Arrangement Of Muscles Research Articles

Musculature of the male genitalia of Xylophagus cinctus (De Geer) and relationships within the superfamily Xylophagoidea (Diptera, Brachycera)

There is no general agreement on relationships within Xylophagoidea (Diptera, Brachycera). The musculature of the male genitalia of Xylophagus cinctus (De Geer) (Xylophagidae, the most primitive family of Brachycera) is described and compared with that of some other Xylophagoidea: Exeretonevridae (Exeretonevra angustifrons Hardy), Coenomyiidae (Anacanthaspis biafasciata Roder), and Rhagionidae (Rhagio montanus Becker, Chrysopilus dives Loew, and Ch. helvolus Meigen) discussed earlier (Ovtshinnikova, 1989, 1998; Palmer et al., 2000). In spite of the differences in the structure of the genital sclerites, Xylophagidae possess all the muscles found in Coenomyiidae and Rhagionidae. The musculature of the male genitalia of Xylophagus cinctus includes two muscle pairs of the aedeagus sheath (M1 and M2); three muscle pairs of the ejaculatory complex (M30, M31, and M32); one muscle pair of the gonocoxites (M33); two muscle pairs of the gonostyli (M27 and M28); one muscle pair of the proctiger (M21), one muscle pair of the cerci (M29); two pairs of the tergosternal muscles (M51 and M52); and two pairs of the pregenital muscles (M18 and M19). Muscles of the family Exeretonevridae are mostly the same, except for the muscles of the cerci M29, proctiger M29, and pregenital muscles M18 and M19, that are subdivided into two parts. This fact and also a different degree of the development of muscles M32 and M52 clearly distinguish Exeretonevridae from closely related families. The attachment places of the muscles of the aedeagus sheath M2 and of the gonostyli M28, as well as the split character of the tergosternal muscle pair M51 makes it possible to distinguish two sister groups, Xylophagidae plus Exeretonevridae, versus Coenomyiidae plus Rhagionidae. It should be noted that the muscles of the male genitalia of Xylophagidae, Exeretonevridae, Coenomyiidae, and Rhagionidae possess similar plesiomorphic characters, and these families should be united into the superfamily Xylophagoidea. This superfamily is the most primitive superfamily of Brachycera Orthorrhapha and possesses the most stable set and arrangement of male genital muscles within the entire suborder. An improved dendrogram of the phylogenetic relationships between the known groups of Xylophagoidea is proposed on the basis of the structure of male genital muscles.

Hyobranchial skeleton and hypobranchial muscles of rhipidistians

The hyobranchial skeleton of the porolepiform rhipidistian Laccognathus panderi Gross is described. The double composition of the ceratohyal in crossopterygians is proposed. The urohyal of porolepiforms, like that of Latimeria, consists of cartilaginous axial and membranous peripheral portions. The differences between porolepiforms and osteolepiforms in the structure of the hyobranchial skeleton, particularly, in the shape of the urohyal are attributable to different arrangements of the hypobranchial muscles. Porolepiforms and coelacanths have retained the coracomandibularis muscle inherited from early gnathostomes, whereas the same muscle of osteolepiforms was transformed into the geniohyoideus muscle. This transformation is accounted for by functional changes in the hyobranchial apparatus.

Muscles of facial expression in the chimpanzee (Pan troglodytes): descriptive, comparative and phylogenetic contexts

Facial expressions are a critical mode of non-vocal communication for many mammals, particularly non-human primates. Although chimpanzees (Pan troglodytes) have an elaborate repertoire of facial signals, little is known about the facial expression (i.e. mimetic) musculature underlying these movements, especially when compared with some other catarrhines. Here we present a detailed description of the facial muscles of the chimpanzee, framed in comparative and phylogenetic contexts, through the dissection of preserved faces using a novel approach. The arrangement and appearance of muscles were noted and compared with previous studies of chimpanzees and with prosimians, cercopithecoids and humans. The results showed 23 mimetic muscles in P. troglodytes, including a thin sphincter colli muscle, reported previously only in adult prosimians, a bi-layered zygomaticus major muscle and a distinct risorius muscle. The presence of these muscles in such definition supports previous studies that describe an elaborate and highly graded facial communication system in this species that remains qualitatively different from that reported for other non-human primate species. In addition, there are minimal anatomical differences between chimpanzees and humans, contrary to conclusions from previous studies. These results amplify the importance of understanding facial musculature in primate taxa, which may hold great taxonomic value.

Morphology and ultrastructure of the pharynx in Solenofilomorphidae (Acoela)

The homology of pharynges within the mostly pharynx-less Acoela has been a matter of discussion for decades. Here, we analyze the pharynges of three members of the Solenofilomorphidae, Myopea sp. and two species of the genus Solenofilomorpha, by means of light and transmission electron microscopy. Special focus is placed on the ultrastructure of the pharyngeal musculature, epidermis surrounding the mouth, pharyngeal epithelium, and junction with the digestive parenchyma. The main goal of this study was to evaluate the usefulness of certain characters for broader comparisons within the Acoela. Among the three species, characters relating to position of the mouth, presence and elaboration of sphincter muscles, presence of pharyngeal glands, and ultrastructure of epitheliosomes proved to be variously species- and genus-specific. The arrangement of pharyngeal muscles and their connection with body wall musculature, ultrastructure of receptor cells, and morphology of a nonciliated glandular region in the posterior pharynx, in contrast, appear to be characteristic of the family Solenofilomorphidae and thus of predominant interest for comparisons with other acoel families.

Postcranial myology of the California newt, Taricha torosa

Salamanders are generally agreed to represent the primitive tetrapod body plan, as well as a postural analog for early tetrapods. Dissection and description of the muscles of the forelimb, trunk, and hindlimb of the California newt, Taricha torosa, were undertaken to provide baseline data on the locomotor structures in this species. Hypaxial trunk muscles are similar to those of other vertebrates. As in other salamanders, limb muscles show a simple parallel-fibered architecture and often span multiple joints. Several differences in limb musculature were also noted. The extensor iliotibialis muscle possesses a single head in T. torosa, rather than the two heads common in larger salamander species. The ischioflexorius muscle, while divided into proximal and distal sections, is not distinct from the puboischiotibialis in its proximal portion. The femorofibularis is enlarged in this species; it is suggested that the femorofibularis and ischioflexorius muscles may be functionally analogous systems. Forelimb and hindlimb musculature show similar morphological patterns, particularly in distal limb segments, which may provide insight into the primitive arrangement of tetrapod limb muscles.

Extreme tadpoles: The morphology of the fossorial megophryid larva, Leptobrachella mjobergi

The bizarre larvae of Leptobrachella mjobergi are fossorial and live in the gravel beds of small streams. These tadpoles are vermiform in body shape. Here we present details on their skeleton and musculature, particularly of the head. The entire cranium and its associated musculature are reconstructed in three dimensions from serial histological sections. The hyobranchial apparatus is highly reduced. The head of the L. mjobergi larva is more mobile than in other anuran species. This mobility can largely be ascribed to the exclusion of the notochord from the cranial base and an articulation of the foramen magnum floor with the atlas of the tadpole. The articulation is unique among anuran species, but design parallels can be drawn to salamanders and the articulation between atlas and axis in mammals. In L. mjobergi, the atlas forms an anterior dens that articulates with the basal plate in an accessory, third occipital articular face. The muscle arrangements deviate from the patterns found in other tadpoles: For instance, epaxial and ventral trunk muscles reach far forward onto the skull. The post-cranial skeleton of L. mjobergi is considerably longer than that of other anurans: it comprises a total of 35 vertebrae, including more than 20 post-sacral perichordal centra. Despite a number of features in cranial and axial morphology of L. mjobergi, which appear to be adaptations to its fossorial mode of life, the species clearly shares other features with its megophryid and pelobatid relatives.

Musculoskeletal support of lumbar spine stability

Using a biomechanical model and experimental data the self-stabilising behaviour of antagonistic trunk muscles was analyzed. The biomechanical model is constituted of a pair of antagonistic Hill-type muscles, their geometric arrangement with respect to the spine, and the instantaneous centre of rotation in frontal plane. Using Ljapunov's theory, the stability of certain motion and loading situations was analyzed. Applying a sensitivity analysis, the influence of different muscle properties and the geometric arrangement on stability was investigated. The simulations revealed that the stability of spinal movements depended primarily on the geometrical arrangement of muscles and the position of the centre of rotation of the spine, the latter was affected in turn by the activities of the profound muscles. To stabilize the situations simulated oblique muscle arrangements were necessary. In order to define an instantaneous centre of rotation in the lower region of the spine negative attachment angles (medio-lateral decline) of muscles were necessary, corresponding to the real anatomy of obliquus externus muscles. More cranially located instantaneous centres of rotation required positive attachment angles for stability, corresponding to obliquus internus or multifidus muscles. Furthermore, the fibre-type distribution of muscles influenced the stability of the system, i.e. a high percentage of fast-twitch-fibres supported the stabilisation. Conclusions drawn from the simulations were supported by experimental data. Sudden loads and quick-release perturbations with two different amplitudes were applied to the upper body of ten male subjects. In comparison to sudden load situations preactivation of muscles due to an external load, i.e. quick-release perturbation, led to significantly less dependency of the amplitude of deflection on the amplitude of the perturbation. This observation relates to the self-stabilising properties of the musculoskeletal system. In conclusion, training seems to be advantageous if directed towards not only enhancing the endurance capacity of the muscles, but also increasing the cross-sectional area of oblique fast-twitch-fibres. Training should also improve the co-ordination of deep and superficial trunk muscles. These findings may influence physiotherapy and training programs for low back pain patients.

The anatomical arrangement of the myocardial cells making up the ventricular mass

The architectural arrangement of the myocytes within the ventricular mass remains a highly contentious topic. It has recently been suggested by several distinguished surgeons that the overall myocardial structure is disposed in the form of a 'ventricular myocardial band'. There are, however, major anatomic deficiencies in this hypothesis, because the heart is formed on the basis of a modified blood vessel, rather than a collection of discrete muscular entities resembling the skeletal musculature. There is ample alternative evidence, nonetheless, already existing to provide a suitable explanation for the 'forceful reciprocal twisting' of the ventricular mass that is seen by cardiac surgeons during operative procedures. We provide here, therefore, a review of the anatomical studies we have performed separately and conjointly over a period of nearly 30 years. As before, we show that there is no anatomic evidence to support the concept of the 'ventricular myocardial band'. The overall arrangement is for the myocytes to be supported as the muscular components of a continuous and complex mass, the supporting collagenous fibrous matrix possessing epimysial, perimysial, and endomysial components. It had already been discussed at length during the previous century why there was no anatomic evidence to support the existence of separate 'muscles' within the ventricular continuum. There are no fibrous sheaths within the ventricular walls that permit the myofibres to be dissected on the basis of muscle bundles having a discrete origin and insertion, as is the case with the arrangement of the skeletal muscles. We have never sought ourselves, however, to deny the central helical nature of the overall architecture of the ventricular walls. The anatomic evidence supporting an overall helical nature for the ventricular myocardium has existed for over 150 years. All the available evidence, nonetheless, shows that these helical patterns are to be found throughout the walls, and in no way constitute a unique myocardial band.

Functional shape of the skull in vertebrates: Which forces determine skull morphology in lower primates and ancestral synapsids?

In order to determine the extent to which the shape of the synapsid skull is adapted for resisting the mechanical loads to which it is subjected, block- or simple plate-shaped finite-element models were constructed and loaded with external muscle and bite forces in locations estimated to resemble points of application of these forces. These 2D or 3D finite-element models were iteratively loaded and modified by removing elements that experience only low stresses, and the resulting morphologies of the models were compared with fossil skulls of synapsids and the skulls of extant mammals. The results suggest that the stress flows in these unspecific models are very similar to the arrangement of bone material in real skulls. Morphological differences between taxa depend on a few a priori conditions: length and position of the tooth rows in relation to the braincase, arrangement of muscles, position of the orbits, and position of the nasal opening. Given these initial conditions, finite-element analysis consistently reveals the close similarity between stress flows and real skulls. The major difference between mammal-like reptiles and primates is the size of the braincase. This difference accounts for most of the morphological divergence. The postorbital bar seems to be a constructional element of the skull, rather than a means to protect the eyes. The skull shapes of higher primates are determined mainly by masticatory forces and less by external forces acting on the head. This study demonstrates the utility of finite-element modeling for testing hypotheses regarding relationships between form and function in vertebrate skulls.

Dental Functional Morphology: How Teeth Work (review)

Reviewed by: Dental Functional Morphology: How Teeth Work Jaimin D. Weets Dental Functional Morphology: How Teeth Work, by Peter W. Lucas. New York: Cambridge University Press, 2004. 372 pp. $130.00 (hardcover). Who can get excited about teeth? How do teeth work? Why write a book about how teeth work? These are just a few of the questions that are asked in the preface of Peter Lucas's outstanding work on dental functional morphology. The answer to the first question is that lots of people would find this work interesting and informative, including physical anthropologists, a broad range of paleontologists, and anatomists. If you are a researcher interested in studying the evolution of teeth over a broad geological scope and want to be aware of discussions about the forces that have shaped teeth in humans (and a diverse range of other species), then Dental Functional Morphology is a book you should have. Beginning with the preface and other information preceding the main body of the text, there is a clear sense of how passionate Lucas is about his research, how many diverse avenues of investigation are available in studying dentition, and how much fun it can be to discuss them. A perfect example of this is an innovative presentation of the evolution of the human molar that causes immediate involvement with the book. We are not given a static diagram that tracks 300 million years of change from simple cone to multicusped molar. Instead, we are given a "flick art" or "flick-page animation" situated in the lower right-hand corner of the page, beginning on page xv and continuing to page 159. An explanation of the flick art is given on pages xv and xvi, in which Lucas cautions us about the idealized forms seen in the presentation and what we are seeing as we speed through 300 million years in a few seconds. There was much work put into this presentation, and I am hesitant to say anything negative about it. However, if additional information (e.g., particular species represented and the geologic time ranges when they were present) could have accompanied some of the drawings in the lower-right hand corner, the flick art would be an even more useful, and fun, teaching tool. Chapter 1 is titled "How to Get Excited About Teeth." Lucas takes us through some interesting and familiar topics here. The chapter begins with a brief presentation of the debate of the origins of teeth. Did they begin as dermal scales or not? This is followed by a discussion of why teeth are so important, especially to mammals in comparison to other vertebrates. And, we are reminded of the distinct changes in the human diet that have occurred over the last few thousand years and that have been detrimental to our dental health. Lucas continues the [End Page 715] chapter with a discussion of how teeth are involved in the basic functions of chewing and swallowing, sensing food, and communication. He then limits the scope of the remainder of the book to the function of teeth as they are involved in ingesting, chewing, and swallowing food and how the properties of food drive the evolutionary changes in tooth form. Chapter 2 is a strong and engaging presentation of the structure of the mammalian mouth. At first glance the terminology and description of anatomy seemed a bit brief. But, as one continues through the chapter, Lucas provides well-written explanations of tooth structure, the individual tissues that make up the teeth, jaw, tooth socket, and the like, and then adds information on such subjects as the workings and anatomy of tongue muscles, facial muscles, and neck muscles for a complete overview. Consistent with the broad perspective of the text, there are numerous, intriguing comparisons of anatomy between different mammals and between mammals and reptiles. In keeping with another theme of the book, there are also opportunities to be actively involved with the subject matter. An example of this is the "game" illustrated in Figure 2.18 that helps the reader to understand the arrangement of jaw muscles in mammals. In this game two people manipulate a jaw to understand how different controlling muscles work...

Scanning electron microscopic study of the muscle fiber arrangement in the rat cricopharyngeal muscle

Conclusions. Myomyous junctions comprise a complex muscle fiber network, which is thought to synchronize the activity of the cricopharyngeal (CP) muscle fibers. Myomyous and myotendinous junctions explain the heterogeneity in muscle fiber length which contributes to the efficient behavior of the muscle. This scanning electron microscopy (SEM) study demonstrated the complex muscle fiber arrangement of the CP muscle and improved on the previous description of its morphological specificity. Objective. To examine the 3D ultrastructure of the inferior pharyngeal constrictor muscle fibers to obtain further knowledge of their morphological characteristics with regard to the specific functions of the muscle in deglutition. Material and methods. Six adult rats were used. Their CP and thyropharyngeal (TP) muscles were obtained and processed using the HCl hydrolysis method to remove i.m. connective tissue. The fine muscle fiber structure was observed by means of SEM. Results. Multifaceted muscle fiber interconnections (myomyous junctions) were identified in the CP muscle. The myomyous junctions were characterized by the tight connection of many finger-like processes at the ends of a lateral branch or bifurcating trunk of the muscle fibers. In addition, muscle fibers occasionally tapered and ended within the muscle belly, forming myotendinous junctions. The TP muscle lacked these structures.

The Effect of Posture on Respiratory Activity of the Abdominal Muscles

The purpose of this study was to determine the influence of posture on the expiratory activity of the abdominal muscles. Fifteen young adult men participated in the study. Activities of the external oblique abdominis, internal oblique abdominis, and rectus abdominis muscles were measured electromyographically in various postures. We used a pressure threshold in order to activate the abdominal muscles as these muscles are silent at rest. A spirometer was used to measure the lung volume in various postures. Subjects were placed in the supine, standing, sitting, and sitting-with-elbow-on-the-knee (SEK) positions. Electromyographic activity and mouth pressure were measured during spontaneous breathing and maximal voluntary ventilation under the respiratory load. We observed that the lung volume changed with posture; however, the breathing pattern under respiratory load did not change. During maximal voluntary ventilation, internal oblique abdominis muscle expiratory activity was lower in the SEK position than in any other position, external oblique abdominis muscle inspiratory activity was lower in the supine position than in any other position, and internal oblique abdominis muscle activity was higher in the standing position than in any other position. During spontaneous breathing, external oblique abdominis muscle activity was higher during expiration and inspiration in the SEK position than in any other position. The internal oblique abdominis muscle activity was higher during both inspiration and expiration in the standing position than in any other position. The rectus abdominis muscle activity did not change with changes in posture during both inspiration and expiration. Increase in the external oblique abdominis activity in the SEK position was due to anatomical muscle arrangement that was consistent with the direction of lower rib movement. On the other hand, increase in the internal oblique abdominis activity in the standing position was due to stretching of the abdominal wall by the viscera. We concluded that differences in activity were due to differences in the anatomy of the abdominal muscles and the influence of gravity.

Jump Mechanism using Coordination Function of Bi-articular Muscle in Knee and Ankle Joint

The effectiveness of jump model by mono-articular muscle and bi-articular muscle which imitated the human muscle arrangement was examined by the comparison of next three models. Models are (1) the serial link model in which two actuators of knee joint and ankle joint are independent, (2) the pantograph model in which two actuators receive the restraint by the biarticular muscle and (3) pantograph model which placed the actuator only in the knee joint. The effectiveness of jump model was theoretically verified from the static ground reaction force before the jump. The pantograph model (3) can jump only at the torque of extension muscle of the knee joint. In addition, the jump mechanism was produced experimentally, and the effectiveness of the model was verified. This conclusion is one of a solution to the general question too. “Why cruris of the animal which makes jump and high speed running good are very thinner than the femoral region”.

Evolution of proboscis musculature in Lepidoptera

The suctorial proboscis of adult Lepidoptera represents a key morphological innovation that enabled these insects to gain access to new food sources. In the ancestral condition of the lepidopteran proboscis only extrinsic galeal muscles are present in the basal joint region. The presence of additional muscles (i.e., the intrinsic galeal muscles) is regarded as a morphological novelty of the Myoglossata that evolved after the galeae were modified to form suctorial mouthparts. The present comparative investigation of the galeal anatomy in representatives of all major taxa revealed that the intrinsic galeal muscles are derived from the basal galeal musculature. In the examined Neopseustoidea, Exoporia, Nepticuloidea, Incurvarioidea, and Tischerioidea all galeal muscles have their origin in the stipes-galea joint and/or in the proximal region of the galea. Two muscle units form the basal galeal musculature of the joint region and one to three longitudinal muscles extend into the galea lumen. Multiple intrinsic galeal muscles, of which both the origin and attachment sites are markedly distal from the basal joint region are regarded as a groundplan autapomorphy of the Ditrysia. Some slightly oblique muscles may occur along the lateral wall; these were lost in species with extremely slender galeae. In most investigated Obtectomera two series of intrinsic galeal muscles occur; these are the (1) oblique lateral intrinsic galeal muscles, which are arranged one upon the other along the lateral proboscis wall and (2) the median intrinsic galeal muscles, which run more or less longitudinally along the ventral wall. Oblique muscle arrangement probably evolved in concert with the functional demands of a long lepidopteran proboscis. A likely evolutionary pathway to account for the serial arrangement of galeal muscles is propo sed.

Neuromusculature of Macrogyrodactylus clarii, a monogenean gill parasite of the Nile catfish Clarias gariepinus in Egypt.

Phalloidin fluorescence technique, enzyme cytochemistry and immunocytochemistry in conjunction with confocal scanning laser microscopy have been used for the first time to describe the nervous and muscle systems of the viviparous monogenean gill parasite, Macrogyrodactylus clarii. The gross spatial arrangement of muscle and associated cholinergic, peptidergic and aminergic innervations has been examined. The central nervous system (CNS) consists of paired cerebral ganglia from which emanate three pairs of longitudinal ventral, lateral and dorsal nerve cords, connected at intervals by transverse connectives. The CNS is better developed ventrally than dorsally or laterally, and has the strongest reactivity for all neuroactive substances examined. Structural and functional correlates of the neuromusculature of the pharynx, haptor and reproductive tracts have been examined. Results implicate acetylcholine, FMRFamide-related peptides (FaRPs) and serotonin in sensory and motor function in this monogenean, although confirmatory physiological data are obviously required.

Communication between the buccal nerve (V) and facial nerve (VII) in the human face

Terminal arrangements of communicating branches between the buccal nerve (V) and the facial nerve (VII) have yet to be precisely determined. To clarify distributions and relationships to facial muscles, detailed morphological examination of the two nerves was performed in the buccal region. The facial skin and underlying tissues of three cadavers were removed en bloc from the surface of the skulls and dissected from outside and inside. Arrangements of the facial muscles, nerves, and associated structures were observed. In all specimens, the communicating buccal nerve (CBN) was detected, largely covering the buccal region. The CBN gave off multidirectional twigs around the facial vein, some of which reached the anterior part of the zygomaticus major muscle. Several twigs of the CBN joined proximally with the zygomatic and buccal branches of the facial nerve. Ramified junctions that interconnected the lower zygomatic and upper buccal branches of the facial nerve were observed near sites where the CBN joined. Anterior twigs of the CBN supplied the longitudinal area lateral to the mouth, where many muscles converged. This study presents a precise morphological pattern of the CBN, suggesting functional contribution of the CBN to control of orofacial movements.

舌筋配置を模した三角要素分割による人工舌用要素の機構設計 : 機械式音声合成装置の構成要素のデザイン(バイオメカトロニクス/ミメティクス)

舌筋配置を模した三角要素分割による人工舌用要素の機構設計 : 機械式音声合成装置の構成要素のデザイン(バイオメカトロニクス/ミメティクス)

ヒト肩関節を規範としたロボットアーム関節機構の開発

The purpose of this study was to develop a new joint system based on the human shoulder mechanism. The human shoulder joint is constrained by multiple muscles and ligaments which surround the ball joint, and is driven by the balance of those forces. It is thought that the construction of the human shoulder mechanism could provide motion with three degrees of freedom and with compact size and light weight in comparison with an industrial robot arm composed of the usual pin joints. Therefore, the authors thought that the new joint mechanism for a robot arm with three degrees of freedom should be a ball joint mechanism driven by wires.In the development of the new joint mechanism, we tried to construct two types of joints. These were a five-wire model and a six-wire model. An anatomical skeletal structure has been introduced to the mechanism, especially on the muscle arrangements of the human shoulder.The movability of the new joint mechanism was evaluated by the ratio of moment arm to ball radius produced from the wires that surround the ball joint. The method of estimating moment arm was to find the slope of the wire excursion against the joint angle. Thus, to compensate some deficiency of moment arm, occurring in a specific area of flexion-extension or rotation motion, the wire position corresponding to the lack of moment arm was adjusted to an adequate position using evaluation of the moment arm. As a result of improvement processes, the effective movability was ascertained in the specified movable area for the six-wire model. Sufficient movability was not acquired in the five-wire model, however, because the movable area was considerably reduced.When the joint is driven as a robot arm, an inverse kinematics must be solved. In the present study, the problem was solved by utilizing an artificial neural network (NN), which learns data sets for arm posture and wire displacement. The additional differential outputs installed in the learned NN and consideration of a theory of virtual work balance were applied to a control system to drive the joint by a feedback control system in the range of three degrees of freedom. It was properly and precisely driven by the control system on the six-wire model. Thus, the movability and capability of the new joint system of a robot arm based on the human shoulder mechanism, as described in this paper, was demonstrated to be satisfactory.

Conformation and musculoskeletal problems in the racehorse

Conformation is the form (outline) or physical appearance of a horse from the arrangement of muscles, bones, and tissues. In Thoroughbreds long bone and segmental limb lengths are proportional and relationships exist between these measurements and withers height. Carpal conformation progressively changes from “back at the knee” to slightly “over at the knee” between the weanling and 3-year-old year and this is an important consideration when evaluating weanlings and yearlings, as one should avoid selecting individuals that are over-at-the-knee at an early age. Likewise, a foal that is back-at-the-knee will likely improve considerably with age. The angle of the scapula, shoulder joint, and radiometacarpus significantly increases between all ages. Therefore, long bone growth and the increase in upper angles may influence mature height. Horses with longer shoulders had decreased odds and horses with long pasterns had increased odds of forelimb fractures. Scapula and front pastern lengths were both correlated with withers height for 3-year-old horses. In racing Quarter Horses increased length of humerus was associated with osteochondral fractures of the proximal phalanx and synovitis/capsulitis in both carpal joints. Leg length increased the odds of sustaining osteochondral fracture in the carpus, implying that longer legs could predispose to an increased incidence of fracture. Increased length of toe increased the odds of sustaining a carpal chip fragment. As shoulder angle increased, the odds of an osteochondral fracture of the carpus increased. As the pastern became more upright there was decreased chance of sustaining carpal synovitis/capsulitis. As carpal offset ratio increased by 10% the odds of synovitis/capsulitis in left and right forelimbs increased. As the hoof length ratio increased the odds of sustaining carpal osteochondral fracture increased.

Influences of tongue biomechanics on speech movements during the production of velar stop consonants: a modeling study.

This study explores the following hypothesis: forward looping movements of the tongue that are observed in VCV sequences are due partly to the anatomical arrangement of the tongue muscles, how they are used to produce a velar closure, and how the tongue interacts with the palate during consonantal closure. The study uses an anatomically based two-dimensional biomechanical tongue model. Tissue elastic properties are accounted for in finite-element modeling, and movement is controlled by constant-rate control parameter shifts. Tongue raising and lowering movements are produced by the model mainly with the combined actions of the genioglossus, styloglossus, and hyoglossus. Simulations of V1CV2 movements were made, where C is a velar consonant and V is [a], [i], or [u]. Both vowels and consonants are specified in terms of targets, but for the consonant the target is virtual, and cannot be reached because it is beyond the surface of the palate. If V1 is the vowel [a] or [u], the resulting trajectory describes a movement that begins to loop forward before consonant closure and continues to slide along the palate during the closure. This pattern is very stable when moderate changes are made to the specification of the target consonant location and agrees with data published in the literature. If V1 is the vowel [i], looping patterns are also observed, but their orientation was quite sensitive to small changes in the location of the consonant target. These findings also agree with patterns of variability observed in measurements from human speakers, but they contradict data published by Houde [Ph.D. dissertation (1967)]. These observations support the idea that the biomechanical properties of the tongue could be the main factor responsible for the forward loops when V1 is a back vowel, regardless of whether V2 is a back vowel or a front vowel. In the [i] context it seems that additional factors have to be taken into consideration in order to explain the observations made on some speakers.