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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.
Maxillary Incisors of the Horse before and at the Beginning of the Teeth Shedding: Radiographic and CT Study. To gain insight into the radiographic appearance of maxillary deciduous incisors and dental germs of maxillary permanent incisors in the period prior to teeth shedding, radiographs and computed tomography (CT) of 25 horse skulls, with an estimated age of between 12 and 42 months, were studied. Data regarding morphology and development were obtained. Dental germs of first maxillary permanent incisors were identified radiographically as rounded radiolucent areas at the level of the apical parts of the first deciduous incisors, in skulls with an estimated age of twelve months. The first sign of c...
Morphometric analysis of the intercarpal ligaments of the equine proximal carpal bones during simulated flexion and extension of cadaver limbs. Despite many reported cases of carpal lameness associated with intercarpal ligament injuries in horses, the morphometry, movement pattern and general intrinsic biomechanics of the carpus are largely unknown. Using osteoligamentous preparation of the carpus prepared from 14 equine cadaver forelimbs (aged 9.62 ± 4.25 years), locomotory simulations of flexion and extension movements of the carpal joint were carried out to observed carpal biomechanics and, thereafter, the limbs were further dissected to obtain morphometric measurements of the medial and lateral collateral ligaments (MLC and LC...
Ultrasonographic Appearance of Elbow Joints in a Population of Amiata Donkeys. Ultrasound (US) is a well-established technique for investigating joint diseases in horses, complementary to radiography. Few studies have been performed on the ultrasonographic aspect of the elbow joint in horses and no reports are available on donkeys. The aim of this study is to describe the ultrasonographic appearance of the elbow joint in healthy donkeys. Descriptive cohort study included 34 elbow joints, which were evaluated in 17 donkeys. Inclusion criteria included no lameness or musculoskeletal diseases in the donkeys. The structures evaluated were the lateral and medial collateral li...
Radiographic Description of a Bone Exostosis Lesion on the Caudal Aspect of the Proximal Tibia in Three Thoroughbred Yearlings (2014-2019). This manuscript describes exostosis lesions originating from the caudal aspect of the proximal tibia identified in three Thoroughbred yearlings as part of the routine review of presale radiographic images. These lesions are hypothesized to be osteochondromas. The identification of bony exostoses on the proximal tibia has not been reported before in current literature. As they have not been described, the future effect on performance or soundness is unknown. Although these cases were not lame at the time of detection, the future growth of the lesion and its impact on surrounding soft tissues is...
Locomotion on the edge: Structural properties of the third metacarpal in Thoroughbred and Quarter Horse racehorses and feral Assateague Island ponies. The elongated, distally tapered limbs of horses are adapted for high-speed locomotion. Because these traits are artificially selected for in modern racehorses, they operate at a morphological extreme with a high risk of fracture. Racehorses are subject to different training and racing regimes depending on their breed and gait, and are therefore an interesting model to examine bone functional adaptation under variable biomechanically intense conditions. This study compares bone structural properties in the third metacarpal (MCIII) of Thoroughbred (n = 9) and Quarter Horse (n = 11) racehorses, u...
The equine diaphragm: A novel technique for repeatable ultrasound measurement. The diaphragm is an important respiratory muscle, playing a key role during exercise. In humans, diaphragm thickness increases in response to training and is correlated with inspiratory strength. In order to assess respiratory strength in the horse, new evaluation techniques are required and measurement of diaphragm thickness, in a non-invasive and repeatable manner, is a possible approach. The purposes of this four-part, prospective, pilot study were to develop and describe a repeatable method to measure the diaphragm thickness, using ultrasonography, in Thoroughbred racehorses. A standardize...
Effect of Scan Plane and Arthrography on Visibility and Interobserver Agreement of the Equine Distal Sesamoidean Impar Ligament on Magnetic Resonance Images. In magnetic resonance imaging (MRI) examinations, moderate to severe changes of the distal sesamoidean impar ligament (DSIL) were found in horses with lameness localized to their feet. Histologic abnormalities were detected more commonly in lame horses. Because of its heterogeneity and small thickness, evaluation of the DSIL in MRI can be challenging. The aim of the study was to determine the optimal sequence and the ideal transverse perpendicular angle for visualization of the DSIL before and after arthrography of the distal interphalangeal joint (DIPJ). Twenty-five cadaver forelimbs were exa...
The Effect of Increasing Fracture Site Stiffness on Bone-Pin Interface Stress and Foot Contact Pressure within the Equine Distal Limb Transfixation Cast: A Finite Element Analysis. The aim of this study was to determine how increasing stiffness of fracture site tissues distal to the pins in an equine distal limb transfixation cast influences stress at the bone-pin interface, within the bones distal to the transcortical pins, and contact pressure between the foot and the cast. Methods: A transfixation cast finite element model was used to compare the bone-pin interface stress, pin stress, bone stress distal to the pins and contact pressure between the foot and the cast, using six stiffness values for a composite tissue block representing progressive stages of fractu...
Agenesis and Dysgenesis of the Navicular Bone as Cause of Lameness and Malalignment in Two Foals. A three-week-old warmblood colt was referred for a two-week history of lameness on the left thoracic limb, and a two-month-old Quarter Horse-mix filly was referred for malaligned pelvic limbs since birth. The foals were diagnosed with agenesis and dysgenesis of the navicular bone, respectively. In this report, we present clinical signs, diagnostics, and postmortem workup of the two cases.
Progression of shallow medial femoral condyle radiographic lucencies in Thoroughbred repository radiographs and their influence on future racing careers. Shallow lucencies less than 4 mm deep into the medial femoral condyle (MFC) are frequent in Thoroughbred horses undergoing screening sales radiographs. It is unclear if these shallow defects are precursors to larger cystic lesions or if they are fully developed defects that remodel into a flattened femoral condyle. Objective: To evaluate radiological lucencies of the MFC and their progression in size, in a cohort of Thoroughbred horses, ranging from 5 to 18 months of age and to report on the racing careers of these horses compared to their maternal siblings free of stifle pathology. Methods:...
Computed Tomography and Magnetic Resonance Imaging of an Epidermoid Cyst in a Foot of a Horse. An 18-year-old Quarter Horse mare was evaluated because of moderate left forelimb lameness of 4 weeks' duration. The clinical evaluation and diagnostic perineural analgesia localized the lameness to the distal portion of the left forelimb. There was swelling on the dorsal and lateral aspect of the coronary band. Radiography, ultrasound, magnetic resonance imaging, and computed tomography of the foot revealed circumscribed well-capsulated soft tissue mass causing a focal deformation of the dorsolateral border of the middle phalanx. The treatment aimed to remove the mass surgically and stabiliz...
Complications Following Mandibular Cheek Tooth Extraction in 20 Horses. The objectives of this retrospective study were to describe the prevalence and characteristics of post-operative complications that occur following equine mandibular cheek tooth extractions and to assess for possible associated risk factors. Clinically significant post-extraction complications necessitating repeat referral developed following 20/302 (6.6%) mandibular cheek tooth extractions. Horses developing complications were younger than the overall population having mandibular cheek teeth extractions and the most commonly affected teeth were the Triadan 07 s and 09 s. Alveolar sequestratio...
Correlational Characteristics of Hoof Conformation and Midstance Kinetics at Walk. Variations in hoof conformation may alter stress distribution, thus predisposing horses to pathologies and lameness; however, experimental studies are scarce. Our objective was to investigate the correlation between midstance hoof kinetics at the walk and hoof conformation in horses. Nine clinically sound, unshod horses were walked over a pressure plate, and force (F), contact area (CA), contact pressure (CP), and peak contact pressure (PCP) were recorded at the dorsal, palmar, medial, and lateral regions, as well as for the whole hoof. By using digital radiography and digital pictures, 55 var...
Tensile strength and early healing of self-locking and surgeon’s knots. To compare the biomechanical properties and healing of ventral midline celiotomies (VMC) closed with a self-locking knot combination and forwarder start and Aberdeen end (F-A) vs a traditional knot combination and surgeon's start and end (S-S). Methods: In vivo, experimental. Methods: Twenty-one horses. Methods: Fourteen horses underwent VMC, which was closed with either an F-A (n = 7) or an S-S (n = 7) knot combination. Incisions were subjectively graded by masked evaluators for dehiscence, edema, and drainage. Biomechanical testing was performed on three abdominal segments, and histology was...
Anatomy and Ultrasound-Guided Injection of the Medial Branch of the Dorsal Ramus of the Cervical Spinal Nerves in the Horse: A Cadaveric Study. The aim of this study was to describe the anatomy of the nerves supplying the cervical articular process joint and to identify relevant anatomical landmarks that could aid in the ultrasound-guided location and injection of these nerves for diagnostic and therapeutic purposes. Methods: Twelve cadaveric equine necks were used. Five necks were dissected to study the anatomy of the medial branch of the dorsal ramus of the cervical spinal nerves 3 to 7. Relevant anatomical findings detected during dissections were combined with ultrasonographic images obtained in one other neck. Six additiona...
Congenital Osteoma of the Frontal Bone in an Arabian Filly. Congenital frontal osteoma has not been previously described in horses. This report records-for the first time-a congenital osteoma of the frontal bone in a 4-month-old Arabian filly. The filly had a frontal hard mass that was present at birth and then showed a slow and continuous growth. This mass appeared as a solitary, painless, oval dense tumor of compact bone, about 2 cm in diameter and 3 cm in length. The tumor was asymptomatic, and the skin over the mass was normal. Radiography revealed a well-defined oval, radio-dense mass projecting from the surface of the right frontal bone with no...
Evaluation of the Olecranon Bursa: An Anatomical Structure in the Normal Horse. This study aimed to determine whether a true synovial structure exists over the olecranon tuberosity, which could be attributed to a noninflamed olecranon bursa. Contrast radiography, gross anatomical dissection, and histopathology were used to evaluate the olecranon bursa in horses with no previous elbow pathology. The radiographic study revealed that the contrast was positioned subcutaneously, superficial to the long head of the triceps and its insertion on the olecranon tuberosity and did not extend cranial to the triceps tendon. The contrast region was consistent in shape, size, and locati...
White line disease in a 19-year-old appendix mare. A 19-year-old appendix mare was presented with severe, acute right forelimb lameness and a history of significant hoof wall defect. The defect began as progressive toe separation affecting the dorsal hoof wall, which was eventually resected by a farrier. Placement of bar shoes by a farrier to stabilize the hoof was ineffective. Radiographs showed hoof wall separation, palmar rotation, and displacement of the coffin bone, consistent with failure of the laminar structures. Treatment included phenylbutazone, radiographic-guided therapeutic farriery consisting of derotation with a wedge shoe, and ...
Evaluation of vascularization in the walls of preovulatory follicles in mares with endometritis. Endometritis is a major cause of infertility in mares. The aim of this study is to evaluate the preovulatory follicle (POF) vascularization (A mix, A red, A blue), POF diameter, POF wall thickness, and uterine diameters in mares with or without endometritis. Ten healthy mares and 10 mares with endometritis diagnosed by the combination of transrectal palpation, ultrasonographic examination, and cytology brush were enrolled in the study. Data of the groups obtained at 2 days before the ovulation (day -2) were compared with Student's t-test. Correlations of the parameters were determined by the ...
Diffusion Tensor Imaging Tractography of White Matter Tracts in the Equine Brain. Tractography, a noninvasive technique tracing brain pathways from diffusion tensor magnetic resonance imaging (DTI) data, is increasingly being used for brain investigation of domestic mammals. In the equine species, such a technique could be useful to improve our knowledge about structural connectivity or to assess structural changes of white matter tracts potentially associated with neurodegenerative diseases. The goals of the present study were to establish the feasibility of DTI tractography in the equine brain and to provide a morphologic description of the most representative tracts in t...
Computed Tomography (CT)-Assisted 3D Cephalometry in Horses: Interincisal Angulation of Clinical Crowns. The angle encompassed between opposing incisors in horses is assumed to decline with age. Previous studies merely consider the overall profile view of clinical crowns presuming a generalized angle, neglecting potential tooth position-dependent differences. Cephalometric measurements from 3D computed tomographic thick-slab reconstructions of single incisors within a global reference frame were used to determine clinical crown interincisal angulation (IIA) of 48 horses. Based on predefined dentoalveolar landmarks, IIA was defined as the angle enclosed by the respective labial axis of the clinica...
Computed tomographic cervical myelography in horses: Technique and findings in 51 clinical cases. Three-dimensional computed tomographic (CT) evaluation of the cervical vertebral column enables more accurate identification of osseous and soft tissue lesions than traditional latero-lateral radiography. However, examination of the complete cervical vertebral column has been limited by horse size, preventing evaluation of the caudal cervical vertebrae. Objective: To describe a technique to enable CT myelography of the complete cervical spine and describe the findings in 51 horses. Methods: Records of 51 horses presented for evaluation of cervical vertebral lesions. Methods: A retrospective re...
Quantitative analysis of astrocyte and axonal density relationships: Glia to neuron ratio in the optic nerve laminar regions. Astrocytes are critical for the maintenance of retinal ganglion cell (RGC) axonal function and viability, and form a key component of the functional neurovascular unit. Recently, we described the quantitative properties of astrocytes in relation to the capillary distributions in optic nerve laminar regions. Here, we provide a quantitative analysis of astrocytes and RGC axons in longitudinal sections of optic nerve tissue. Histological and immunocytochemical techniques are used to demonstrate the density of astrocytes, RGC axons and glia-neuron ratios across the pre laminar, lamina cribrosa and...
Catheter-based electrical interventions to study, diagnose and treat arrhythmias in horses: From refractory period to electro-anatomical mapping. Minimally-invasive catheter-based interventional cardiology is a mainstay for the diagnosis and treatment of arrhythmias in human medicine. Very accurate imaging using fluoroscopy, CT and MRI is essential during interventional cardiology procedures. Because these imaging techniques are either not possible or provide too little anatomical detail in horses, echocardiography is currently the best technique to visualize catheters in horses. Over the past decades, catheter-based techniques have been applied to induce arrhythmias using pacing and to perform arrhythmia research using electrophysiolog...
Ex vivo modeling of the airflow dynamics and two-and three-dimensional biomechanical effects of suture placements for prosthetic laryngoplasty in horses. To identify the degree of left arytenoid cartilage (LAC) abduction that allows laryngeal airflow similar to that in galloping horses, assess 2-D and 3-D biomechanical effects of prosthetic laryngoplasty on LAC movement and airflow, and determine the influence of suture position through the muscular process of the arytenoid cartilage (MPA) on these variables. Methods: 7 equine cadaver larynges. Methods: With the right arytenoid cartilage maximally abducted and inspiratory airflow simulated by vacuum, laryngeal airflow and translaryngeal pressure and impedance were measured at 12 incremental LAC...
Relationship Between Magnitude and Direction of Asymmetries in Facial and Limb Traits in Horses and Ponies. Directionality of limb and facial asymmetries in nonelite equine populations has been previously reported with results indicating strong similarities to those reported in racehorses. This investigation aimed to consider the relationship between the magnitude of the asymmetries presented within the general equine population, and their previously reported directionality. Direct measurements of 15 bilateral traits (four facial and 11 limb) were captured from a mixed population of 100 horses and ponies. The pooled (whole) population was considered further as horse (withers height >148 cm) and ...
Subchondral focal osteopenia associated with proximal sesamoid bone fracture in Thoroughbred racehorses. Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress-related process. However, the aetiopathogenesis of PSB fracture is poorly understood. Objective: To characterise bone abnormalities that precede PSB fracture. Methods: Two retrospective case-control groups of PSBs from TB racehorses with, and without, unilateral biaxial PSB fracture. Methods: Proximal sesamoid bones were harvested post-mortem from TB raceho...
The use of the geometric morphometric method to illustrate shape difference in the skulls of different-aged horses. The geometric morphometrics method (GMM) is a technique to study scale and shape relationships of structures using Cartesian geometric coordinates rather than linear, areal (of area), or volumetric variables. GMM has been of great value in many biological studies, but does not appear to have been used to examine equine skulls.In this exploratory study, twenty-nine normal equine heads of three different age groups: 16 years old (N = 10) were examined.Computed tomography (CT) bone window DICOM images were reconstructed into isosurfaces (3-dimensional contoured surfaces), onto which landm...
Effect of Caudal Traction on Mechanical Nociceptive Thresholds of Epaxial and Pelvic Musculature on a Group of Horses With Signs of Back Pain. Direct muscular attachment from lumbar vertebrae to the caudal vertebrae of the tail suggests that caudal traction, also described as a tail pull, may affect lumbar vertebral segments and/or associated soft tissues in horses. Traction is a commonly used human manual therapy technique used for pain relief and anecdotally observed to relieve pain in horses. However, research is lacking validating the efficacy of manual caudal traction on the horse. The objective of this study was to determine if caudal traction has an effect on mechanical nociceptive thresholds (MNTs) in a group of horses with c...
Prevalence of Radiographic Signs of Osteoarthritis in Lusitano Purebred Horses. Radiographic prevalence and correlation of radiographic findings has not been performed in Lusitano Purebred horses. The aim of this study was to (1) evaluate the prevalence of primary osteoarthritis radiographic findings in Lusitano Purebred horses; (2) to assess correlations between radiographic findings in different joints of the same limb and different limbs; and (3) elucidate the effect of age in the radiographic findings. A radiographic protocol of the stifle, tarsi, fetlocks and distal limbs was done in 98 Lusitanos and the classification of the radiographs was performed using a 0-4 sc...
