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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.
Morphological, histochemical, and myosin isoform analysis of the diaphragm of adult horses, Equus caballus. The horse provides an interesting model for study of the structure and function of the mammalian diaphragm. Multiple regions of diaphragm from seven adult horses were prepared for histochemistry, immunocytochemistry, myosin heavy chain electrophoresis, and native myosin electrophoresis. Two additional adults were dissected to demonstrate myofiber and central tendon morphology and stained for acetylcholinesterase to demonstrate motor endplates. All regions of the adult diaphragm were histochemically characterized by a preponderance of type I fibers with some type IIa fibers. Type IIb fibers wer...
An ultrastructural study of intranuclear bodies in granular epithelial cells of the equine small intestine. Gastrointestinal disorders and colic are common problems of
horses. In spite of its clinical importance, only a few reports
deal with the normal morphology of the equine intestinal barrier
(Roberts and Hill 1974). Furthermore, the intestinal epithelium
of horses presents some characteristics which are uncommon in
other species, e.g. the presence of conspicuous Paneth cells
(Meyer et al. 1970) or granular epithelial cells. Paneth cells
occur in the small intestinal crypts and sporadically in the caecum, while granular cells occur along the lining of the small
and large intestine in hors...
Jugular vein wall repair after intravenous injection in equids. The evolution of the healing process of venous puncture wounds was studied macroscopically and light-microscopically in order to determine the time of venipuncture. Seven small equids of various ages, all in normal healthy condition, were experimentally injected in the external jugular vein with a physiological Hartmann solution at different times before euthanasia. Two types of needle diameters i.e. 16.5 G and 19 G, were used. A fairly good uniformity in the healing process was seen in the 7 animals. In most cases the lesions induced within 5 weeks before death were macroscopically visible, w...
Pulmonary intravascular macrophages in horses and ponies. Seven horses (4 anesthetized and 3 awake) and 2 ponies (anesthetized) were studied to evaluate the high sensitivity of the pulmonary circulation of the horse to various blood-borne particles, and to establish the presence of intravascular macrophages in the lung. Pulmonary and systemic pressures and cardiac output before and during particle injection were measured in some animals. An anesthetized foal had a large increase in pulmonary arterial pressure (32 and 34 mm of Hg) within 1 minute of IV administration of small test doses of radioactively labeled liposomes (2.5 mumol/kg of body weight) ...
Jean-François Bouley (Bouley jeune). Pioneer investigator in intermittent claudication. Reports of pathologic investigations as to the cause of intermittent claudication in horses were made in France in October, 1831, by veterinarian Jean-François Bouley. Obstructive clots in the femoral arteries were found to be responsible for the muscular changes causing limping. Bouley's work in the horse was used by Charcot in 1858 to understand the mechanism of claudication in the case of a soldier with gunshot wound in whom a traumatic aneurysm, clotting, and ischemia of the legs developed. This was not, however, the first medically reported case of human claudication from vascular occlus...
Enterolithiasis in two zebras. Enterolithiasis, as a cause of colic, was diagnosed and treated during surgical intervention in 2 Grant's zebras (Equus burchelli bohmi). The zebras were part of a wild herd in a zoo in the western United States. The clinical signs of enterolithiasis in both zebras were similar to those reported for horses. Analysis of the enterolith from 1 zebra revealed a composition identical to enteroliths that have been analyzed from horses. Three other zebras from this herd had enteroliths at necropsy. Enterolithiasis should be considered as a differential diagnosis for zebras with low-grade obstructive ...
Preparation and characterization of monoclonal antibodies against equine chondrocytes, osteoblasts and osteocytes. Three monoclonal antibodies capable of individually recognizing chondrocytes, osteoblasts and osteocytes were prepared. EB-1 reacted with a 55-kDa antigen on the chondrocyte membrane, EB-2 with a 110-kDa antigen on the membrane of osteoblasts and/or partial osteocytes, and EB-3 with a 130-kDa antigen on the membrane of osteocytes. These monoclonal antibodies may be useful probes for studying the differentiation and maturation of osteogenic cells.
Effect of oxytetracycline on metacarpophalangeal and distal interphalangeal joint angles in newborn foals. Thirty-five newborn foals were assigned to 1 of 3 groups and treated with 0.9% NaCl solution (saline; group 1; n = 12), oxytetracycline (44 mg/kg of body weight; group 2; n = 12), or 2-pyrrolidone (oxytetracycline vehicle; group 3; n = 11) in saline solution during the first 36 hours after birth. Serum biochemical analyses were performed on samples obtained from group-1 and group-2 foals before treatment and 24 and 96 hours after treatment. Lateral to medial radiographic views of the forelimbs were obtained before treatment and 24 and 96 hours after treatment in all foals. Metacarpophalangeal ...
Ameloblastomas in the horse: a critical review and report of an additional example. Previously published cases of ameloblastoma in the horse are reviewed in detail for their acceptability as examples of that tumor; an additional one is described. So far, this rare equine lesion has been shown to have two histologic patterns. The first consists of islands and sheets of epithelium that exhibit the basal cell characteristics of ameloblastoma; the central cells comprise stellate reticulum. The second exhibits these basal cell features less markedly and the central cells are spindle-shaped and closely packed. The biologic behavior of the equine ameloblastoma is thought to be the s...
[Pathology of cardiac ventricular aneurysms in the horse]. The authors describe pathologic and histopathologic findings of three cardiac aneurysms in horses, two of which in the left ventricle and one in the right ventricle. The aneurysms were always associated with multiple foci of myocardiac fibrosis. A hypothesis concerning histogenesis of the lesion is formulated.
Natural outcome and ultrasonic identification of equine fetal twins. The natural outcome of bilateral twins (one in each uterine horn) that were viable on Day 40 was studied in 15 pony mares. Fetuses were monitored by transrectal ultrasonography until the outcome was determinable. One fetus (2 mares) or both fetuses (8 mares) died (cessation of heartbeats) during Months 2 and 3. Loss of fetuses was externally observed in 4 additional mares during the late fetal stage (Months 8 to 11); 2 mares lost 1 fetus and 2 lost both fetuses. Birth of 2 live foals occurred in only 1 of 15 mares (7%) First day of detected apposition between portions of the 2 allantochorions ...
Measurements of urethral pressure profiles in the male horse. Urinary tract pressure profiles were evaluated in 6 clinically normal geldings over 3 consecutive days. This was performed by introducing a 1.3 m-long cuffed catheter into the urinary tract, under xylazine sedation (0.8 mg/kg, iv). The method was reproducible. The mean (+/- sd) intra-vesicular pressure (IVP) and maximal urethral closure pressures (MUCP) were 10.3 (+/- 1.7) and 129.8 (+/- 19.6) cmH2O, respectively, and the ratio between MUCP and IVP was 13.2 (+/- 2.5). A gelding with urinary incontinence showed a significantly lower MUCP (73.4 cmH2O), and an MUCP to IVP ratio of 8.0. It was con...
Solitary osteochondroma of the nasal bone in a horse. A 3-year-old Appaloosa stallion with a 4 cm x 4 cm x 2.5 cm mass protruding from his nasal bone was evaluated. Radiographs revealed an osseous mass, with a radiopaque outer margin and several radiolucent areas within the body of the mass. The mass was surgically removed and evaluated histopathologically. The histopathological diagnosis was osteochondroma. This case represent the first reported occurrence of an osteochondroma arising from intramembraneous bone in the horse.
Cystic adenomatous hyperplasia of the equine allantois: a report of eight cases. No abstract available
[Ultrasonography of ovarian pathology in the mare: a review for the practitioner]. The aim of this review is to give the practitioner the ability to be familiar with the echographic exam of ovarian abnormalities. He should be able to recognize different stages of the development of these important structures and to estimate the effect that they can have on the normal cycle of the mare. Various specific criteria and details regarding the equine echography of ovarian abnormalities are reported and illustrated, using the last scientific data published on that particular topic.
[Ultrasonography of the formation and development of the corpus luteum in the mare: review for the practitioner]. Because of the anatomical position of the Corpus luteum within the ovary, rectal palpation is of little value for identification and evaluation. The aim of this review is to familiarize the practitioner with the echographic examination of the Cl. He should be able to recognize different stages of this important structure and to correlate ovulation and the existence of the Cl. Various specific criteria and details regarding equine echography are reported and illustrated, using the the most recently published scientific data.
Equine fetal kinetics: entry and retention of fetal hind limbs in a uterine horn. Transrectal ultrasonic examinations were made in 31 pregnant pony mares once a week during Months 6 to 11. Each uterine horn was divided into 3 approximately equal segments (caudal, middle, cranial). The percentage of examinations with cranial fetal presentation increased (P<0.05) progressively from 58% at Month 6 to 99% at Month 9 and was followed in all mares by entry of the fetal hind limbs into one uterine horn. The mean number of uterinehorn segments with limb parts increased (P<0.05) between each set of consecutive months from Month 6 to Month 10. Initially (Months 7 and 8), retrac...
Respiratory mechanics of the horse during the first year of life. This study investigated the developmental changes in the mechanical properties of the respiratory system in growing horses. Pulmonary mechanics and lung volumes were serially measured in anesthetized foals during the first year of life. Quasi-static pressure-volume curves were generated, and functional residual capacity (FRC) was measured using a closed nitrogen equilibration technique. At birth, chest wall compliance normalized to body weight was substantially less than that reported in other less precocious newborn species, while lung compliance normalized to body weight was similar to value...
Idiopathic peripheral neuropathy in a horse with knuckling. We report the pathological findings of the skeletal muscle and peripheral nerves from a male 14-months-old thoroughbred horse showing idiopathic knuckling. The affected animal, when in staining position, presented knuckling at the fetlock joint of both forelegs, and dragged both fore- and hindlegs when attempting forward movement. The skeletal muscles demonstrated neurogenic atrophy characterized by the scattering of single angular fibers, groups consisting of five to ten angular fibers, and multiple fascicles of atrophic and hypertrophic fibers. The severity of changes tended to be a distal g...
Ultrasonographic assessment of the proximal digital annular ligament in the equine forelimb. Ultrasonography was used with 6 normal cadaver forelimbs of Dutch Warmblood horses to delineate the ultrasonographic anatomy of the palmar pastern region, with emphasis on the proximal digital annular ligament. Using a 5.5 MHz sector scanner, the thin proximal digital annular ligament was not visible on offset sonograms. Only if the digital sheath in the normal limb was distended was the distal border of this ligament outlined. In all normal limbs the palmarodistal thickness of the combined skin-proximal digital annular ligament layer in the mid-pastern region was 2 mm. The flexor tendons and ...
Inhibitory nerve distribution and mediation of NANC relaxation by nitric oxide in horse airways. The distribution of inhibitory nerves and the mediator of the inhibitory nonadrenergic noncholinergic (iN-ANC) nervous system were investigated in smooth muscle preparations from seven regions of equine airways. In tissues incubated with atropine and precontracted with histamine, electrical field stimulation produced frequency-dependent relaxation, and the magnitude of the relaxation decreased from trachea to central bronchi and was absent in peripheral airways. The degree of relaxation in bronchi was not simply a function of bronchial size or generation. Propranolol inhibited part of the rela...
[The discovery of a horse skeleton from the 17th century in Kiesen in Bern canton]. In 1968 a skeleton of a horse was found in Kiesen (Switzerland). This discovery could be dated by radiocarbon method: According to that this 13 years old gelding with a withers-height of 135 to 140 cm must have lived during the first third of the 17th century. Apparently it died by an accident. The bones are fully documented with pictures and scales and the findings described and discussed in detail.
Assessment of vertebral canal diameter and bony malformations of the cervical part of the spine in horses with cervical stenotic myelopathy. Magnification of cervical radiographs prevents accurate interpretation of vertebral canal absolute minimum sagittal diameter (MSD) values and application of the established MSD values for diagnosis of cervical stenotic myelopathy (CSM). Variability in MSD determination in human beings, owing to radiographic magnification, is minimized by assessing a ratio of the vertebral canal diameter to the sagittal width of the vertebral body. This relative measurement technique improves the accuracy of diagnosis of cervical spinal stenosis in human beings. The MSD of the vertebral canal was determined in ...
The relationship of daily sperm production with number of Sertoli cells and testicular size in adult horses: role of primitive spermatogonia. The number of Sertoli cells is important in spermatogenesis as noted by significant correlations between the number of Sertoli cells and the number of germ cells observed as early as type B2 spermatogonia in the horse. However, the stage within spermatocytogenesis at which these relationships first occur is unclear. The relationships between the number of Sertoli cells and parenchymal weight and the number of germ cells during the mitosis of spermatogenesis were determined in 184 adult horses to identify the developmental stage (that is, the earliest germ cell) at which significant relationshi...
Ultrastructure of the epithelium that lines the ductuli efferentes in domestic equidae, with particular reference to spermatophagy. The epithelium that lines the ductuli efferentes in the horse, donkey and mule has been examined by electron microscopy. The epithelium consists of columnar ciliated and non-ciliated cells. Lymphocytes and macrophages are also present, together with cells that are rich in lipofuscin. These 'lipofuscin-rich' cells are a peculiar feature of the excurrent ducts of Equidae and are characterized by a large number of highly heterogeneous residual bodies. The general morphology of the epithelium and, in particular, of the non-ciliated cells implies that the epithelium is involved in the absorption an...
Histochemical and morphometric study of the cricoarytenoideus lateralis muscle in the horse. Histochemical and morphometric parameters of the cricoarytenoideus lateralis muscle of the horse are presented. Using myosin ATPase staining after acid preincubation, 3 fibre types (I, IIA and IIC) were identified. Using NADH-TR staining, type I fibres showed high oxidative capacity, whereas type II fibres had high or low oxidative capacity. The type I to type II ratio was of 35:65. This ratio remained constant in the age range examined. Statistically significant (p < 0.01) differences were found in values for fibre size between groups of horses weighing more than 500 kg and less than 400 k...
