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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.
Equine odontoclastic tooth resorption and hypercementosis. A poorly described, painful disorder of incisor and canine teeth, variably causing periodontitis, with resorptive or proliferative changes of the calcified dental tissues, has recently been documented in aged horses. No plausible aetiopathogenesis for this syndrome has been recorded. Eighteen diseased teeth from eight horses were examined grossly and microscopically and showed the presence of odontoclastic cells by tartrate resistant acid phosphatase (TRAP) staining. A chronological sequence of odontoclastic resorption followed by hypercementosis was demonstrated and, consequently, the term eq...
Prevalence of occlusal pulpar exposure in 110 equine cheek teeth with apical infections and idiopathic fractures. Examination of 110 cheek teeth (CT) that were clinically extracted (between 2004 and 2008) because of apical infection (n=79; mean dental age 3.5 years) or idiopathic CT fractures (n=31; median dental age 8.5 years), including examinations of transverse and longitudinal sections, showed the apical infections to be mainly (68%) due to anachoresis, with the residual cases caused by periodontal spread, infundibular caries spread, fissure fractures and dysplasia. The idiopathic fracture patterns were similar to previously described patterns. Occlusal pulpar exposure was found in 32% of apically in...
Ocular toxicity and distribution of subconjunctival and intravitreal rapamycin in horses. In vitro photosensitivity of rapamycin (RAPA) and ocular toxicity and distribution of intravitreal and subconjunctival RAPA was evaluated in normal horses. RAPA (2.5 mg, 5 mg, and 10 mg) was placed in 10 mL of PBS and maintained in a water bath at 37 degrees C, kept in the dark or subjected to room light, and sampled for up to 3 months for RAPA levels. Six normal adult horses received either 5 mg (n = 2) or 10 mg (n = 2) of RAPA intravitreally or 10 mg (n = 2) subconjunctivally. Ophthalmic exams and electroretinography (ERG) were performed prior to injection and on days 1, 7, 14, and 21 post-i...
Bilateral testicular mixed germ cell-sex cord-stromal tumours in a stallion. An 18-year-old Friesian stallion was examined approximately one week after reportedly presenting scrotal swelling due to torsion of the spermatic cords. Upon presentation no scrotal swelling was noted, the testes were normally oriented, and no abnormalities of the spermatic cords were noted. However, both testes were smaller than expected for a mature stallion and deep palpation revealed that the consistency of the testes was nodular. Ultrasonographic evaluation of the testes revealed diffuse heterogeneous parenchyma with multiple hypoechoic nodular areas. Grossly, the testicular parenchyma wa...
Fibropapilloma of the glans penis in a horse. An 18-year-old Arabian stallion was presented for recent onset of stranguria. Physical examination of the distal portion of the glans penis revealed multiple, smooth, glistening, grayish-pink, variably sized, exophytic, nodular masses circumferentially surrounding the external urethral orifice. Partial penile amputation was performed, and the entire specimen was submitted for histological evaluation. Microscopically, the masses consisted of abundant amounts of loosely arranged fibrovascular stroma with low numbers of spindloid to stellate fibrocytes. The overlying epithelium was mildly to mode...
Gross anatomy of the female genital organs of the domestic donkey (Equus asinus Linné, 1758). Although donkeys play an important role as companion or pack and draught animals, theriogenological studies and anatomical data on the genital organs of the jenny are sparse. To provide anatomical descriptions and morphometric data, the organa genitalia feminina, their arteries and the ligamentum latum uteri of 10 adult but maiden jennies were examined by means of gross anatomical and morphometric techniques. In comparison with anatomical data of horses obtained from literature the genital organs of jennies appear to be more voluminous in relation to the body mass and the position of the ovari...
Structural characterization of subchondral bone in the distal aspect of third metacarpal bones from Thoroughbred racehorses via micro–computed tomography. To characterize the microstructure of subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the condyles of third metacarpal bones (MC3s) from Thoroughbred racehorses at 2 different stages of SCB disease via micro-computed tomography (CT). Methods: 12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons. Methods: MC3s were collected from horses with mild (n = 6) or severe (6) SCB disease, as determined via micro-CT. Cubic (6 x 6 x 6-cm) specimens of SCB plate and TBB were cut from the palmar aspect of condyles and sagittal ridges and examined ...
Pathological studies of cheek teeth apical infections in the horse: 3. Quantitative measurements of dentine in apically infected cheek teeth. Histological measurements of dimensions of primary, regular secondary and irregular secondary dentine, pulp diameter and assessment of the levels of predentine, resting lines and enlarged areas of intertubular dentine were performed in apically infected mandibular and maxillary cheek teeth (CT). These examinations showed significantly reduced regular and irregular secondary dentine thickness in diseased as compared to control CT, with 21/26 infected maxillary CT and 15/18 infected mandibular CT having reduced regular secondary dentine (varying between 27.4% and 89.1% reduced secondary dentine ...
Primary unilateral fibroleiomyoma of the ovary in a pregnant mare: a case report. Fibroleiomyomas of the ovary are rare. This smooth muscle tumour may develop and increase in size during pregnancy. Diagnosis is based on histological and immunohistochemical analyses. Histologically, the ovarian fibroleiomyoma consists of non-invasive bundles of smooth muscle cells that synthesize collagen-like extracellular matrix. This case report describes an ovarian fibroleiomyoma in a pregnant multiparous broodmare with a history of intermittent signs of colic.
Conservative management of a distal epiphyseal metacarpal fracture in a skyros pony. Epiphyseal fracture, also known as epiphysiolysis, is the loosening or separation, either partial or complete, of an epiphysis from the shaft of a long bone. Distal epiphyseal fractures in foals pose a substantial challenge due to their guarded prognosis. This report describes the clinical signs, diagnosis, successful conservative treatment of an 1-month-old, male Skyros pony with an epiphyseal fracture of the right third metacarpal bone (type II Salter-Harris). The owner declined surgical treatment because of financial considerations along with the unfavorable prognosis. Conservative fracture...
Immunohistochemical characterization and quantitative analysis of neurons in the myenteric plexus of the equine intestine. The present study was performed on whole-mount preparations to investigate the chemical neuroanatomy of the equine myenteric plexus throughout its distribution in the intestinal wall. The objective was to quantify neurons of the myenteric plexus, especially the predominant cholinergic and nitrergic subpopulations. Furthermore, we investigated the distribution of vasoactive intestinal polypeptide and the calcium-binding protein calretinin. Samples from different defined areas of the small intestine and the flexura pelvina were taken from 15 adult horses. After fixation and preparation of the ti...
[The horse as an athlete: an animal model of choice for sports medicine: sonographic studies of joint disorders]. Equine diagnostic sonography was initially used for the diagnosis and documentation of tendon injuries. Since 1990, this technique, along with radiography, has become an indispensable imaging procedure for the diagnosis of equine joint injuries. Sonography provides precise diagnostic information on the synovial membrane and fluid, the articular cartilage, subchondral bone and joint margins, the ligaments and menisci, and the anatomical structures involved in periarticular swelling or enlargement. Improvements in ultrasound machines and better superficial and deep image resolution allow us to e...
Correlation of quantitative computed tomographic subchondral bone density and ash density in horses. The purpose of this study was to compare subchondral bone density obtained using quantitative computed tomography with ash density values from intact equine joints, and to determine if there are measurable anatomic variations in mean subchondral bone density. Five adult equine metacarpophalangeal joints were scanned with computed tomography (CT), disarticulated, and four 1-cm(3) regions of interest (ROI) cut from the distal third metacarpal bone. Bone cubes were ashed, and percent mineralization and ash density were recorded. Three-dimensional models were created of the distal third metacarpal...
Alveolar ridge regeneration with equine spongy bone: a clinical, histological, and immunohistochemical case series. In the case of localized ridge atrophy, a ridge augmentation procedure, with the use of bone substitutes and barrier membranes, may then be necessary. Objective: The aim of the present study was a clinical, histological, and immunohistochemical evaluation of an equine spongy bone in alveolar ridge augmentation procedures. Methods: Five patients showing horizontal mandibular ridge defects participated in this study. A ridge augmentation was performed through an onlay apposition of equine bone covered by a titanium-reinforced membrane. After 6 months of healing, five bone cores from nonaugmented...
Immunohistochemical identification and localization of orexin A and orexin type 2 receptor in the horse gastrointestinal tract. The aim of the present study was to investigate the presence and the distribution of cells containing orexin A and orexin type 2 receptor in the horse stomach and gut, by means of immunohistochemical techniques. Orexin A was identified in the stomach fundic and pyloric regions and in the duodenum. In the same stomach regions, a large subset of orexin A-positive cells also showed orexin type 2 receptor-like immunoreactivity. Moreover, in the duodenum, many of them, seemed to store serotonin. Characteristically, enteric neurons or ganglia also displayed orexin A and, sometimes, orexin type 2 rec...
Changes in subchondral bone mineral density and collagen matrix organization in growing horses. The effects of growth and maturation on the mineral deposition and the collagen framework of equine subchondral bone (SCB) were studied. Methods: Osteochondral specimens (diameter 6 mm) from the left metacarpophalangeal joint of 5-(n=8), 11-(n=8) and 18-month-old (n=6) horses were investigated at two differently loaded sites (Site 1 (S1): intermittent peak loading; Site 2 (S2): habitual loading). The SCB mineral density (BMD) was measured with peripheral quantitative computer tomography (pQCT), and the data were adjusted against the volume fraction (Vv) of the bone extracellular matrix (ECM). ...
Kisspeptin immunoreactive neurons in the equine hypothalamus Interactions with GnRH neuronal system. To determine if kisspeptin could be implicated in the control of reproduction in equine species, we studied the distribution of kisspeptin neurons and their anatomical interactions with GnRH neurons in the hypothalamus of pony mares. Brains were collected in three pony mares between 2 and 4h after ovulation. One major population of kisspeptin immunoreactive cell bodies was found in the arcuate nucleus (ARC), where they extended from the middle of the nucleus to the premammillary recess. Kisspeptin immunoreactive varicose fibers extended from the preoptic area to the mammillary nuclei, with imp...
Comparative bone histology of adult horses (Equus caballus) and cows (Bos taurus). Bone microstructure of domestic herbivores is still not completely understood. Indeed, works focused on the bone histology of numerous Mammalian species frequently led to misunderstandings because of the high number of variations such as the kind of bone, section orientation, species, breed and age. Moreover, attempts to identify the species in archaeozoological studies by a mere qualitative approach have not been encouraging and in recent years quantitative methods, based on image processing and statistical analysis, have appeared. The present study was undertaken to determine whether morphom...
Exophthalmus secondary to a sinonasal cyst in a horse. A 13-year-old female Miniature Horse was evaluated for progressive unilateral exophthalmia of the left globe of 3 weeks' duration. Results: Results of a physical examination were unremarkable. Ophthalmic examination identified exophthalmus of the left globe with complete resistance to retropulsion and mild blepharoconjunctivitis. Computed tomography revealed a large, space-occupying mass within the left caudal maxillary and left conchofrontal sinuses. The mass extended into the left retrobulbar space and contacted the cribriform plate. Trephination yielded copious amounts of turbid yellow flui...
Novel optical imaging technique to determine the 3-D orientation of collagen fibers in cartilage: variable-incidence angle polarization-sensitive optical coherence tomography. To investigate a novel optical method to determine the three dimensional (3-D) structure of articular cartilage collagen non-destructively. Methods: Polarization-sensitive optical coherence tomography was used to determine the apparent optical birefringence of articular cartilage for a number of different illumination directions. A quantitative method based on the theory of light propagation in uniaxial crystalline materials was validated on equine flexor tendon. Qualitative maps of fiber polar and azimuthal orientation at sites on the posterior and anterior segments of the equine third metaca...
Elucidation of the MD-2/TLR4 interface required for signaling by lipid IVa. LPS signals through a membrane bound-complex of the lipid binding protein MD-2 and the receptor TLR4. In this study we identify discrete regions in both MD-2 and TLR4 that are required for signaling by lipid IVa, an LPS derivative that is an agonist in horse but an antagonist in humans. We show that changes in the electrostatic surface potential of both MD-2 and TLR4 are required in order that lipid IVa can induce signaling. In MD-2, replacing horse residues 57-66 and 82-89 with the equivalent human residues confers a level of constitutive activity on horse MD-2, suggesting that conformational...
A musculoskeletal model of the equine forelimb for determining surface stresses and strains in the humerus-part II. Experimental testing and model validation. The first objective of this study was to experimentally determine surface bone strain magnitudes and directions at the donor site for bone grafts, the site predisposed to stress fracture, the medial and cranial aspects of the transverse cross section corresponding to the stress fracture site, and the middle of the diaphysis of the humerus of a simplified in vitro laboratory preparation. The second objective was to determine whether computing strains solely in the direction of the longitudinal axis of the humerus in the mathematical model was inherently limited by comparing the strains measured...
A musculoskeletal model of the equine forelimb for determining surface stresses and strains in the humerus–part I. Mathematical modeling. Knowledge of the forces that act upon the equine humerus while the horse is standing and the resulting strains experienced by the bone is useful for the prevention and treatment of fractures and for assessing the proximolateral aspect of the bone as a site for obtaining autogenous bone graft material. The first objective was to develop a mathematical model to predict the loads on the proximal half of the humerus created by the surrounding musculature and ground reaction forces while the horse is standing. The second objective was to calculate surface bone stresses and strains at three cross se...
Renal mucus gland cystadenomas in a horse. A 35-year-old horse was submitted to the necropsy service at the University of Kentucky Livestock Disease Diagnostic Center. At necropsy, multiple 1-4-cm-diameter cystic structures were incidentally identified unilaterally in the right renal medulla and the cortex. On histologic examination, the cystic structures compressed the normal renal architecture, were lined by tall columnar epithelium that formed occasional papillary projections, and contained large amounts of mucicarmine and periodic acid-Schiff-positive mucinous material. The masses were diagnosed as renal mucus-gland cystadenomas. T...
Mucosal distribution of eosinophilic granulocytes within the gastrointestinal tract of horses. To establish reference values for the range of the number of eosinophils found in equine gastrointestinal mucosa and to describe the distribution of this cell within the equine gastrointestinal mucosa. Methods: Gastrointestinal mucosal specimens from 14 adult horses euthanatized for reasons other than gastrointestinal disease. Methods: Gastrointestinal mucosal specimens were collected and grouped according to their anatomic regions. For histologic examination slides were stained with Luna's eosinophil stain to determine eosinophil accumulation and distribution. The mucosa was divided into 5 se...
Comparison of mean bone densities of three preparations of the distal portion of the equine third metacarpal bone measured by use of quantitative computed tomography. To evaluate whether cutting equine subchondral bone to demarcate specific regions of interest (ROIs) influences the mean density for that bone as measured via quantitative computed tomography (QCT). Sample population-2 metacarpophalangeal joints from equine cadavers. Methods: The distal portion of the third metacarpal bone of each intact metacarpophalangeal joint was scanned via CT to simulate in vivo conditions. Each joint was subsequently disarticulated and dissected, and the distal portion of the dissected third metacarpal bone in air was scanned. Then, six 1-cm(2) areas representing ROIs w...
Development of a technique for continuous perineural blockade of the palmar nerves in the distal equine thoracic limb. To develop a technique for placing continuous peripheral nerve block (CPNB) catheters adjacent to palmar nerves in horses and to evaluate the effect of low-volume local anesthetic (LA) infusion on nociception in the distal equine thoracic limb. Methods: In vitro and in vivo laboratory investigation. STUDY MATERIAL AND ANIMALS: Forty-two thoracic limbs from 22 equine cadavers and five horses. Methods: Thoracic limb specimens were dissected to find landmarks for catheter insertion adjacent to medial and lateral palmar nerves. Based on the anatomy of the proximal metacarpus, a technique for placi...
