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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.
Effect of foot balance on the intra-articular pressure in the distal interphalangeal joint in vitro. Increased joint pressure has been implicated in the progression of osteoarthritis. Objective: That intra-articular pressure in the distal interphalangeal joint (DIP) is significantly higher in legs loaded with heel up (HU), low heel (TU), lateral side up (LU) and medial side up (MU) imbalance compared to the balanced position. Methods: Twelve elbow down limbs were compressed in a hydraulic loading jig and DIP pressure measured. Results: Elevating the heels by 5 degrees significantly increased DIP pressure. After 5 ml of contrast was injected into the joint, heel elevation caused a greater incr...
The effect of gait and digital flexor muscle activation on limb compliance in the forelimb of the horse Equus caballus. A horse's legs are compressed during the stance phase, storing and then returning elastic strain energy in spring-like muscle-tendon units. The arrangement of the muscle-tendon units around the lever-like joints means that as the leg shortens the muscle-tendon units are stretched. The forelimb anatomy means that the leg can be conceptually divided into two springs: the proximal spring, from the scapula to the elbow, and the distal spring, from the elbow to the foot. In this paper we report the results of a series of experiments testing the hypothesis that there is minimal scope for muscle cont...
Cellular architecture of the synovium in the tendon sheath of horses: an immunohistochemical and scanning electron microscopic study. The intimal lining cells of the synovium in joints have been studied morphologically and histochemically and shown to consist of macrophagic cells (type A) and fibroblast-like cells (type B). It is believed that the structure of the synovium in the tendon sheath is similar to that in the joint, but there have been only a few morphological studies of the tendon sheath. The present study revealed the cellular architecture of synovium in the tendon sheath of horses by histochemistry and scanning electron microscopy (SEM). Like the joint, the inner surface of the tendon sheath was covered with a c...
Effect of perineural anesthesia on the ultrasonographic appearance of equine palmar metacarpal structures. The purpose of this study was to describe ultrasonographic changes of the equine palmar metacarpal area attributed to the infiltration of local anesthetic solution and to determine whether these changes were noted immediately or at 24 h. The palmar metacarpal region of one forelimb in each of six horses was examined ultrasonographically with a 10-MHz linear array transducer and a 7.5-MHz curvilinear transducer. Transverse and longitudinal images were recorded at 5-cm intervals distal to the accessory carpal bone. High and low palmar and palmar metacarpal nerve blocks were performed with a 2% m...
Antagonism of adenosine receptors by caffeine and caffeine metabolites in equine forebrain tissues. To determine the presence of adenosine receptor subtypes A1 and A2a in equine forebrain tissues and to characterize the interactions of caffeine and its metabolites with adenosine receptors in the CNS of horses. Methods: Brain tissue specimens obtained during necropsy from 5 adult male research horses. Methods: Membrane-enriched homogenates from cerebral cortex and striatum were evaluated by radioligand binding assays with the A1-selective ligand [3H]DPCPX and the A2a-selective ligand [3H]ZM241385. Functional responses to adenosine receptor agonists and antagonists were determined by a nucleot...
Value of histopathology in vitiligo. Histopathologic studies of vitiligo have been rather limited in number, thus the microscopic features of this common disorder are not very well known. Methods: Skin specimens from 20 human vitiligo patients and skin specimens from five equine vitiligo patients were studied by light and transmission electron microscopy. Conclusions: Absence of melanocytes, increased number of Langerhans' cells, epidermal vacuolization, thickening of the basement membrane, T-cell inflammatory infiltrate, and neural alterations were noted in the vitiligo lesions. These results may explain the development of depig...
Use of a hydroxyapatite orbital implant in a cosmetic corneoscleral prosthesis after enucleation in a horse. A hydroxyapatite orbital implant was used after enucleation of an eye from a 5-year-old performance horse. A custom-made corneoscleral prosthesis was made and fitted over the hydroxyapatite implant. The implant and surgery were well tolerated. Placement of a cosmetic prosthesis is desired after enucleation of equine eyes to allow horses to return to competition. Synthetic spheres consisting of methylmethacrylate or silicone have been used, although reported complications have included extrusion, infection, and poor cosmetic results. Hydroxyapatite orbital implants made from marine coral allow ...
Estimates of heritability for ossification of the cartilages of the front feet in the Finnhorse. Ossification of the cartilages in the foot is common in coldblooded horses, but prevalence as well as ossification pattern varies between breeds; research on estimation of heritability for the condition has been limited. Objective: Our purpose was to calculate estimates of 1) heritability for ossification parameters of the cartilages in the front feet of the Finnhorse and 2) genetic correlations between the different ossification parameters. Methods: Estimates of heritability for different ossification parameters of the cartilages in the front feet and of genetic correlations between different...
Magnetic resonance imaging of the equine foot: 15 horses. Foot pain is a common cause of equine lameness and there have been significant limitations of the methods available for the diagnosis of the causes of foot pain (radiography, nuclear scintigraphy and ultrasonography). Until recently, magnetic resonance imaging (MRI) in the horse has been limited to examination of cadaver limbs. Objective: Our purpose was to 1) describe MRI of the foot in live horses, 2) describe MRI findings in horses with foot pain in which a definitive diagnosis could not be established by alternative means and 3) correlate MRI findings with other methods of clinical investi...
Ultrasonographic abnormalities detected in the sacroiliac area in twenty cases of upper hindlimb lameness. The pelvis is covered with extensive musculature and often presents a challenge in diagnostic imaging. Ultrasonography provides diagnostic information about soft tissue, articular cartilage and bone surfaces, although little information exists about the normal ultrasonographic appearance of the equine sacroiliac region. Objective: To determine the clinical applicability of ultrasonographic examination in horses with sacroiliac pain. Methods: Horses presented to the University of Minnesota Veterinary Teaching Hospital for hindlimb lameness were evaluated and lower limb lameness was ruled out wi...
Ultrasonographic abnormalities detected in the sacroiliac area in twenty cases of upper hindlimb lameness. The pelvis is covered with extensive musculature and often presents a challenge in diagnostic imaging. Ultrasonography provides diagnostic information about soft tissue, articular cartilage and bone surfaces, although little information exists about the normal ultrasonographic appearance of the equine sacroiliac region. Objective: To determine the clinical applicability of ultrasonographic examination in horses with sacroiliac pain. Methods: Horses presented to the University of Minnesota Veterinary Teaching Hospital for hindlimb lameness were evaluated and lower limb lameness was ruled out wi...
Deformation behaviour and damage accumulation of cortical bone specimens from the equine tibia under cyclic loading. Despite its clinical importance, the fatigue behaviour of cortical bone has not been examined as widely as its static behaviour. In the present study, specimens from the tibiae of horses have been subjected to load-controlled single step tests. The cyclic deformation behaviour was described by the development of stress-strain hysteresis parameters over the lifetime. The fatigue behaviour of bone is characterised by cyclic softening which is most distinctive towards the end of the lifetime. The microstructural damage accumulated during cyclic loading results in a loss of stiffness, asymmetrical...
Equine cortical bone exhibits rising R-curve fracture mechanics. Previous studies of the fracture properties of cortical bone have suggested that the fracture toughness increases with crack length, which is indicative of rising R-curve behavior. Based on this indirect evidence and the similarity of bone to ceramic matrix composites, we hypothesized that bone would exhibit rising R-curve behavior in the transverse orientation and that the characteristics of the R-curves would be regionally dependent within the cortex due to variations in bone microstructure and toughening mechanisms. To test these hypotheses, we conducted R-curve experiments on specimens fro...
New approach for quantitative assessment of articular cartilage degeneration in horses with osteoarthritis. To evaluate a modified digital imaging technique for quantitative assessment of the grade of osteoarthritis across the proximal articular surface of the first phalanx in horses. Methods: 6 metacarpophalangeal (fet-lock) joint specimens from 6 horses with various stages of osteoarthritis. Methods: First phalanx specimens, together with 4 gray scale reference calibration targets, were positioned in a bath with the proximal articular cartilage surface submerged in saline (0.9% NaCl) solution. Digital images were obtained from the articular surface before and after staining with Indian ink. Comput...
Muscarinic receptors in equine airways. The distribution of muscarinic receptors in equine airways was investigated using autoradiography. Frozen sections of tissue from six different levels in the bronchial tree, from the trachea to the distal bronchioles, were incubated in vitro with 1.5 nmol/L of the muscarinic receptor antagonist 1-[N-methyl-3H]scopolamine methyl chloride (3H-NMS). In addition, the subtype pattern of muscarinic receptors was investigated in equine tracheal smooth muscle using radioligand binding with methoctramine, tripinamidc, 4-DAMP-methiodide and pirenzipine as competitors against the binding of 1.3 nmol/L 3H...
Overview of horse body composition and muscle architecture: implications for performance. Locomotion requires skeletal muscle to sustain and generate force. A muscle's force potential is proportional to its weight. Since the larger the muscle the larger its potential power output, a better understanding of the proportion of skeletal muscle a horse possesses may lead to a better understanding of horse performance. Several techniques exist to assess body composition, which include dual energy X-ray absorption, underwater (hydrostatic) weighing, derivation from total body water, bio-electric impedance, air displacement, body condition scoring, cadaver dissection and ultrasound. The re...
Computed tomographic appearance of osteochondritis dissecans-like lesions of the proximal articular surface of the proximal phalanx in a horse. A 6-year-old Thoroughbred gelding presented with a left forelimb lameness. The results of lameness examination, radiography, nuclear scintigraphy, and computed tomography are presented. Based on the diagnostic imaging, subchondral fractures and osteochondritis dissecans lesions of the proximal articular surface of the proximal phalanx were diagnosed. A brief discussion of osteochondritis dissecans is presented.
Electromyographic activity of the hyoepiglotticus muscle and control of epiglottis position in horses. To determine whether the hyoepiglotticus muscle has respiratory-related electromyographic activity and whether electrical stimulation of this muscle changes the position and conformation of the epiglottis, thereby altering dimensions of the aditus laryngis. Methods: 6 Standardbred horses. Methods: Horses were anesthetized, and a bipolar fine-wire electrode was placed in the hyoepiglotticus muscle of each horse. Endoscopic images of the nasopharynx and larynx were recorded during electrical stimulation of the hyoepiglotticus muscle in standing, unsedated horses. Dorsoventral length and area of ...
[Initial management of congenital varus equinus clubfoot by Ponseti’s method]. The choice of first-line treatment for congenital varus equine clubfoot remains a controversial issue largely dependent on experience. In France, functional treatment predominates. In 1948, Ponseti proposed reducing the deformity with successive casts. Although cast treatment is a very old method, Ponseti's method is original because it is based on strict rules established from anatomic evidence. The goal is not to correct the apparent deformation, but on the contrary to impose a simultaneous supination and abduction of the foot. Once the calcaneopedal block has been derotated, percutaneous te...
Analysis of strain and stress in the equine hoof capsule using finite element methods: comparison with principal strains recorded in vivo. Finite-element (FE) methods have great potential in equine biomechanics in evaluating mechanical stresses and strains in tissues deep within the hoof. In this study, we critically assessed that potential by comparing results of FE analyses of capsular strain with in vivo data. Nine FE models were developed, corresponding to the shape of hooves for which in vivo principal strain data are available. Each model had the wall, laminar junction, sole and distal phalanx (PIII). In a first loading condition (LC1), force is distributed uniformly to the bearing surface of the wall to determine reaction ...
A gross and histopathological study of an ectopic white line development in equine laminitis. In horses with chronic laminitis, an abnormal horny structure called lamellar wedge, is generated between the hoof wall and the laminar epidermis. To be able to manage horses with chronic laminitis correctly, more information about the pathological state of this abnormal horn is required. The aim of this study was to collect and analyze objective morphological data about the abnormal horn in order to understand its morphology and development. In the study, the abnormal horn was grossly visible on the sagittal hoof section from approximately 20 days after the onset of disease. In the histologic...
Use of a condylar screw plate for repair of a Salter-Harris type-III fracture of the femur in a 2-year-old horse. A 2-year-old sexually intact male Paint horse weighing 427 kg (940 lb) was admitted for examination and treatment of intermittent non-weight-bearing lameness of the right hind limb of 1 week's duration. Radiography revealed a displaced Salter-Harris type-III fracture of the right femoral condyle with the sagittal component of the fracture line located in the intercondylar space and the transverse component exiting on the medial aspect of the femur. The fracture was repaired with a condylar screw plate designed for repair of femoral condylar fractures in humans. The owner reported by telephone ...
A radiographic technique to assess the longitudinal balance in front hooves. The aim of this study was to validate a radiographic technique to measure objectively the longitudinal hoof balance in the horse. Ten left third phalanges (P3) obtained from front hooves and 19 left front hooves were used in order to assess the reliability of the radiographic technique and to identify any effect of rotation or alignment of specimens or distance between the X-ray machine and the radiographic cassette, in measuring P3s structures and balance related parameters. A rotational support was made to hold specimens in order to standardise some of the conditions of X-raying. The main ax...
Do regional variations in flexor tendons predispose to site-specific injuries? Partial rupture occurs most often to the superficial digital flexor tendon (SDFT) of the forelimb at the mid-metacarpal level. In this study, we tested the hypothesis that the mid-metacarpal region of the SDFT has the smallest cross sectional area (CSA) and a similar collagen content to other regions and, therefore, represents a weak point in the tendon. The SDFT was collected from the forelimbs of 9 horses. Each tendon was marked at 7 different levels from the origin of the accessory ligament to the phalangeal region. The CSA, water content and collagen content was measured at each level. The...
Structural and oxidative enzyme characteristics of the diaphragm. During exercise, the horse can achieve oxygen uptakes and ventilations in excess of 200 ml/kg/min and 1800 l/min, respectively. Whether the diaphragm has the capacity to contribute substantially to inspiratory effort in the exercising horse is not known. To investigate the potential for the horse diaphragm to generate tension, lung displacement and sustain ventilatory function, we measured diaphragm thickness, muscle length and oxidative enzyme activity (citrate synthase) within the ventral, medial and dorsal costal and crural diaphragm. In the diaphragms of 6 mature horses (5 Thoroughbreds, o...
Three-dimensional kinematics of the tarsal joint at the trot. The tarsal joint is a common site of injury for many sport horses. Understanding the biomechanics of this complex joint begins with developing a clear picture of the kinematics during normal locomotion. This study describes the 3D kinematics of the tarsal joint by measuring the motion of the tibia and third metatarsus in 4 sound Quarter Horses with targets attached directly to the bones via steel pins. The objective was to determine if the tarsus had significant motion outside the tarsocrural joint. Two Steinmann pins were inserted into the lateral side of the right hindlimb and marker triads ...
Dorsal metacarpal cortex ultrasound speed and bone size and shape. In Thoroughbred racehorses, the dorsal cortex (DC) of the third metacarpal bone (MC3) enlarges when horses are first exposed to fast exercise speeds. It is now possible to measure ultrasound speed through 3 to 5 mm depths of bone around the bone shaft using Sunlight Medical's 'Omnisense' machine. The aim of this experiment was to determine whether the ultrasound speed measured in the surface 3-5 mm of the midshaft dorsal cortex of MC3 could be related directly to the midshaft shape and size of the MC3s of young Thoroughbred racehorses at the same stage of training. Sixteen 2-year-old and sixte...
Quantitative analysis of the organization of the inner nuclear layer of the horse retina. Four cell types including the bipolar, amacrine, horizontal and Muller cells were investigated quantitatively in the inner nuclear layer of the retina in the horse. Cells were identified on the basis of the morphology and distribution of processes leaving from their somata, cytological features and positional features. The average percentages of the above 4 cell types were 44%, 24%, 1% and 29%, respectively. The average total cell densities in the inner nuclear layer in the visual streak, the nasal and temporal regions, the dorsal and ventral regions of the retina were also estimated. It is ex...
