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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.
The fibrous tapetum of the horse eye. The tapetum lucidum is a light-reflective tissue in the eyes of many animals. Many ungulates have a fibrous tapetum. The horse has one of the largest eyes of any living animal and also has excellent vision in low-light environments. This study aimed to clarify the macroscopic tapetal shape, relationship between the tapetal thickness and the degree of pigmentation of the retinal pigment epithelium (RPE), spatial relationship between the visual streak and the tapetum, and wavelength of the light reflected from the tapetum in the horse. Macroscopically, weak light revealed the tapetum as a horizo...
Constraints on Mammalian forelimb development: insights from developmental disparity. Tetrapod limb development has been studied extensively for decades, yet the strength and role of developmental constraints in this process remains unresolved. Mammals exhibit a particularly wide array of limb morphologies associated with various locomotion modes and behaviors, providing a useful system for identifying periods of developmental constraint and conserved developmental mechanisms or morphologies. In this study, landmark-based geometric morphometrics are used to investigate levels and patterns of morphological diversity (disparity) among the developing forelimbs of four mammals with...
Three dimensional, radiosteriometric analysis (RSA) of equine stifle kinematics and articular surface contact: a cadaveric study. Studies examining the effect of stifle joint angle on tibial rotation, adduction-abduction angle and articular contact area are lacking. Objective: To test the hypothesis that tibial rotation, adduction-abduction angle and articular contact area change with stifle joint angle. Methods: Descriptive study of normal kinematics and articular contact patterns of the equine stifle through the functional range of motion using 3 dimensional (3D) radiosteriometric analysis (RSA) and equine cadaver stifles. Methods: Multiple, radiopaque markers were embedded in the distal femur and proximal tibia and se...
Contrast-enhanced computed tomographic evaluation of the deep digital flexor tendon in the equine foot compared to macroscopic and histological findings in 23 limbs. Distal deep digital flexor tendinopathy is an important cause of foot lameness in horses that is difficult to diagnose with radiography and ultrasonography. Magnetic resonance imaging is a well-accepted and validated technique for the identification of deep digital flexor tendon (DDFT) lesions, but has some practical and financial drawbacks. Contrast-enhanced computed tomography (CECT) has been proposed as a suitable alternative, but validation studies are currently lacking. Objective: To assess the accuracy of CECT for the identification and characterisation of deep digital flexor tendinopath...
Equine ulnar fracture repair with locking compression plates can be associated with inadvertent penetration of the lateral cortex of the radius. To evaluate if the use of locking head screws (LHS) in the distal holes of a locking compression plate (LCP) applied to the caudal aspect of the ulna to treat equine ulnar fractures is associated with a risk of injury to the lateral cortex of the radius. Methods: Controlled laboratory study. Methods: Cadaveric equine forelimbs (n = 8 pair). Methods: After transverse ulnar osteotomy, osteosynthesis was performed with a narrow 10-13 hole 4.5/5.0 LCP applied to the caudal aspect of each ulna. The distal 3 holes were filled with 4.5 mm cortex screws (CS) in 1 limb (group 1) and with 5.0 mm LHS con...
Area of cartilage accessible to curettage for subsequent arthrodesis of the equine proximal interphalangeal joint. Comparison of conventional and collateral ligament sparing approaches. This study compared the areas of cartilage accessible for curettage in arthrodesis of the equine proximal interphalangeal joint using the conventional and collateral ligament sparing approaches. For this purpose, forelimbs and hindlimbs of six equine cadavers without radiographic evidence of proximal interphalangeal joint disease were used. One limb of each pair of limbs was randomly assigned to a dissection using a standard approach to the proximal interphalangeal joint including transection of the collateral ligaments, while each contralateral limb was exposed using the same approach but lea...
Comparison of basilar and axial sesamoidean approaches for digital flexor tendon sheath synoviocentesis and injection in horses. To define a method for the basilar sesamoidean approach (BSA) to the digital flexor tendon sheath (DFTS) in horses and compare it with the axial sesamoidean approach (ASA) for DFTS synoviocentesis and injection. Methods: Evaluation study. Methods: 12 healthy adult mares without evidence of abnormalities related to the lower limbs. Methods: Each horse had 1 forelimb and 1 hind limb assigned to each DFTS approach (basilar vs axial, relative to the proximal sesamoid bones) in a Latin square design. The order of horses and of limb injection for each horse was randomly selected. All procedures were...
Two- and three-dimensional anatomy of paranasal sinuses in Arabian foals. The 2- and 3-dimensional (3D) anatomy and the morphometric properties of the paranasal sinuses of the foal have received little or no attention in the literature. The aim of this study was to obtain details of the paranasal sinuses using multiplane CT imaging to create 3D models and to determine morphological and morphometric data for the sinuses using the 3D models. The heads of five female foals were used in this study. The heads were scanned using computed tomography (CT) in the rostrocaudal direction. After the heads had been frozen, anatomical sections were obtained in the scan position. ...
Arthroscopic anatomy of the equine cervical articular process joints. Although arthropathy of the cervical articular process joints (APJs) is common, descriptions of the arthroscopic technique of the cervical APJ have not been reported previously. Objective: To develop an arthroscopic approach to the APJ and to describe the arthroscopic anatomy of the APJ. Methods: Descriptive cadaver study and clinical case report. Methods: The regional anatomy was reviewed and the technique developed on fresh cadaver necks. A series of cadaveric APJ arthroscopies from C2-C3 to C6-C7 were performed to evaluate the procedure, which was then used in 3 clinical cases. A descriptio...
Ultrasound-guided injection of the maxillary nerve in the horse. Infiltration of the equine maxillary nerve with local anaesthetic can be useful for both diagnostic and surgical procedures. The deep location and proximity of the nerve to surrounding vascular and orbital structures make an accurate, complication-free injection a challenge using traditional techniques reliant upon surface anatomical landmarks. Objective: To develop an ultrasound-guided injection technique of the maxillary nerve in equine cadavers and to evaluate its efficacy and potential for complications in vivo. Methods: Descriptive cadaver anatomical and clinical study. Methods: The relev...
Magnetic resonance microscopy atlas of equine embryonic development. Equine embryogenesis post implantation is not well studied, and only two-dimensional illustrations are available. A thorough appreciation of the complex three-dimensional relationship between tissues and organs and their development is, however, crucial for understanding physiological and pathological mechanisms. Objective: The goals were 2-fold: 1) to establish a freely accessible online atlas as a reference tool for the scientific and pedagogic communities; and 2) to create a framework for integration of data with known spatiotemporal distribution, such as gene expression or cell lineage. Me...
Qualitative and quantitative interpretation of computed tomography of the lungs in healthy neonatal foals. To qualitatively describe lung CT images obtained from sedated healthy equine neonates (≤ 14 days of age), use quantitative analysis of CT images to characterize attenuation and distribution of gas and tissue volumes within the lungs, and identify differences between lung characteristics of foals ≤ 7 days of age and foals > 7 days of age. Methods: 10 Standardbred foals between 2.5 and 13 days of age. Methods: Foals were sedated with butorphanol, midazolam, and propofol and positioned in sternal recumbency for thoracic CT. Image analysis software was used to exclude lung from nonlung str...
Intradiploic hematoma of the frontal bone with secondary exophthalmos in a mare. A 13-year-old cob mare was presented with exophthalmos and periocular swelling of the left eye. The diagnostic work-up included ocular ultrasound, sonographic examination through the thinned frontal bone, radiography, standing computed tomography of the skull and exploratory osteoplastic surgery. Histopathology was consistent with an organized hematoma. An intradiploic hematoma of the frontal bone was diagnosed 5 years after head trauma, with progressive expansion and deformation of the skull resulting in exophthalmos. Exophthalmos with facial bone deformation was the only clinical finding of ...
Keratinization of the esophageal epithelium of domesticated mammals. We studied the esophageal epithelium for keratinization characteristics from samples of domesticated mammals of three nutrition groups (herbivores: horse, cattle, sheep; omnivores: pig, dog, rat; carnivores: cat) using histochemistry (keratins, disulfides), sulfur measurements, and cryo-SEM. Keratins were found in all esophageal layers of all species, except for the equine Stratum corneum. The positive reaction staining of Pan-keratin was remarkable, but decreased in intensity toward the outer layers, whereas in the pig and cat, staining was confined to the corneal layer. The herbivores reveal...
Characterization of prostaglandin E2 receptors (EP2, EP4) in the horse oviduct. Biological effects of prostaglandin E2 are mediated via one of four receptors designated EP1, EP2, EP3 and EP4 which are encoded by separate genes. In general, EP1 and EP3 induce smooth muscle contraction whereas EP2 and EP4 induce smooth muscle relaxation. The objective of the current study was to characterize the expression of the genes for PGE2 receptors (EP2 and EP4) in the horse oviduct based upon immunohistochemistry (IHC) and quantitative PCR (qPCR). Oviductal tissue was collected from mares at estrus (n=5), at 5 days post-ovulation (n=4), and from prepubertal mares (n=5). Isthmic and a...
Expression of β2 adrenoceptors within enteric neurons of the horse ileum. The activity of the gastrointestinal tract is regulated through the activation of adrenergic receptors (ARs). Since data concerning the distribution of ARs in the horse intestine is virtually absent, we investigated the distribution of β2-AR in the horse ileum using double-immunofluorescence. The β2-AR-immunoreactivity (IR) was observed in most (95%) neurons located in submucosal plexus (SMP) and in few (8%) neurons of the myenteric plexus (MP). Tyrosine hydroxylase (TH)-IR fibers were observed close to neurons expressing β2-AR-IR. Since β2-AR is virtually expressed in most neurons located...
Foetal and postnatal equine articular cartilage development: magnetic resonance imaging and polarised light microscopy. Adult articular cartilage (AC) has a well described multizonal collagen structure. Knowledge of foetal AC organisation and development may provide a prototype for cartilage repair strategies, and improve understanding of structural changes in developmental diseases such as osteochondrosis (OC). The objective of this study was to describe normal development of the spatial architecture of the collagen network of equine AC using 1.5 T magnetic resonance imaging (MRI) and polarised light microscopy (PLM), at sites employed for cartilage repair studies or susceptible to OC. T2-weighted fast-spin e...
A fresh look at the anatomy and physiology of equine mastication. There have been many significant and interesting developments in equine dental anatomy during the past 20 years that are of major clinical significance in better understanding the physiology of equine mastication, the etiopathogenesis of some dental disorders, and their safe treatment. The many recent significant developments include descriptions of the enamel infolding of cheek teeth and of infundibular anatomy, including the frequent absence of cementum infilling in many infundibulae, which can lead to infundibular caries. Many important developments in equine dental anatomy are summarized i...
A new understanding of oral and dental pathology of the equine cheek teeth. Equine dental disease has a high prevalence. Because of developmental, functional, and anatomic differences, limited inference can be made from brachydont dental pathology to that of equine cheek teeth. This article reviews the pathology of equine cheek teeth and their associated oral tissues, with specific information on periodontitis, pulpitis, maxillary infundibular changes, dental fractures, dental overgrowths, mucosal ulceration, and the regenerative capacity of equine teeth.
A new understanding of oral and dental disorders of the equine incisor and canine teeth. This article discusses the classification systems for dental fractures and how the assessment affects treatment options. Diagonal incisor malocclusion is discussed in relation to skull asymmetry and how this commonly relates to premolar and molar occlusion. Oral and radiographic assessment of incisive bone fracture and incisor avulsion is reviewed for determining treatment options. A summary of incisor and canine resorption and hypercementosis is presented. Clinical presentations, staging, and classifications of tooth resorption as well as canine odontoplasty are discussed. Excessive plaque an...
Pilonidal sinus disease. Pilonidal disease is a frequent suppurative condition that occurs twice as often in men as in women, usually between the ages of 15 and 30. Pilonidal disease is located beneath the skin of the sacro-coccygeal region. It presents acutely as an abscess under tension while the chronic form gives rise to intermittent discharge from pilonidal sinus(es). Diagnosis is clinical and usually straightforward. In the large majority of cases, treatment is surgical but there is no consensus as to the 'ideal' technique. Acute abscess must be evacuated and an off-midline incision seems preferable. Excision is...
Epidermal-like architecture obtained from equine keratinocytes in three-dimensional cultures. Despite the high prevalence of skin conditions in the horse, there is a dearth of literature on the culture and biology of equine skin cells, and this is partially attributable to the lack of suitable in vitro skin models. The objective of this study was to develop a three-dimensional (3D) culture system that would support the proliferation and differentiation of equine keratinocytes, similar to that observed in natural epidermis. Cell monolayers were obtained from explants of equine skin and serially passaged as highly pure keratinocyte populations (> 95% of cells), based on their express...
Using semi-automated segmentation of computed tomography datasets for three-dimensional visualization and volume measurements of equine paranasal sinuses. The system of the paranasal sinuses morphologically represents one of the most complex parts of the equine body. A clear understanding of spatial relationships is needed for correct diagnosis and treatment. The purpose of this study was to describe the anatomy and volume of equine paranasal sinuses using three-dimensional (3D) reformatted renderings of computed tomography (CT) slices. Heads of 18 cadaver horses, aged 2-25 years, were analyzed by the use of separate semi-automated segmentation of the following bilateral paranasal sinus compartments: rostral maxillary sinus (Sinus maxillaris ros...
3-D technology used to accurately understand equine ileocolonic aganglionosis. Ileocolonic aganglionosis (ICA) is the congenital and hereditary absence of neurons that constitute the enteric nervous system and has been described in various species including humans - Hirschsprung's disease - and horses - overo lethal white syndrome (OLWS). Hirschsprung's disease affects circa 1 in 5,000 live births. At best, this disease means an inability to absorb nutrients from food (humans). At worse, in horses, it always means death. Despite our general understanding of the functional mechanisms underlying ICA, there is a paucity of reliable quantitative information about the structu...
Computed tomographic features of lesions detected in horses with tarsal lameness. Tarsal pain is a common cause of hindlimb lameness in horses. Diagnosis can usually be made with radiography and ultrasonography; however, in some cases, these techniques are inconclusive and additional imaging is necessary. No studies describing computed tomography (CT) features of different tarsal lesions in horses with tarsal lameness are reported. Objective: Our aims were as follows: 1) to characterise CT abnormalities in horses with tarsal lameness; 2) to compare CT findings with those from other imaging techniques; and 3) to assess whether CT can help to diagnose tarsal pathology. ...
Use of bovine carpal joints as a training model for cruciate ligament repair. Currently, there is a lack of cheap and effective training models to allow orthopaedic surgery trainees to learn the basics of anterior cruciate ligament reconstruction. The aim of this paper was to investigate the viability of using various animal joints as models for the training of anterior cruciate ligament reconstruction. Methods: Equine stifles, bovine stifles and carpal joints, sheep stifles and porcine stifles, were sourced from a local abattoir. Each joint was assessed for the following criteria: suitable tendons for harvesting, ease of arthroscopy access, adequacy of arthroscopy view...
Fractures of the third trochanter in horses: 8 cases (2000-2012). To determine history; clinical, radiographic, ultrasonographic, and scintigraphic features; management; and outcome associated with third trochanter fractures in horses. Methods: Retrospective case series. Methods: 8 horses. Methods: Records from 2000 to 2012 were reviewed, and signalment, case history, severity and duration of lameness, results of physical and lameness examinations, imaging findings, management, and outcome were evaluated. Results: All horses had a history of acute onset of severe lameness. Four of the 8 horses had localizing physical signs of fracture. No specific gait chara...
Radiographic configuration and healing of 121 fractures of the proximal phalanx in 120 Thoroughbred racehorses (2007-2011). Although fractures of the proximal phalanx are one of the most common long bone fractures of Thoroughbred horses in training, limited details on variations in morphology and radiological progression have been published. Objective: To describe in detail the configuration of parasagittal fractures of the proximal phalanx in a group of Thoroughbred racehorses, to report fracture distribution within this group of horses and to document radiological progression of fracture healing in cases treated by internal fixation. Methods: Restrospective case series. Methods: Case records and radiographs of Th...
Are there radiologically identifiable prodromal changes in Thoroughbred racehorses with parasagittal fractures of the proximal phalanx? Fractures of the proximal phalanx are generally considered to result from monotonic supraphysiological loads, but radiological observations from clinical cases suggest there may be a stress-related aetiology. Objective: To determine whether there are radiologically identifiable prodromal changes in Thoroughbred racehorses with confirmed parasagittal fractures of the proximal phalanx. Methods: Retrospective cross-sectional study. Methods: Case records and radiographs of Thoroughbred racehorses with parasagittal fractures of the proximal phalanx were analysed. Thickness of the subchondral bone p...
