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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.
A comparison of the traditional Chinese versus transpositional zangfu organ association acupoint locations in the horse. The traditional Chinese (TC) and transpositional (TP) methods of animal acupoint location result in different acupoint charts. Representative TC and TP equine zangfu organ shu-association acupoint charts are compared to each other and to a human chart. Despite their differences, practitioners of both methods appear to achieve equally effective therapeutic results--a phenomenon termed "traditional Chinese/transpositional equal efficacy" (TTEE). Common veterinary acupuncture practices, traditional Chinese medical theory, spinal cord anatomy, and a preliminary equine "association segment" chart a...
Strain of the musculus interosseus medius and its rami extensorii in the horse, deduced from in vivo kinematics. The in vivo strains of the musculus interosseus medius (suspensory ligament) and its rami extensorii (extensor branches) in the forelimb of the horse were determined from angular changes of the metacarpophalangeal and the distal interphalangeal joints. For this purpose, regression models were fitted to strains and joint angle combinations measured in in vitro limb loading experiments. The in vivo strains were computed from the kinematics of 8 horses at the walk, the trot and the canter. It was found that the extensor branches were strained about 1.0% at hoof impact, which indicates that they p...
Recommended terminology for researchers in locomotion and biomechanics of quadrupedal animals. This paper summarizes recommendations for terminology to be used in the description of quadrupedal locomotion and selected aspects of biomechanics. Directional terms and planes of the body (anatomical position, spatial reference systems), joint angulation, conformation, general locomotion terminology, phases of the stride and limb cycle (e.g. step, cadence) and terminology for the description of jumping are described.
Neurones in autonomic ganglia of normal horses contain phosphorylated neurofilaments. Neurofilaments (NF) are composed of three polypeptides of differing molecular size, termed NF-L, NF-M and NF-H. The NF-H and, to a lesser degree, NF-M components are phosphorylated. In the majority of normal neurones, the location of phosphorylated NF is confined to neuronal processes, particularly the axon, and excluded from the perikaryon. Cell bodies of autonomic neurones of the rat do not contain phosphorylated NF. In many disease states, phosphorylated NF accumulate in the neuronal cell body and therefore in most circumstances their presence indicates abnormality. This paper reports that ...
Changes in cross-sectional area and capillary supply of the muscle fiber population in equine gluteus medius muscle as a function of sampling depth. The right and left gluteus medius muscles of 4 mature Andalusian stallions were examined by repeated needle biopsy over a specific area and depth, as well as at different depths, to determine whether the cross-sectional area and capillary supply of the various fiber types are homogeneous throughout the muscle. The muscle biopsy specimens were histochemically analyzed for fiber types (myofibrillar adenosine triphosphatase) and capillaries (amylase-periodic acid-Schiff method). Differences between contralateral sites were not identifiable for any of the analyzed variables. Differences between sa...
Stress reactions and stress fractures of the proximal palmar aspect of the third metacarpal bone in horses: 58 cases (1980-1990). The case records, radiographs, and nuclear bone scans of 58 horses with stress reactions or stress fractures of the proximal palmar aspect of the third metacarpal bone (MC3) were reviewed. There were 47 Standardbreds, 4 Quarter Horses, 3 Thoroughbreds, 2 Arabians, 1 Oldenburg, and 1 Pony of America. Fifty-six of the horses were racehorses or performance horses. The mean and median ages of affected horses were 4 and 3 years, respectively. Lameness ranged from mild to severe. Physical findings were usually subtle and included signs of pain on deep palpation of the proximal palmar aspect of MC3 a...
[Prenatal development of the horse ovary]. To answer the many open questions concerning the development of the horse's ovary, first the prenatal development was investigated. It resulted that follicles derive from the germinal epithelium and its cords, whereas the Leydig cells and the rete blastema originate from the mesonephros. In the second third of pregnancy the Leydig cells undergo an enormous proliferation, in the last third they degenerate. However this degeneration is not connected with the postnatal development of the ovulation groove.
Equine vision and optics. Vision is a marvelous sense, critical to the well-being and functional use of horses. Anatomic, optical, and visual acuity generalities are presented. The constituents of unsoundness due to equine ocular disease are discussed, and recommendations are made.
Specialized veins in the submucosa of the equine ileocecal junction. Spirally arranged bundles of sub-endothelial smooth muscle enfold the small to medium-sized submucosal veins in the equine ileocecal junction. The muscle bundles, accompanied by the endothelial lining, bulge into the lumen of the vessels, partly occluding the latter. Transmission electron microscopy of the muscle cells reveals features consistent with vascular smooth muscle ultrastructure. It is proposed that the throttling effect of the muscle bundles causes engorgement of the submucosal venous plexus, which then assists in the closing of the ileocecal orifice.
Histological features of the dorsal cortex of the third metacarpal bone mid-diaphysis during postnatal growth in thoroughbred horses. The dorsal cortex of the equine third metacarpal mid-diaphyseal bone was characterised during growth by the histological and microradiographic examination of specimens from 30 horses ranging in age from 2 months to 8 y. Bone from horses aged less than 6 months was characterised by rapid periosteal apposition of circumferential trabeculae of woven bone that were next connected by radial trabeculae to the parent cortex. Deposition of lamellar bone on the inner trabecular surfaces resulted in rows of primary osteons. Replacement of primary bone occurred only after 4 months of age and preferential...
Eyelid and nasolacrimal disease. An understanding of normal structure and function of the equine eyelid is essential to make an accurate diagnosis and appropriately treat equine eyelid diseases. Entropion, eyelid trauma, neoplasia, and nasolacrimal disorders are reviewed. Methods of diagnosis and treatment are presented.
Presence of pulmonary intravascular macrophages in the equine lung: some structuro-functional properties. The pulmonary intravascular macrophages (PIMs) have been described in several species of animals. This study demonstrates for the first time that the equine lung has PIMs as resident phagocytes in its microvasculature. Their salient features such as globular surface coat, structures of the endocytic pathway, and related cell organelles closely resemble those of the calf, goat, and sheep. The exquisite organization of the coat globules in the form of a linear chain was structurally similar to the lipolytic lipase and the heparin-sensitive globular coat from PIMs of calf, goat, and sheep. Monast...
Normal equine ocular anatomy and eye examination. When compared with small domestic animals, the horse has unique ocular characteristics (complete bony orbit, well-developed eyelid muscles, a nasal and temporal gray limbal line, granulae iridica, paurangiotic fundus). Knowledge of normal equine ocular anatomy is essential for ocular lesion interpretation. It is important to obtain a full history and general examination before sedation, nerve blocks, or other diagnostic ophthalmic tests are performed. All ocular examinations should include a systematic evaluation of both the anterior and posterior segments. Selection of other diagnostic tests ...
Primary pulmonary neoplasm in a horse. A 16-year-old Thoroughbred gelding was evaluated for respiratory disease and found to have a primary lung tumor on postmortem examination. A tentative antemortem diagnosis was made on the basis of results of radiography and cytologic examination of a needle aspirate guided by ultrasonography. A histologic diagnosis of bronchioalveolar adenocarcinoma was made. Thoracic neoplasia is rare in horses. The most frequently reported primary pulmonary tumor is the granular cell tumor.
Ultrasonographic and quantitative histologic assessment of sequelae to testicular biopsy in stallions. A sample of testicular parenchymal tissue, approximately 2 x 7 x 7 mm, was aseptically removed from 1 testis in each of 9 stallions on day 0. Slight to moderate hemorrhage from the tunica albuginea was observed in 8 stallions, but bleeding from the parenchyma was detected in only 2 stallions. Stallions were castrated 27 days later. Normal development of granulation tissue was evident at the biopsy site, but hematomas were not observed. In situ measurement of the widths of the right and left testes, total scrotal width, and evaluation of testicular echogenicity during ultrasonography were varia...
Fractures of the lateral malleolus of the tibia in 16 horses. Clinical and radiological features of 16 horses with fractures of the lateral malleolus of the tibia are reported. The paper describes surgical techniques used, results obtained and discusses justification for removal. Fourteen fractures were unilateral and two bilateral. There was no left:right disparity. The history included a known traumatic incident in 14 cases. All animals had a tarsocrural joint effusion and 10 had palpable thickening of the lateral collateral ligaments. Crepitus was also palpable in 10 horses. The fracture was identified in all dorsoplantar and 14 of 18 dorsomedial-plan...
Anatomy of the prepubic tendon in the horse, cow, sheep, goat, and dog. Analyses of the fibers in the prepubic tendon of the horse and ruminants have shown that it is composed of the crossed and uncrossed tendons of origin of the pectineus muscles, the pelvic tendons of the rectus and obliquus abdominis muscles, and the tendons of origin of the cranial parts of the gracilis muscles. Pelvic attachments of the linea alba and the yellow abdominal tunic are incorporated in it. It is not a transverse ligament, and it is not homologous to the human superior (cranial) pubic ligament. The dog differs in 4 respects: (1) the pectineus tendons do not cross, but each originat...
Ultrastructural mucosal injury after experimental ischemia of the ascending colon in horses. The ultrastructural injury that develops sequentially in the ascending colon during experimentally induced ischemia was examined in 6 halothane-anesthetized horses. Colonic ischemia was created by 2 types of vascular occlusion 24 cm proximal and distal to the pelvic flexure. In all horses, transmural vascular compression was created. The colonic venous circulation was obstructed in 3 horses, whereas in the other 3 horses, arterial and venous circulation was obstructed. Two additional horses were anesthetized as controls for determination of any morphologic alterations associated with the exper...
Ultrastructure of cilia in horses. This paper presents some ultrastructural details of cilia from the ciliated tracheal epithelium of healthy horses. By using a new fixation method, the Authors were able to describe minute details, some of which have been only rarely observed in other species and mostly by means of the freeze-etch technique (i.e. electron dense particles of ciliary necklace). The Authors justify the need to investigate the ultrastructural details of cilia in various species since the minute morphological differences might be functionally significant.
Ovarian mass in three mares with regular estrous cycles. Three mares with regular estrous cycles and a large ovary were examined. In each case, the ovary was composed of a single, fluid-filled cavity with a thick capsule. The ovarian mass was surgically removed from each mare. Histologic diagnosis of each mass was different.
Low energy laser irradiation treatment for second intention wound healing in horses. Low energy helium-neon laser irradiation was administered to full thickness skin wounds (3 cm x 3 cm) on the dorsal surface of the metacarpophalangeal/metatarsophalangeal joints and cranial surface of the tarsocrural joints of eight horses. The effects on wound healing were analyzed statistically. There were no differences (p > 0.55) observed in the rate of wound healing between the low energy laser irradiated wounds and the control wounds. There was a significant difference (p < 0.006) observed in the rate of healing between the anatomical sites. Tarsal wounds healed more rapidly than f...
Ultrastructure of Brunner’s glands in the horse. Investigation of the duodenal submucosal glands of Brunner in the horse for the first time at the ultrastructural level has clarified some of the unique features of these equine glands. The horse is one of the very few mammals in which Brunner's glands are comprised of both mucous and serous tubuloacinar glands. Although the ultrastructural differences between the serous and mucous cell types are marked, particularly with respect to secretory granules and rough endoplasmic reticula, these cell types closely correspond to serous and mucous cells in the upper digestive system of other mammals. A...
Bronchoscopy of the horse. The endobronchial anatomy of 12 lung specimens from horses and 12 healthy, standing, sedated horses was evaluated, using a 200-cm-long, 9.5-mm-diameter videoendoscope. On the basis of these findings, the nomenclature system of Amis and McKiernan was modified for identification of airways of horses during bronchoscopy. Lobar bronchi are identified on the basis of the side of the bronchial tree on which they were found and the order in which they originated from the primary bronchus. Thus, RB1, RB2, and RB3 referred to right cranial lobar bronchus, respectively. On the left side, the designation...
Keratin and associated proteins of the equine hoof wall. In this study, we described water-insoluble proteins extracted from the germinative regions (stratum internum and coronary band epithelium) and the cornified outer surface (stratum medium) of the equine hoof wall. Two major types of polypeptides were identified: the intermediate filaments (IF) and the IF-associated proteins. The IF, including keratins, composed a major portion of this fraction, had electrophoretic mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the range of 40 to 80 kDa, and reacted with acidic or basic keratin-specific monoclonal antibodies. Differe...
Autonomic neurone degeneration in equine dysautonomia (grass sickness). Histological investigations were undertaken on four sympathetic autonomic ganglia and on the myenteric and sub-mucosal plexuses of the jejunum in healthy animals, in naturally occurring cases of acute, sub-acute and chronic equine dysautonomia and in ponies in which neuronal damage had been induced by the injection of acute grass sickness sera. The degree of neuronal damage is related to the type of dysautonomia. The coeliac-mesenteric ganglion reacts differently from other ganglia and is less severely damaged in cases of short duration. Extensive experimentally induced damage to the coeliac-m...
