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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.
Electromyographic activity of the palatinus and palatopharyngeus muscles in exercising horses. Determining the respiratory related activity of the palatinus and palatopharyngeus muscles in exercising horses is relevant because dysfunction of these muscles has been implicated in the pathogenesis of dorsal displacement of the soft palate. Objective: To determine if the palatinus and palatopharyngeus muscles have respiratory activity that increases with intensity in exercising horses. Methods: Electromyographic activity was measured in the palatinus and palatopharyngeus muscles using bipolar fine-wire electrodes while the horses completed an incremental exercise treadmill protocol. Results...
Decreased radiopharmaceutical uptake (photopenia) in delayed phase scintigraphic images in three horses. Decreased radiopharmaceutical uptake, photopenia, in delayed phase scintigraphic images is recognized in people but has only been reported rarely in horses. We describe three horses with septic osteitis, bone sequestrum formation, or distal limb thrombosis that had photopenia of the affected extremity. Photopenia may indicate the presence of ischemia and can be used to facilitate clinical decision making and prognosis assessment
Effect of ultrasound beam angle on equine articular cartilage thickness measurement. The purpose of this study was to determine if variation in the ultrasound beam angle would affect cartilage thickness measurement performed with B-mode ultrasonography. Transverse sections of six fresh equine middle phalanges were obtained from necropsy. Ultrasonographic images of the proximal articular cartilage were obtained in a water bath, in a plane parallel and adjacent to the section plane using a 5-10 MHz linear transducer. Static images were acquired for all six bone specimens with an ultrasound beam angle of 0 degree, 30 degrees, 45 degrees, and 60 degrees. Proximal articular cartila...
Comparative examination of percussional and echocardiographic determination of the cardiac dullness area in healthy horses. Since percussion started to be a method forgotten and not trusted by many practitioners, the aim of the study was to demonstrate whether this procedure could deliver exact data if done accurately and by a practised examiner. The trial presented here included 31 healthy warm-blooded horses. Percussion of the area of cardiac dullness and then echocardiographic imaging of the same region were performed. To obtain the relevant measurement points, the 4th and 5th intercostal spaces (ICS) were used on the left and the 4th ICS on the right side. On the left side, the dorsal border of cardiac dullness...
Omental leiomyoma in a male adult horse. A well-circumscribed mass 70 x 35 x 28 cm in size and 41 kg in weight was detected at necropsy in a male adult horse within the omentum major without any association to the gastrointestinal tract. The tumor consisted of multiple white-to-yellow lobules and displayed a firm consistency. In addition, multiple cysts filled with blood-like fluid, and multifocal areas of necrosis were observed. Histologically, the mass consisted of slightly pleomorphic spindloid-shaped cells arranged in interlacing bundles containing elongated nuclei with blunt ends. The majority of tumor cells revealed a positive ...
Morphologic changes associated with functional adaptation of the navicular bone of horses. Failure of functional adaptation to protect the skeleton from damage is common and is often associated with targeted remodeling of bone microdamage. Horses provide a suitable model for studying loading-related skeletal disease because horses are physically active, their exercise is usually regulated, and adaptive failure of various skeletal sites is common. We performed a histologic study of the navicular bone of three groups of horses: (1) young racing Thoroughbreds (n = 10); (2) young unshod ponies (n = 10); and (3) older horses with navicular syndrome (n = 6). Navicular syndrome is a painfu...
Persistent dorsal displacement of the soft palate attributable to a frenulum of the epiglottis in a racing Thoroughbred. A 7-year-old sexually intact male Thoroughbred racehorse was evaluated because of exercise intolerance, respiratory tract noise, and coughing when eating. Results: A persistent dorsal displacement of the soft palate was identified during endoscopic examination of the upper portions of the respiratory tract. Radiography of the pharyngeal and laryngeal regions revealed a hypoplastic epiglottis that was ventral to, and not in contact with, the soft palate. The horse was anesthetized, and an oral endoscopic examination revealed a subepiglottic frenulum that had resulted in the dorsal displacement ...
Dorsolateral approach for arthrocentesis of the centrodistal joint in horses. To develop a dorsolateral approach to the centrodistal (distal intertarsal) joint in horses and compare its success rate with that of the traditional medial approach in that joint. Methods: 25 cadaveric equine hind limbs, ultrasonographic images, and radiographic views of the tarsal region of 5 and 59 healthy horses, respectively, and 22 horses with a clinical indication for centrodistal joint centesis. Methods: The dorsolateral approach was established anatomically (3 cadaveric limbs), ultrasonographically (5 horses), and radiographically (59 horses). Centrodistal joint arthrocentesis was per...
Comparison of 2 methods of centesis of the bursa of the biceps brachii tendon of horses. Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. Objective: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. Methods: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium a...
Equine laminitis: ultrastructural lesions detected 24-30 hours after induction with oligofructose. The pathology of equine laminitis has been well-documented 48 h after dosing with oligofructose when clinical lameness and lamellar disintegration is well advanced. Further analysis of the earliest lesions, by collecting lamellar samples at the first sign of foot lameness after oligofructose dosing is required in order to increase understanding of the disease. Objective: To investigate lamellar epidermal hemidesmosome damage and basement membrane dysadhesion by transmission electron microscopy (TEM). Methods: Eight clinically normal, mature Standardbred horses were divided randomly into 2 grou...
Magnetic resonance imaging evaluation of 264 horses with foot pain: the podotrochlear apparatus, deep digital flexor tendon and collateral ligaments of the distal interphalangeal joint. To improve understanding of the interrelationships between injuries of the podotrochlear apparatus and deep digital flexor tendon (DDFT). Objective: There is a difference in frequency of different types of lesions at different anatomical sites of the DDFT. Lesions of the collateral sesamoidean ligament (CSL), distal sesamoidean impar ligament (DSIL), distal interphalangeal (DIP) joint and navicular bursa are seen in association with lesions of the navicular bone. Methods: The magnetic resonance (MR) images of 264 horses with unilateral or bilateral foot pain were analysed and graded. Descripti...
Scintigraphic evaluation of the stifle in normal horses and horses with forelimb lameness. We tested the hypotheses that mature horses without lameness have a repeatable radiopharmaceutical uptake pattern in the stifle, which is bilaterally symmetric; immature horses have a different radiopharmaceutical uptake pattern; and forelimb lameness alters the radiopharmaceutical uptake pattern in the stifle. The objectives of the study were to describe the normal radiopharmaceutical uptake patterns using region of interest (ROI) analysis; to compare uptake patterns between left and right stifles of the same horse and between mature and immature horses; to compare radiopharmaceutical uptake ...
Three-dimensional ultrasonographic in vitro imaging of lesions of the meniscus and femoral trochlea in the equine stifle. The purpose of this in vitro study was to evaluate the value of three-dimensional (3D) ultrasonography for the diagnosis of equine meniscal and trochlear ridge lesions under in vitro conditions. Lesions were created in the isolated meniscus and femoral trochlea of 25 cadaver stifle joints. Cylindric, conic, and cuboid lesions were created on the trochlear ridge. Five different meniscal tear configurations were created. A total of 107 lesions of the trochlear ridge and 103 lesions of the meniscus were created. 3D ultrasonography was performed in a waterbath, using a 7.5 MHz 3D scanner. Trochlea...
Repair of sinocutaneous fistulae in two horses. Chronic facial defects extending into the sinuses of two mares were repaired using periosteal flaps. Partial osseous bridging was established over the defects following repair. Previous attempts to close the defects with skin alone had failed. A periosteal flap is a simple surgical technique that provides the foundations for successful repair, despite the chronicity of some fistulae.
Papillary renal adenoma of distal nephron differentiation in a horse. A 20-year-old thoroughbred mare had a mass in the right kidney. The mass was encapsulated with fibrous capsule and composed of variably-sized papillary projections lined by a single layer of flattened to cuboidal neoplastic epithelial cells with no cytological and nuclear atypia. Immunohistochemically, the neoplastic cells were broadly positive for cytokeratin AE1/AE3 and granular staining for alpha-1-antitrypsin was focally detected; this immunohistochemical property was similar to that of the normal distal nephron. From these results, this case was diagnosed as papillary renal adenoma of dis...
Evaluation of increased subchondral bone density in areas of contact in the metacarpophalangeal joint during joint loading in horses. To quantitatively evaluate contact area under 2 loads and subjectively compare contact areas with subchondral bone (SCB) density patterns in intact metacarpophalangeal joints of horses. Methods: 6 forelimbs from horses without musculoskeletal disease. Methods: Computed tomographic scans of intact metacarpophalangeal joints were analyzed to obtain SCB density measurements. Each limb was loaded on a materials testing system to 150 degrees and 120 degrees extension in the metacarpophalangeal joint, and the joint was stained via intra-articular injection with safranin-O or toluidine blue, respecti...
Congenital retrosternal (Morgagni) diaphragmatic hernias in three horses. 3 Horses were examined and treated because of sudden onset of signs of abdominal pain. Results: All horses had a retrosternal (Morgagni) hernia involving the right side of the diaphragm. In each horse, the large colon was incarcerated in a right muscular defect in the diaphragm with a large hernial sac. Results: Definitive surgical repair of the hernia was not performed during the initial celiotomy. The hernia was repaired with mesh herniorrhaphy, but without resection of the hernia sac in 2 horses. For 1 horse, conservative management was applied. In the 2 horses treated with surgical correct...
Subchondral bone density and cartilage degeneration patterns in osteoarthritic metacarpal condyles of horses. To evaluate and correlate patterns of subchondral bone density and articular cartilage degeneration (derived by use of gross, histologic, and computed tomographic [CT] examinations) in equine third metacarpal condyles with and without osteoarthritis. Methods: 8 metacarpophalangeal (MCP) joints (n = 4 horses) without osteoarthritis and 6 osteoarthritis-affected MCP joints (4). Methods: Horses were euthanized. The third metacarpal condyles of the joints were examined grossly and via CT (3 slice images/condyle). For 6 condylar zones, mean bone density and pattern of density distribution were dete...
Imaging features and decision making in retrobulbar neuroendocrine tumours in horses–case report and review of literature. A 25-year-old Haflinger gelding was evaluated for chronic-progressive unilateral exophthalmos. Ultrasonographic investigation and magnetic resonance (MR) imaging revealed a retrobulbar space-occupying mass to be the cause of eyeball displacement. Ultrasonographic features were not sufficient to specify the type and extension of the lesion. Magnetic resonance scans, however, clearly displayed an infiltrative intracranial growth pattern but sparing of orbital soft tissues. Based on MR appearance, tentative diagnosis of an orbital soft tissue neoplasia was made and subsequently confirmed by histo...
Immunocytochemical localization of lysozyme and beta-defensin in the apocrine glands of the equine scrotum. The present study revealed in detail the subcellular localization of lysozyme and beta-defensin in the apocrine glands of the equine scrotal skin, a specific body region. The apocrine glandular cells were equipped with a varying number of secretory granules, a well-developed Golgi apparatus and abundant cisternae of the rough endoplasmic reticulum within their cytoplasm. In these cells, reactive gold particles representing lysozyme were detectable in the secretory granules as well as the Golgi apparatus and elements of the rough endoplasmic reticulum. Additionally, the antimicrobial peptide gr...
Radiographic closure time of appendicular growth plates in the Icelandic horse. The Icelandic horse is a pristine breed of horse which has a pure gene pool established more than a thousand years ago, and is approximately the same size as living and extinct wild breeds of horses. This study was performed to compare the length of the skeletal growth period of the "primitive" Icelandic horse relative to that reported for large horse breeds developed over the recent centuries. This information would provide practical guidance to owners and veterinarians as to when the skeleton is mature enough to commence training, and would be potentially interesting to those scientists inve...
Volume effects on fatigue life of equine cortical bone. Materials, including bone, often fail due to loading in the presence of critical flaws. The relative amount, location, and interaction of these flaws within a stressed volume of material play a role in determining the failure properties of the structure. As materials are generally imperfect, larger volumes of material have higher probabilities of containing a flaw of critical size than do smaller volumes. Thus, larger volumes tend to fail at fewer cycles compared with smaller volumes when fatigue loaded to similar stress levels. A material is said to exhibit a volume effect if its failure prop...
An evidence-based assessment of the biomechanical effects of the common shoeing and farriery techniques. The first aim of this article is to review the progress made in the field of distal limb biomechanics. By understanding limb biomechanics, it is then possible to review the rationale behind a few of the more common techniques that veterinarians routinely use when treating their patients and to evaluate the evidence in support of them.
Tri-level surgical treatment of cervical spinal cord compression in a Thoroughbred yearling. A Thoroughbred yearling was presented with neurological, radiographic, and myelographic abnormalities consistent with cervical vertebral stenotic myelopathy. Surgical correction was performed by using ventral cervical interbody fusion at 3 intervertebral spaces. The patient recovered uneventfully from surgery. The neurological status remained unchanged initially; however, significant improvement was noted 37 weeks postoperatively. Un Thoroughbred d’un an a été présenté avec des anomalies neurologiques, radiographiques et myélographiques compatibles avec une myélopathie sténosée des ...
Evidence-based equine upper respiratory surgery. The purpose of this article is to review the veterinary literature for various surgical procedures of the equine upper respiratory tract in an effort to evaluate the evidence supporting various therapies. This article focuses on the therapeutic benefit from more widely occurring conditions, such as laryngeal hemiplegia, dorsal displacement of the soft palate, arytenoid chondritis, and epiglottic entrapment.
An evidence-based approach to clinical questions in the practice of equine neurology. The practice of equine neurology has special challenges posed by the size of the animal being examined. Many diagnostic procedures routinely used in small animal practice are unsafe when applied to the equine patient or unavailable to the equine practitioner. Therefore, astute observation is the mainstay of making a neuroanatomic diagnosis, and detailed evidence on the deficits present may be difficult to obtain. Because clinical observation can sometimes be ambiguous and somewhat subjective, it is even more important to approach equine neurology from an evidence-based point of view. Here, suc...
Preliminary anatomic investigation of three approaches to the equine cranium and brain for limited craniectomy procedures. To describe surgical approaches to the equine cranium and brain for limited craniectomy. Methods: Descriptive anatomic study. Methods: Equine cadavers (n=7). Methods: Head and neck sections from cadavers were used to establish techniques for exposing areas of the equine brain. Three basic approaches were used: rostrotentorial, suboccipital, and transfrontal. Techniques were adapted from small animal descriptions and modified to account for anatomic differences. Results: Descriptions of the rostrotentorial, suboccipital, and transfrontal approaches to the equine cranium and brain were defined. ...
