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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 modulus of elasticity of equine hoof wall: implications for the mechanical function of the hoof. During normal weight-bearing and locomotion, the equine hoof wall deforms in a consistent pattern; the proximal dorsal wall rotates caudo-ventrally about the distal dorsal border and there is latero-medial flaring posteriorly. The aim of this study is to examine whether there are regional differences in the modulus of elasticity of hoof wall material and whether such differences correlate with the pattern of deformation which occurs in vivo. The modulus of elasticity of equine hoof wall was determined in tension and compression for samples from six forefeet. Samples were tested at the mid-poin...
Instrumentation and techniques for laparoscopic and thoracoscopic surgery in the horse. Equine surgery continues to benefit from advances in laparoscopic techniques. Descriptions of the normal anatomy of the standing horse and advances in instrumentation have improved our ability to perform laparoscopic surgery in both standing and dorsally recumbent horses. The common uses for laparoscopy are diagnostic laparoscopy, cryptorchidectomy, ovariectomy, and diagnostic thoracoscopy. Other reported uses include inguinal hernia repair, ruptured bladder repair, and ventral colopexy.
Structure of equine infectious anemia virus proteinase complexed with an inhibitor. Equine infectious anemia virus (EIAV), the causative agent of infectious anemia in horses, is a member of the lentiviral family. The virus-encoded proteinase (PR) processes viral polyproteins into functional molecules during replication and it also cleaves viral nucleocapsid protein during infection. The X-ray structure of a complex of the 154G mutant of EIAV PR with the inhibitor HBY-793 was solved at 1.8 A resolution and refined to a crystallographic R-factor of 0.136. The molecule is a dimer in which the monomers are related by a crystallographic twofold axis. Although both the enzyme and t...
Removal of the premaxillae and rostral portions of the maxillae of a horse. The incisive bones (premaxillae) and rostral portions of the maxillae of a horse were infected with dermatiaceous fungi causing phaeohyphomycosis. The pre-maxillae were exposed by creating and reflecting labial and palatal mucoperiosteal flaps, and obstetrical wire was used to remove the affected bones. Labial and palatal flaps were apposed in 2 layers, using absorbable sutures. The sutured wound healed without complication. The horse was able to prehend hay and long grass without difficulty, and the owner considered the horse's facial appearance to be nearly normal. This technique may be usef...
In vitro evaluation of four methods of attaching transfixation pins into a fiberglass cast for use in horses. To compare the axial stability provided by 4 methods of attaching transfixation pins into a fiberglass cast. Methods: Axial stability of 4 methods of transfixation pin attachment to a fiberglass cast cylinder was determined in vitro. Methods of attachment included simple incorporation of the pins into the cast, placement of a washer and nut on the pin and incorporation into the cast, extension of pins beyond the cast and attachment to a steel halo, and washers within the cast and attachment to a steel halo. Methods: A model was designed to simulate a transfixation cast applied to the equine me...
Radiological appearance of air introduced during equine regional limb anaesthesia. Twelve horses were injected intra-articularly into the metacarpophalangeal joint and extra-articularly in the region of the lateral palmar digital nerve with 1 ml air and local anaesthetic to simulate gas accidentally introduced during regional anaesthesia. Half the horses underwent limited exercise after which all horses were radiographed at 15 and 45 min and then every 24 h until all evidence of gas had disappeared. Intra-articular gas appeared as gas capped radiolucencies (GCR) in the proximal aspect of the joint. Extra-articular gas appeared as linear radiolucencies (LR) which initially te...
Ultrasonographic examination of the femorotibial articulation in horses: imaging of the cranial and caudal aspects. The aim of this study was to determine the normal ultrasonographic features of the cranial and caudal aspects of the femorotibial articulation and, in particular, to establish a method of examining the menisci, cruciate and meniscal ligaments ultrasonographically. Twenty hindlimbs isolated post mortem from 10 horses were used to study the normal ultrasonographic and gross anatomy of the femorotibial joint. Five stifles from 3 normal, live horses were also examined with B-mode, real-time ultrasound imaging. The results of the anatomical study are presented. The joint surfaces, menisci, cruciate...
Ionic mechanisms of Ca(2+)-dependent electrolyte transport across equine sweat gland epithelium. 1. The ionic mechanism involved in Ca(2+)-stimulated electrolyte transport in cultured equine sweat gland epithelial cells was studied using the short-circuit current (ISC) technique. 2. Microscopy revealed that the cultured cells grown on Millipore filters formed polarized monolayers with tight junctions. Monolayers exhibited a mean transepithelial resistance of 333.9 +/- 40.4 omega cm2. 3. Ca(2+)-mobilizing agents, A23187 (1 microM) or thapsigargin (0.01-1 microM), stimulated ISC while forskolin exerted little effect on the ISC. 4. Replacement of external Cl- by gluconate significantly reduc...
[Polydactyly in a foal–a case report]. Polydactylism, an excess deformity in a foal is described. The hereditary pathology and etiopathogenesis are discussed. A method of surgical correction of the deformed extremity is introduced. Indication and prognosis of the surgical correction of polydactylism and aspects concerning the breeding management are discussed.
Laparoscopic anatomy of the abdomen in dorsally recumbent horses. To provide an accurate and detailed description of the laparoscopic anatomy of the abdomen of horses positioned in dorsal recumbency and to compare those observations with laparoscopic anatomy of standing horses. The effects of laparoscopy and positional changes on arterial blood pressure and blood gas values also were investigated. Methods: Descriptive anatomic study. Methods: Laparoscopy was performed on 6 horses (2 mares, 2 geldings, and 2 stallions) to record the normal laparoscopic anatomy of the abdomen in dorsal recumbency. Methods: Feed was withheld from all horses for 36 hours. Horses...
Blue-cone horizontal cells in the retinae of horses and other equidae. The morphology of horizontal cells chiefly of the horse, but also of asses, mules, and a zebra, has been examined by Lucifer yellow injections into lightly fixed retinae and by immunocytochemistry. In common with other mammals, equids have a B-type horizontal cell, i.e., a cell with dendrites synapsing with cones and possessing a single axon synapsing with rods. Most mammalian retinae have a further type of horizontal cell, the A-type, also synapsing with cones but without an axon. The second type of horizontal cell in equids also has no axon; otherwise, it is most unusual. Compared with other...
Accessory ossification centres associated with osteochondral fragments in the extremities of horses. Fifty-six tarsocrural joints and 94 metatarsophalangeal joints were examined, at necropsy, from horses aged < or = 2 years. Osteochondral fragments at the cranial aspect of the intermediate ridge of the distal part of the tibia were seen in six horses, and at the proximoplantar aspect of the proximal phalanx in seven horses. Defects in the proximoplantar aspect of the proximal phalanx without osteochondral fragments were seen in a further two horses. Inflammatory and degenerative changes were not observed in any of the joints examined. From the incidence and natural course of these fragment...
Expression of types II, VI and X collagen in equine growth cartilage during development. The synthesis and expression of collagen types II, VI and X were investigated in growth cartilage selected from a group of 31 horses and ponies in the age range 157 days of gestation to 12 years. Collagen isolation, immunolocalisation and in situ hybridisation techniques were used in order to provide information on the pattern of synthesis of these 3 collagens during endochondral ossification in normal horses. Type II collagen immunoreactivity and mRNA expression was found in each of the 3 zones of growth cartilage chondrocytes in all samples studied, whereas the localisation of both collagen ...
Equine adenocarcinomas of the large intestine with osseous metaplasia. Large intestinal adenocarcinoma with osseous metaplasia was diagnosed in two horses, a 15-year-old standard bred gelding and a 9-year-old Haflinger mare. Clinically, both animals had displayed weight loss and anaemia. A presumptive diagnosis of abdominal neoplasia was made and the horses were humanely killed. At necropsy, the gelding and the mare were found to have ulcerated tumours growing into the lumen of the caecum and colon, respectively. In the mare, the mass extended through the mesocolon and was evident in the left dorsal and ventral colon. Histopathologically, the tumours consisted of...
Strain-rate-dependent mechanical properties of the equine hoof wall. The mechanical properties of fully hydrated equine hoof wall were examined at various loading rates in compact tension (CT) fracture, tensile and three-point bending dynamic tests to determine possible effects of hoof wall viscoelasticity on fracture toughness and tensile parameters. Four cross-head rates were used in CT tests: 1.7 x 10(-5), 1.7 x 10 (-3), 1.7 x 10(-2) and 2.5ms-1; four strain rates were used in tensile tests: 1.6 x 10(-3), 3.2 x 10(-2), 0.33 and 70s(-1). Speeds for the highest test rates were achieved using a large, custom-built impact pendulum. Bending test frequencies range...
Influence of chronic degenerative endometritis (endometrosis) on placental development in the mare. Placentation between 80 and 220 days of gestation was studied by measurement of fetal dimensions and gross, light and transmission and scanning electron microscopic examinations of the allantochorion and endometrium from 4 fertile mares with no, or very mild, endometrial histopathology and 6 subfertile Thoroughbred mares suffering varying degrees of age-related chronic degenerative endometritis (endometrosis). Spontaneously occurring twin gestation was observed in 3 animals. Several of the subfertile mares had endometrial cysts which showed 2 distinct features during pregnancy: those located n...
Characterization of bone mineral crystals in horse radius by small-angle X-ray scattering. The size and the orientation of the bone salt (mineral) crystals in the cranial and caudal zones in the transverse midshaft section of the equine radius were investigated by small-angle X-ray scattering (SAXS). The results are interpreted as indicating that the crystals had an elongated shape with an average thickness of T = 3.17 +/- 0. 15 nm in the caudal region and T = 3.79 +/- 0.20 nm in the cranial region. Their orientation was predominantly in the longitudinal direction of the bone. There was no preferential orientation within the transverse plane. The distribution of tilt angles with res...
Spinal accessory nerve biopsy as an ante mortem diagnostic test for equine motor neuron disease. The effectiveness of spinal accessory nerve branch biopsy evaluation as a means to confirm the diagnosis of equine motor neuron disease (EMND) was investigated. Sixteen horses with histories and clinical signs suggestive of EMND and 16 control horses with neither histories nor clinical signs of any neurological disorder, were subjects of the study. Biopsy samples of the ventral branch of the spinal accessory nerve were obtained either surgically, under general anaesthesia or post mortem immediately after euthanasia. Evaluation was done on the spinal cord of all horses to serve as the definitiv...
Transvaginal aspiration. This article describes in detail the procedures for collection of equine oocytes using a transvaginal ultrasound probe. Success in obtaining oocytes from humans, bovines, and horses are presented. The effect of repeated follicular aspiration of both cattle and horses is reviewed.
Immunohistolocalization of the carbonic anhydrase isoenzymes (CA-I, CA-II, and CA-III) in the reproductive tract of male horses. To elucidate locations of cytosolic carbonic anhydrase isoenzyme (CA-I, CA-II, and CA-III)-positive epithelial cells in equine male reproductive organs. Methods: Descriptive and immunohistochemical study. Methods: 4 clinically normal male horses. Methods: The testis (seminiferous tubules, rete tubules), epididymis (initial, middle, and terminal segments), proximal and distal portions of the ductus deferens, ampulla ductus deferentis, seminal vesicle, prostate, and bulbourethral gland were excised from euthanatized horses after administration of an overdose of pentobarbital. The tissue specimen...
Ageing horses by an examination of their incisor teeth: an (im)possible task? It is generally considered that the age of a horse can be determined by examining its incisor teeth. However, the criteria used to determine age from dental configurations differ widely. The existence of this variety of rules and guidelines was the challenge for the present examination. Detailed descriptions of the incisor teeth of 212 horses of registered age were recorded and the results were compared with the age criteria of various authors. The time at which teeth were shed and the appearance of dental stars seemed to be more reliable features than the disappearance of the cups. The disapp...
The zygomatic branch of the auriculopalpebral nerve: can it be normally palpated in the live horse? A detailed description is given of the methods to locate and palpate a subcutaneous part of the zygomatic branch of the auriculopalpebral nerve in 9 out of 10 adult horses examined. This permits the exact placing of local anaesthetic along the nerve branch at the described site, resulting in the akinesis of the m orbicularis oculi and the elimination of the blink reflex. This facilitates ophthalmologic examination and possible treatment of some eye conditions.
Surgical treatment of subchondral cyst-like lesions in the tibia of an adult pony. A 13 year-old pony was evaluated because of right hind limb lameness of acute onset. Radiographs of the right tarsus obtained shortly after the onset of lameness were normal, but results of nuclear scintigraphy were abnormal. Two radiolucent subchondral cyst-like lesions of the distal part of the tibia were seen on radiographs obtained 9 months later. The lesions were surgically decompressed, and the pony was sound 1 year later. It is hypothesized that a traumatic insult created a crack or split in the articular cartilage that allowed subsequent development of the cyst-like lesions.
Computed tomographic evaluation of head diseases in the horse: 15 cases. The rapid development of software and technology now allows a large amount of diagnostic information to be obtained from a computed tomographic examination. This imaging technique can also be usefully applied to the horse, given appropriate premises and a custom built table for accurate positioning. Computed tomography of the skull has considerable advantages over other techniques, as structures are viewed without superimposition. Fifteen cases are used to demonstrate how through high image quality (precise detail, reduction in artefacts) and objective measurement of density, various pathologi...
Similarities and differences in supporting and chromaffin cells in the mammalian adrenal medullae: an immunohistochemical study. The adrenal medulla is a typical paraganglion, having the same origin as the sympathetic ganglia, and contains at least two types of parenchymal cells: chromaffin cells and supporting cells. We previously reported that the extent of cellular association of chromaffin cells with supporting cells was remarkably higher in noradrenaline (NA)-than in adrenaline (A)-cell regions in the adrenal medullae of the rat and pig. Methods: Cryostat sections of adrenal medullae of nine mammalian species fixed with Zamboni fluid for 24 h were immunostained by ABC methods using antisera to S-100 protein and PNM...
Radiographic and arthroscopic findings associated with subchondral lucency of the distal radial carpal bone in 71 horses. Case records and radiographs of 71 horses with subchondral lucency, without radiographic evidence of fracture, located on the distal radial carpal bone were examined retrospectively. All horses had lameness and/or joint effusion referable to the carpus. Distal radial carpal bone subchondral lucency was found as a solitary lesion or as a lesion concurrent and symmetric to a contralateral distal radial carpal bone chip fracture. The lesion appeared radiographically as a lucency or shadow on the distal dorsal margin of the radial carpal bone and was most evident on the flexed lateromedial and dor...
