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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.
Horner’s syndrome in the horse: a clinical, experimental and morphological study. A clinical case of Horner's syndrome is described in a Standardbred horse, and the various symptoms of cranial sympathetic denervation are studied in two ponies after experimental transection of the left cervical sympathetic trunk and vagosympathetic trunk, respectively. The most prominent symptoms of equine Horner's syndrome were ptosis, local sweating and increased cutaneous temperature in the denervated area. Enophthalmos, miosis and increased lacrimation were also observed but these symptoms were mild, variable and difficult to ascertain. Prolapse of the third eyelid was not noticed. Conco...
Histologic and ultrastructural studies of dermal sarcoma of walleye (Pisces: Stizostedion vitreum). Sixty-seven adult walleye fish were examined by light and transmission electron microscopy. The fish were affected by a mesenchymal tumor previously termed Walleye Dermal Sarcoma that commonly affects up to 27% of the population seasonally. Biopsies from 24 fish were collected, and complete postmortem examinations were performed on 43 fish. Grossly, the tumors had the appearance of randomly distributed, often clustered, spherical nodules, 2-5 mm in diameter with a smooth and often ulcerated surface. The tumors arose from the superficial surface of scales and consisted of fibroblast-like cells ...
Alteration in intestinal morphologic features associated with extensive large-colon resection in horses. Light microscopy, morphometry, and scanning electron microscopy were used to examine the mucosal morphologic features of 7 intestinal specimens (3 from the small intestine; 4 from the large intestine) from each of 8 horses 1 year after sham operation (group 1; n = 3) or extensive large-colon resection (group 2; n = 5). Qualitative light microscopic examination did not reveal differences between groups, but morphometry revealed significantly (P less than 0.05) greater intercrypt area and distance in horses with colon resection and this was most pronounced in the cecum and remaining right ventra...
Use of the forced oscillating airflow technique to measure the resistance of the equine upper airway: effects of laryngoventriculectomy and laryngoplasty. Investigations were carried out to determine whether measurements of total respiratory resistance (TRR) made in resting animals could detect changes due to laryngeal hemiplegia. Control values of TRR were obtained in eight ponies and in six of these the measurements were repeated after division of the left recurrent laryngeal nerve in the mid-cervical region; two were retained as controls. A further set of measurements were made before two of the operated animals were subjected to left laryngoventriculectomy (Hobday operation). A laryngoplasty ('tie-back' operation) was performed on another tw...
Atelectasis causes gas exchange impairment in the anaesthetised horse. The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the de...
Follow-up report of a case of surgical aphakia with an analysis of equine visual function. More work is necessary to establish corneal dimensions and retinal structure and neural organisation in the equine eye. This paper reports a case of surgical management of bilateral cataracts in a pony and the results of a survey of refractive error in normal horses. Aspects of accommodation are discussed. It is suggested that a difference in retinal receptor organisation between horse and human eyes could explain the good visual performance of the aphakic pony; and that the degree of blurring of vision in the aphakic situation is less, both in absolute terms and in proportion to presumed norm...
The morphology of the equine iridocorneal angle: a light and scanning electron microscopic study. The present investigation of 20 equine eyes shows that the iridocorneal angle of the horse is characterised by a very distinct pectinate ligament and a large ciliary cleft. The pectinate ligament consists of long and broad pigmented trabeculae which form a firm, flat and dense network that encircles the eye. On meridional sections, the ciliary cleft is visible as a wide triangular space comprising the trabecular meshwork which consists of two parts. The inner part is the larger and forms a three-dimensional network of large pigmented trabeculae with very wide intertrabecular spaces. The outer ...
Ten cases of bladder paralysis associated with sabulous urolithiasis in horses. Bladder paralysis and sabulous urolithiasis were diagnosed in 10 horses with urinary incontinence. Additional neurological deficits in the hindquarters were detected in five of them. Treatment by catheter drainage and bladder lavage was unsuccessful, and all the horses were destroyed within 14 months of presentation. Neuritis of the cauda equina was diagnosed post mortem in one horse, but the cause of the paralysis was not identified in the others, although radiography revealed abnormal lumbosacral vertebral angulation in one case.
Histochemical profile of articularis humeri muscle in the horse. In this study the histochemical fiber type analysis of the articularis humeri muscle of the horse was performed. This muscle is composed of type I and type IIA fibers. A large number of spindles has been observed and the presence of these receptors could help to understand the role played by this muscle.
Effects of clustered drill holes on the breaking strength of the equine third metacarpal bone. The breaking strength (stress at failure) of equine third metacarpal bones, with and without clustered drill holes, was determined in vitro. Paired ossa metacarpalia II-IV of 39 horses (n = 39) between 2 and 7 years old were tested in palmarodorsal 3-point bending. Four treatments were compared. Clustered 2.7- or 3.5-mm drill holes, in a 4- or 7-hole pattern, were made in the dorsal cortex of the distal diaphysis of the left third metacarpal bone. Undrilled right third metacarpi were used as controls. Bones with clustered drill holes failed by an oblique fracture through 1 or more drill holes,...
[Radiographic diagnosis of abdominal diseases in foals and ponys. II. Pathologic findings in 60 cases]. A diagnostic approach based on clinical and radiographic examinations for evaluation of young foals and small ponies with acute abdominal discomfort is presented. Standing right to left lateral abdominal radiographs were taken of 54 foals and 6 ponies using a previously described technique. Interpretation of the radiographs was in conjunction with all clinical and laboratory findings and patient management. Using this approach, the site and cause of acute abdominal discomfort could be diagnosed accurately in 55 of 60 (91%) patients as confirmed by clinical, surgical or necropsy findings. Typic...
Chronic proliferative synovitis of the equine metacarpophalangeal joint. Chronic proliferative synovitis of 27 metacarpophalangeal joints in 16 horses is described. The diagnosis was based on a history of lameness and, or, poor performance, pain on flexion of the metacarpophalangeal joint, the response to intra-articular anaesthesia, and plain and contrast radiography. Radiographic findings included concavity of the distal dorsal metacarpus proximal to the sagittal ridge, and an increase in size of the synovial tissue adjacent to the proximal, dorsal attachment of the joint capsule. Mineralisation of the synovial tissue was present in some joints, and chip fracture...
Endoscopy of the digital flexor tendon sheath in horses. An arthroscopic procedure for examination of the digital flexor tendons and tendon sheath was developed in 16 equine limbs and 12 horses. Distension of the tendon sheath and insertion of the arthroscope was accomplished through a cul-de-sac on the palmar or plantar surface of the tendon sheath 1 to 2 cm palmar or plantar to the digital neurovascular structures and between the annular ligament and proximal digital annular ligament. A single arthroscope entry point allowed examination of all regions of the tendon sheath cavity and most surfaces of the digital flexor tendons within the sheath. Di...
Equine synovial tendon sheaths and bursae: an histological and scanning electron microscopical study. The structure of equine synovial tendon sheaths and bursae has been examined by light and scanning electron microscopy. Tissue samples were obtained from horses of various types and ages with no clinical evidence of sheath or bursal disorders. The interior of both structures was lined by a cellular layer superimposed on a vascular zone supported by a fibrous layer. The pattern of cell distribution of the lining varied from site to site within the same structure depending on the nature of the underlying tissue and on the amount of movement to which the structure was subjected. The cellular laye...
Vascular response of the equine radius to cerclage devices. The arterial blood supply to the diaphysis of the radius, and the vascular reaction when three cerclage devices (cerclage wire, Parham-Martin band, and a partially contacting band) were applied 2 cm apart, were studied in six adult ponies. The opposite radial diaphysis served as the control. Ponies were euthanatized at weeks 4 and 8. A centrifugal blood flow pattern was demonstrated by microangiography. Larger numbers of medullary arteries exist in equine than in canine and human long bones. Changes in centrifugal blood supply were not identified beneath any of the cerclage devices.
High-resolution study of the three-dimensional structure of horse heart metmyoglobin. The three-dimensional structure of horse heart metmyoglobin has been refined to a final R-factor of 15.5% for all observed data in the 6.0 to 1.9 A resolution range. The final model consists of 1242 non-hydrogen protein atoms, 154 water molecules and one sulfate ion. This structure has nearly ideal bonding and bond angle geometry. A Luzzati plot of the variation in R-factor with resolution yields an estimated mean co-ordinate error of 0.18 A. An extensive analysis of the pattern of hydrogen bonds formed in horse heart metmyoglobin has been completed. Over 80% of the polypeptide chain is involv...
Identification of anatomic features of the equine clitoris as potential growth sites for Taylorella equigenitalis. A median clitoral sinus, as a space canalized from epithelial cells, was distinguishable developmentally in equine fetuses from 33-mm crown-rump length (CRL) to 500-mm CRL (including a mule of 21-mm CRL). In saggital sections of the clitoris of a 480-mm CRL fetus, indentations under the transverse frenular fold were identified as lateral sinuses of the clitoris. Unlike the median sinus, they were shallow; it therefore could not be anatomically substantiated that the lateral sinuses were of sufficient depth to support the growth of the partial anaerobe Taylorella equigenitalis, the organism of ...
Melanoma as a cause of spinal cord compression in two horses. Spinal cord compression by melanomas at C7-T1 is described in 2 horses. Despite similar location of the lesions, the onset of neurologic signs and clinical progression varied. Both horses were gray, but few cutaneous melanomas were found. Internal dissemination, however, was extensive in both horses. Antemortem diagnosis was made in one horse, and surgical decompression of the spinal cord was performed. Neoplasms of the vertebral canal and spinal cord are uncommon in horses. Melanoma in the spinal canal should be included in the differential diagnosis of neurologic disease, especially in matur...
The role of the reciprocal apparatus in the hind limb of the horse investigated by a modified CODA-3 opto-electronic kinematic analysis system. The function of the reciprocal apparatus in the hind limb of the horse was studied by kinematic gait analysis. For recording purposes a modified opto-electronic CODA-3 kinematic analysis system was used. The raw kinematic data were corrected for skin displacement artifacts by use of recently developed correction models. It was concluded that contradictory findings about the coupling of tarsal and stifle joints by the reciprocal apparatus, when comparing in vitro and in vivo studies, can be fully attributed to artifacts due to the movement of the skin markers over the underlying bony structures...
Staging equine seminiferous tubules by Nomarski optics in unstained histologic sections and in tubules mounted in toto to reveal the spermatogenic wave. Nomarski optics were used to identify stages of the spermatogenic cycle of seminiferous tubules in sectioned tissue or in whole dispersed tubules and to characterize the equine spermatogenic wave. Embedded tissues were sectioned at 20 microns. Whole dispersed tubules were obtained by enzymatic digestion of thin slices of fresh testis. Dispersed tubules were fixed, dehydrated in graded levels of alcohol, infiltrated with Epon, and mounted in toto on glass slides. Stages of the spermatogenic cycle could be identified under Nomarski optics in both histologic sections and tubules mounted in toto. ...
Quantification of skin displacement in the proximal parts of the limbs of the walking horse. Displacement of skin over the underlying skeletal structures in the proximal parts of the limbs was investigated in four walking Dutch Warmblood horses. Movement of the skin was visualised with self adhesive spot labels whereas that of the skeletal parts was visualised indirectly by means of a plastic strip connected to a transcutaneous Steinmann pin, driven into the bone of interest. Consistent results for all four horses were found. Individual and mean total displacements ranged from 1 to 4 cm (distal scapula) to 13 to 17 cm (caudal part of the greater trochanter of the femur). Displacements...
Accuracy of formulae for calculating left ventricular volumes of the equine heart. Echocardiography may be an accurate method of measuring left ventricular (LV) volumes and mass of the horse's heart. If so, studies of the heart size and hypertrophy would be possible. This study evaluated geometric models of the external and internal LV shapes, to determine which could be applied to echocardiographic measurements. We preserved 30 horses' hearts and measured their dimensions and cross sectional areas. These measurements were entered into seven formulae representing different geometric models of the ventricle and its chamber. We derived a correction factor to estimate the long ...
Ultrasonographic findings in horses with cholelithiasis: eight cases (1985-1987). Cholelithiasis and/or obstructive biliary tract disease was diagnosed ultrasonographically in 8 horses, 5 to 15 years old. Ultrasonographic findings revealed greater than normal amount of hepatic parenchyma in the right side of the abdomen in 8 horses and in the left side in 3 horses. The echogenicity of the liver was greater than normal, and thick distended bile ducts were seen in all horses. Choleliths were imaged ultrasonographically in 6 horses. Subsequently, postmortem findings in 6 horses revealed periportal and intralobular fibrosis, moderate bile duct dilatation, proliferation, and cho...
[X-ray diagnosis of abdominal diseases in foals and ponies. I. Technics and normal findings]. Clinical examination of foals and small ponies with abdominal disorders is limited by the inability to perform rectal palpation. In these patients, radiographic evaluation of the abdomen may contribute to the clinical diagnosis and may help to localize the site of abdominal diseases. The technique for lateral standing survey and contrast radiography of the abdomen in foals and the normal radiographic anatomy are described.
Identification of a free skin flap from the region vascularized by the deep circumflex iliac artery of horses. Areas of skin vascularized by large axial vessels potentially suitable for microvascular anastomosis were investigated in 10 horse cadavers. Eleven such areas were dissected, and the skin over the flank region vascularized by the deep circumflex iliac artery was most suitable. The anatomy of this area was further defined, using angiography and latex injection studies on 10 cadavers.
A surgical approach to the ramus of the mandible in cattle and horses. Case reports of a bull and a horse. A surgical approach to the ramus of the mandible was developed. Subperiosteal elevation of the masseter muscle from the ramus allowed reduction and plate fixation of ramus fractures in a bull and a horse. Results of follow-up examinations, 2 years after surgery, showed excellent functional and cosmetic results.
