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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.
Morphology of the nerve endings in laryngeal mucosa of the horse. To discuss the significance of laryngeal sensation on various disorders of the horse, we studied the morphological and topographical characteristics of sensory structures in the laryngeal mucosa using immunohistochemistry and immunoelectron microscopy. Various sensory structures, i.e. glomerular endings, taste buds and intraepithelial free nerve endings, were found in the laryngeal mucosa by immunohistochemistry for protein gene product 9.5 (PGP 9.5) and neurofilament 200kD (NF200). Glomerular nerve endings were distributed mainly in the epiglottic mucosa; some endings were also found in the a...
Relationships of age and shape of the navicular bone to the development of navicular disease: a radiological study. Estimating the shape of the proximal articular border of the navicular bone and grading the radiological navicular bone condition (grades 3 and 4 representing the most severe changes), the aim of this study was to assess potential age-related implications of the previously reported shape predisposition to navicular disease in 746 normal and 174 clinically affected Dutch Warmbloods age 3-19 years. A significant, age-independent, shape-grade association found in normal and affected horses emphasises the fundamental character of the shape predisposition to navicular disease. A significant age-rel...
In situ zymography: topographical considerations. In situ gelatin zymography is a simple technique providing valuable information about the cellular and tissue localization of gelatinases. Until recently, the use of this technique has been confined to soft, relatively homogeneous tissue. In this report in situ zymography has been utilized to assess the sub-lamellar location of gelatinases in the hard, semi-keratinized epidermal layer and the adjacent soft connective tissue matrix of the dermis of the equine hoof. We show that alterations in the orientation at which the tissue is dipped and withdrawn from the emulsion cause profound alteration...
Scanning electron microscopic study of the posterior ciliary veins in domestic ungulates. Vascular corrosion casts of 12 equine, 15 bovine and 50 porcine eyes were studied scanning electron microscopically for the presence of posterior ciliary veins. These veins drain a postequatorial segment of the choroid and emerge near the posterior bulbar pole. They complement the four vorticose veins that emerge near or at the equatorial zone of the eyeball and the slender choroidoretinal veins that drain the peridiscal area of the choroid. Posterior ciliary veins were observed in all equine and bovine eyes examined. In these species they presented a large variation in size, number and positi...
Cytokeratins of the stratum medium and stratum internum of the equine hoof wall in acute laminitis. The cytoskeleton of living keratinocytes consists mainly of cytokeratins that have polymerised into intermediate filaments. The aim of this study was to describe the expression of cytokeratins in the living epidermal cells of the weight-bearing parts of the equine hoof wall during acute spontaneous laminitis. A total of 9 hooves from 3 horses subjected to euthanasia within 48 h of the first clinical signs of laminitis were sectioned and examined. The cytokeratins in the stratum medium and stratum internum of the hoof wall were characterized by 1- and 2-dimensional gel electrophoresis, and the ...
Immunohistochemical analysis of equine pulmonary granular cell tumours. Histopathological and immunohistochemical examinations were made on four female horses aged 9-12 years with pulmonary granular cell tumours (GCTs). The tumours, which were multiple, of varying size, firm and off-white in colour, surrounded the bronchi and bronchioles. Metastatic lesions were not detected. The tumour cells had abundant eosinophilic cytoplasm filled with prominent coarse eosinophilic granules. Immunohistochemically, these tumour cells reacted uniformly with vimentin and S100 antibodies. Most were immunolabelled by antibodies against glial fibrillary acidic protein (GFAP), myelin...
Muscle thickness and neuron density in the caecum of horses with chronic recurrent caecal impaction. In this study, the hypothesis that caecal smooth muscle layers would be thinner and the linear neuron density of myenteric plexus greater was tested in normal horses compared to those with chronic recurrent caecal impaction. Four normal horses and 18 horses with chronic recurrent caecal impaction were subjected to euthanasia and 7 tissue samples were collected from each horse at different regions of the caecum (apex, dorsal body, cranial base, dorsal base, caudal base, caudal body, ventral body). Twelve horses with chronic recurrent caecal impaction were treated surgically. Only one tissue sam...
The hindlimb in walking horses: 1. Kinematics and ground reaction forces. The objective was to study associations between kinematics and ground reaction forces in the hindlimb of walking horses. Video (60 Hz) and force (2000 Hz) data were gathered for 8 strides from each of 5 sound horses during the walk. Sagittal plane kinematics were measured concurrently with the vertical and longitudinal ground reaction forces. The hindlimb showed rapid loading and braking in the initial 10% stride. The stifle, tarsal and coffin joints flexed and the fetlock joint extended during this period of rapid loading. The vertical ground reaction force showed 2 peaks separated by a dip; ...
Evaluation of uniformity of morphological injury of the large colon following severe colonic torsion. This report describes the evaluation of uniformity of morphological injury of the large colon following severe colonic torsion in 17 horses presented to the Veterinary Medical Teaching Hospital. In 16 horses, twist occurred at the colonic base and in 1 at the sternal and diaphragmatic flexure. Eleven of the 17 horses were subjected to euthanasia at surgery and 6 of 17 following surgical correction within 4 days postoperatively. The objective of this study was to determine if the degree of histological changes present at the pelvic flexure were uniformly distributed throughout the regions of th...
Neurological signs in a horse due to metastases of an intestinal adenocarcinoma. A 22-year-old Dutch Warmblood mare was referred to Utrecht University with progressive left hind limb paresis and hyporeflexia. The preliminary clinical diagnosis was the neurological form of equine herpes virus (EHV-1) infection. Within 1 day of admission, the mare became recumbent and deteriorated rapidly. Postmortem examination revealed an adenocarcinoma of the caecum, with metastases in all regional lymph nodes and extending from the lumbar nodes into the vertebral canal, causing spinal cord compression and destruction of the left 4th and 5th lumbar nerves.
Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse. Scintigraphy, with 99mTechnetium methylenediphosphonate (99mTc-MDP) and 99mTc-labelled leucocytes, was compared to radiography in the diagnosis of dental disease in the horse in a prospective case-controlled study, comprising 30 horses with clinical signs of dental disease and 30 control horses. In each case, right and left lateral, ventral and dorsal soft tissue and bone phase scintigraphic images were obtained after i.v. injection of 1 GBq/100 kg bwt 99mTc-MDP, using a gamma camera. The same views were acquired in 10 horses with clinical signs of dental disease and 12 control horses after in...
The distribution of intratubular dentine in equine incisors: a scanning electron microscopic study. The distribution of intratubular (peritubular) dentine was studied by scanning electron microscopy in 12 equine incisor teeth. High levels of intratubular dentine were found in the peripheral regions of the dentine. In these areas, a marked asymmetry occurred, as intratubular dentine was predominantly deposited onto the side of the dentinal tubular walls nearest to the dentino-enamel junction. The quantity and asymmetry of intratubular dentine were reduced towards the centre of the tooth. The significance of these variations in the amount and distribution of intratubular dentine between the di...
The radiographic development of the distal and proximal double contours of the equine navicular bone on dorsoproximal-palmarodistal oblique (upright pedal) radiographs, from age 1 to 11 months. The aim of this study was to monitor the postnatal radiographic development of the proximal and distal double contours and the modelling of the shape of the proximal articular border. In mature horses, the proximal and distal contours of the navicular bone on dorsopalmar dorsoproximal-palmarodistal oblique (upright pedal) radiographs are commonly visualised as 2 lines, one being the articular border and the second representing the border of the cortex facing the deep digital flexor tendon (flexor border). The shape of the proximal articular border may be concave, undulating, straight or convex...
Repeatability of diagnostic ultrasonography in the assessment of the equine superficial digital flexor tendon. A quantitative investigation of the variation that can occur during the course of ultrasonography of the equine superficial digital flexor tendons (SDFT) was undertaken. The aim of this investigation was to use an objective measure, namely the measurement of CSA, to quantify the variability occurring during the course of the ultrasonographic assessment of the equine SDFT. The effects of 3 variables on the CSA measurements were determined. 1) Image acquisition operator (IAc): two different operators undertaking the ultrasonographic examination; 2) image analysis operator (IAn): two different op...
Strangulating obstruction caused by intestinal herniation through the proximal aspect of the cecocolic fold in 9 horses. To report the clinical and surgical findings and outcome for horses with strangulating obstruction caused by herniation through the proximal aspect of the cecocolic fold. Methods: Retrospective study. Methods: Nine horses. Methods: Medical records were reviewed for clinical signs, surgical findings and technique, and outcome. Cadaver ponies and necropsy specimens were also used to study the regional anatomy of the cecocolic fold. Results: The ileum and distal jejunum were strangulated in 8 horses, whereas in 1 horse the small intestine and the left ascending colons were incarcerated in a rent ...
The “galloping” history of intermittent claudication. Intermittent claudication (IC) due to arterial occlusive disease was first diagnosed by the French veterinary surgeon Jean-François Bouley jeune in a horse drawing a cabriolet in the streets of Paris as early as 1831. The animal was repeatedly exercised and always started to limp with the hind legs at similar work loads. Autopsy revealed partially thrombosed aneurysm of the abdominal aorta and occlusions of both femoral arteries which were correctly identified as the cause of IC. In 1858 the famous neurologist Jean-Martin Charcot working at the Salpêtrière in Paris first discovered the cond...
Computed tomographic imaging of the equine head. The head from three horses euthanized due to diseases unrelated to the head and neck was imaged using computed tomography (CT). Gross cross-sectional slices of equine head #1 and skeleton of equine head #2 were compared with the CT images of the three equine heads to identify normal structures of the cranium, brain, paranasal sinuses, nasal cavity, and teeth. Labeled transverse CT images of the equine head are presented sequentially as a reference for normal anatomy.
Topography of ganglion cells in the retina of the horse. Topography of ganglion cells in the retina of the horse (Thoroughbred) was analyzed in the wholemount retina stained with cresyl violet, and a total number of ganglion cells were estimated. Sizes of ganglion cells were also measured and size spectra were analysed. The main results showed that: (1) a common point in 4 wholemount retinae, based on cell densities and retinal locations, was that a retina could be divided into 5 regions, namely visual streak, nasal, temporal, dorsal and ventral region to the visual streak. A maximum cell density of 4,000 cells/mm2 was found in the visual streak. An...
Expression of vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, and intermediate neurofilaments in nasal mucosal nerve fibers of horses without nasal disease. To determine the distribution of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and intermediate neurofilaments in nasal mucosa of horses. Methods: 6 horses without evidence of nasal disease. Methods: Full-thickness nasal tissue specimens were obtained from the rostral portion of the nasal septum at necropsy, and fluorescence immunohistochemistry was performed to assess mucosal distribution of nerve fibers. Results: Nerve fibers with CGRP-like immunoreactivity (CGRP-Li) formed a dense subepithelial network, and a large num...
A comparison of the palmaroproximal-palmarodistal view of the isolated navicular bone to other views. A collection of 69 isolated navicular bones, normal or affected with navicular disease, was examined radiographically using dorsopalmar, lateromedial and palmaroproximal-palmarodistal views. Radiographic findings on each view were recorded. A radiographic diagnosis of normality or navicular disease was made, first on each view separately and afterwards based on the combination of the 3 views. Forty-four navicular bones were considered radiographically normal and 25 navicular bones had distinct signs of radiographic navicular disease. The dorsopalmar and the lateromedial views of each navicular...
Transitional cell carcinoma of the urinary bladder in a Thoroughbred, with intra-abdominal dissemination. A 14-year-old Thoroughbred gelding with a history of acute onset of hematuria was presented for necropsy. Transitional cell carcinoma of the urinary bladder with intra-abdominal dissemination was diagnosed. Tumor masses were observed on the splenic capsule and surrounding the distal abdominal aorta. Tumor cells showed diffuse cytoplasmic reactivity for cytokeratin but were negative for epithelial membrane antigen, carcinoembryonic antigen, tumor-associated glycoprotein 72, and vimentin.
Computed tomography of normal cranioencephalic structures in two horses. The purpose of this investigation was to define the anatomy of the cranioencephalic structures in horses using computed tomography (CT). Transverse images of two isolated equine cadaver heads were obtained using a Toshiba 600 HQ (third-generation equipment TCT). CT images were compared to corresponding frozen cross-sections of the cadaver head. Relevant anatomical structures were identified and labelled at each level. The resulting images provided excellent anatomic detail of the structures of the central nervous system and associated formations. Annotated CT images from this study are intende...
Fourier analysis of acetabular shape in native American Arikara populations before and after acquisition of horses. The goal of this study was to identify changes in acetabular morphology associated with the use of horses by Native Americans. Previous studies reported "elongate" acetabula in horseback-riding members of the Omaha and Ponca populations. Such a difference in acetabular shape is a potentially useful osteological marker of habitual horseback riding. This report compares acetabula of adult males from two Native American Arikara populations known to have differed substantially in their use of horses. Population samples were from separate sites in South Dakota: Larson (nonriding) and Leavenworth (r...
Clinical findings associated with chronic ischial fracture in a gelding. An 8-year-old show-jumper gelding was referred for examination as a result of a purchase dispute for reported back pain. Clinical examination identified back pain and atrophy of the left semimembranosus and semitendinosus muscles, but no lameness. Standing pelvic radiography demonstrated a chronic nonunion fracture of the left ischium, the clinical significance of which was uncertain. The apparent back pain was thought to be probably unrelated to the pelvic lesion. We conclude that chronic ischial fracture in the horse can lead to specific atrophy of the semimembranosus and semitendinosus musc...
Evidence for surfactant contributing to the gastric mucosal barrier of the horse. This study was undertaken to determine the hydrophobicity of the luminal surface of the equine stomach and to elucidate the ultrastructure of the lining imparting that property. Gastric and duodenal mucosal samples from 5 horses were collected immediately after euthanasia and subjected to surface contact angle measurement using a goniometer. Gastric mucosal samples from 4 horses and a foal were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. Contact angles for the equine gastric glandular mucosal surface (mean +/- s.e...
4-nitroimidazole binding to horse metmyoglobin: evidence for preferential anion binding. The ionization of 4-nitroimidazole to 4-nitroimidazolate was investigated as a function of ionic strength. The apparent pKa varies from 8.99 to 9.50 between 0.001 and 1.0 M ionic strength, respectively, at 25 degrees C. The ionic strength dependence of this ionization is anomalous. The binding of 4-nitroimidazole by horse metmyoglobin was studied between pH 5.0 and 11.5 and as a function of ionic strength between 0.01 and 1.0 M. The association rate constant is pH-dependent, varying from 24 M(-1)s(-1) at pH 5 to a maximum value of 280 M(-1)s(-1) at pH 9.5 and then decreasing to 10 M(-1)s(-1) a...
Studies on the experimental induction of ptosis in horses. The precise appearance of ptosis due to lesions at different sites was investigated in experimental ponies. The angles of the eyelashes to the head was used as an objective measurement of ptosis after local anaesthesia of the sympathetic trunk or the palpebral nerve and the administration of an ocular alpha agonist or antagonist. It was shown that ptosis is not an inevitable consequence of palpebral nerve pathology, that ocular alpha antagonists can induce ptosis, and that alpha agonist eyedrops have an inconsistent effect on the equine pupil, but are consistent at reversing ptosis induced by ...
