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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.
Estimate of size and total number of neurons in superior cervical ganglion of rat, capybara and horse. The superior (cranial) cervical ganglion was investigated by light microscopy in adult rats, capybaras (Hydrochaeris hydrochaeris) and horses. The ganglia were vascularly perfused, embedded in resin and cut into semi-thin sections. An unbiased stereological procedure (disector method) was used to estimate ganglion neuron size, total number of ganglion neurons, neuronal density. The volume of the ganglion was 0.5 mm3 in rats, 226 mm3 in capybaras and 412 mm3 in horses. The total number of neurons per ganglion was 18,800, 1,520,000 and 3,390,000 and the number of neurons per cubic millimetre was...
Comparison of the navicular region of newborn foals and adult horses by magnetic resonance imaging. Magnetic resonance imaging (MRI) was tested for evaluation of the soft tissue structures of the equine digit in 16 limbs, derived from three adult warmblood horses and two newborn warmblood foals. The following measuring sequences were used in sagittal, transversal and coronal planes: spin echo, gradient echo, inversion recovery. The images were made with a 1.5 Tesla Siemens scanner in a CP-Helmholtz circular coil. To compare the visualization of the same tissue structures in adult and in newborn cases the limbs were imaged with the routinely used MRI sequences that are used for mature tissues...
Ultrasound-guided biopsy as a diagnostic aid in three horses with a cranial mediastinal lymphosarcoma. An ultrasound examination of the thorax of three horses which were performing poorly or had mild signs of colic showed that they had a cranial mediastinal mass and a pleural effusion. A cytological examination of the pleural fluid showed that it did not contain neoplastic cells. A histological examination of an ultrasound-guided core biopsy of the cranial mediastinal mass showed that in each of the three horses it was a lymphosarcoma.
Tracing axons of peripheral nerves in rats: a potential technique to study the equine recurrent laryngeal nerve. To study the fascicular anatomy of peripheral nerves, three different groups of retrograde axonal tracers were evaluated: fluorophores, horseradish peroxidase conjugated to subunit B of cholera toxin (CT-HRP), and adeno-associated virus (AAV). The hindlimb nerves in rats served as a model to identify the most efficient tracer in regard to labeling axons within peripheral nerves. The rat's tibial and common peroneal nerves were injected with the different tracers and the sciatic nerve was subsequently examined for evidence of labeled axons. The CT-HRP clearly provided the best results in this r...
Technique for equine cervical articular process joint injection. Degenerative changes and osteochondrosis of articular processes are common sources of stiffness or pain in the equine cervical spine. Temporary relief of the clinical signs related to these maladies may be achieved by injecting corticosteroids into the joint. This is routinely done by ultrasound-guided needle placement. The cervical articular processes and joint form an easily identifiable sonographic landmark, a step-like echogenic surface described as having the appearance of a "chair."
Magnetic resonance imaging of the palmar aspect of the equine podotrochlear apparatus: normal appearance. The purpose of this study was to describe the normal magnetic resonance (MR) imaging characteristics of the palmar structures of the equine podotrochlear apparatus by means of retrospective evaluation of MR imaging studies of 16 cadaver limbs. The articular aspect of the distal sesamoid bone was not evaluated in this study. Equine digits were imaged with a human knee radiofrequency coil in a 1.5 T magnetic field, using spin echo (SE) T1-weighted, turbo spin echo proton density (TSE PD)-weighted with and without fat saturation (FS), and FS TSE T2-weighted sequences. The limbs were dissected aft...
Magnetic resonance imaging of a brain abscess in a 10-month-old filly. The purpose of this paper was to correlate the magnetic resonance imaging (MRI) characteristics of a mature brain abscess in a horse with histopathologic alterations of brain tissue. Eight months after the onset of clinical signs, MRI of the brain of a 10-month-old filly was performed. A large space-occupying lesion in the right cerebral hemisphere was identified. This space-occupying lesion was delineated by a thick and well-defined capsule that was isointense to brain parenchyma on the T1-weighted images and with a markedly hypointense on the T2-weighted images. The identification of such a ...
Determination of muscle architecture and fiber characteristics of the superficial and deep digital flexor muscles in the forelimbs of adult horses. To provide a quantitative description of the architecture of superficial digital flexor (SDF) and deep digital flexor (DDF) muscles in adult horses to predict muscle-tendon behavior and estimate muscle forces. Methods: 7 forelimb specimens from 7 adult Thoroughbreds. Methods: Muscle and tendon lengths and volumes were measured from 6 fixed forelimbs. After processing, fiber bundle and sarcomere lengths were measured. Optimal fascicle lengths and muscle length-to-fascicle length, muscle length-to-free tendon length, and fascicle length-to-tendon length ratios were calculated, as were tendon and...
Facilitated ankylosis of the distal interphalangeal joint in a foal. A 3-month-old Quarter Horse colt sustained a penetrating injury over the coronary band on the right forelimb resulting in an articular bone sequestrum and septic arthritis of the distal interphalangeal joint. Despite aggressive treatment for septic arthritis, severe osteoarthritis and ongoing sepsis resulted in persistent lameness. Facilitated ankylosis of the distal interphalangeal joint was performed using a combination of open surgical debridement, placement of an autogenous cancellous bone graft and stabilisation within a transfixation cast. Bony ankylosis of the joint was observed radiogr...
Effects of stylopharyngeus muscle dysfunction on the nasopharynx in exercising horses. Nasopharyngeal collapse has been observed in horses as a potential cause of exercise intolerance and upper respiratory noise. No treatment is currently available and affected horses are often retired from performance. Objective: To determine the effect of bilateral glossopharyngeal nerve block and stylopharyngeus muscle dysfunction on nasopharyngeal function and airway pressures in exercising horses. Methods: Endoscopic examinations were performed on horses at rest and while running on a treadmill at speeds corresponding to HRmax50, HRmax75 and HRmax, with upper airway pressures measured with ...
Development and validation of a periarticular injection technique of the sacroiliac joint in horses. Sacroiliac joint osteoarthritis has been recognised as a significant cause of poor performance in competition and racehorses. Reliable diagnostic tools are currently lacking. The diagnosis has been based typically on exclusion of other possible causes of poor performance, back pain and hindlimb lameness. Objective: To develop a safe, reliable and minimally invasive periarticular or intra-articular injection technique of potential use for diagnosis and therapy of sacroiliac joint disease in horses. Methods: Twenty-six horses were used to develop and assess a medial approach to the sacroiliac jo...
Equine laminitis: cleavage of laminin 5 associated with basement membrane dysadhesion. The key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. For this to happen the structural and adhesion proteins of the basement membrane zone must be altered. Which proteins and how damage to them leads to the lamellar separation of laminitis is unknown. Objective: To investigate lamellar hemidesmosome and cytoskeleton damage and basement membrane dysadhesion using light microscopy (LM) and immunofluorescence microscopy (IFM). Methods: Cryostat sections of lamellar tissues from 2 control and 6 Standardbred horses with oligofructose induced laminitis were stud...
Equine laminitis: loss of hemidesmosomes in hoof secondary epidermal lamellae correlates to dose in an oligofructose induction model: an ultrastructural study. Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention. Objective: To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage. Methods: Three pairs of normal...
Hoof wall wound repair. Surgical stripping of the hoof wall results in a wound that heals remarkabley well. In contrast, lamellae recovering from laminitis are often deformed. Investigating lamellar wound healing may aid understanding of laminitis. Objective: To document temporal changes in the lamellar basement membrane (BM), dermis and epidermis after surgery. Methods: Wall strips were made in the dorsal hoof wall midline of 6 mature horses. Immunohistochemistry was used to document changes in the basement membrane (BM) and detect proliferation of epidermal cells in lamellar tissues harvested at intervals. A confor...
Epidermal cell proliferation in the equine hoof wall. Current theories explaining how the hoof wall 'grows' and moves past the stationary distal phalanx are speculative and based on incomplete evidence. Movement in the lamellar region could occur by cell proliferation or an enzyme-based remodelling process. Since laminitis pathogenesis appears to involve increased transcription and activation of enzymes normally involved in tissue remodelling, it is important to know precisely which process dominates the lamellar region of the hoof.. Objective: To investigate epidermal cell proliferation in the equine hoof wall and calculate a proliferative index...
Sirius red is able to selectively stain eosinophil granulocytes in bovine, ovine and equine cervical tissue. The aim of the present study was to examine the suitability of sirius red staining for selective light microscopic demonstration of eosinophil granulocytes in cervical tissue of mares, cows and sheep. For this purpose, tissue was fixed in 4% neutral buffered formol or in Bouin's solution. Paraffin sections of 5-microm thickness were stained with sirius red. In cows, mares and sheep a selective distinction of eosinophilic infiltration is successful after both fixation methods.
Desmoplakin and Plakoglobin–specific markers of lymphatic vessels in the skin? Monoclonal antibodies against Desmoplakin and Plakoglobin were tested for their suitability as specific markers of lymphatic vessels. The tissue samples were taken from horse skin in an attempt to establish the horse as a model for human lymphatic diseases. To obtain a clear, positive identification of blood and lymphatic vessels, immunohistochemical staining with antibodies against vascular endothelial growth factor receptor 3 (VEGFR-3) and platelet endothelial adhesion molecule (PECAM-1, CD31), was compared with Desmoplakin and Plakoglobin. Because anti-VEGFR-3 is specific for lymphatic vess...
Assessment of apoptosis in epidermal lamellar cells in clinically normal horses and those with laminitis. To determine and compare the number, type, location, and distribution of apoptotic epidermal cells in the laminae of clinically normal horses and horses with laminitis. Methods: Formalin-fixed samples of digital lamellar tissue from 47 horses (including clinically normal horses [controls; n = 7], horses with acute [4] and chronic [7] naturally acquired laminitis, and horses with black walnut extract-induced [11] or carbohydrate overload-induced [18] laminitis). Methods: Blocks of paraffin-embedded lamellar tissues were stained for DNA fragmentation with the terminal deoxynucleotidyl transferas...
Assessment of subchondral bone mineral density in equine metacarpophalangeal and stifle joints. Functional relationships between articular cartilage and underlying subchondral bone have been shown to be associated with the progression of osteoarthritis (OA). However, quantifiable factors substantiating this relationship do not exist. Therefore, the study objective involved quantifying subchondral bone mineral density (BMD) of the equine metacarpophalangeal (MCP) and stifle joints as a step in determining if regional subchondral BMD may be associated with OA changes. BMD was bilaterally quantified using dual energy xray absorptiometry (DEXA) for four subchondral regions: palmer and dorsal...
Equine cardiovascular pathology: an overview. The few data collections that evaluate the involvement of organ systems in horse diseases are in agreement that the locomotor, gastrointestinal and nervous systems are the sites of primary disease in the vast majority of sick horses. When compared with diseases of these organ systems, equine cardiovascular diseases occur infrequently. The most detailed and comprehensive survey of equine cardiac pathology was reported in 1972 by Else and Holmes, who summarized the gross and microscopic cardiac findings from 1500 abattoir horses. This paper reviews the pathology of the cardiovascular diseases ty...
A simple fluorescence labeling method to visualize the three-dimensional arrangement of collagen fibers in the equine periodontal ligament. In order to display the collagen-fiber arrangement in the equine periodontal ligament an inexpensive and easy staining procedure with fluorescein was applied to paraffin sections. After fluorescein labeling a section was suitable for successful examination with three special microscopical systems: a) fluorescence microscopy b) phase contrast microscopy and c) polarized light microscopy. Collagen fibers were clearly displayed as compact structures in the fluorescence microscope. This distinct feature of the fluorescent image generated an almost three-dimensional impression of the fiber arrangem...
Radiotherapy of a recurrent ossifying fibroma in the paranasal sinuses of a horse. A 7-year-old female Thoroughbred was admitted with a history of labored breathing, stridor, and exercise intolerance. Examination revealed a mass in the left paranasal sinuses that was determined to be an ossifying fibroma. Initial treatment consisted of surgical removal of the mass alone; however, the mass recurred 9 months after surgery. The mass was again removed, and adjunctive radiotherapy consisting of 3,000 cGy of cobalt radiation was administered. This time, the tumor did not recur for > 6 years. A third surgery was performed to remove the mass, and adjunctive radiotherapy consisting o...
The effects of extracorporeal shock-wave therapy on the ultrasonographic and histologic appearance of collagenase-induced equine forelimb suspensory ligament desmitis. Extracorporeal shock-wave therapy (ESWT) may stimulate healing of desmitis in multiple species. The objective of this study was to evaluate the ultrasonographic and histologic appearance of collagenase-induced suspensory ligament (SUL) desmitis in untreated ligaments and ligaments treated with ESWT in horses. Four mature horses had SUL desmitis induced in both forelimbs. Beginning 3 weeks after induction of the lesions, one ligament per horse was treated 3 times at 3-week intervals with ESWT. The percent lesion, echogenicity and fiber alignment scores of the SULs were evaluated at 3-week inter...
A biomechanical comparison of headless tapered variable pitch compression and ao cortical bone screws for fixation of a simulated midbody transverse fracture of the proximal sesamoid bone in horses. To compare mechanical properties and failure characteristics of 2 methods of fixation for repair of a transverse, midbody fracture of the proximal sesamoid bone (PSB): 4.5-mm AO cortical bone screw (AO) placed in lag fashion and 4/5-mm Acutrak (AT) self-compressing screw. Methods: An in vitro biomechanical evaluation of intact forelimb preparations and forelimb preparations with a simulated midbody PSB fracture stabilized by a bone screw. Methods: Sixteen paired and 8 unilateral cadaveric equine forelimbs. Methods: A midbody transverse osteotomy was created in the medial PSB of bilateral forel...
