Muscular anatomy of the forelimb of tiger (Panthera tigris)

Five-headed triceps brachii muscle, with an unusual communication between the musculocutaneous and median nerves in a cross-breed dog cadaver: a case report

In the domestic dog, the medial head (caput mediale) of the triceps brachii muscle arises via a distinct tendon from the crest of the lesser tubercle and the accessory head (caput accessorium) from the proximal caudal part of the neck of the humerus. Here the author presents a previously unreported additional point of origin of the triceps brachii muscle on both antimeres of an adult male cross-breed domestic dog cadaver. The variant head arose via fleshy fibers from the medial aspect of the neck of the humerus, just caudal to the lesser tubercle and fused at insertion with the caudal aspect of the proximal half of the medial head. Thus, it can simply be considered as the second accessory head of the triceps brachii muscle. The radial collateral artery on the left limb passed distolaterally between the medial and variant heads, whereas it passed caudal to the variant head on the right limb. The communicating branch between the musculocutaneous and median nerves extended in both directions on the left brachium. Besides a potential clinical significance, knowledge of this variant can be useful in understanding the embryogenic and phylogenetic perspectives.

Is the Articularis Humeri Muscle Homologous to the Coracobrachialis Muscle in Carnivorans? An Evolutionary and Terminological Answer Based on the Shoulder Myology of the Coati (Nasua nasua, Carnivora, Procyonidae)

South American coati (Nasua nasua) is a carnivoran of the suborder Caniformia and family Procyonidae. Anatomical and functional studies have been performed on the thoracic limb muscles of this species. The topology and innervation are necessary to establish a more suitable anatomical terminology and to infer the muscle evolutionary derivation in anatomical studies. Within the shoulder muscles, the articularis humeri muscle is found caudal to the shoulder joint capsule and is innervated by the axillary nerve. The coracobrachialis muscle is medial and is innervated by the musculocutaneous nerve. However, some studies in N. nasua and other carnivorans describe the coracobrachialis muscle with the name articularis humeri muscle. Therefore, the present study aimed to analyse the terminology and evolutionary derivation inferences of the shoulder intrinsic muscles in N. nasua based on their attachments, topology, and innervation. We dissected 15 thoracic limbs from eight formaldehyde-fixed specimens. Most muscles conserved the evolutionary derivation proposed to other procyonids. Ten limbs presented the articularis humeri muscle similar to that described in the ursid Ursus maritimus (polar bear) and the felids Felis catus (domestic cat) and Panthera leo (lion). This muscle could have derived from the subscapularis muscle and potentially be present in the last common ancestor of carnivorans. Based on most references in myological studies of Carnivora, the present study is the first record of the presence of the articularis humeri muscle in N. nasua. Therefore, the name m. articularis humeri should not be used as a synonym or homologous muscle to the coracobrachialis or coracobrachialis brevis.

Muscular anatomy of the forelimb of Leopardus geoffroyi: Functional and phylogenetic aspects in Feliformia, part I. Proximal forelimb

Anatomical knowledge is fundamental for all species. In particular, myology allows a deeper understanding of ecomorphology-especially for those species hard to observe in the wild-and may be an important source for phylogenetic information. In this study, we analyzed the myological variation of the musculature of the shoulder and arm of the forelimb in species of the suborder Feliformia and its relationship with the phylogenetic history and the locomotor behavior, habitat, and predatory habits of the species within this group, using Leopardus geoffroyi as a case study. We used gross-anatomy dissections of the shoulder and arm of three specimens of L. geoffroyi and contrasted these results to other previously described feliform species. Additionally, we optimized 15 myological characters to search for phylogenetic patterns. We present the first description and the first complete muscular maps of the forelimb shoulder and upper arm of L. geoffroyi. A small number of muscular characteristics allow L. geoffroyi to be distinguished from other feliforms, such as a possible partial division of m. biceps brachii, although they did not relate to any analyzed ecological habit. Some myological characteristics studied in this work contribute to the knowledge of the phylogenetic relationships and the morphological evolution of Feliformia. Felids are the only feliforms with a constantly present m. pectoantebrachialis (although it has been reported in some caniforms). Muscle rhomboideus capitis is present only in Felidae and Herpestidae, resembling various caniforms. Its presence could indicate a retention linked to their carnivoran ancestry. The Felidae and Hyaenidae represent two quite conservative morphotypes, as they present particular muscular configurations compared to other feliform families, but also, relatively little variation within each family. Functionally, some myological characters recorded in hyenids, L. lynx, P. uncia, A. jubatus (e.g., radio-ulnar insertion of m. biceps brachii), distinguish them from the rest of the species of the same suborder or family, and are convergent with other carnivorans with cursorial habits (e.g., canids). The functional and evolutionary analysis of the myology of the forelimb of L. geoffroyi and the different species of the suborder Feliformia allowed a better understanding of how muscle configurations reflect functional specialization to different ways of life. The muscle maps presented here, being the first available for a small Neotropical felid, can be considered a valuable source of information, useful for future studies of comparative anatomy in neontological and paleobiological contexts.

An arch worth revisiting: a study on the feline humeral supracondylar foramen and its evolutionary significance

The supracondylar foramen with a (seemingly) osseous peripheral arch noticed on the medio-distal feline humeri had remained disputed among anatomists. Some scholars have argued in favor of homology between this foramen and the supracondyloid foramen formed in presence of the ligament of Struthers in humans. Other theories include its presence as a retinaculum holding the median nerve and brachial artery to their anatomical position in a flexed elbow. Unfortunately, these theories lack investigative rigor. The emergence of non-invasive imaging modalities, such as micro-computed tomography, has enabled researchers to inspect the internal anatomy of bones without dismantling them. Thus, a micro-computed tomographic investigation was conducted on three feline (Felis catus) humeri specimens while the internal anatomy of the supracondylar foramina was examined. Unlike the humerus, the thin peripheral arch of the feline supracondylar foramen failed to elicit any osseous trabeculae or foci of calcification. While adhering to the humeral periosteum at its origin, the non-osseous arch, typical of a muscular tendon, attaches into the bony saddle related to the medial humeral epicondyle suggestive of a tendon or aponeurotic extension of a (vestigial) brachial muscle, with the coracobrachialis longus emerging to be the most likely candidate.

CT reconstruction based 3D model of the digital cushion's blood supply in the hind foot of an African savanna elephant (Loxodonta africana)

Introduction

Foot health is crucial for elephants, as pathological lesions of the feet are a leading cause of euthanasia in captive elephants, which are endangered species. Proper treatment of the feet, particularly in conditions affecting the digits and the digital cushion, requires a thorough understanding of the underlying anatomy. However, only limited literature exists due to the small population and the epidemiological foot diseases which often precludes many deceased elephants from scientific study. The aim of this study was to provide a detailed anatomical description of the blood supply to the African elephant's hindfoot.

Methods

The healthy right hindlimb of a 19-year-old deceased female African savanna elephant was examined using computed tomography. Following a native sequence, 48 mL of barium-based contrast agent was injected into the caudal and cranial tibial arteries, and a subsequent scan was performed. The images were processed with 3D Slicer software.

Results

The medial and lateral plantar arteries run in a symmetrical pattern. They each have a dorsal and a plantar branch, which reach the plantar skin before turning toward the axial plane of the sole to reach the digital cushion from the proximal direction. An accurate 3D model of the arteries and the bones of the foot, a set of labeled images and an animation of the blood supply have been created for ease of understanding.

Discussion

In contrast to domestic ungulates, the digital cushion of the hindlimb is supplied differently from that of the forelimb. The lack of large vessels in its deeper layers indicates a slow regeneration time. This novel anatomical information may be useful in the planning of surgical interventions and in emergency medical procedures.

CT based 3D reconstruction of the forefoot's blood supply in a white rhinoceros

BACKGROUND

The white rhinoceros (Ceratotherium simum) is close to extinction, listed as "Near Threatened", with a decreasing population on the Red List of Threatened Species of the International Union for Conservation of Nature. In at least 50% of the specimens in captivity, podiatric diseases, such as osteitis, osteomyelitis, chip fractures, enthesophytes, fractures and osteoarthritis were found during necropsy. These osteal deformations cause further pathogenic alterations in the soft tissues, particularly in the digital cushion. The literature provides good description of the skeleton of the rhino's limbs, but similar for the vascular system is non-existent. In order to recognize the symptoms in an early state and for a successful surgical treatment, precise knowledge of the vascular anatomy is essential. The purpose of our study was to provide detailed anatomical description of the blood supply of the digits and that of the digital cushion.

RESULTS

The blood supply of the distal foot, digits and digital cushions were perfectly visible on the reconstructed and coloured 3D models. The deep palmar arch provided not only the blood supply to the digits but had a palmaro-distal running branch which developed a trifurcation proximal to the proximal sesamoid bones of the third digit. Two of its branches participated in the blood supply of the digits' proximal palmar surface, while the major branch supplied the digital cushion from proximal direction.

CONCLUSIONS

Our findings show a unique blood supply: the main vessels of the digital cushion stem both directly from the deep palmar arch and from the digits' own arteries. The detailed description of vessels may be useful in planning surgery of the region and also in cases where the veins of the ear are not accessible.

Intraspecific anatomical variations of the extensor tendons of the carpus and digits with a reexamination of their insertion sites in the domestic dog (Canis lupus familiaris): a cadaveric study

BACKGROUND

The aim of the current study was to investigate the frequency of variations of the extensor tendons of the carpus and digits in the domestic dog (Canis lupus familiaris) with a reexamination of their insertions as well as the morphometric measurements of the tendons and the brachioradialis muscle. In total, we investigated 68 paired thoracic limbs of the domestic dog (16 females and 18 males) which were fixed in a 10% formalin solution.

RESULTS

The extensor carpi radialis (ECR) tendons showed striking variations in both splitting and insertion sites. In 4.4% of dissections, ECR had three tendons. Of these tendons, the extra tendon either attached independently on the fourth metacarpal bone (one right) or joined its counterpart tendon at the distal end (cross-connections) (one bilateral). It is worth mentioning that one of the ECR tendons split into two or three slips which inserted on the first, second, third, or fourth metacarpal bone in 11 (16.2%) of the specimens. In addition, we found a long tendinous slip originating from the ECR tendons to digit II or III in 7.4% of the distal limbs. The most common type of contribution to digit III was a third tendon of the extensor digiti I et II (ED III) joining the extensor digitorum lateralis (EDL III) with a frequency of 17.6%. In other types of variations, the contribution to digit III was incomplete. A part of the abductor pollicis longus (APL) deep to the superficial part of the flexor retinaculum seemed to continue up to the flexor digitorum superficialis (FDS) tendon.

CONCLUSIONS

The rare intraspecific variations of the extensor tendons of the manus described in the current research are valuable from both clinical and phylogenetic perspectives. Nonetheless, their functional importance needs more studies.

Comparative anatomy of the felid brachial plexus reflects differing hunting strategies between Pantherinae (snow leopard, Panthera uncia) and Felinae (domestic cat, Felis catus)

The brachial plexus, a network of ventral rami providing somatic sensory and motor innervation to the forelimb, is of particular importance in felids. Large-bodied pantherines require powerful rotatory and joint stabilizing forelimb muscles to maintain secure holds on large prey, while smaller-bodied felines are small prey specialists reliant on manual dexterity. Brachial plexus dissections of two snow leopards (Panthera uncia) and two domestic cats (Felis catus) revealed that generally the morphology of the brachial plexus is quite conserved. However, differences in the nerves supplying the shoulder and antebrachium may reflect differing prey capture strategies between the subfamilies. The brachial plexus of both species derives from ventral rami of C6-T1. In P. uncia, an extensive musculus (m.) subscapularis with multiple pennations is innervated by a larger number of nn. subscapulares, deriving from more spinal cord levels than in F. catus. C6 continues to become n. suprascapularis in both taxa; however, in F. catus, it also gives branches that join with C7, while in P. uncia, it is dedicated to musculi (mm.) supraspinatus, infraspinatus, and a small branch to cervical musculature. In F. catus, nervus (n.) medianus receives direct contributions from more ventral rami than P. uncia, possibly reflecting a greater reliance on manual dexterity in prey capture in the former. In addition to primary innervation by n. thoracodorsalis, m. latissimus dorsi is also innervated by n. thoracicus lateralis near the axilla in both taxa, suggesting that it may belong to a complex of proximal forelimb musculature along with mm. pectoralis profundus and cutaneus trunci.

The Effects of Onychectomy (Declawing) on Antebrachial Myology across the Full Body Size Range of Exotic Species of Felidae

While people are familiar with the practice of declawing domestic cats, "onychectomy", as it is also known, is also performed on non-domesticated species, including pantherines, to prolong their use for entertainment purposes. Although the surgery (the partial or complete removal of the distal phalanx) has clear osteological implications, its myological effects have never been studied. As the mass of an animal increases cubically as a product of its volume, while the areas of its paws only increase as a square, larger felids have higher foot pressures and, therefore, the surgery may have particularly substantial functional effects on larger cats. In this study, we evaluate the forearms of clawed and declawed non-domestic felid specimens that spanned the body size range of the whole family to evaluate the effects of onychectomy on muscle fiber architecture. We found that the deep digital flexors (the muscles most directly affected by onychectomy) of declawed felids are significantly lighter (~73%) and less powerful (46-66%) than those of non-declawed felids, while other muscles do not make up for these reductions. Thus, onychectomy has a substantial effect on the myological capabilities of cats, and because these deficiencies are not compensated for in biomechanically disadvantaged larger felids, it probably has even more functionally devastating consequences for these species.

Functional and phylogenetic interpretation of the forelimb myology of two South American carnivorans, the ring-tailed coati (Nasua nasua) and crab-eating raccoon (Procyon cancrivorus)

A comparative analysis of the forelimb myology of two neotropical procyonids (Nasua nasua and Procyon cancrivorus) was performed to assess how observed differences in their myological configuration would be related to their diverse ecological behaviors and phylogeny. Although both species are associated with the arboreal substrate, N. nasua is a more agile climber that usually digs; whereas P. cancrivorus spends most of its time on the ground foraging, climbing on the trees as shelter and is a good swimmer. Here, myological descriptions, muscle maps, phylogenetic optimizations, and muscle mass data of the forelimb of these two procyonids are presented. The main functional muscular groups are discussed in a comparative framework with other carnivorans that present a wide ecological diversity. Also, muscular characters were mapped onto a phylogeny to explore their evolution and to obtain ancestral state reconstructions. Results indicate clear myological differences among the two neotropical procyonids associated with their ecological preferences. One of the most remarkable anatomical differences is the arrangement and relative mass of the extrinsic musculature, mainly the musculus rhomboideus and the delto-pectoral complexes. In Nasua nasua, these suggested a greater stability in their shoulder girdle for climbing and digging and probably would provide stronger neck and head movements when they use them for foraging on the ground. Conversely, P. cancrivorus has a different extrinsic muscular configuration, which would allow an increment on the stride length and faster movements of the forelimb associated with more frequent terrestrial gaits. Also, significant differences are observed in the distal musculature, associated with strong movements of forepaws when climbing and digging in N. nasua; whereas, P. cancrivorus configuration suggested precise forearm and digits movements, related to manipulation of food items when they are catching prey or feeding. Most of the codified features of P. cancrivorus would reflect retention of plesiomorphies acquired in the common ancestor of caniforms or arctoids, whereas N. nasua shows derived traits, particularly in the proximal forelimb region. The present work increases the information available on the myology of these particular taxa and extant generalized arctoid models in general. The analyses presented here will be useful both for other comparative myological studies (morpho-functional and phylogenetic) and for muscular reconstruction in extinct procyonids, as well as other carnivorans.