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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 biomechanics of simulated laryngeal abduction in horses. To investigate the influence of simulated contraction of the cricoarytenoideus dorsalis (CAD) muscle on the 3-D motion of the arytenoid cartilage. Methods: 5 larynges from equine cadavers. Methods: Serial computed tomographic scans of each larynx were conducted at 7 incremental forces simulating contraction of medial, lateral, and combined bellies of the left CAD muscle. Three-dimensional reconstruction of radiopaque markers placed at anatomic landmarks on the left arytenoid and cricoid cartilages enabled quantification of marker displacement according to a Cartesian coordinate system. Rotatio...
Influence of the chemical shift artifact on measurements of compact bone thickness in equine distal limb MR images. The effect of the chemical shift artifact, resulting from misregistration or phase cancellation at the interface between compact and trabecular bone, on apparent bone thickness was quantified in six isolated equine limbs. Sagittal T1-weighted spin echo (SE) and in-phase three-dimensional spoiled gradient echo (SPGR) images were acquired twice with a 1.5 T magnetic resonance (MR) unit, switching the frequency encoding direction between acquisitions. Out-of-phase SPGR images were also obtained. MR images with different frequency encoding directions were compared with each other and to radiograph...
The use of small (2.7 mm) screws for arthroscopically guided repair of carpal chip fractures. Removal of large chip fractures of the carpal bones and the osteochondral deficits that result, have been associated with a worse prognosis than removal of small fragments in similar locations. Objective: Reducing the articular defects by repair of large osteochondral fragments may have advantages over removal. Methods: Horses with osteochondral chip fractures that were of sufficient size and infrastructure to be repaired with small (2.7 mm diameter) AO/ASIF cortex screws were identified and repair effected by arthroscopically guided internal fixation. Results: Thirty-three horses underwent su...
Sympathetic innervation of the ileocecal junction in horses. The distribution and chemical phenotypes of sympathetic and dorsal root ganglion (DRG) neurons innervating the equine ileocecal junction (ICJ) were studied by combining retrograde tracing and immunohistochemistry. Immunoreactivity (IR) for tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), neuronal nitric oxide synthase (nNOS), calcitonin gene-related peptide (CGRP), substance P (SP), and neuropeptide Y (NPY) was investigated. Sympathetic neurons projecting to the ICJ were distributed within the celiac (CG), cranial mesenteric (CranMG), and caudal mesenteric (CaudMG) ganglia, as well ...
Preliminary study of capsule endoscopy in the small intestine of horses. To evaluate the visibility of various portions of the small intestine in healthy horses using capsule endoscopy. Methods: Six healthy, conscious adult Thoroughbreds were restrained and an endoscopic capsule (PillCam SB capsule) was inserted into the oesophagus using an intranasal catheter aided by a guide wire. Water (500 mL) flushed the capsule down the gastrointestinal tract. Data were collected and stored in the recorder of the endoscopic system for 6 hours after capsule insertion and the images were evaluated using an image reader and scored using a visual analogue scale. Results: Capsule ...
Cross-sectional area of the tendons of the tarsal region in Standardbred trotter horses. The assessment of a normal range for cross-sectional area (CSA) of tendons in the tarsal region is important in order to use them as reference values in the identification of pathological changes of dimensions. Objective: To provide normal reference values for the CSA of the tendons of the tarsus of Standardbred trotter horses (STH) by means of ultrasonography. Methods: Transverse echographic images of the tendons were obtained at different levels proximodistally; these images were digitised and CSA values (mean ± s.d.) were obtained for each structure. Results: The largest structure correspo...
Investigation of the sensitivity and specificity of radiological signs for diagnosis of periapical infection of equine cheek teeth. Radiography is commonly used for the diagnosis of equine cheek teeth (CT) infection but, to our knowledge, no study to date has evaluated the relative values of individual specific radiographic signs when making a diagnosis. Objective: To investigate the sensitivity and specificity of individual radiographic signs identified from the literature for the diagnosis of CT apical infection using a retrospective case-control study. Methods: Cropped radiographs taken using computed radiography of 41 apically infected CT and 41 control CT were independently blindly evaluated by 3 clinicians for the pr...
Distances between thoracic spinous processes in Warmblood foals: a radiographic study. The aetiological factors behind impinged or overriding of dorsal spinous processes ('kissing spine syndrome', KSS) are not clearly understood. Back conformation, breed, age, training and gender may play important roles in this condition. Radiographic changes vary and abnormalities are seen in many clinically normal horses, but the conclusion of previous studies in mature horses is that interspinous spaces <4 mm are considered too narrow and potentially indicative of KSS. Objective: To evaluate whether narrowing of the interspinous space was present in a population of normal Warmblood foals....
Is there an association between ossification of the cartilages of the foot and collateral desmopathy of the distal interphalangeal joint or distal phalanx injury? Associations between degree of ossification of the cartilages of the foot and injuries to other structures of the foot have been suggested, but have not been investigated by large scale studies. Objective: To describe the frequency of grade >3 ossification of the cartilages of the foot (possibly significant ossification, PSO), mediolateral symmetry of ossification and left-right symmetry between feet; and to investigate associations between PSO and injury of either the collateral ligaments (CLs) of the distal interphalangeal (DIP) joint or the distal phalanx. Objective: Possibly significant os...
Which anatomical region determines a positive flexion test of the distal aspect of a forelimb in a nonlame horse? The flexion test is used routinely as part of lameness and prepurchase examinations. However, little is known about the mechanisms that cause a positive response to a flexion test. Objective: To determine which anatomical regions play a role in a positive outcome of a flexion test of the distal aspect of a forelimb in a nonlame horse. Methods: Eight clinically sound Dutch Warmblood horses were subjected to a standardised flexion test (force 250 N, time 60 s) inducing a consistent lameness. To discriminate between different areas of the distal aspect of a forelimb, effects of various nerve bloc...
A cadaver study comparing two approaches to perform a maxillary nerve block in the horse. Anaesthesia of the maxillary nerve of the horse has been described using several approaches, but sparse data exist to evaluate the accuracy of these methods. Objective: This study compared 2 previously described approaches to the maxillary nerve to assess their relative accuracies. Methods: Thirty severed heads from horse cadavers were arranged to approximate the position of a live horse. Methylene blue (0.25 or 0.1 ml) was injected using a 19 gauge 90 mm spinal needle by one of 2 approaches, the method used being randomly allocated in each instance. Method ANG: angulated needle insertion on t...
Pathology of lethal peripartum broad ligament haematoma in 31 Thoroughbred mares. Broad ligament haemorrhage in peripartum mares is a life-threatening disease and there are few reports on the aetiology and pathogenesis of broad ligament haematoma. Objective: To obtain information regarding the sites for the early diagnosis and pathogenesis of broad ligament haematoma of mares. Methods: Thirty-one mares that died of broad ligament haematoma peripartum were examined pathologically for bleeding sites. The arterial distribution of 5 young mares with several parities served as negative controls. Results: Age and/or multiparity were the predisposing factors for the disease. Arter...
Distribution of radiodense contrast medium after perineural injection of the palmar and palmar metacarpal nerves (low 4-point nerve block): an in vivo and ex vivo study in horses. Evidence-based information is limited on distribution of local anaesthetic solution following perineural analgesia of the palmar (Pa) and palmar metacarpal (PaM) nerves in the distal aspect of the metacarpal (Mc) region ('low 4-point nerve block'). Objective: To demonstrate the potential distribution of local anaesthetic solution after a low 4-point nerve block using a radiographic contrast model. Methods: A radiodense contrast medium was injected subcutaneously over the medial or the lateral Pa nerve at the junction of the proximal three-quarters and distal quarter of the Mc region (Pa inject...
Assessment of the mineral density and mineral content of the equine third metacarpal and first phalanx bone by dual energy x-ray absorptiometry. In the first part of this methodological study eleven metacarpi of 9 skeletally normal horses were examined from 4 directions by dual energy x-ray absorptiometry (DXA). The differences between the dorsopalmar-palmarodorsal and lateromedial-mediolateral (opposite sites) bone mineral density (BMD) values were found to be nonsignificant. In the second part of the study the precision of the Norland XR-26 densitometer was tested by measuring 34 metacarpal bones and 34 proximal phalanges, each of them three times, from a single direction. The difference between the individual measurements of the fir...
A weighted osteon morphotype score outperforms regional osteon percent prevalence calculations for interpreting cortical bone adaptation. Using circularly polarized light microscopy,we described a weighted-scoring method for quantifying regional distributions of six secondary osteon morphotypes(Skedros et al.: Bone 44 (2009) 392-403). This osteon morphotype score (MTS) strongly correlated with "tension" and "compression" cortices produced by habitual bending. In the present study, we hypothesized that the osteon MTS is superior to a relatively simpler method based on the percent prevalence (PP) of these osteon morphotypes. This was tested in proximal femoral diaphyses of adult chimpanzees and habitually bent bones: calcanei from...
Functional electrical stimulation of the left recurrent laryngeal nerve using a vagus nerve stimulator in a normal horse. The aim of this study was to assess the feasibility of implanting an existing vagus nerve stimulating (VNS) electrode around the recurrent laryngeal nerve. The stimulus response characteristics required to achieve abduction of the ipsilateral arytenoid by the VNS electrode in the normal horse could then be determined. The electrode was wound around the left recurrent laryngeal nerve at the cervical level and connected to a pulse generator. Stimulus response characteristics were obtained by measuring stimulated arytenoid displacement endoscopically in the standing, non-sedated horse. A full and...
Digital venography in horses and its clinical application in Europe. Clinical diagnostic venography allows in vivo visualization of the digital venous system and the effects of venocompression related to foot load and laminitis pathology. Venography has predictive potential and helps the clinician anticipate and treat laminitis tissue damage before it is detectable by plain radiography. The authors describe the podiatry radiographic technique to correctly perform digital venography and the modifications they have developed. The authors provide guidelines for the interpretation of laminitis venograms in the context of laminitis chronology. Frequent venographic m...
Chronic laminitis: foot management. Laminitis is a disease of the suspensory apparatus of the distal phalanx, which can advance to the chronic stage with varying degrees of structural failure. Because the disease may ultimately lead to mechanical failure of the digit, a foot management plan is required to effectively and mechanically treat these cases. Many laminitis cases can be successfully rehabilitated back to athletic soundness, light use, breeding, or pasture soundness, whereas others suffer from permanent instability and never enjoy an acceptable level of comfort. To understand how to minimize damage in the acute laminiti...
Supporting limb laminitis. Supporting limb laminitis poses a threat to all horses suffering from severe unilateral lameness. Despite its devastating effects, relatively little is known about the precise pathologic processes that lead to its development. This article reviews the potential mechanisms of supporting limb laminitis, and the authors present some preliminary data based on advanced imaging and computer-based modeling techniques aimed at further elucidating the etiology of this unique form of laminitis. Gaining a better understanding of the pathologic processes that lead to supporting limb laminitis is essential...
Laser vaporization of the dorsal turbinate as an alternative method of accessing and evaluating the paranasal sinuses. To report a technique for stoma creation into the conchofrontal sinus (CFS) through the dorsal turbinate and to evaluate stoma as a site for sinoscopy. Methods: Prospective experimental study. Methods: Cadaveric equine heads (n=2) and normal adult horses (5). Methods: Technique feasibility was established on 2 cadaver heads. A diode laser fiber with a contact probe was passed into the nasal passage through a custom built, laser introducer rod (LIR). A videoendoscope was passed ventral to the LIR. A site on the caudal, medial aspect of the turbinate overlying the dorsal conchal sinus (DCS) was ...
Evaluation of a transvaginal laparoscopic natural orifice transluminal endoscopic surgery approach to the abdomen of mares. To report natural orifice transluminal endoscopic surgery (NOTES) using laparoscopic and endoscopic instrumentation transvaginally into the mare's abdomen and identify structures visible using this approach. Methods: Descriptive experimental study. Methods: Mares (n=8). Methods: A standing, transvaginal approach was made in the cranial vaginal vault at either the 1 (right; 4 mares) or 11 (left; 4 mares) o'clock position relative to the cervix. The abdomen was visually explored and the viscera evaluated using a 2 m flexible endoscope followed by a 62 cm laparoscope. Incisional healing was monit...
Morphology and diagnosis of the fourth-stage larva of Coronocyclus labratus (Looss, 1900) (Nematoda: Strongyloidea) parasitising equids. The fourth larval stage (L4) of Coronocyclus labratus (Looss, 1900) Hartwich, 1986, one of the common species of the Cyathostominae found in equids, is identified and described. The larvae found were identified as C. labratus by finding moulting forms possessing characters of both larval and adult stages. The larvae are similar to those of Cylicocyclus leptostomum (Kotlán, 1920) Foster, 1936, Cyathostomum catinatum Looss, 1900 and Cylicostephanus goldi (Boulenger, 1917) Lichtenfels, 1975. The buccal capsule (BC) wall of the L4 of Cylicocyclus leptostomum is thinner than that of Coronocyclus l...
Contractile properties of muscle fibers from the deep and superficial digital flexors of horses. Equine digital flexor muscles have independent tendons but a nearly identical mechanical relationship to the main joint they act upon. Yet these muscles have remarkable diversity in architecture, ranging from long, unipennate fibers ("short" compartment of DDF) to very short, multipennate fibers (SDF). To investigate the functional relevance of the form of the digital flexor muscles, fiber contractile properties were analyzed in the context of architecture differences and in vivo function during locomotion. Myosin heavy chain (MHC) isoform fiber type was studied, and in vitro motility assays w...
The effect of variable waveform low-intensity pulsed ultrasound in a fourth metacarpal osteotomy gap model in horses. The objective of this study was to evaluate the effects of variable waveform low-intensity ultrasound on the healing of a fracture gap of the fourth metacarpal bone in horses. A randomized, blinded, controlled trial was conducted in eight healthy adult horses. In each horse, a 1-cm osteotomy of the fourth metacarpal bone was created. One randomly selected metacarpal gap was treated daily with a 40-min session of ultrasound and the opposite gap was managed similarly with an inactive transducer. The fourth metacarpal bones were radiographed weekly. Fluorescent markers were administered at 14, 28...
Thymic epithelial tumor with heart metastasis in a horse. Thymic malignancy is rare in horses. Thymic epithelial tumor was diagnosed in an 18-year-old mare with invasion and metastasis to the pericardium and heart. At necropsy, the cranial thoracic cavity was obliterated by a large mass located in the thymic region and the right atrium was also expanded and effaced by a similar mass. Histologically, the neoplasm was composed of sheets of spindle cells with intraparenchymal Hassall's corpuscles and formation of pseudorosettes around blood vessels compatible with type A thymic epithelial tumor according to World Health Organization classification. The ...
In vitro comparison of two centrally threaded, positive-profile transfixation pin designs for use in third metacarpal bones in horses. To compare heat generation during insertion, pullout strength, and associated microdamage between a self-tapping positive profile transfixation pin (STTP) and nontapping positive profile transfixation pin (NTTP). Methods: 30 pairs of third metacarpal bones (MC3s) from adult equine cadavers. Methods: One MC3 of each pair was assigned to the STTP group; the other was assigned to the NTTP group. The assigned pin was inserted into the diaphysis in a lateral to medial direction. Bone temperature increase during pilot-hole drilling and pin insertion was recorded at 1 mm from the final thread positio...
A plausible explanation for heart rates in mammals. We consider a simple model to give a plausible mechanical explanation of what are the actual resting heart rates of mammals optimized for. We study what is the optimal frequency for a viscoelastic fluid circulating in a pulsatile way through a network of tubes and conclude that the heart rate is not optimized to transport blood through the whole net. Rather, actual resting heart rates of mammals happen at frequencies that optimize flow in vessels of radii that correspond to large arteries, which bring oxygenated blood rapidly far away from the heart, towards head and limbs. Our results for the...
Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone. Bone modelling and remodelling reduce the risk of fatigue fractures; the former by adapting bone to its loading circumstances, the latter by replacing fatigued bone. Remodelling transiently increases porosity because of the normal delay in onset of the formation phase of the remodelling sequence. Protracted intense loading suppresses remodelling leaving modelling as the only means of maintaining bone strength. We therefore hypothesized that race horses with fatigue fractures of the distal third metacarpal bone (MC3) will have reduced porosity associated with suppressed remodelling while contin...
CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal equine skin. Summary A small population of resident T lymphocytes is present in the healthy human and murine epidermis. However, resident epidermal lymphocytes have not been reported in normal skin of the horse. Skin biopsy specimens from the normal skin of 27 horses were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelia of normal horse skin. Hence, the presence of lymphocytes in these st...
Catastrophic biaxial proximal sesamoid bone fractures in UK Thoroughbred races (1999-2004): horse characteristics and racing history. Catastrophic biaxial proximal sesamoid bone fractures (PSBF) have not yet been described in detail in the UK racing population. Objective: To determine the incidence and relative risk (RR) of PSBF in different types of racing in the UK; and to describe horse-level characteristics and racing histories of horses sustaining these injuries. Methods: Distal limbs were collected from all racehorses suffering catastrophic fractures during racing at all 59 racecourses in the UK, in a prospective study from February 1999 to December 2004. Post mortem investigation identified the anatomical location and...
