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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.
Effects of exercise on tenocyte cellularity and tenocyte nuclear morphology in immature and mature equine digital tendons. The injury-prone, energy-storing equine superficial digital flexor tendon (SDFT) of the mature performance horse has a limited ability to respond to exercise in contrast with the noninjury-prone, anatomically opposing common digital extensor tendon (CDET). Previous studies have indicated low levels of cellular activity in the mature SDFT, but in foal tendons the tenocytes may still have the ability to adapt positively to increased exercise. Objective: To measure tenocyte densities and types in histological sections from the SDFT and CDET of horses from controlled long-term, short-term and foal...
Ultrasound-guided periarticular injections of the sacroiliac region in horses: a cadaveric study. The traditional techniques for injection of the sacroiliac (SI) region are based on external landmarks. Because of the depth of the SI joint and pathological modifications, SI injections are sometimes challenging in horses. Objective: An ultrasound-guided techniques would allow placement of the needle without depending on external landmarks. Methods: Fourteen pelvic specimens were isolated from mature horses. A 20 cm bent spinal needle was positioned with ultrasonographic guidance under both iliac wings aiming for SI joints using 5 approaches: cranial, craniomedial, medial and 2 caudal approac...
Neuroanatomy of the equine dorsal cricoarytenoid muscle: surgical implications. Studies are required to define more accurately and completely the neuroanatomy of the equine dorsal cricoarytenoid muscle as a prerequisite for developing a neuroprosthesis for recurrent laryngeal neuropathy. Objective: To describe the anatomy, innervation, fibre types and function of the equine dorsal cricoarytenoid muscle. Methods: Thirty-one larynges were collected at necropsy from horses with no history of upper airway disease and 25 subjected to gross dissection. Thereafter, the following preparations were made on a subset of larynges: histochemical staining (n = 5), Sihler's and acetylch...
Radiographic, scintigraphic and magnetic resonance imaging findings in the palmar processes of the distal phalanx. Increased radiopharmaceutical uptake (IRU) in the palmar processes of the distal phalanx is recognised but its clinical significance has not been established. Objective: To investigate the relationship between radiographic, scintigraphic and MRI findings in the palmar processes of the distal phalanx. Objective: Increased radiopharmaceutical uptake in the palmar processes of the distal phalanx is associated with MRI abnormalities; IRU and MRI abnormalities are over-represented in lame limbs. Methods: Clinical data, radiographic, scintigraphic and MRI findings of 258 horses with unilateral or bi...
Review of genetic aspects of radiological alterations in the navicular bone of the horse. Navicular disease or podotrochlosis has long been known to cause forelimb lameness in horses. It had been proposed that the development of podotrochlosis has similarities to the human osteoarthritis (OA) complex. Alterations of the navicular bone can be made visible early in life only on the basis of radiographs. Reports on the prevalences of navicular disease indicate that radiological alterations in the navicular bone are present in different warmblood populations at frequencies of between 14.9% and 87.6%. Genetic factors play an important role in the development of the radiological signs. E...
Graded arrangement of collagen fibrils in the equine superficial digital flexor tendon. By using ultramorphological and biochemical methods, we analyzed the regional differences between the three parts of the equine superficial digital flexor tendon (SDFT), namely, the myotendinous junction (MTJ), middle metacarpal (mM), and osteotendinous junction (OTJ). Cross-sectional images showed unique distributions of collagen fibrils of varying diameters in each region. Small collagen fibrils (diameter 200 nm). In the mM region, the collagen fibrils were intermediately distributed between the MTJ and OTJ. The results indicate a graded arrangement of collagen fibrils in the tendon. Type V ...
In vitro evaluation of a single injection technique for diagnostic analgesia of the proximal suspensory ligament of the equine pelvic limb. To examine the anatomic relationship of the deep branch of the lateral plantar nerve (DBLPN) with structures of the proximal metatarsal region, and to define the anatomic location of a solution injected using a single injection technique for diagnostic analgesia of the proximal suspensory ligament (PSL). Methods: Descriptive study. Methods: Cadaveric equine pelvic limbs (n=29). Methods: The proximal metatarsal region of both pelvic limbs (n=5 horses, 10 limbs) was dissected and measurements were made of anatomic structures relative to the head of the 4th metatarsal bone (HMT4). A single inject...
Examination of the urinary tract in the horse. Pathologic conditions of the urinary tract may produce specific clinical signs, but they are more than likely to be nonspecific clinical signs, which often occur with chronic renal disease in addition to countless other diseases. Further, clinical signs that may seem to be directly related to the urinary tract may be the result of other systemic diseases. Thus, before embarking on diagnostics, it is important to obtain a thorough history and physical examination.
Essentials of equine renal and urinary tract physiology. Knowledge of urinary tract anatomy and the numerous functions of the kidney in regulating fluids, electrolytes, acid-base balance, and waste products improves the ability of the clinician to diagnose, treat, and make appropriate recommendations for the management of the horse with renal disease. Several conditions can directly or indirectly affect renal function on a temporary or permanent basis. Endogenous and exogenous compounds (eg, drugs, toxins, hemoglobin) alone or in combination with inappropriate renal blood flow can promote or exacerbate renal disease.
Development of an in vitro three dimensional loading-measurement system for long bone fixation under multiple loading conditions: a technical description. The purpose of this investigation was to design and verify the capabilities of an in vitro loading-measurement system that mimics in vivo unconstrained three dimensional (3D) relative motion between long bone ends, applies uniform load components over the entire length of a test specimen, and measures 3D relative motion between test segment ends to directly determine test segment construct stiffness free of errors due to potting-fixture-test machine finite stiffness.Intact equine cadaveric radius bones, which were subsequently osteotomized/ostectomized and instrumented with bone plates were su...
Ultrasonographic appearance of the lower urinary tract in fifteen normal horses. The purpose of this study was to describe the normal ultrasonographic appearance of the caudal portion of the equine ureters, pelvic urethra, and urinary bladder and to assess ureteral contractility. Fifteen horses with no evidence of urinary tract disease (five females, five intact males and five geldings) were studied. The lower urinary tract was evaluated ultrasonographically using a transrectal approach. The normal ultrasonographic appearance and anatomic location of structures of the lower urinary tract were evaluated and anatomic relationships described. Both ureters were identified dors...
Comparison of magnetic resonance contrast arthrography and arthroscopic anatomy of the equine palmar lateral outpouching of the middle carpal joint. The objective of this report was to provide an anatomic description of the equine palmar lateral outpouching of the middle carpal joint by comparing its arthroscopic and magnetic resonance (MR) contrast arthrography appearance and to define the structures within the palmar lateral outpouching of the middle carpal joint that can be assessed arthroscopically. MR contrast arthrography was performed on seven cadaveric limbs; images were compared with those obtained during arthroscopic exploration of the palmar lateral outpouching of the middle carpal joint. Gross dissection was performed to confir...
Comparison of gross and histopathologic findings with quantitative computed tomographic bone density in the distal third metacarpal bone of racehorses. Comparison of subchondral bone density determined by quantitative computed tomography (CT) with gross and histopathologic changes have not been made in horses. The goal of this study was to determine if mean quantitative CT density and mean voxel standard deviation are associated with the presence and severity of osteochondral lesions in the palmar aspect of the distal third metacarpal bone in racing horses. Metacarpophalangeal joints from nine racehorses were imaged using CT and scored for gross damage. Four-millimeter-thick sagittal and 30 degrees palmar dorsal plane sections were cut, decal...
Radiographic technique and anatomy of the equine sacroiliac region. Radiography is part of evaluating horses with poor performance and pelvic limb lameness; however, the radiographic appearance of the sacroiliac region is poorly described. The goal of the present study was to describe the use of a simple technique to obtain radiographs of the sacroiliac region in the anesthetized horse and to describe the radiographic appearance of this region. Seventy-nine horses underwent radiography of the pelvis under general anesthesia in dorsal recumbency. During a 5s exposure time the horse was actively ventilated to blur the abdominal viscera, which allowed assessment ...
Volume effects on yield strength of equine cortical bone. Volume effects are a fundamental determinant of structural failure. A material exhibits a volume effect if its failure properties are dependent on the specimen volume. Many brittle ceramics exhibit volume effects due to loading a structure in the presence of "critical" flaws. The number of flaws, their locations, and the effect of stress field within the stressed volume play a role in determining the structure's failure properties. Since real materials are imperfect, structures composed of large volumes of material have higher probabilities of containing a flaw than do small volumes. Consequen...
Determination and use of mechanical nociceptive thresholds of the thoracic limb to assess pain associated with induced osteoarthritis of the middle carpal joint in horses. To establish reference mechanical nociceptive threshold (MNT) values of the equine thoracic limb and to assess the use of MNT values to detect pain associated with induced osteoarthritis in the middle carpal joint. Methods: 24 adult horses. Methods: MNT values were evoked by a pressure algometer at 17 sites within each thoracic limb during 2 baseline sessions conducted an average of 5 days apart. Effects of age, sex, weight, and wither height on MNT values were assessed separately for each site. Tolerance of horses to the procedure was graded subjectively and correlated with MNT values. Synovi...
Comparison of insertion characteristics of two types of hydroxyapatite-coated and uncoated positive profile transfixation pins in the third metacarpal bone of horses. To determine the effect of 2 hydroxyapatite pin coatings on heat generated at the bone-pin interface and torque required for insertion of transfixation pins into cadaveric equine third metacarpal bone. Methods: Third metacarpal bone pairs from 27 cadavers of adult horses. Methods: Peak temperature of the bone at the cis-cortex and the hardware and pin at the trans-cortex was measured during insertion of a plasma-sprayed hydroxyapatite (PSHA)-coated, biomimetic hydroxyapatite (BMHA)-coated, or uncoated large animal transfixation pin. End-insertional torque was measured for each pin. The bone-pi...
Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 1: the soft tissues. The equine tarsus is the most commonly affected hindlimb region associated with lameness. Diagnostic imaging is routinely applied but because of its complexity, being composed of 10 multifaceted bones and different joints, multiple ligaments, tendons and bursae, imaging this region can be a challenge. This is the first part of a two-part review of the structures and disorders of the equine tarsus. It describes the principal disorders affecting the soft tissues of the tarsal region and addresses some of the technical aspects in taking radiographic, ultrasonographic and scintigraphic images of t...
Retrobulbar dermoid cyst in a horse: a case report. A 4-year-old Andalusian horse was presented for examination following a 3-month history of exophthalmos of the right eye and a soft swelling of the right supraorbital fossa noted after blunt head trauma. Ultrasonographic examination of the swelling showed an anecogenic mass of 5 cm in diameter involving the retrobulbar space. Centesis of the mass through the supraorbital fossa was performed and yielded a serous fluid with 7.2 g/dL of total protein and density of 1040. No cells were seen in the sample. A tentative diagnosis of cyst was made. The cyst was surgically removed and the definitive hi...
Neuropathic changes in equine laminitis pain. Laminitis is a common debilitating disease in horses that involves painful disruption of the lamellar dermo-epidermal junction within the hoof. This condition is often refractory to conventional anti-inflammatory analgesia and results in unremitting pain, which in severe cases requires euthanasia. The mechanisms underlying pain in laminitis were investigated using quantification of behavioural pain indicators in conjunction with histological studies of peripheral nerves innervating the hoof. Laminitic horses displayed consistently altered or abnormal behaviours such as increased forelimb lifti...
Calcified tumours of the paranasal sinuses in three horses. Three horses, a 10-year-old Thoroughbred mare, a 9-year-old Thoroughbred gelding and a 6-year-old Arab gelding, with calcified tumours of the paranasal sinuses, are described. All horses presented with purulent nasal discharges and facial distortion. Exophthalmos, blepharospasm and ocular discharge were also a feature in individual horses. A presumptive diagnosis of a calcified tumour was made on the basis of clinical signs and radiographic and endoscopic findings. The tumours ranged from 15 to 25 cm in diameter. A large frontonasal bone flap was used to expose the tumours, which were cleaved ...
Immunohistochemical detection of matrix metalloproteinase-1 in the periodontal ligament of equine cheek teeth. The hypsodont equine cheek tooth erupts continuously throughout life. The collagen fibers of the periodontal ligament (PDL) have to remodel constantly to allow the tooth to move in an occlusal direction. Remodeling of the collagen fiber bundles needs to be well-coordinated in order to maintain functional tooth support. The aim of this study was to examine the role of matrix metalloproteinase-1 (MMP-1) in the collagen remodeling of the equine PDL under physiological conditions. Specimens containing the PDL interposed between the dental cementum and the alveolar bone were taken from nine Warmblo...
Comparative study of fibrillar collagen arrangement in the corneas of primates and other mammals. This study is a comparative study of the relationship between corneal structure, morphology, and function in a range of mammalian species. X-ray scattering patterns were gathered at regular spatial intervals over the excised cornea (and in most cases also the scleral rim) of humans, marmosets, horses, cows, pigs, rabbits, and mice. All patterns were analyzed to produce quantitative information regarding the predominant orientation of fibrillar collagen throughout the tissue. The predominant direction of corneal collagen varies between mammals. This variation is not related to the size, shape, ...
Detection of fibrin deposits in horse tissues by immunohistochemistry. Histochemical and immunohistochemical techniques have been used to detect fibrin deposits in different tissues in humans and experimental animal models with disseminated intravascular coagulation (DIC). Fibrin deposits also have been observed in horses with severe ischemic and inflammatory disorders by histochemical stainings (phosphotungstic acid hematoxylin [PTAH]). Objective: Immunohistochemical (IHC) methods can be used to accurately detect fibrin deposits in horses at risk of DIC. Methods: Tissue-organ samples collected on postmortem examination from 87 horses with severe inflammatory and...
Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 2: bony disorders. This is the second part of a two-part review of the structures and disorders of the equine tarsus. In this part the bones of the tarsal region are considered and the technical aspects of taking radiographic, ultrasonographic and scintigraphic images of the different lesions are addressed. The diagnostic use of arthroscopy, computed tomography and magnetic resonance are discussed. In current clinical practice the most frequently used combination to arrive at a diagnosis is still radiography and ultrasonography.
Surgical management and outcome of a type-III Salter-Harris fracture of the frontal plane of the distal radial physis in a foal. A 4-week-old Thoroughbred filly presented with lameness of acute, severe onset of the left foreleg (LF) of 3 days' duration. Results: Diffuse swelling was present around the distal radius and carpus of the LF. Carpal varus that could be reduced manually was present. Radiographs revealed an intra- articular frontal-plane fracture in the distal radial epiphysis, which continued cranially through the distal radial physis (DRP). The lateral aspect of the DRP was wider than expected. Latero-medial carpal instability was resolved by placement of a lag screw from the dorsal midline through the epiphy...
