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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.
Three-dimensional analysis of patterns of skin displacement over the equine radius. Surface markers are usually used to track bone movement. However, skin movement related to the bone has a large effect on the analysis of skeletal kinematics. A 2-dimensional (2D) skin displacement correction model has been successfully developed, but no 3D skin displacement model exists. Objective: To develop a 3-dimensional (3D) skin displacement model for the equine radial segment during trot. Methods: The 3D trajectories of 6 skin-based markers and a bone-fixed triad were captured at trot in 4 horses. Skin displacements in the bone-based coordinate system were calculated using a singular-v...
Three-dimensional carpal kinematics of trotting horses. Descriptions of 3D kinematics assist in understanding joint function and dysfunction, and are an essential step toward 3D inverse dynamic analysis. Objective: To measure 3D carpal joint motion during trotting. Methods: Three-dimensional trajectories of bone-fixed markers on the radius and third metacarpus of the right forelimb of 3 healthy horses were recorded at 120 Hz using a 6-camera analysis system. Joint kinematics were calculated in terms of helical angles between the 2 segments using a spatial attitude method. Results: All horses showed carpal extension and internal rotation of the meta...
Three-dimensional kinematics of the equine distal forelimb: effects of a sharp turn at the walk. Sharp turns are suspected to increase expression of several distal forelimb lamenesses even at the walk but the biomechanical consequences of such a movement remain unknown. Objective: To quantify the effects of a sharp turn at the walk on the 3-dimensional movements of the distal segments of the forelimb. Methods: Kinematics of the distal segments were measured in 4 healthy horses invasively with an ultrasonic system. Three-dimensional rotations of the digital joints were calculated by use of a joint coordinate system. Data obtained for a turn at the walk were compared to those obtained in a ...
The effect of bilateral glossopharyngeal nerve anaesthesia on swallowing in horses. Dysfunction of the glossopharyngeal nerve has been implicated as a cause of dysphagia in horses. However, recent studies have indicated that this is not the case. Objective: To determine whether bilateral glossopharyngeal nerve anaesthesia would cause dysphagia in horses or result in measurable alterations in the timing, function, or sequence of swallowing. Methods: Swallowing was evaluated in 6 normal horses with and without bilateral glossopharyngeal nerve anaesthesia. Swallowing dynamics were assessed subjectively and objectively based on time from prehension of food until swallowing, numbe...
Passive and active mechanical properties of the superficial and deep digital flexor muscles in the forelimbs of anesthetized Thoroughbred horses. The superficial (SDF) and deep digital flexor (DDF) muscles are critical for equine forelimb locomotion. Knowledge of their mechanical properties will enhance our understanding of limb biomechanics. Muscle contractile properties derived from architectural-based algorithms may overestimate real forces and underestimate shortening capacity because of simplistic assumptions regarding muscle architecture. Therefore, passive and active (=total - passive) force-length properties of the SDF and DDF muscles were measured directly in vivo. Muscles from the right forelimbs of four Thoroughbred horses we...
Three-dimensional reconstruction of the equine ovary. The equine ovary has a very unique structure in terms of its extreme large size, the presence of the ovulation fossa and the inverted location of its cortex and medulla. In the previous study, it was recognized that the application of three-dimensional internal structure microscopy (3D-ISM) to observe the mare ovary is very effective. Three-dimensional reconstruction of serially sliced images made by 3D-ISM was successful in this study with the aid of the sophisticated image processing technique. The rotation of the reconstructed ovary has been carried out with and without the application of t...
Histology and ultrastructure of the equine lingual tonsil. I. Crypt epithelium and associated structures. The microstructural and ultrastructural features of the equine lingual tonsil were studied in five young horses. Located at the root of the tongue it presented an irregular surface with rounded elevations, numerous folds and crypts. Stratified squamous non-keratinized epithelium lining its outer surface was modified by heavy infiltration of lymphoid cells to form reticular epithelium within the crypt. The latter implies a role in initiating and maintaining immune responses to incoming infectious agents and antigens. Lamellated structures resembling Hassall's corpuscle were observed towards the...
Histomorphology of the equine cervix. The cervix provides an effective, morphological barrier between the uterus and the outside world. The aim of this study was to characterize the epithelial morphology and the vascular structures of the equine cervix along the longitudinal and horizontal axis in more detail by light microscopy. For this purpose, cervical tissue specimens that had been removed from five different regions along the caudocranial axis of 10 genitally healthy mares were available. The histological staining was carried out with haematoxylin-eosin, azan according to Heidenhain, periodic acid-Schiff reaction and resorci...
Unusual vascular ring anomaly in a foal. A 2.5-month-old filly was presented with signs of esophageal obstruction. The filly was euthanized and postmortem examination revealed a vascular ring anomaly. The vascular ring anomaly was not caused by a persistent right aortic arch, which is the only vascular ring anomaly reported to occur in horses. Une pouliche de 2 1/2 mois a été présentée avec des signes d’obstruction œsophagienne. Après euthanasie, l’examen a révélé une malformation vasculaire annulaire. L’anomalie vasculaire annulaire n’était pas due à la persistance de l’arc aortique droit, seule malformation va...
Assessment of the ultrasonographic characteristics of the podotrochlear apparatus in clinically normal horses and horses with navicular syndrome. To characterize the normal ultrasonographic appearance of the podotrochlear apparatus in horses by use of standardized measurements and identify soft tissue changes associated with navicular syndrome. Methods: Prospective study. Methods: 7 clinically normal horses and 28 horses with navicular syndrome. Methods: The feasibility of identifying and measuring the soft tissue structures of the podotrochlear apparatus ultrasonographically via the transcuneal approach was assessed in 2 additional horses without navicular syndrome; both horses were euthanatized, and the structures identified ultrasono...
Evaluation of pituitary gland anatomy and histopathologic findings in clinically normal horses and horses and ponies with pituitary pars intermedia adenoma. To determine size and weight of the pituitary gland and associations between pituitary gland size and weight and sex and age in horses without clinical signs associated with pituitary pars intermedia adenoma (PPIA) and horses and ponies with PPIA. Methods: Pituitary glands from 100 horses without clinical signs of PPIA and 19 horses and 17 ponies with PPIA. Methods: Pituitary glands were weighed, measured, and examined histologically by use of H&E stain. Masson trichrome and periodic acid-Schiff staining were used, when appropriate. Histologic lesions in the pars intermedia, pars distalis,...
The role of the extrinsic thoracic limb muscles in equine locomotion. Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cros...
Articular calcified cartilage canals in the third metacarpal bone of 2-year-old thoroughbred racehorses. We describe morphological aspects of the articular calcified cartilage mineralizing front 'tidemark' in the distal joint surface of the third metacarpal bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the 'wedges' intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at o...
Radiographic and pathologic characterization of lateral palmar intercarpal ligament avulsion fractures in the horse. In this study, the radiographic and histologic appearance of lateral palmar intercarpal ligament (LPICL) avulsion in the horse was characterized. Thirty-seven horses with radiographic evidence of avulsion fragments originating from the medial palmar aspect of the ulnar carpal bone were examined. The dorsolateral to palmaromedial projection was useful for evaluating the size and shape of the avulsed bone fragment, and the dorsopalmar projection added information on the relative proximity of the fragment to its fracture bed. Radiographic features that differentiated LPICL avulsion from subchondr...
Evaluation of a standardised radiographic technique of the equine hoof. Radiography of the equine hoof is often used to obtain a diagnosis. Quantitative interpretation, especially for research purposes requires high quality and accuracy of radiographs. The purpose of this study was to describe and evaluate a radiographic technique for the lateromedial (LM) and the dorsopalmar (DP) view of the equine hoof. Ten radiographs for each view from one cadaver limb and from both front feet in a standing horse were taken in order to assess repeatability of the radiographic technique. The method requires easy to use adjustable and portable equipment and strictly defined exte...
The displaced equine soft palate as a source of abnormal respiratory noise during expiration. To develop the technique of respiratory sound analysis for the diagnosis of dorsal displacement of the equine soft palate. Objective: To show that 1) the displaced soft palate can spontaneously vibrate in the presence of expiratory airflow; 2) the observed frequency of vibration can be detected in respiratory sound recordings; and 3) the frequency of vibrations measured in cadaveric specimens are similar to those obtained from audio spectra in exercising horses with DDSP. Methods: Palatal movements and respiratory sounds were recorded from artificially ventilated cadaveric heads. The fundament...
Distinct fibro-vascular arrangements in the periodontal ligament of the horse. The periodontal ligament (PDL) of the hypsodont cheek teeth of the horse meets specific requirements of tooth support: (1) to fix the tooth; (2) to withstand pressure and tension during the laterolateral mastication movement; (3) to restore the original tooth position. These requirements are assumed to be met by the periodontal collagen fiber apparatus and by the vascular system. Distinct fibro-vascular arrangements are described here in order to reveal the structural prerequisites for these distinct functions. Methods: Specimens from nine horses were processed for (1) collagen labeling with f...
Ultrasonographic examination of the equine sacroiliac region. Little information exists about the normal ultrasonographic appearance of the equine sacroiliac region, but knowledge of the ultrasonographic anatomy is necessary to understand the possible pathological changes in sacroiliac diseases. Objective: The normal ultrasonographic appearance of soft tissues and bony structures of the sacroiliac region in horses was studied in order to establish clinically relevant reference parameters. Methods: Thirteen cadaver specimens were examined using a transcutaneous approach above the tubera sacrale to image the dorsal sacroiliac ligament and the tendon of the...
Metastatic esthesioneuroblastoma in a horse. A 17-year-old horse developed severe proptosis of the left eye over a period of 1.5 years. At post-mortem examination a neoplasm was found involving the left ethmoid bone, left maxillary sinus, left orbit, left superior turbinate, and the left eye. Tumour cells were arranged in nests separated by a fine fibrovascular stroma. Immunohistochemically, the tumour cells were labelled by antibodies against neurofilament protein, synaptophysin, glial fibrillary acidic protein and S-100 protein antigen, but were negative for chromogranin A, cytokeratin and desmin. Electronmicroscopically, the cells sho...
An oral choristoma in a foal resembling hairy polyp in humans. A neonatal foal was presented with a 6.5-cm pedunculated mass arising from the upper deciduous incisors. The distal end was soft and covered by haired skin, whereas the proximal end was firm, covered with mucosal epithelium, and at the point of transection contained a fully developed tooth. Microscopically, the mass was covered by epidermis and mucosal epithelium and the remaining portion of the mass consisted of mature collagen, nonneoplastic fat and smooth muscle, and a single tooth within a bony socket. The mass is consistent with an oral choristoma and has features similar to those describ...
Congenital cystic polypoid rectal hamartoma in a newborn foal. A neonatal foal with signs of rectal bleeding was diagnosed with an intraluminal rectal mass and intussusception on surgical exploration of the abdomen. Histologically, the mass consisted of cystic spaces lined by simple columnar epithelium with numerous goblet cells and was surrounded by thin bands of smooth muscle in a myxomatous stroma. Although the mass shared similarities with retrorectal cystic hamartoma (tailgut cyst) and juvenile polyps, described in human medicine, location and histologic findings were not entirely consistent with either condition.
Correlations between mean echogenicity and material properties of normal and diseased equine superficial digital flexor tendons: an in vitro segmental approach. The objective of this study was to test the hypothesis that tendon echogenicity is associated with the material properties of the corresponding tendon site, especially in case of lesions, due to local changes in tendon matrix composition. Four normal and nine spontaneously injured equine superficial digital flexor tendons (SDFT) were isolated then ultrasonographically examined under tension, in a special device placed in a water bath. Ultrasonographic transversal images (7.5MHz linear transducer) of five segments along each tendon were digitized, and analyzed in order to measure the mean cross...
Factors associated with the prevalence of osseous fragments in the limb joints of Hanoverian Warmblood horses. Factors associated with the prevalence of osseous fragments (OF) in fetlock and hock joints were investigated in a population of young Hanoverian Warmblood horses selected for sale at auction from 1991 to 1998. The study was based on results of a standardized radiological examination of 3127 horses. The prevalences of OF in the two joints were significantly dependent on the date, type and quality of the auction, the region of origin and on the anticipated suitability of the horses for dressage and/or show-jumping. The probability of finding OF increased with wither-height. Furthermore, there w...
Fibrocartilaginous embolic myelopathy in a horse. Fibrocartilaginous embolic myelopathy was diagnosed in a 11-year-old, male, Tennessee Walking Horse by histopathological examination of the spinal cord after the horse was killed because of severe neurological dysfunction. Both ventral funiculi of C6 and C7 cervical spinal cord had extensive necrosis with blood vessels containing fibrocartilaginous emboli. A similar fibrocartilaginous embolus was observed in a single large spinal artery adjoining the vertebral leptomeninges.
Use of computed tomography angiography to evaluate the vascular anatomy of the distal portion of the forelimb of horses. To provide a detailed description of the vascular anatomy of the distal portion of the forelimbs of horses by use of computed tomography angiography (CTA). Methods: 6 forelimbs of 5 horses and 1 forelimb from an equine cadaver; none of the horses had orthopedic or vascular disease. Methods: Horses were anesthetized and CTA was conducted on the dependent forelimb. A catheter was inserted in the median artery, and contrast medium was infused at a rate of 3 mL/s. A computed tomography (CT) scanner was used to obtain contiguous slices from the region of the proximal sesamoid bones to the toe. All ...
Effects of ischemia and the cyclooxygenase inhibitor flunixin on in vitro passage of lipopolysaccharide across equine jejunum. To determine whether ischemia and flunixin affect in vitro lipopolysaccharide (LPS) absorption in samples of the jejunum of horses. Methods: 12 horses. Methods: Horses were anesthetized, a midline celiotomy was performed, and the jejunum was located. Two 30-cm sections of jejunum (60 cm apart) were selected. One segment was designated as control tissue; ischemia was induced in the other segment for 120 minutes. Horses were then euthanatized. Mucosa from each jejunal segment was mounted on Ussing chambers and treated with or without flunixin. Tissues from 6 horses were used to assess permeabili...
