鸟类胸骨的形态结构多样性及其与飞行能力的关系

不同生态类型的鸟类,其胸骨具有多样性的特征,同时还与鸟类的飞行能力强弱有卣接的关系.根据胸骨形态学特征差异及数据的统计分析得出:鸟类胸骨的前侧突、后侧突的排列方式以及后缘凹13的形态是判断其生态习性的有效形态标志.此外,当胸骨深度加大,且胸骨宽度不断加长的鸟类其飞行能力也加强;反之,胸骨的长度加长,深度、宽度渐小的鸟类,其飞行能力较弱或已经丧失飞行能力.     

Skeletal defects in paternal uniparental disomy for chromosome 14 are re-capitulated in the mouse model (paternal uniparental disomy 12)

Human paternal uniparental disomy for chromosome 14 (upd(14)pat) presents with skeletal abnormalities, joint contractures, dysmorphic facial features and developmental delay/mental retardation. Distal human chromosome 14 (HSA14) is homologous to distal mouse chromosome 12 (MMU12) and both regions have been shown to contain imprinted genes. In humans, consistent radiographic findings include a narrow, bell-shaped thorax with caudal bowing of the anterior ribs, cranial bowing of the posterior ribs and flaring of the iliac wings without shortening or dysplasia of the long bones. Mice with upd(12)pat have thin ribs with delayed ossification of the sternum, skull and feet. In both mice and humans, the axial skeleton is predominantly affected. We hypothesize that there is an imprinted gene or genes on HSA14/MMU12 that specifically affects rib/thorax development and the maturation of ossification centers in the sternum, feet and skull with little effect on long bone development.     

Triangularis sterni: a primary muscle of breathing in the dog

The isolated action, pattern of neural activation, and mechanical contribution to eupnea of the triangularis sterni (transversus thoracis) muscle were studied in supine anesthetized dogs. Linear displacement transducers were used to measure the axial displacements of the ribs and sternum. Tetanic stimulation of the triangularis sterni in the apneic animal caused a marked caudal displacement of the ribs, a moderate cranial displacement of the sternum, and a decrease in lung volume. During quiet breathing, there was invariably a rhythmic activation of the muscle in phase with expiration that was independent of the presence or absence of activity in the abdominal and internal interosseous intercostal muscles. This phasic expiratory activity in the triangularis sterni was of large amplitude and caused the ribs to be more caudal and the sternum to be more cranial during the spontaneous expiratory pause than during relaxation. Additional studies on awake animals showed that rhythmic activation of the triangularis sterni occurs in all body positions and is not caused by anesthesia. These findings indicate that expiration in the dog is not a passive process and that the end-expiratory volume of the rib cage is not determined by an equilibrium of static forces alone. Rather, it is actively determined and maintained below its relaxation volume by contraction of the triangularis sterni throughout expiration. The use of this muscle is likely to facilitate inspiration by increasing the length of the parasternal intercostals and taking on a portion of their work.     

Elastostatic analysis of the human thoracic skeleton

An elastostatic, finite element model (designated THORAX I) of the human thoracic skeleton has been developed. The model includes the primary load-carrying members of the thorax; namely, the sternum, costal cartilage, ribs, and vertebral column. The soft tissue has been neglected.

Using gross geometric data measured from a skeleton with an apparent ‘small’ frame and approximate cross-sectional properties, the THORAX I model has been subjected to three loading distribution applied to the anterior chest wall in the anterior-posterior direction. Calculations were carried out on the IBM 7094 computer, and primary attention was focused upon the displacement fields of the sternum, costal cartilage and ribs and stresses in costal cartilage and ribs. The sternum and rib nodal point displacement fields are reported in detail, and a simple 2-degree-of-freedom model for the sternum, which correlates well with the analytic results, is also presented. Maximum normal stresses in the cartilage and bony regions of the individual ribs for one loading condition are also given.     

In-vivo analysis of sternal angle,sternal and sternocostal kinematics in supine humans during breathing

This paper aims at contributing to the understanding of the combination of in vivo sternum displacement, sternal angle variations and sternocostal joints (SCJ) kinematics of the seven first rib pairs over the inspiratory capacity (IC). Retrospective codified spiral-CT data obtained at total lung capacity (TLC), middle of inspiratory capacity (MIC) and at functional residual capacity (FRC) were used to compute kinematic parameters of the bones and joints of interest in a sample of 12 asymptomatic subjects. 3D models of rib, thoracic vertebra, manubrium and sternum were processed to determine anatomical landmarks (ALs) on each bone. These ALs were used to create local coordinate system and compute spatial transformation of ribs and manubrium relative to sternum, and sternum relative to thoracic vertebra. The rib angular displacements and associated orientation of rotation axes and joint pivot points (JPP), the sternal angle variations and the associated displacement of the sternum relative to vertebra were computed between each breathing pose at the three lung volumes. Results can be summarized as following: (1) sternum cephalic displacement ranged between 17.8 and 19.2 mm over the IC; (2) the sternal angle showed a mean variation of 4.4° ± 2.7° over the IC; (3) ranges of rib rotation relative to sternum decreased gradually with increasing rib level; (4) axes of rotation were similarly oriented at each SCJ; (5) JPP spatial displacements showed less variations at first SCJ compared to levels underneath; (6) linear relation was demonstrated between SCJ ROMs and sternum cephalic displacement over the IC.     

Proposal of a thorax segment coordinate system for the 3D kinematical analysis of the cervical spine

The International Society of Biomechanics detailed the recommendations for 3D kinematics of intervertebral movements (Wu, et al. 2002. J Biomech. 35:543-548), but does not specify how to adapt this proposal to describe the kinematics of the cervical spine, between the head and the thorax. The analysis of the literature shows that no consensus exists at the present time on this subject. The objective of our study was to identify the reference points that formed the most rigid triplet allowing building an optimal thorax segment coordinate system (SCS). We thus measured the variations of distances between markers placed on various anatomical landmarks, and then the deformations of the combinations of three markers on different cervical movements of a sample of 10 asymptomatic subjects. The results show that the triplet formed by the sternum and both acromions undergoes less deformation on the flexion-extension movement. For all the other movements (lateral bending, axial rotation and complex movements), the triplet formed by sternum, T3 and TH (positioned on the thoracic spinal column, in a horizontal plane containing the sternal marker), undergoes less deformation. As a conclusion, the optimal triplet to define the thorax SCS for 3D kinematical analysis of the cervical spine is that formed by the markers: sternum, T3 and TH. This triplet makes it possible to define an orthonormal SCS, the axes of which coincide with anatomical directions, i.e. with the functional axes of the movement.     

Proposal of a thorax segment coordinate system for the 3D kinematical analysis of the cervical spine

The International Society of Biomechanics detailed the recommendations for 3D kinematics of intervertebral movements (Wu, et al. 2002. J Biomech. 35:543–548), but does not specify how to adapt this proposal to describe the kinematics of the cervical spine, between the head and the thorax. The analysis of the literature shows that no consensus exists at the present time on this subject. The objective of our study was to identify the reference points that formed the most rigid triplet allowing building an optimal thorax segment coordinate system (SCS). We thus measured the variations of distances between markers placed on various anatomical landmarks, and then the deformations of the combinations of three markers on different cervical movements of a sample of 10 asymptomatic subjects. The results show that the triplet formed by the sternum and both acromions undergoes less deformation on the flexion–extension movement. For all the other movements (lateral bending, axial rotation and complex movements), the triplet formed by sternum, T3 and TH (positioned on the thoracic spinal column, in a horizontal plane containing the sternal marker), undergoes less deformation. As a conclusion, the optimal triplet to define the thorax SCS for 3D kinematical analysis of the cervical spine is that formed by the markers: sternum, T3 and TH. This triplet makes it possible to define an orthonormal SCS, the axes of which coincide with anatomical directions, i.e. with the functional axes of the movement.     

Changes in chest wall structure and elasticity in elastase-induced emphysema

The present study examined the effects of elastase-induced emphysema on the structure and elasticity of the chest wall. Specifically, we examined the passive pressure-volume relationship of the intact chest wall in anesthetized animals and the stress-strain relationship of the isolated rib cage devoid of respiratory musculature. The structure of the isolated rib cage was assessed by measuring its circumferential, anterior-posterior, and transverse dimensions, the angles of articulation of the ribs at the costovertebral and sternochondral joints, and the length of the sternum and individual ribs. Studies were performed in 10 Syrian Golden hamsters, 26-27 wk after intratracheal injection of elastase, and 9 saline-injected hamsters that served as controls. Mean functional residual capacity of emphysematous animals was 239% of the value obtained in control animals. In emphysematous animals, the pressure-volume curve of the chest wall was shifted parallel and to the left of the curve obtained in controls. That is, at any given esophageal pressure, lung volume was significantly greater in emphysematous animals compared with controls, but the slope of the pressure-volume relationship was similar in the two groups. In the relaxed position, the circumference, anterior-posterior, transverse, and rostral-caudal dimensions of the thorax were significantly greater in emphysematous than control animals. Although the length of the thoracic spinal column was the same in both groups, the length of the ribs and sternum were greater in emphysematous animals and the angles of articulation of the ribs with the vertebrae and sternum were altered.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dinosaur speed demon: the caudal musculature of Carnotaurus sastrei and implications for the evolution of South American abelisaurids

In the South American abelisaurids Carnotaurus sastrei, Aucasaurus garridoi, and, to a lesser extent Skorpiovenator bustingorryi, the anterior caudal ribs project at a high dorsolateral inclination and have interlocking lateral tips. This unique morphology facilitated the expansion of the caudal hypaxial musculature at the expense of the epaxial musculature. Distinct ridges on the ventrolateral surfaces of the caudal ribs of Aucasaurus garridoi are interpreted as attachment scars from the intra caudofemoralis/ilio-ischiocaudalis septa, and confirm that the M. caudofemoralis of advanced South American abelisaurids originated from a portion of the caudal ribs. Digital muscle models indicate that, relative to its overall body size, Carnotaurus sastrei had a substantially larger M. caudofemoralis than any other theropod yet studied. In most non-avian theropods, as in many extant sauropsids, the M. caudofemoralis served as the primary femoral retractor muscle during the locomotive power stroke. This large investment in the M. caudofemoralis suggests that Carnotaurus sastrei had the potential for great cursorial abilities, particularly short-burst sprinting. However, the tightly interlocking morphology of the anterior caudal vertebrae implies a reduced ability to make tight turns. Examination of these vertebral traits in evolutionary context reveals a progressive sequence of increasing caudofemoral mass and tail rigidity among the Abelisauridae of South America.     

Osteogenesis,homology, and function of the intercostal plates in ornithischian dinosaurs (Tetrapoda,Sauropsida)

Intercostal plates are bony structures positioned lateral to the anterior dorsal ribs in some ornithischian dinosaurs. Some propose these plates are homologous, or functionally analogous, with the uncinate processes of extant avian dinosaurs that assist in breathing, while others suggest they served a defensive function. To elucidate their osteogenesis, homology, and function, a histological survey of intercostal plates from three taxa (Hypsilophodon, Talenkauen, and Thescelosaurus) was undertaken. This study reveals that osteogenesis of intercostal plates closely resembles that of secondary centers of ossification in endochondral bone, typically present in the epiphyses of mammalian long bones. In contrast, ossification of avian uncinate processes begins at a primary ossification center via the development of a bony collar around a cartilaginous model. Based on these data, intercostal plates and avian uncinate processes are likely not evolutionary homologs. Dense packets of obliquely oriented Sharpey’s fibers within the parallel-fibered bone of somatically mature intercostal plates indicate these plates were positioned medial to at least a portion of the hypaxial musculature, which does not support their use as bony armor. Rather, we propose that intercostal plates performed some biomechanical function, either assisting in breathing in a way analogous to avian uncinate processes, or working together with the sternal ribs and sternal plates of these ornithischian taxa to provide increased rigidity to the anterior portion of the ribcage.     

An analysis of possible movements of human upper rib cage

A geometrically realistic mathematical model of the first six ribs and vertebrae of the human rib cage is described. Under the assumption that the individual elements of the rib cage do not deform significantly, the possible range of movements of the model are determined subject to the constraint that the joint surfaces remain in contact. It is shown that normal movements of the ribs cannot be described as a rotation about a single fixed axis. The possible movements of the ribs are analyzed in terms of the misfit incurred at the costovertebral joint surfaces. This analysis shows that there is a movement, corresponding to lateral expansion of the rib for an increase in anteroposterior diameter, in which the misfit at the joint is minimized and also that small deviations from this movement involve only very small degrees of misfit at the joint surfaces. It is concluded that many observed "deformations" of the chest wall can be explained by rigid ribs and normal movements at the costovertebral joints. The interaction between the ribs and the spine is analyzed. It is shown that there can be considerable independent movement of the sternum and the spine, thus allowing mobility of the spine without forcing concomitant movements of rib cage.     

The axial skeleton of the labyrinthodont Eogyrinus attheyi

An articulated length of vertebral column is used as a basis for the reconstruction of the salient features of the axial skeleton of the embolomerous anthracosaur Eogyrinus attheyi Watson, together with other material, including the holotype, in the Hancock Museum, Newcastle upon Tyne.
The trunk vertebrae are typically emboloinerous, with disoshaped notochordal pleuro-centra, firmly attached by broad facets to this neural arches, and much thinner intercentra. Regional variation is chiefly concerned with the span of the transverse processes, which diminishes posteriorly, and the associated separation of the two heads of each rib. A longitudinal series of trunk ribs, of diminishing length from the mid-trunk backwards, is reconstructed.
Eogyrinus has a normal tetrapod sacrum with one characteristic sacral rib. The first few caudal vertebrae bear ribs of unusual form, (of which four are preserved in sequence in the articulated specimen. The fifth caudal intercentrum bears the first and largest haemal arch and the pleurocentrum of the seventh caudal is distinguished by marked muscle origins presumably for the caudifemoral muscles.
The probability that Eogyrinus, like the few other embolomeres known, had an unusually long vertebral column for a labyrinthodont, is supported by an orthometric comparison using Romer's data on the American form Archeria.     

Respiratory effect of the lower rib displacement produced by the diaphragm

The diaphragm acting alone causes a cranial displacement of the lower ribs and a caudal displacement of the upper ribs. The respiratory effect of the lower rib displacement, however, is uncertain. In the present study, two sets of experiments were performed in dogs to assess this effect. In the first, all the inspiratory intercostal muscles were severed, so that the diaphragm was the only muscle active during inspiration, and the normal inspiratory cranial displacement of the lower ribs was suppressed at regular intervals. In the second experiment, the animals were given a muscle relaxant to abolish respiratory muscle activity, and external, cranially oriented forces were applied to the lower rib pairs to simulate the action of the diaphragm on these ribs. The data showed that 1) holding the lower ribs stationary during spontaneous, isolated diaphragm contraction had no effect on the change in lung volume during unimpeded inspiration and no effect on the fall in pleural pressure (Ppl) during occluded breaths; 2) the procedure, however, caused an increase in the caudal displacement of the upper ribs; and 3) pulling the lower rib pairs cranially induced a cranial displacement of the upper ribs and a small fall in Ppl. These observations indicate that the force applied on the lower ribs by the diaphragm during spontaneous contraction, acting through the interdependence of the ribs, is transmitted to the upper ribs and has an inspiratory effect on the lung. However, this effect is very small compared to that of the descent of the dome.     

Dynamic changes in body form during swimming in the water snake Nerodia sipedon

Video records of swimming water snakes show that during moderate to rapid swimming, the rear half to two-thirds of the trunk is compressed laterally, approaching the body form of some sea snakes. Body form of swimming snakes differed significantly from their shape when resting on a flat surface or when anesthetized and suspended in water. The extent of lateral flattening is positively correlated with swimming speed, a relationship generally supported by tests of trunk models in a flow tank. In Nerodia, the ability to temporarily flatten the trunk depends on kinetic costovertebral joints, a large compressible body cavity, and the absence of ventral skeletal support - features found in most snakes. Histological studies and manipulations of partially dissected preserved specimens showed that the resting angle of the ribs is maintained by localized elastic hypertrophy of the costovertebral capsular ligament. Trunk form during swimming in Nerodia is proposed to arise from anteromedial movement of the distal rib powered by deep muscles acting in concert with those proposed to generate undulation of the vertebral column.     

Effect of respiratory muscle tension on lung volume.

The chest wall is modeled as a linear system for which the displacements of points on the chest wall are proportional to the forces that act on the chest wall, namely, airway opening pressure and active tension in the respiratory muscles. A standard theorem of mechanics, the Maxwell reciprocity theorem, is invoked to show that the effect of active muscle tension on lung volume, or airway pressure if the airway is closed, is proportional to the change of muscle length in the relaxation maneuver. This relation was tested experimentally. The shortening of the cranial-caudal distance between a rib pair and the sternum was measured during a relaxation maneuver. These data were used to predict the respiratory effect of forces applied to the ribs and sternum. To test this prediction, a cranial force was applied to the rib pair and a caudal force was applied to the sternum, simulating the forces applied by active tension in the parasternal intercostal muscles. The change in airway pressure, with lung volume held constant, was measured. The measured change in airway pressure agreed well with the prediction. In some dogs, nonlinear deviations from the linear prediction occurred at higher loads. The model and the theorem offer the promise that existing data on the configuration of the chest wall during the relaxation maneuver can be used to compute the mechanical advantage of the respiratory muscles.     

Cardio‐pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs

Although crocodilian lung and cardiovascular organs are markedly less specialized than the avian heart and lung air‐sac system, all living archosaurs possess four‐chambered hearts and heterogeneously vascularized, faveolar lungs. In birds, normal lung function requires extensive, dorsally situated nonvascularized abdominal air‐sacs ventilated by an expansive sternum and specially hinged costal ribs. The thin walled and voluminous abdominal air‐sacs are supported laterally and caudally to prevent inward (paradoxical) collapse during generation of negative (inhalatory) pressure: the synsacrum, posteriorly directed, laterally open pubes and specialized femoral‐thigh complex provide requisite support and largely prevent inhalatory collapse. In comparison, theropod dinosaurs probably lacked similarly enlarged abdominal air‐sacs, and skeleto‐muscular modifications consistent with their ventilation. In the absence of enlarged, functional abdominal air‐sacs, theropods were unlikely to have possessed a specialized bird‐like, air‐sac lung. The likely absence of bird‐like pulmonary function in theropods is inconsistent with suggestions of cardiovascular anatomy more sophisticated than that of modern crocodilians. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Effect of diaphragmatic contraction on the action of the canine parasternal intercostals.

The inspiratory intercostal muscles enhance the force generated by the diaphragm during lung expansion. However, whether the diaphragm also alters the force developed by the inspiratory intercostals is unknown. Two experiments were performed in dogs to answer the question. In the first experiment, external, cranially oriented forces were applied to the different rib pairs to assess the effect of diaphragmatic contraction on the coupling between the ribs and the lung. The fall in airway opening pressure (deltaPa(O)) produced by a given force on the ribs was invariably greater during phrenic nerve stimulation than with the diaphragm relaxed. The cranial rib displacement (Xr), however, was 40-50% smaller, thus indicating that the increase in deltaPa(O) was exclusively the result of the increase in diaphragmatic elastance. In the second experiment, the parasternal intercostal muscle in the fourth interspace was selectively activated, and the effects of diaphragmatic contraction on the deltaPa(O) and Xr caused by parasternal activation were compared with those observed during the application of external loads on the ribs. Stimulating the phrenic nerves increased the deltaPa(O) and reduced the Xr produced by the parasternal intercostal, and the magnitudes of the changes were identical to those observed during external rib loading. It is concluded, therefore, that the diaphragm has no significant synergistic or antagonistic effect on the force developed by the parasternal intercostals during breathing. This lack of effect is probably related to the constraint imposed on intercostal muscle length by the ribs and sternum.     

Vertebral and rib anatomy in Caperea marginata: Implications for evolutionary patterning of the mammalian vertebral column

The pygmy right whale, Caperea marginata, is a rare mysticete cetacean with an unusual suite of axial skeletal characters. Distally expanded first ribs, a long thorax with broadly overlapping vertebral transverse processes, plate‐like posterior ribs, and a short tail contrast with other cetaceans and suggest unique developmental patterning. Twenty‐four individuals of diverse ontogenetic age were available for analysis. Multiple, variable examples of incomplete rib fusion in dependent calves indicate that the first rib of adults is an ontogenetic fusion product of ribs 1 and 2. The composite rib articulates by way of its anterior (Rib1) component to the sternum and by way of its posterior (Rib2) component with thoracic vertebra 2. Thoracic vertebra 1 lacks rib articulations. When rib fusion is taken into account, the most frequent column formulas are C7T18L1Cd16–17 = 42–43 and C7T17L1Cd16–18 = 41–43. Thoracic and lumbar series are not reciprocal in count, arguing against their developmental linkage. Instead, parallel reduction in both lumbar and caudal counts supports the existence of neocete patterning in Caperea, as in all other living cetaceans. Ontogenetic vertebral column elongation is most marked in the posterior thorax, lumbos, and anterior tail. Vertebrae in these column regions are excellent predictors of total body length.     

Evidence for avian intrathoracic air sacs in a new predatory dinosaur from Argentina

Background

Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bellow-like air sacs in living birds only rarely penetrate (pneumatize) skeletal bone and thus leave a record of their presence.

Methodology/Principal Findings

We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia (“stomach ribs”), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax.

Conclusions/Significance

We present a four-phase model for the evolution of avian air sacs and costosternal-driven lung ventilation based on the known fossil record of theropod dinosaurs and osteological correlates in extant birds:(1) Phase I—Elaboration of paraxial cervical air sacs in basal theropods no later than the earliest Late Triassic.(2) Phase II—Differentiation of avian ventilatory air sacs, including both cranial (clavicular air sac) and caudal (abdominal air sac) divisions, in basal tetanurans during the Jurassic. A heterogeneous respiratory tract with compliant air sacs, in turn, suggests the presence of rigid, dorsally attached lungs with flow-through ventilation.(3) Phase III—Evolution of a primitive costosternal pump in maniraptoriform theropods before the close of the Jurassic.(4) Phase IV—Evolution of an advanced costosternal pump in maniraptoran theropods before the close of the Jurassic.In addition, we conclude:(5) The advent of avian unidirectional lung ventilation is not possible to pinpoint, as osteological correlates have yet to be identified for uni- or bidirectional lung ventilation.(6) The origin and evolution of avian air sacs may have been driven by one or more of the following three factors: flow-through lung ventilation, locomotory balance, and/or thermal regulation.