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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.
The distribution of inhibited early third stage Cyathostominae larvae in the large intestine of the horse. The distribution of inhibited early third stage Cyathostominae larvae in different parts of the large intestine of the horse was studied in 20 Shetland ponies necropsied in autumn 1982, 1983 and 1984. The location of the larvae in the large intestinal wall was studied by histological examination of the intestines of the eight ponies from 1984. Inhibited larvae were located predominantly and more or less equally in the caecum and the ventral colon. Generally fewer early L3 were in the dorsal colon. In 1984 a considerable proportion (mean 17%, range 9.7-36.9%) of the inhibited larvae was found i...
[Frontal sinusitis in a horse with a neurological complication]. The case of a horse affected with frontal sinusitis, in which neurological complications occurred following trepanation, is reported. The previous history of the animal as well as the clinical, radiological and pathological findings are discussed.
Morphologic features of the cervical intervertebral disks and adjacent vertebral bodies of horses. The intervertebral disks and adjacent vertebral bodies of the 2nd to 7th cervical vertebrae from 17 horses (3 months to 19 years of age) were examined grossly and by light microscopy. In each specimen, the disk tissue was fibrocartilagenous centrally and became more fibrous peripherally, but without a distinct demarcation between the nucleus pulposus and anulus fibrosus. Demarcation between the anulus fibrosus and the dorsal longitudinal ligament was not apparent. With increasing age of the horses, cellularity of the central fibrocartilagenous portion of the disk decreased. The caudal end plat...
In vitro mechanical properties of equine tendons in relation to cross-sectional area and collagen content. The mechanical properties of the deep digital flexor tendon (DDFT), the superficial digital flexor tendon (SDFT) and the suspensory ligament (SL) of the hindlimb of the horse were studied in vitro. The tendons were observed at several morphologically distinct sites. The loaded tendon is homogeneously strained, in spite of large variations in cross-sectional area. Consequently the modulus of elasticity was inversely proportional to the corresponding cross-sectional area and ranged from 738 MPa (megaPascal, N mm-2) to 1398 MPa within the DDFT, from 1000 MPa to 1282 MPa within the SDFT and from 5...
Interpreting radiographs 6: Radiology of the equine head (Part 2). The value of radiology as part of an examination of the equine head is emphasised and the radiological appearances of more commonly occurring conditions are described. Even the normal anatomy of this complex site is subject to great variation and the aspiring radiologist should, therefore, have a good knowledge of the possible normal variations. A flexible approach must be used rather than a limitation to one or two ritual projections. The use of contrast media, wherever it might be useful, is advocated so that the maximum amount of information may be obtained from each examination. Finally, e...
Preliminary studies on long distance, retrograde transport of horseradish peroxidase in equine peripheral nerves. As a prelude to studies on retrograde axonal transport of neurotoxin (ie, so-called suicide transport) as a means to prevent post neurectomy neuroma formation, preliminary studies were conducted with an innocuous enzymatic marker, horseradish peroxidase (HRP). The proximal stumps of resected medial and lateral palmar digital nerves in six ponies were injected via a tuberculin syringe and needle with 50 micron 1 of a 30 per cent solution of HRP in order to assess long distance retrograde axonal transport. The dorsal root ganglion of the cervical spinal enlargement (ie, C6, C7, C8, T1, T2) were ...
Echocardiographic detection of ventricular septal defects in large animals. Ventricular septal defects in a foal, a 2-year-old filly, and 2 calves were demonstrated with M-mode and two-dimensional real-time echocardiography. The studies were performed with the animals unsedated, either standing or in lateral recumbency. Cardiac windows were located between the 4th and 7th intercostal spaces, approximately at the level of the olecranon. In each case, the septal defect was visualized high in the membranous portion of the interventricular septum. Defects were visualized by use of sector scanning or linear-array ultrasonic equipment, with transducer frequencies of 2.25 to...
Effects of estrous cycle and season on ultrasonic uterine anatomy in mares. The morphological changes in ultrasound images of the uterus at various times of the year were characterized in nonbred mares, using a linear-array scanner. The uterus was recorded as having an ultrasonic morphology characteristic of diestrus (uterine score 1, endometrial folds not visible), estrus (score 3, distinct endometrial folds), or an intermediate stage (score 2). In Experiment I, uterine scores for the first ovulatory period of the year were compared to scores for the second period in 23 pony mares. More mares (P<0.05) showed endometrial folding prior to the second ovulation of the...
Pudendal and caudal rectal nerve blocks in the horse – An anesthetic procedure for reproductive surgery. The pudendal and caudal rectal nerves in four male and five female adult crossbred horses were anesthetized with a local solution. The injection site was located at the foramen for the caudal gluteal artery and vein in the sacrosciatic ligament. Twenty milliliters of local anesthetic solution were injected via a 15-cm, 18-gauge needle. Quantitative data on anesthesia were determined from these injections. Dye was injected with the anesthetic in four additional horses so that accurate placement of the solution could be determined at postmortem examination. Satisfactory anesthesia of the anus, p...
Arthroscopic anatomy of the intercarpal and radiocarpal joints of the horse. Arthroscopic anatomy of the equine intercarpal and radiocarpal joints was documented in six cadaver limbs and on observations made during surgical treatment of horses with carpal osteochondral fractures. Instrument positions and arthroscopic visualisation were recorded. The cadaver limbs were dissected and iatrogenic lesions recorded. A single arthroscopic portal examination was adequate in both joints; however, a second arthroscopic portal improved visualisation. The intercarpal joint was more easily examined than the radiocarpal joint because of anatomical differences. Iatrogenic lesions wer...
Role of hilar nerve afferents in hyperpnea of exercise. The objective of this study was to determine the role of hilar nerve (lung vagal) afferents in the hyperpnea of exercise. Ten ponies were studied before and 2-4 wk and 3-12 mo after sectioning only the hilar branches of the vagus nerves (HND). After HND, lung volume feedback to the medullary centers was attenuated as indicated in the anesthetized state by 1) attenuation or absence of the Hering-Breuer inflation reflex (P less than 0.01) and 2) attenuation of the lengthened inspiratory time (TI) when the airway was occluded at end expiration (P less than 0.01). Moreover, after HND in the awake ...
Periosteal transection of the proximal phalanx in foals with angular limb deformities of the metacarpo/metatarsophalangeal area. Bilateral angular limb deformities of the metacarpo/metatarsophalangeal regions in 2 foals are discussed. Periosteal transection was used to correct the deformity in both foals. In one foal, only the right forelimb was treated because the deformity in the left forelimb did not appear to warrant surgery. Subsequently, an angular limb deformity, which could have been prevented, developed in the left forelimb. A third foal developed a deformity in the proximal phalanx after periosteal transection of the distal third metatarsal bone.
In vivo bone strain in the equine tibia before and after transection of the peroneus tertius muscle. The present study was undertaken to determine the influence of the peroneus tertius muscle on the loading regime of the tibia in the horse. Strain gauge rosettes were bonded to the cranial and caudal cortices of the left and right tibiae in six Shetland ponies. In vivo bone strain recordings were made before and after unilateral transection of the peroneus tertius muscle. Relatively large individual variations in response to transection were observed in both the experimental and the contralateral control limbs. The principal strain values on the cranial and caudal cortices increased during the...
Comparison of echocardiographic and autopsy measurements of cardiac dimensions in the horse. This study was initiated to determine the accuracy of M-mode echocardiography in measuring left ventricular dimensions and estimating heart weights in horses. Left ventricular free wall and interventricular septal thickness and left ventricular external and internal diameters were measured and heart weights estimated from the echocardiograms of 47 horses. Autopsy measurements of the same parameters were then recorded. Statistical comparison of the data demonstrated: (1) Systolic measurements of wall thickness more closely resembled the heart in death than the diastolic measurements; (2) good c...
Diagnostic radiology and nuclear cardiology. Their use in assessment of equine cardiovascular disease. Survey thoracic radiography, although limited by physical considerations in the adult horse, can supply clinically useful information about changes in cardiac size and function. The radiographic features of cardiomegaly, altered pulmonary circulation, pulmonary edema, and pleural effusion as manifested in the horse are discussed. Nuclear cardiology can be performed in the standing horse. The initial transit of a radioactive tracer through the central circulation provides information about cardiac chamber size, efficiency of ventricular contraction, valvular competence, and presence of intracar...
Use of cancellous bone graft in treatment of navicular bone osteomyelitis in a foal. A 3-month-old Quarter Horse filly stepped on a fence staple and developed navicular bone osteomyelitis of the right hindfoot. A 1.5-cm spherical portion of medullary cavity containing purulent material was debrided and flushed with 0.9% NaCl solution. Cancellous bone was collected from a caudal sternebra and placed into the defect. The solar defect had filled with granulation tissue and was epithelialized 6 weeks after surgery. At 6-month follow-up evaluation, the navicular bone defect had healed and the foal was sound on the limb. Cancellous bone grafting may have merit for the treatment of n...
Pathogenesis of helminths in equines. This review summarizes information on the clinical signs, gross and microscopic lesions associated with nematode and cestode infections and discusses the development of these conditions in the equine host.
Arterial thrombosis as the cause of lameness in a foal. A 3-day-old foal was examined because of forelimb lameness. Brachial artery occlusion was diagnosed. The foal was euthanatized. Necropsy revealed brachial artery thrombosis and an atrial septal defect.
Periosteal transection and stripping for treatment of angular limb deformities in foals: radiographic observations. Radiographs of 23 foals (35 forelimbs) with carpal region angular limb deformities, which later were corrected by hemicircumferential transection of the periosteum and periosteal stripping, were evaluated as to geometric and morphologic abnormalities. Geometric evaluation included deviation angle and deviation pivot point. Morphologic abnormalities were categorized as: asymmetric width of the distal radial physis; asymmetric width of the distal radial epiphysis; carpal bone collapse or fracture; carpal bone hypoplasia; carpal bone displacement; and metacarpal bone displacement. Fifty-seven per...
Ultrastructural variations in the sweat glands of anhidrotic horses. The ultrastructure of sweat glands from the skin of free sweating horses was compared with that of glands from anhidrotic cases. Evidence of atrophied and abnormal sweat glands in the anhidrotic horses indicates that the condition involves progressive failure of the glandular mechanism of sweat production.
Chronic eosinophilic dermatitis: a manifestation of a multisystemic, eosinophilic, epitheliotropic disease in five horses. A generalized, chronic, progressive, exfoliative dermatitis in five horses is described. Histologically, the lesion is characterized by a superficial and deep perivascular dermatitis which is eosinophil-rich with a marked lymphocytic and plasmacytic component, accompanied by marked acanthosis and hyperkeratosis. More severe cases progress to a lichenoid pattern with the same cellular composition with focal eosinophilic spongiosis and eosinophilic subcorneal pustules. Clinically, the disease is associated with chronic, severe weight loss and is fulminating. The skin lesions are accompanied by l...
Fracture of the greater tubercle of the humerus in a filly. A fracture of the caudal portion of the greater tubercle of the humerus was diagnosed in a 16-month-old Thoroughbred filly. Initially the fracture caused severe lameness. Radiography of the affected shoulder revealed the fracture fragment to be extra-articular, with a surrounding bony callus and no evidence of joint disease. After 5 weeks rest in a stall and 11 months at pasture, the filly was trained and raced without lameness.
Muscle fibre variation in the gluteus medius of the horse. The gluteus medius of two killed Thoroughbred horses were sampled along the muscle and across the muscle at four different depths. The distribution of fibre types in these two horses was assessed by staining cross sections of the muscle sample for ATPase. A non-uniform distribution of fibre types was found within the gluteus medius in both horses and there was a significant increase in percentage of slow twitch (ST) fibres from the surface to the deeper regions of the muscle. The rate of increase, however, depended on the individual site along the muscle. Averages ranges from a low of 2.4 per ...
Occipitoatlantoaxial malformation in two non-Arabian horses. Occipitoatlantoaxial malformation was diagnosed in a 19-month-old mare of Appaloosa breeding and in a 3-year-old Quarter Horse gelding. Both horses had abnormal head and neck carriage since birth, but neurologic deficits did not become evident clinically until the horses reached 2 and 3 years of age, respectively. Palpation and manipulation of the base of the skull and cervical area proved to be useful diagnostically. Movement could not be elicited at the atlantooccipital joint but, in comparison with clinically normal horses, the range of dorsoventral motion at the atlantoaxial joint was incr...
Case of quadrilateral flexural contracture in a 10-year-old pony. The management of a case of quadrilateral flexural contracture in a 10-year-old pony is described. The animal was restored to normal appearance and function through a combination of surgical desmotomy and management techniques; the importance of analgesia and exercise as adjuncts to surgery is emphasised. The aetiology and pathogenesis of the condition in the immature animal and the adult is compared and a possible association is made between this condition and palmar fibromatosis (Dupuytren's contracture) occurring in man.
Effects of enterocentesis on peritoneal fluid constituents in the horse. Peritoneal fluid was collected from 15 clinically normal horses and was analyzed for nucleated cell (NC) counts and specific gravity. Six horses (controls, group 1) were subjected to abdominocentesis only, with a teat cannula, every 24 hours for 5 days. There were no marked changes in the peritoneal fluid of these horses over the 5-day period. Peritoneal fluid was collected from 6 other horses (group 2) with an 8.89-cm 18-gauge needle. The needle was then advanced until intestinal fluid was obtained. Peritoneal fluid was then collected with teat cannulas at 24-hour intervals for an additional ...
