mechanical stability, tailored pore geometries, and superior immunoisolation for encapsulated cells over conventional encapsulation approaches. By using microfabrication techniques, structures can be fabricated with spatial features from the sub-micron range up to several millimeters. These multi-scale structures correspond well with hierarchical biological structures, from proteins and sub-cellular organelles to the tissue and organ levels.     

The mechanical properties of cranial bone: The effect of loading rate and cranial sampling position

Linear and depressed skull fractures are frequent mechanisms of head injury and are often associated with traumatic brain injury. Accurate knowledge of the fracture of cranial bone can provide insight into the prevention of skull fracture injuries and help aid the design of energy absorbing head protection systems and safety helmets. Cranial bone is a complex material comprising of a three-layered structure: external layers consist of compact, high-density cortical bone and the central layer consists of a low-density, irregularly porous bone structure.In this study, cranial bone specimens were extracted from 8 fresh-frozen cadavers (F=4, M=4; 81±11 years old). 63 specimens were obtained from the parietal and frontal cranial bones. Prior to testing, all specimens were scanned using a μCT scanner at a resolution of 56.9 μm. The specimens were tested in a three-point bend set-up at different dynamic speeds (0.5, 1 and 2.5 m/s). The associated mechanical properties that were calculated for each specimen include the 2nd moment of inertia, the sectional elastic modulus, the maximum force at failure, the energy absorbed until failure and the maximum bending stress. Additionally, the morphological parameters of each specimen and their correlation with the resulting mechanical parameters were examined.It was found that testing speed, strain rate, cranial sampling position and intercranial variation all have a significant effect on some or all of the computed mechanical parameters. A modest correlation was also found between percent bone volume and both the elastic modulus and the maximum bending stress.     

Morphological and videofluorographic study of the hyoid apparatus and its function in the rabbit (Oryctolagus cuniculus)

The anatomy of the hyoid apparatus and positional changes of the hyoid bone during mastication and deglutition are described in the New Zealand White rabbit (Oryctolagus cuniculus). A testable model is constructed to predict the range of movement during function of the hyoid, a bone entirely suspended by soft tissue. Frame-by-frame analysis of a videofluorographic tape confirms the accuracy of the prediction through observation of hyoid bone excursion during oral behavior. During chewing, translation of the hyoid bone is diminutive and irregular, lacking a clearly discernible path of excursion. However, some movements of the hyoid occur with regularity. During fast opening, anterodorsal movement of the hyoid is interrupted with an abrupt posteroventral depression when the bolus is moved posteriorly toward the cheek teeth by the tongue. This clockwise rotation (when viewed from the right side) of the hyoid accompanies jaw opening and is reversed (posteroventral movement) for the jaw closing sequence. Lateral movements of the hyoid may be slightly coupled to mandibular rotation in the horizontal plane. The findings suggest that the hyoid bone maintains a relatively static position during the dynamics of chewing. The primary function would be to provide a stable base for the movements of the tongue. Another possible function would be to control the position of the larynx within the pharyngeal cavity. Some characteristic features of the rabbit hyoid apparatus may be consequential to relatively erect posture and a saltatory mode of locomotion.     

Modelling of intracranial behaviour on occiput impact in judo

Acute subdural hematoma (ASDH) sometimes occurred in judo because of the bridging veins’ failure by rotation of the brain in the skull. However, the relationship between intracranial behaviour and the motion of the body on occiput impact has not yet been clarified. In this study, we developed an intracranial mechanical model based on multibody dynamics and compared it with experimental results. The results show the importance of modelling bridging veins and cerebral spinal fluid to the relative displacement between brain and skull. The proposed model will contribute to accident analyses or the optimum design of supporting devices.     

The mechanical behaviour of intracondylar cancellous bone of the femur at different loading rates

The compressive properties of human cancellous bone of the distal intracondylar femur in its wet condition were determined. Specimens were obtained from six cadaveric femora and were tested at a strain rate of 0.002, 0.10 and 9.16 sec⁻¹. It was found that the compressive strength decreases with an increasing vertical distance from the joint. The highest compressive strength level was recorded in the posterior medial condyle. Correlations among the mechanical properties, the bulk specimen density and the bone mineral content yield (i) highly significant correlations between the compressive strength and the elastic modulus (ii) highly significant correlations between the compressive strength or the modulus of elasticity and the bulk specimen density (iii) a doubtful correlation between the compressive strength and the bone mineral content. All recorded graphs of the impact loaded specimens displayed several well defined stress peaks, unlike the graphs recorded at low loading rates. It can be concluded that upon impact loading the localized trabecular failure which is associated with each peak, does not affect the spongy bone's stress capacity in a detrimental way.     

基于Micro-CT断层扫描图像的啄木鸟颅骨不同部位显微结构参数研究

选取大斑啄木鸟、灰头绿啄木鸟、百灵鸟、山雀和戴胜鸟作为样本,其中百灵鸟、山雀和戴胜鸟作为对照,研究啄木鸟颅骨颞部、额部和枕部的显微结构参数.样本经Micro-CT扫描后,在断层扫描图像的基础上,可以得到的显微结构参数包括体积分数、结构模型指数、骨小梁数量、骨小梁厚度、骨小梁分离度和骨质密度.通过与其他鸟类的对比分析发现,啄木鸟具有更加独特的颅骨结构,其骨小梁厚度、体积分数和骨小梁数量显著高于其他鸟类,结构模型指数小于其他鸟类,其颅骨所具有的这种特点是啄木鸟长期进化过程中为适应啄木行为所形成的,也是其抗冲击的重要原因.     

Developmental changes in the shape of the supralaryngeal vocal tract in chimpanzees

The hyoid bone and larynx in human neonates are positioned as high as in other mammals. However, during postnatal life, they descend relative to the hard palate more rapidly compared with the horizontal growth of the oral cavity. This process is completed through the descent of the laryngeal skeleton relative to the hyoid, and through the descent of the hyoid relative to the cranial base. Thus, the human supralaryngeal vocal tract (SVT) develops to form a two-tube configuration with equally long horizontal and vertical parts. Longitudinal studies on living chimpanzee infants show that the descent of the larynx is more rapid than the horizontal growth of the oral cavity. This is primarily attributed to the descent of their larynges relative to the hyoid bone, but this is not accompanied by the descent of the hyoid. The present study, using embalmed specimens of chimpanzees, also shows that the horizontal and vertical parts of the SVT grow in chimpanzees similarly to humans during infancy. However, in chimpanzees, the horizontal part of the SVT grows greatly, whereas the vertical part of the SVT grows only slightly during the juvenile period. As a result, the chimpanzee larynx does not descend rapidly relative to the oral elongation during that period. Such differences may be related to the structural and morphological development of the facial skeleton and mandible, which affects prognathism and hyoid descent. These results support the hypothesis that the descent of the larynx evolved in at least two steps during hominoid evolution.     

A modified human head model for the study of impact head injury

A recently published finite element (FE) head model is modified to consider the viscoelasticity of the meninges, the spongy and compact bone in the skull. The cerebrospinal fluid (CSF) is simulated explicitly as a hydrostatic fluid by using a surface-based fluid modelling method, which allows fluid and structure interaction. It is found that the modified model yields smoother pressure responses in a head impact simulation. The baseline model underestimated the peak von Mises stress in the brain by 15% and the peak principal stress in the skull by 33%. The increase in the maximum principal stress in the skull is mainly caused by the updation of the material's viscoelasticity, and the change in the maximum von Mises stress in the brain is mainly caused by the improvement of the CSF simulation. The study shows that the viscoelasticity of the head tissue should be considered, and that the CSF should be modelled as a fluid, when using FE analysis to study head injury due to impact.     

Apparent Young's modulus of human radius using inverse finite-element method

The ability to assess the elastic and failure properties of cortical bone at the radial diaphysis has a clinical importance. A new generation of quantitative ultrasound (QUS) devices and peripheral quantitative computed tomography (p-QCT) has been developed to assess non-invasively bone material and structural properties at the distal radius. This anatomical site is characterized by a thin cortical thickness that complicates traditional mechanical testing methods on specimens. Until now, mechanical properties of cortical bone at distal radius (e.g., elastic modulus, yield stress and strain) remain rarely studied probably due to experimental difficulties. The present study introduces an inverse finite-element method strategy to measure the elastic modulus and yield properties of human cortical specimens of the radial diaphysis. Twenty millimeter-thick portions of diaphysis were cut from 40 human radii (ages 45-90) for biomechanical test. Subsequently the same portion was modeled in order to obtain a specimen-specific three dimensional finite-element model (3D-FEM). Longitudinal elastic constants at the apparent level and stress characterizations were performed by coupling mechanical parameters with isotropic linear-elastic simulations. The results indicated that the mean apparent Young's modulus for radial cortical bone was 16 GPa (SD 1.8) and the yield stress was 153 MPa (SD 33). Breaking load was 12,946 N (SD 3644), cortical thickness 2.9 mm (SD 0.6), structural effective strain at the yield (epsilon(y)=0.0097) and failure (epsilon(u)=0.0154) load were also calculated. The 3D-FEM strategy described here may help to investigate bone mechanical properties when some difficulties arise from machining mechanical sample.