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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.
Femoral fracture repair complicated by vascular injury in a foal. A comminuted, mid-diaphyseal femoral fracture was diagnosed radiographically in a 4-month-old Quarter Horse colt. Disruption of the distal blood supply was suspected, as evidenced by coolness and diminished pulses of the distal portion of the limb. The fracture was repaired by compression plating but the foal's condition continued to deteriorate. A femoral arteriogram of the affected limb was obtained. Positive contrast agent was visible only as far as the mid-shaft of the femur. The foal was euthanatized and the postmortem examination revealed a transected popliteal artery accounting for isch...
Characterization of intrauterine mobility of the early equine conceptus. Intrauterine mobility patterns of the embryonic vesicle were characterized on Days 9 to 17 after ovulation in pony mares using real-time ultrasonography (n=5 or 7 mares per day). The location of the vesicle was determined by dividing the uterus into right horn, left horn, and body. Each uterine horn was further divided into three approximately equal portions (cranial third, middle third, caudal third), yielding seven segments (body plus three portions of each horn). Location of the vesicle within the uterus was recorded every five minutes for two consecutive hours (25 location determinations p...
Papillomas and squamous cell carcinomas of horses. In a retrospective study encompassing 13 years of diagnostic work, papillomas and squamous cell carcinomas from horses were screened for papilloma-virus antigens, using the peroxidase-antiperoxidase technique. Papillomas were most commonly found on the penis and vulva, followed by cutaneous, ocular, and oral locations. Squamous cell carcinomas were most frequently located on the third eyelid and cornea, followed by genital, oral, maxillary sinus, and cutaneous sites. Papillomavirus structural antigens were detected in 7 cutaneous and 5 genital papillomas, but not in squamous cell carcinomas.
Chondrosarcoma in the radius of a horse. An aged Thoroughbred stallion was examined because of progressive lameness, carpal swelling, and weight loss. Radiography revealed a destructive lesion in the caudomedial, distal portion of the radius. Chondrosarcoma was diagnosed by tumor-core biopsy. Gross and histologic evaluation of the neoplasm after necropsy revealed a locally invasive chondrosarcoma at the distal end of the radius that infiltrated the radiocarpal joint capsule and invaded the carpal bones. The malignant nature of this tumor was evident by its invasiveness and histologic features of cell pleomorphism and presence of mito...
Observations on structure and function of the equine mitral valve. The anatomy of the equine mitral valve and certain variations observed in 60 adult horses are described. The functional role of this valve, sited between the left atrium and the high pressure-generating left ventricle, is discussed in relation to its anatomical structure. A method of examining the left side of the heart post mortem is described.
Hypoplastic left ventricular syndrome in a foal. A necropsy diagnosis of hypoplastic left ventricular syndrome was made in a day-old foal. The cardiac abnormalities included mitral and aortic valve atresia, patent ductus arteriosus, and a secundum atrial septal defect. The left ventricle was hypoplastic and nonfunctional. The brief survival of the foal was a consequence of left-to-right shunting through the atrial septal defect and right-to-left shunting through the patent ductus. The information is presented to demonstrate the existence of the syndrome as a congenital defect in the horse and to clarify the necropsy findings for the practiti...
Radiological investigations of osteochondrosis dissecans in Standardbred Trotters and Swedish Warmblood horses. A total of 106 Standardbred Trotters and 27 Swedish Warmblood horses, with a radiological diagnosis of osteochondrosis dissecans, were studied over a six year period. The majority were young horses. No statistical difference in frequency between the sexes was demonstrated. In both breeds osteochondrosis was most common in the hock joints, the site of predilection being the distal dorsal tip of the intermediate tibial ridge. On radiographs the lesions of the hock joints were graded on a scale from 0 to 5 according to size, number and localisation of defects and visible loose bodies. The sizes o...
Aetiology and pathogenesis of congenital torticollis and head scoliosis in the equine foetus. In 214 cases of severe dystocia in mares, of which 141 (66 per cent) were Draught horses, deviation of the head and neck, with or without torticollis, malformed head and limbs were found to be the cause of dystocia. No evidence of a genetic lethal factor was found and torticollis was often combined with scoliosis of the head and, frequently, with malformation of one or more limbs. This is considered evidence of a common aetiology and pathogenesis of the syndrome of malformation. The malformations were found to be associated with an increased incidence of caudal and, particularly, transverse pr...
Purchase examinations for performance horses. Performance horses should be thoroughly examined before sale to detect any defects that could render them unsuitable for the purchaser's intended use. With the horse in its stall, the eyes, nasolacrimal puncta, external ear canals and mouth are examined, the rectal temperature measured and the heart, lungs, trachea and sinuses auscultated. Moving the horse out of the stall, the head, parotid glands, mandibular lymph nodes, larynx, neck muscles, jugular veins and cervical vertebrae are inspected. The scapula, point of the shoulder, withers, tuber sacrale and point of the hip are palpated, after...
Ventral approach for stabilization of atlantoaxial subluxation secondary to odontoid fracture in a foal. Atlantoaxial subluxation secondary to odontoid fracture in a 30-day-old foal was corrected by alignment of the atlantoaxial joint and stabilization with 2 ventrally placed dynamic compression plates. At 90 days after surgery, healing of the fracture, with adequate alignment of the atlantoaxial joint, was confirmed radiographically. The foal was only slightly tetraparetic at that time. At 1 year after surgery, the gait was normal. It was concluded that the technique has advantages over the use of Steinmann's pins or external coaptation for stabilization. The ventral approach allows decompressio...
Relationship between intervertebral joint morphology and mobility in the equine thoracolumbar spine. The anatomical features of 21 equine thoracolumbar spines, obtained from horses with clinically normal backs, were examined and the results compared with recent data on the mobility of the joint complexes of the horse's spine. The thoracolumbar spine can be divided into four regions based upon the morphology of the joint complexes: the first thoracic intervertebral joint (T1-2), the cranial and mid thoracic region (T2-T16), the caudal thoracic and lumbar region (T16-L6) and the lumbosacral joint. The mobility of the intervertebral joints in each of these regions can be related to their morphol...
Congenital phalangeal hypoplasia in Equidae. Three cases of unilateral congenital phalangeal hypoplasia are described in 2 horses and 1 mule. Radiographic lesions include severe hypoplasia of the 3rd phalanx, and associated hypoplasia of the 2nd phalanx in 2 cases, and hypoplasia or aplasia of the navicular bone in 2 cases. All animals could ambulate but were lame. Two cases had palpable laxity at the level of the coronary band. Documented etiology was not determined for the dysgenesis, but possibilities include inherited transmission or an environmental teratogen.
The regulatory peptide system of the large bowel in equine grass sickness. In recent years, distinct changes in regulatory peptides have been found in a number of gastrointestinal diseases. Grass sickness is a fatal disease of horses for which the etiology has yet to be fully ascertained. In this study, the peptide-containing nerves and ganglionic and mucosal endocrine cells of the ileum, colon and rectum were investigated in horses with sub-acute or chronic grass sickness and compared with normal controls using immunocytochemistry, at both the light and electron microscopical levels, and radioimmunoassay. A substantial loss of both peptide-containing cells and nerve...
Topographic distribution of pulmonary ventilation and perfusion in the horse. The regional distribution of ventilation to perfusion ratios (VA/Q) in the lungs of 8 healthy standing Thoroughbred geldings (4.4 +/- 1.5 years, 465.7 +/- 46.6 kg) was studied, using steady-state inhalation and IV infusion of the radioactive gas krypton-81m. The VA/Q was uniformly distributed within a vertical lung strip centered over the 9th rib on the right side. Ventilation per unit of alveolar volume (V/VA) assessed from the clearance of inhaled radioactive gas in 5 horses increased from 0.49 +/- 0.13 (arbitrary units) in nondependent lung zones to 1.45 +/- 0.16 in dependent lung zones. Se...
Quantitative analysis of long-bone growth in the horse. Long-bone growth at the distal ends of the radial bones, the distal ends of the 3rd metacarpal bones, the distal ends of the 3rd metatarsal bones, and the proximal ends of the proximal phalangeal bones (of thoracic and pelvic limbs) was quantitatively analyzed in 9 Thoroughbred-Quarter Horse foals from birth to 2 years of age. Metal growth markers were surgically implanted in the bones of the animals at 2 to 4 days of age. Radiographs of the bones were made on the day of surgical manipulation, the next day, and then once a week for 8 months, and once a month thereafter for an additional 18 mon...
The distribution and origin of a novel brain peptide, neuropeptide Y, in the spinal cord of several mammals. The distribution of neuropeptide Y [NPY]-immunoreactive material was examined in the spinal cord and dorsal root ganglia of rat, guinea-pig, cat, marmoset, and horse. Considerable concentrations of NPY and similar distribution patterns of immunoreactive nerve fibres were found in the spinal cord of all species investigated. The dorsal root ganglia of the cat and the horse contained numerous immunoreactive nerve fibres, but in these species, as in the other three studied [rat, guinea-pig, marmoset], no positively stained cell bodies were found. Neuropeptide Y-immunoreactive nerves were observed...
Anatomy of the tarsal tendons of the equine tibialis cranialis and peroneus tertius muscles. Tendons of insertion of the equine tibialis cranialis muscle and peroneus tertius muscle (PT) were dissected grossly. Precise areas of tendon attachment and fiber arrangements within the tendons were described for the dorsal and medial tendons of the tibialis cranialis, and for the superficial lateral, deep lateral, dorsal, and medial tendons of the PT. Direct attachment of the dorsal and medial tendons of the PT into the periosteum of the central and 3rd tarsal bones and the 3rd metatarsal bone indicates that the PT may be involved in the pathogenesis of hock lamenesses.
Angiography of the corpus cavernosum penis in the pony stallion during erection and quiescence. Serial arteriography was used to determine the vascular pattern and blood flow in the penis of the pony stallion. Ponies were anesthetized with pentobarbital sodium, and catheters were surgically introduced into the internal pudendal and obturator arteries. The vascular anatomy was visualized by angiography via image-intensified fluoroscopy and was recorded on 70-mm film at 3 frames/s or by direct radiography. Blood flow into the corpus cavernosum penis (CCP) was limited during quiescence because the blood was immediately shunted into the venous system. After vasodilation with mild stimulation...
Midsagittal intraarticular fracture of the third phalanx in a colt. A 6-month-old Quarter Horse colt, with severe left foreleg lameness of 6 weeks' duration, had swelling of the distal interphalangeal joint and a smaller-than-normal left front foot. Radiographs revealed a nondisplaced, midsagittal, intraarticular fracture of P3, which was treated with an eggbar shoe with 2 quarter clips, and stall rest for 10 weeks. The colt was sound after 10 weeks.
