Functional morphology of the mastication muscles in the lesser and greater mouse deer

The mastication muscles were examined in the lesser (Tragulus javanicus) and greater mouse deer (Tragulus napu) to clarify the form of the mastication muscles in these primitive artiodactyls. The M. masseter was well-developed in both species, however the attachment area of its origin was not confirmed in the rostral facial part. The masseter bundles were not observed on the lateral side of the maxilla bone, and their origin was restricted to the zygomatic arch area. This suggests that the M. masseter may not act as a motor raising the mandible rostro-dorsally, but pull the insertion vertically unlike the highly derived grazer of Bovidae. The Crista temporalis was weak and the M. temporalis was thin in the mouse deer, and this indicates that the M. temporalis may not be important in the mastication in the primitive artiodactyls. These findings suggest that the browser such as mouse deer has been adapted for the feeding on soft leaves, and functional-morphologically different in mastication strategy from the grazer such as developed Bovidae species. The architecture of the mastication muscles was not different between the two species. However, in the muscle weight ratios per body weight, the M. temporalis and the M. digastricus were significantly smaller in greater mouse deer than in lesser mouse deer.     

The Structure of the Masseter Muscle in the Giraffe (Giraffa camelopardalis)

In the giraffe (Giraffa camelopardalis), the masseter muscle was divided into several layers. The superficial and more medial (second) tendinous sheets of the masseter muscle fused with each other at the dorso-caudal part and a fleshy portion was located between these tendinous sheets. In the rostral part, the most superficial tendinous sheet turned around as a compact tendon and attached to the facial crest (Crista facialis). The turned tendinous sheet, however, never fused with the second tendinous sheet and this layer of the masseter muscle, that originated from the facial crest with the turned sheet, was inserted into the mandible with its fleshy portion. In the cattle, goat, sheep and Sika deer, the rostral layer of the masseter muscle arises from the facial crest with its fleshy portion and is inserted into the tubercle on the mandible through the strong tendinous sheet. In this study, the takin also showed the same structure of the masseter muscle. In the giraffe, however, the rostral layer inserted into the mandible through the strong tendinous sheet could not be distinguished, thus, there was no conspicuous tubercle on the mandible. Moreover in the masseteric region of the skull.,the giraffe was similar to the Sika deer in several ways. However, it is suggested that the giraffe exerts smaller forces on the cheek teeth than does the Sika deer because of its longer Margo interalveolaris.     

The muscles of mastication in the caspian seal (Phoca caspica)

The muscles of mastication and their related skull characters in the Caspian seal (Phoca caspica) were anatomically examined and compared with those of the Baikal (Phoca sibirica) and ringed (Phoca hispida) seals. A well-developed masseter muscle was observed in the Caspian seal, whereas the temporal muscle consisted of thin bundles. The skull of the Caspian seal possessed the same thin frontal bone and the dorso-ventrally developed zygomatic arch found in the Baikal seal that are required to install the enlarged eyeball into the orbit. The temporal bone was not robust, and the digastric muscle was well-developed in the ventral space of the auditory bulla. The present results suggest that the skull form of the Caspian seal has changed morphologically from its ringed seal-like ancestors, and suggest that the evolutionary strategy of the muscles of mastication in the Caspian seal is principally consistent with that of the Baikal seal.     

Comparative anatomy of the radial sesamoid bone in the polar bear (Ursus maritimus), the brown bear (Ursus arctos) and the giant panda (Ailuropoda melanoleuca).

Since we have clarified the manipulation mechanism using the radial sesamoid (RS) in the giant panda (Ailuropoda melanoleuca), our aim in this study is to examine the position, shape and function of the RS morphologically, and to observe the attachment to the RS of the M. abductor pollicis longus and the M. opponens pollicis in the other Ursidae species. So, we focused on the carpus and manus of the polar bear (Ursus maritimus) and the brown bear (Ursus arctos) in this study. The RS was tightly articulated to the radial carpal, and could not adduct-abduct independently of the radial carpal. The M. abductor pollicis longus tendon and the M. opponens pollicis belly were attached to the RS, independently. In the polar bear, the deep concave and the flat surface were confirmed in attachment area for these two muscles. The morphological relationship between the RS and the M. abductor pollicis longus and the M. opponens pollicis in the two species of bears were essentially consistent with that in the giant panda. It also demonstrated that the manipulation mechanism of the giant panda has been completely based on the functional relationship between the small RS, and the M. abductor pollicis longus and the M. opponens pollicis in Ursidae species.     

Muscle architecture of the elongated nose in the Asian elephant (Elephas maximus).

The architecture of the M. caninus in the elongated nose was examined in the Asian elephant (Elephas maximus). The following complicated musculature of the M. caninus was observed in the proximal and distal regions of the nose: (1) Proximal region: In the superficial layer, the longitudinal bundles are confirmed in the dorsal part, and the obliquely-oriented ones in the ventral part. In the middle layer, some bundles run ventro-distally, while other ones represent longitudinally-oriented running. The deep layer consists of complicated architecture of many bundles. Some muscle bundles run medio-laterally, while the others extend proximo-distally in this space. (2) Distal region: In the dorsal part of the M. caninus, the bundles run at deep-superficial direction, while in the ventral part the bundles are longitudinally arranged. The bundles run at lateral direction near the septum of the nasal conduits. The N. facialis and N. infraorbitalis send many branches in the lateral area of the M. caninus in the trunk. This muscle architecture of multi-oriented bundles and well-developed innervation to them suggest that they enable the elongated nose to act as a refined manipulator in the Asian elephant.     

Surgical Correction of Congenital Bilateral Choanal Atresia in a Foal

Congenital bilateral choanal atresia was corrected surgically in a neonatal foal. Presenting clinical signs included complete obstruction of the upper airway, which had been relieved by tracheotomy. The diagnosis was confirmed by endoscopic examination and contrast radiography. Bilateral nasal flaps were used to gain access to the caudal nasal cavity, allowing removal of obstructive tissue and restoration of normal respiration. Malocclusion developed secondary to surgical intervention and resultant damage to suture lines of developing flat bones of the skull. Nine months postoperatively, the asynchronous growth of the mandible and maxilla had not resulted in difficulty during mastication. Respiration, although audible during periods of exercise, was acceptable to the owners.     

How to Open the Mouth: the Kinetic Skull, and the Jaw and Branchial Apparatus in Sharks

Aims:  Mammals cannot swallow if their necks and, hence, their mm. sternohyoidei et sternothyroidei are stretched. In order to understand the functional morphology of mastication and swallowing in mammals, it is useful to understand its evolutionary origin.
Material and Methods:  Five formalin-preserved specimens of the Spiny Dogfish (Squalus ancanthias) were used for dissection or to prepare sagittal or transverse serial sections.
Results and Conclusions:  The feeding apparatus of the shark Squalus acanthias as a representative of the cartilaginous fishes serves as an excellent model of that of an ancestral vertebrate with a kinetic skull, in which the chondrocranium is movable relative to the jaw apparatus. To open the mouth, the cranium is raised by the epibranchial musculature, the palatoquadrate cartilage (i.e., upper jaw) is entrained, and the mandibular cartilage is held in place and prevented from following the upper jaw by the coracomandibular muscle. At the same time, the branchial basket and oropharyngeal cavity are expanded and held in place by the coracohyoid and coracoarcual muscles, which prevent the hyoid and branchial arches from being entrained cranially by the raised chondrocranium. The mandible is not retracted during the opening of the mouth in sharks because the branchial region would have to be compressed instead of expanded. In the course of the evolutionary modifications leading to mammals, the heart and respiratory apparatus became decoupled from the feeding apparatus through the formation of a neck. The skull became akinetic through the integration of the upper jaw into the base of the cranium. The mouth is not opened any longer by lifting the cranium, but by depressing the mandible through a special muscle, the m. depressor mandibulae . The coracomandibular muscle lost its function as a stabilizer of the mandible during mouth opening and became modified into the lingual and geniohyoid muscles.     

A novel technique for ventral orbital stabilization: the masseter muscle flap

Loss of the caudal maxilla and ventral orbit after tumor resections can have negative functional and esthetic influences on the eye involved. This article reports on a case of a caudal maxillary acanthomatous ameloblastoma involving the ventral orbit that was resected and stabilized with a masseter muscle flap. The masseter muscle flap was generated from the superficial belly of the masseter muscle in order to close a defect in the orbital rim, created by a caudal maxillectomy. None of the published complications such as enophthalmos, excessive lacrimation, globe deviation, or strabismus were noted, 8 months following the procedure. The only clinical sign present at the time of re‐evaluation was mild lacrimation. The authors propose the use of a masseter muscle flap as a viable technique in stabilizing the ventral orbit after caudal maxillectomy and ventral orbitectomy, preventing the complications associated with this surgery.     

Comparative ingestive mastication in domestic horses and cattle: a pilot investigation

It is often assumed that horses chew food more intensively during ingestion than cattle, which ‐ as ruminants ‐ complete part of the mastication during rumination. This has been proposed as a reason for more robust mandibles, larger masseter insertion areas and larger masseter muscles in horses as compared to cattle and other grazing ruminants. In this study, we evaluate results of comparative feeding trials with three horses (338–629 kg) and three cows (404–786 kg), on four different roughages. Ingestion time (s/g dry matter) and chewing intensity (chews/g dry matter) differed among animals within a species, indicating an influence of body mass, and differed significantly between different forages. However, although numerical differences clearly suggest that horses have longer ingestion times and higher chewing intensities on high‐fibre roughage than do cattle, this could not be proven in this dataset, most likely because of the small number of individuals sampled. Further studies are required to corroborate the suspected ingestive behaviour difference between equids and ruminants.     

Xanthosis, an abnormal pigmentation of cattle.

Xanthosis is seen in cattle in the abattoir. It is characterised by a dark brown colour of the heart muscle and certain skeletal muscles such as the masseter because of the presence of lipofuscin pigment. In a survey of its prevalence in 1000 cattle of varying breeds xanthosis was identified in about 25 per cent of Ayrshire cattle and the occasional Ayrshire cross. It was not seen in other breeds. The incidence of one affected and three normal suggests that this condition may result from the inheritance of a simple recessive gene. The relationship of xanthosis to brown atrophy is discussed.     

Computed tomography and cross-sectional anatomy of the head in the giant anteater (Myrmecophaga tridactyla)

The aim of this study was to identify the anatomical structures in the head region of the giant anteater (Myrmecophaga tridactyla) using computed tomography. For this, three giant anteater corpses, adult and female, were used. The tomographic analysis was performed in sequential order in rostrocaudal direction. Subsequently, the heads of these animals were sectioned in cross sections of approximately 1.5 cm each. Tomographic images were compared with anatomical sections. The association between computed tomography and anatomical sections allowed the visualization of anatomical structures found in the nasal, oral, cranial, pharyngeal and ear cavities. An elongated oral cavity delimited by the elongated mandible was observed. The oral cavity was mainly occupied by a thin and elongated tongue formed mainly by the union of the sternoglossal muscles. The nasopharynx and oropharynx extended up to the neck at the level of the fifth cervical vertebra. The findings of this study suggest that the giant anteater has a head with structures morphologically adapted to its feeding habits, such as an elongated skull, tongue, styloid bones and mandible. In addition, based on the results of this study, it is possible to suggest that computed tomography is a pivotal tool for the veterinary routine of wild animals, since it allowed the identification of anatomical structures found in the head of the giant anteater.     

Mobility of the forearm skeleton in the Asiatic black (Ursus thibetanus), brown (U. arctos) and polar (U. maritimus) bears

In several primates and carnivores, pronation/supination angles of the forearm skeleton were examined, and it is thought that a larger angle is useful to acquire dexterous behaviors in feeding and/or life style, including climbing. In this study, the pronation/supination angles in Asiatic black, brown and polar bears were nondestructively examined. These specimens were classified as adult or non-adult. Three or four carcasses of each group of Asiatic black and brown bears were used for CT analysis, whereas only one adult polar bear was used. The forearms were positioned within the gantry of a CT scanner in both maximally supinated and pronated states. Extracted cross-sectional CT images of two positions were superimposed by overlapping the outlines of each ulna. The centroids of the radii were detected, and then the centroid of each radius and the midpoint of a line which connects between both ends of the surface of each radius facing the ulna, were connected by lines to measure the angle of rotation as an index of pronation/supination. In adult brown and polar bears, the angles were smaller as compared with the other groups (Asiatic black and non-adult brown bears). Asiatic black and non-adult brown bears can climb trees, whereas adult brown bears and polar bears cannot. This suggests that the pronation/supination angle is related to arboreal activity in Ursidae.     

Demonstration of the nerve distribution of the masticatory muscles in rabbits (Oryctolagus cuniculus)

Two methods can be used in order to demonstrate the nerve distribution of an organ. One is the three-dimensional reconstruction of the innervation pattern of the organ by tracing images of that organ from serial histological sections. The other is the in toto staining of the organ with subsequent clearing of the muscles. In the present study, in order to visualize the nerve distribution of the organ, that organ was completely cleared and the nerve fibres were stained. Detailed morphological structure of the intramuscular nerve distribution of a certain region and its functions are of importance not only for anatomists and physiologists but also for clinicians. In this study eight New Zealand rabbits were used to visualize the intramuscular nerve distribution of the muscles involved in mastication (temporalis m., pterygoideus medialis m., digastricus m., retractor mandibulae m. and masseter m.). The main nerve bundle was observed entering into the muscle as a single trunk and dividing into three branches in the muscle. These branches were also observed dividing into several subbranches while going to the periphery. When the samples were examined under a stereomicroscope, 'Y'-, 'I'- and 'O'-shaped communications between those branches were observed.     

SUBDURAL INJECTION OF CONTRAST MEDIUM DURING CERVICAL MYELOGRAPHY

Three patients (1 dog, 2 horses) ae described where myelography was complicated, purportedly by injection of contrast medium into the meninges superficial to the subarachnoid space. Contrast medium injected in this locationin a cadaver tended ot accoumulate dorsally within the vertebarel canal, deep to the dura mate but superficial to the subarachnoid space. The ventral marginof the pooled contrast medium had a wavy or undulating margin and the dorsal margin was smooth. Pooled contrast medium was believed to be sequestered within the structurally weak dural border cell layer between the dura mater and arachnoid membrane, or so-called subdural space.     

A case of cranial myodegeneration (atrophic myositis) in a dog

The clinical history, examination and treatment of a case of cranial myodegeneration are described. Observations extended over a period of 3 years, 8 months, and during this period three biopsies were taken from the muscles of mastication (temporal and masseter muscles). The results of the post-mortem examination are also recorded. The histological changes in the muscles of mastication were consistent with a diagnosis of neural atrophy, but it was not possible to confirm this by histological examination of the central nervous system. The differential diagnosis of cranial myodegeneration is discussed. Résumé. On décrit le développement clinique, l'examen et le traitement d'un cas de dégéné-rescence musculaire crânienne. Les observations se sont déroulées sur une période de trois ans huit mois et au cours de cette période, on a fait trois biopsies des muscles de mastication (muscles temporal et masséter). On donne également les résultats de l'autopsie. Les modifications histologiques observées dans les muscles de mastication donnaient appui au diagnostic d'atrophie neurale, mais il n'était pas possible de le confirmer par un examen histologique du système nerveux central. On examine le diagnostic différentiel de la dégénérescence musculaire crânienne. Zusammenfassung. Die klinische Geschichte, Untersuchung und Behandlung eines Falles von cranialer Myodegeneratio werden beschrieben, Die Beobachtungen erstreckten sich über drei Jahre und acht Monate, und während dieser Periode wurden drei Biopsien an den Kaumuskeln (Temporal- und Massetermuskeln) vorgenommen. Die Ergebnisse der Sektion wurden ebenfalls festgehalten. Die histologischen Veränderungen in den Kaumuskeln stimmten mit einer Diagnose auf neurale Atrophie überein, aber es war nicht möglich, dies mit einer histologischen Untersuchung des Zentralnervensystems zu bestätigen. Die Differentialdiagnose der cranialen Myodegeneratio wird besprochen.     

Humeral Chondrosarcoma in a Hokkaido Brown Bear (Ursus arctos yesoensis)

Humeral chondrosarcoma was found in an 18-year-old male Hokkaido brown bear (Ursus arctos yesoensis). Necropsy revealed a large firm mass under the left superficial pectoral muscle at the axillary region. The mass involved the left shoulder joint and peripheral muscles, and connected to the head of the humerus with osteolysis. Histopathologically, the mass was composed of irregularly shaped myxomatous to cartilaginous tumor lobules. The tumor cell showed moderate nuclear atypia with a relatively high mitotic index, especially in the edges of the myxomatous lobules. The tumor cells were positively immunostained with vimentin and S-100 protein. Based on these findings, the tumors were diagnosed as chondrosarcoma. Metastases were found in the left axillary lymph node, lungs, liver and kidney.     

Use of serial standing computed tomography for diagnosis,treatment and monitoring of a horse with acute myonecrosis of the head

An 11-year-old American Quarter Horse gelding was referred to the JT Vaughan Large Animal Teaching Hospital at Auburn University, College of Veterinary Medicine, for investigation of acute and severe right-sided facial swelling and nasal discharge. Standing computed tomographic (CT) examination of the head identified severe soft tissue swelling surrounding the right mandible, emphysema within the soft tissues tracking along fascial planes and right-sided caudal and rostral maxillary sinusitis. Using CT identification and ultrasound guidance, several targeted fasciotomies were created into the right masseter, cranial cervical musculature, supraorbital space and caudo-medial aspect of the mandible. The right-sided sinusitis was treated by right conchofrontal sinus trephination and lavage. Aerobic and anaerobic cultures obtained from the fasciotomy sites and conchofrontal sinus both yielded Prevotella intermedia and Peptostreptococcus asaccharolyticus. During hospitalisation, serial, standing CT examinations were performed for monitoring case progression and guiding further fasciotomies in the face of continued myonecrosis. Follow-up CT performed at 1 month showed resolution of the emphysema and presence of chronic right ventral conchal sinusitis. The sinusitis was treated by fenestration of the right ventral concha with a diode laser via the nasal passage.     

饲养方式对产蛋前母鸡肉质、肌肉物理特征和感官评价的影响

文章旨在研究不同饲养方式对产蛋前蛋鸡胸肌和腿肌化学成分、物理特征和感官评价的影响。试验选择1日龄海兰褐壳蛋鸡900只,随机分为3组,每组5个重复,每个重复60只。蛋鸡在1~10周龄和11~20周龄时分别饲喂相同的生长前期和生长后期日粮,3个组蛋鸡分别通过笼养、平养(稻谷粉作为垫料)和散养。试验结束后,对蛋鸡屠宰,收集胸肌和腿肌进行分析。结果:平养和笼养组蛋鸡胸肌粗脂肪含量较散养组分别显著提高114.81%和74.07%(P<0.05),但散养组蛋鸡胸肌铁含量较平养组显著提高37.99%(P<0.05),同时胶原含量较笼养组显著提高25.28%(P<0.05)。散养组蛋鸡腿肌粗脂肪和能量含量最低(P<0.05),但散养组粗蛋白质、铁、锌含量分别较笼养组显著提高8.85%、40.26%和17.16%(P<0.05)。散养组蛋鸡胸肌硬度和韧性较笼养组分别显著提高42.69%和27.76%(P<0.05)。笼养组腿肌蒸煮损失较平养组显著提高8.01%(P<0.05),散养组腿肌硬度和韧性分别较平养组显著提高35.24%和133.25%(P<0.05)。与笼养组相比,散养组胸肌风味和咀嚼性显著高于笼养组(P<0.05),同时散养组胸肌总可接受度显著高于平养组(P<0.05)。散养组腿肌风味、多汁性和咀嚼性均显著高于笼养和平养组(P<0.05),同时该组总可接受度较平养组显著提高6.72%(P<0.05)。结论:散养产蛋前蛋鸡的感官指标表现最佳,同时腿肌和胸肌粗脂肪含量最低,粗蛋白质和胶原蛋白含量高,可以改善肌肉口感。