Topic:Anatomy
Anatomy in horses encompasses the study of the structural organization of the equine body, including the bones, muscles, organs, and systems that function together to sustain life and enable movement. Understanding equine anatomy is important for veterinarians, equine scientists, and horse owners, as it provides insights into how horses move, how they respond to external stimuli, and how various conditions can affect their health and performance. Key anatomical features in horses include the musculoskeletal system, which provides support and locomotion; the cardiovascular system, which circulates blood and nutrients; and the respiratory system, which facilitates gas exchange. This page compiles peer-reviewed research studies and scholarly articles that explore the detailed anatomy of horses, focusing on the structure and function of different body systems, their interrelationships, and their relevance to equine health, performance, and veterinary care.
A technique of needle redirection at a single craniolateral site for injection of three compartments of the equine stifle joint. OBJECTIVE To determine accuracy for a technique of needle redirection at a single craniolateral site for injection of 3 compartments of the equine stifle joint, describe the external needle position, and identify the location of the needle tip within each joint compartment. SAMPLE 24 equine cadaver stifle joints. PROCEDURES Stifle joints were placed in a customized stand. After the needle was placed, external needle position was measured and recorded. Each joint compartment (medial and lateral compartments of the femorotibial joint and the femoropatellar joint) was injected with a solution con...
18 F-sodium fluoride positron emission tomography of the equine distal limb: Exploratory study in three horses. Positron emission tomography (PET) is a cross-sectional, functional imaging modality that has recently become available to the horse. The use of 18 F-sodium fluoride (18 F-NaF), a PET bone tracer, has not previously been reported in this species. Objective: To assess the feasibility of 18 F-NaF PET in the equine distal limb and explore possible applications in the horse in comparison with other imaging modalities. Methods: Exploratory descriptive study involving three research horses. Methods: Horses were placed under general anaesthesia prior to intravenous (i.v.) administration of 1.5 MBq/kg...
Cheek tooth morphology and ancient mitochondrial DNA of late Pleistocene horses from the western interior of North America: Implications for the taxonomy of North American Late Pleistocene Equus. Horses were a dominant component of North American Pleistocene land mammal communities and their remains are well represented in the fossil record. Despite the abundant material available for study, there is still considerable disagreement over the number of species of Equus that inhabited the different regions of the continent and on their taxonomic nomenclature. In this study, we investigated cheek tooth morphology and ancient mtDNA of late Pleistocene Equus specimens from the Western Interior of North America, with the objective of clarifying the species that lived in this region prior to t...
Uneven distribution of enamel, dentine and cementum in cheek teeth of domestic horses (Equus caballus): A micro computed tomography study. Hypsodont equine cheek teeth possess large dental crowns, resting partly in the bony alveolus. Over a horse's life cheek teeth erupt continuously to compensate for occlusal wear of 3-4 mm per year. Parts of the crown initially resting in the bony alveolus become progressively exposed at the occlusal surface with time. Hitherto, it is unclear whether the typical structure of the equine occlusal surface, composed of a complex arrangement of enamel, dentin and cementum, remains constant or undergoes structural changes with age. Therefore, we tested the hypothesis that the occlusal surface composi...
Equine meniscal degeneration is associated with medial femorotibial osteoarthritis. There is limited information available concerning normal equine meniscal morphology, its degeneration and role in osteoarthritis (OA). Objective: To characterise normal equine meniscal morphology and lesions and to explore the relationship between equine meniscal degeneration and femorotibial OA. Methods: Ex vivo cadaveric study. Methods: Menisci were harvested from 7 normal joints (n = 14 menisci) and 15 joints with OA (n = 30 menisci). A macroscopic femorotibial OA score (cartilage degeneration and osteophytosis) was employed to measure disease severity in each compartment. The femoral and t...
Age associated changes in peripheral airway smooth muscle mass of healthy horses. Peripheral airway smooth muscle (ASM) mass is increased in severe equine asthma, but no information is available on age related changes in ASM. In this study, peripheral ASM dimensions were determined in healthy horses of different ages. The thickness of the peripheral ASM layer was constant in horses of different ages, but ASM occupied a greater proportion of the inner wall area in young horses compared to older horses. This finding suggests that equine airways experience a decrease in the relative abundance of ASM with age.
Correlation of dickkopf-1 concentrations in plasma and synovial fluid to the severity of radiographic signs of equine osteoarthritis. The purpose of this study was to determine whether there was a correlation between circulating and intra-synovial Dkk-1 and radiographic signs of equine osteoarthritis. Methods: Circulating and intra-synovial Dkk-1 levels were measured in clinical cases using a commercially available human Dkk-1 ELISA. Radiographs were performed of the joints from which fluid was collected and these were assessed and scored by a boarded radiologist for joint narrowing, subchondral bone sclerosis, subchondral bone lysis, and periarticular modelling. Comparisons were made between radiographic scores and the conc...
Influence of the Respiratory Cycle on Caudal Vena Cava Diameter Measured by Sonography in Healthy Foals: A Pilot Study. Intravascular volume assessment in foals is challenging. In humans, intravascular volume status is estimated by the caudal vena cava (CVC) collapsibility index (CVC-CI) defined as (CVC diameter at maximum expiration [CVC ] - CVC diameter at minimal inspiration [CVC ])/CVC × 100%. Objective: To determine whether the CVC could be sonographically measured in healthy foals, determine differences in CVC and CVC , and calculate inter- and intrarater variability between 2 examiners. We hypothesized that the CVC could be measured sonographically at the subxiphoid view and that there would be a differ...
Maxillary unicystic ameloblastoma in a 6-week-old filly evaluated with computed tomography. A 6-week-old Thoroughbred filly was presented for evaluation of an expansile mass overlying the right nasal passage and causing respiratory stertor. On skull radiographs, there was a loculated, soft tissue-opaque mass identified dorsal to the right upper premolars and effacing the right nasal cavity. Computed tomography (CT) revealed a locally extensive mass with relatively benign characteristics located centrally on the tooth root apices of the deciduous second premolar (506). The mass extended axially into the right nasal cavity, occluding the meatuses and causing displacement of the nasal s...
Histological Features of the Distal Third Metacarpal Bone in Thoroughbred Racehorses, With and Without Lateral Condylar Fractures. A detailed histopathological study of the distal third metacarpal bone of Thoroughbred racehorses was undertaken to characterize lesions observed previously on magnetic resonance imaging (MRI). The bones were selected and grouped on the basis of MRI features. Representative sections in different planes were processed for histopathology. All lesions observed in the articular cartilage (AC) and subchondral bone (SCB) were recorded and graded with a scoring system, based partially on the Osteoarthritis Research Society International grading system. The scoring system included the severity of the ...
Gestation length and racing performance in 115 Thoroughbred foals with incomplete tarsal ossification. Incomplete ossification of the cuboidal bones of the carpus and tarsus in foals has the potential for significant consequences including chronic lameness and decreased athletic ability. Objective: To determine if the degree of ossification of the cuboidal bones is associated with gestational length and if the diagnosis of incomplete ossification is a predictor of performance in Thoroughbred racehorses. Methods: Retrospective cohort study. Methods: The medical records of Thoroughbred foals less than 90 days of age from 1994 to 2011 were examined and records containing tarsal radiographs identif...
Arterial Patterns of the Face in Perissodactyla. Considerable consistency in the arterial pattern of the head has been observed in species of Artiodactyla, but few studies have examined the order Perissodactyla. Here, we describe arteries supplying the intermandibular, mental, masseteric, buccal, labial, and nasal regions in eight perissodactylans, including representing of all families comprising this order. Observations were made on a total of 45 preparations of head arteries, obtained by injection of arteries with acetone-dissolved stained vinyl superchloride or stained latex LBS3060. In the Equidae species alone it was found that the fac...
Decellularization of Large Tendon Specimens: Combination of Manually Performed Freeze-Thaw Cycles and Detergent Treatment. Reliable decellularization techniques applicable to tendon tissue play a critical role in the field of current tissue engineering. Particularly, an application as three-dimensional culture model for in vitro research and translational approaches to establish graft-based tendon repair as a routine clinical tool represent two main application fields for decellularized tendon scaffolds. Considering methodological issues of tendon decellularization, one of the major challenges lies in the preservation of the tendon-specific extracellular matrix (ECM) architecture to reflect natural tissue characte...
Physeal Fractures in Foals. Physeal fractures are common musculoskeletal injuries in foals and should be included as a differential diagnosis for the lame or nonweightbearing foal. Careful evaluation of the patient, including precise radiographic assessment, is paramount in determining the options for treatment. Prognosis mostly depends on the patient's age, weight, and fracture location and configuration.
The impact of subchondral bone cysts on local bone stresses in the medial femoral condyle of the equine stifle joint. Subchondral lucency (SCL), also referred to as subchondral bone cysts, can cause clinical problems in horses and humans. In humans, SCLs occur in youths and adolescents [1] due to mechanical factors (often related to athletics) and in skeletally mature individuals secondary to osteoarthritis (OA). In horses, SCL most commonly occurs in the medial femoral condyle (MFC) of growing horses (without OA), and causes lameness. The cause of equine SCL is debated, but bone trauma due to overload is the likely mechanism. Investigating the biomechanics of the healthy and cystic MFC is important to unders...
Accuracy of open magnetic resonance imaging for guiding injection of the equine deep digital flexor tendon within the hoof. Lesions of the distal deep digital flexor tendon (DDFT) are frequently diagnosed using MRI in horses with foot pain. Intralesional injection of biologic therapeutics shows promise in tendon healing; however, accurate injection of distal deep digital flexor tendon lesions within the hoof is difficult. The aim of this experimental study was to evaluate accuracy of a technique for injection of the deep digital flexor tendon within the hoof using MRI-guidance, which could be performed in standing patients. We hypothesized that injection of the distal deep digital flexor tendon within the hoof coul...
Regional Nerve Blocks for Equine Dentistry. Regional nerve blocks are necessary to facilitate equine oral surgery in the standing sedated patient. Step-by-step instruction on how to perform common regional nerve blocks are discussed, including infraorbital, maxillary, middle mental, and inferior alveolar nerve blocks. Regional nerve blocks are critical when performing dental procedures in the standing horse. The infraorbital and maxillary nerve blocks provide anesthesia of the infraorbital nerve, which is a branch of the maxillary nerve. Both nerve blocks provide adequate anesthesia for all maxillary dental procedures. When the infraorb...
Cartilage canals in the distal intermediate ridge of the tibia of fetuses and foals are surrounded by different types of collagen. Some epiphyseal growth cartilage canals are surrounded by a ring of hypereosinophilic matrix consisting of collagen type I. Absence of the collagen type I ring may predispose canal vessels to failure and osteochondrosis, which can lead to fragments in joints (osteochondrosis dissecans). It is not known whether the ring develops in response to programming or biomechanical force. The distribution that may reveal the function of the ring has only been described in the distal femur of a limited number of foals. It is also not known which cells are responsible for producing the collagen ring. The a...
The effect of the sagittal ridge angle on cartilage stress in the equine metacarpo-phalangeal (fetlock) joint. Fatigue failure of bones of the metacarpo-phalangeal (fetlock, MCP) joint is common in thoroughbred racehorses. Stresses within the fetlock joint cartilages are affected by the morphology of the third metacarpal bone (MC3) and proximal phalangeal bone, and the steepness of the median sagittal ridge of MC3 is believed to be associated with fracture. This study investigated the influence of the steepness of the sagittal ridge on cartilage stress distribution using a finite element model of the joint. Changes to the steepness of the sagittal ridge were made by applying a parabolic function to the...
The deep fascia and retinacula of the equine forelimb – structure and innervation. Recent advances in human fascia research have shed new light on the role of the fascial network in movement perception and coordination, transmission of muscle force, and integrative function in body biomechanics. Evolutionary adaptations of equine musculoskeletal apparatus that assure effective terrestrial locomotion are employed in equestrianism, resulting in the wide variety of movements in performing horses, from sophisticated dressage to jumping and high-speed racing. The high importance of horse motion efficiency in the present-day equine industry indicates the significance of scientific...
A diagnostic pathologist’s guide to carpal disease in racehorses. As a pathologist, postmortem examination of the equine carpus can be daunting. The anatomy is complex and oftentimes, small or subtle lesions have significant impact on lameness and secondary lesions such as catastrophic musculoskeletal fractures and other injuries. In performance horses, particularly racehorses, the carpus is a common site of injury and source of lameness. Given the predisposition of racehorses to developing carpal disease, familiarity with clinically relevant anatomy and common developmental, degenerative, traumatic, and inflammatory processes are imperative for thorough pos...
Regional distribution and integrity of equine ovarian pre-antral follicles. The goal of this study was to determine the distribution of pre-antral follicles in the ovarian parenchyma of mares. For Experiment 1, each ovary was cut longitudinally at the greater curvature, performing two hemiovaries. After that, six fragments from each hemiovary were obtained, resulting in 12 fragments, which were divided into the innermost region of the parenchyma, the middle region and the outermost region. All the three obtained sections were cut transversally to obtain two fragments from each one. For Experiment 2, each ovary also submitted to a longitudinal cut on the greater curvat...
Relationship between echotextural and histomorphometric characteristics of stallion testes. The goal of this study was to investigate correlations between objective measures of testicular echotexture and histomorphometric attributes related to the histological composition of stallion testes. Fifty-four scrotal testes were obtained from three groups of stallions during routine castrations: colts <1 yr old (n = 18), young stallions 1-5 yrs old (n = 27), mature stallions > 5 yrs old (n = 9). In addition, two scrotal testes with degeneration, 16 retained inguinal and 10 retained abdominal testes were surgically obtained. Cross-sectional and longitudinal ultrasonograms were obt...
The Branching Pattern of the Brachiocephalic Trunk in the Donkey (Equus asinus). Donkeys are a member of the horse family (Equidae) and share a common ancestor. However, in morphological terms, donkeys and horses are regarded as two separate subgenus. Given variations in the branching pattern of the brachiocephalic trunk (BCT) in different species of animals and the use of donkeys in anatomy courses at colleges of veterinary medicine, we conducted this study in order to investigate the branching patterns of BCT and to describe detailed morphological information regarding donkeys. Seventeen mature donkeys were examined following euthanasia by exsanguination from the common ...
Morphological evaluation of Merkel cells and small lamellated sensory receptors in the equine foot. OBJECTIVE To examine the equine foot for the presence of sensory receptors including Merkel cells and small lamellated Pacinian-like corpuscles (SLPCs). SAMPLE Forefeet obtained from 7 horses following euthanasia for reasons other than foot disease. PROCEDURES Disarticulated feet were cut into either sagittal sections or cross sections and immersed in neutral-buffered 4% formalin. Following fixation, samples were obtained from the midline of the dorsal aspect of the hoof wall and from the frog (cuneus ungulae) between the apex and central sulcus. The formalin-fixed, paraffin-embedded hoof wall...
Ileal hypertrophy and associated true diverticulum as a cause of colic in a horse. A 4-year-old Thoroughbred gelding underwent an explorative celiotomy for a suspected small intestinal obstruction. During surgery, an impacted diverticulum of the ileum was suspected, necessitating a jejunocaecostomy. The owner opted for euthanasia. On post-mortem examination and histopathology, a true diverticulum on the mesenteric side of the ileum, with ileal hypertrophy, was diagnosed.
Osteochondritis Dissecans Development. This article reviews current knowledge of osteochondritis dissecans (OCD) development in horses, including normal cartilage development, early osteochondrosis pathogenesis, and factors that result in healing or advancement to OCD fragments. Discussion includes current theories, detection, and therapeutic options.
The association between oral examination findings and computed tomographic appearance of the equine temporomandibular joint. The temporomandibular joint (TMJ) forms the junction between the maxilla and mandible. Movement of the jaw and resulting masticatory forces have been extensively studied in the horse; however, less is known about the inter-relationship between this joint and oral and dental pathology. Objective: To determine the association between specific oral and dental pathologies and anatomical variations of the TMJ imaged with computed tomography (CT) in horses with asymptomatic TMJs. Methods: Retrospective cross-sectional study. Methods: Horses (n = 201) from three practices with a complete oral exami...
Trigeminal Nerve Root Demyelination Not Seen in Six Horses Diagnosed with Trigeminal-Mediated Headshaking. Trigeminal-mediated headshaking is an idiopathic neuropathic facial pain syndrome in horses. There are clinical similarities to trigeminal neuralgia, a neuropathic facial pain syndrome in man, which is usually caused by demyelination of trigeminal sensory fibers within either the nerve root or, less commonly, the brainstem. Our hypothesis was that the neuropathological substrate of headshaking in horses is similar to that of trigeminal neuralgia in man. Trigeminal nerves, nerve roots, ganglia, infraorbital, and caudal nasal nerves from horse abattoir specimens and from horses euthanized due to...