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Topic:Morphology
Morphology in horses refers to the study of the form and structure of the equine body, including the skeletal, muscular, and integumentary systems. This field encompasses the examination of physical characteristics such as body conformation, limb structure, and cranial features, which can influence a horse's performance, health, and suitability for various activities or disciplines. Morphological assessments are often used in breeding programs to select for desirable traits and in veterinary evaluations to identify potential anatomical issues. This page aggregates peer-reviewed research studies and scholarly articles that explore the methodologies, findings, and implications of morphological studies in equine science.
Qualitative and morphometric radiographic findings in the distal phalanx and digital soft tissues of sound thoroughbred racehorses. Lameness examinations and radiography of the distal phalanx and associated soft-tissue structures of the front feet of 103 Thoroughbred racehorses, 4 to 9 years old, were performed to determine normal radiographic appearance and morphometry. Of 103 horses examined, 41 were used in the study that were without clinical signs of foot problems or lameness, had raced at least twice prior to radiography, and had raced at least twice more in the 6 months after radiography. Lateromedial and dorsoproximal-palmarodistal radiographic views of each front distal phalanx were used to measure 28 bone and sof...
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.
Diurnal variation in plasma ir-beta-endorphin levels and experimental pain thresholds in the horse. Diurnal variation in nociceptive sensitivity and plasma immunoreactive beta-endorphin (ir-BEND) concentrations was examined in eight healthy Thoroughbred horses. Pain thresholds, ir-BEND concentrations, rectal temperature, heart rate, respiratory rate and pupil diameter were measured over a 24 hour period. Nociceptive sensitivity was determined using two objective measures of pain: the skin-twitch reflex latency and the hoof withdrawal reflex latency. Significant variation in both nociceptive thresholds and ir-BEND concentrations were noted over the 24 hour period, with elevated pain threshold...
Further observations on the morphology and sensitive innervation of the retractor penis muscle in several species of ungulates. The retractor penis muscle originates from the vertebrae in pigs, horses, cattle and goats; it arises from the rectum in sheep. In all the species considered, sensitive innervation was found. This was represented by encapsulated receptors. Nervous vegetative supply, made up of isolated or assembled ganglion cells, was also present. Among the numerous sensory nerve endings found in pigs, goats and sheep were Pacinian, Pacinian-like, Golgi-Mazzoni corpuscles and Krause's end bulbs (genital corpuscles). Few Pacinian and Pacinian-like corpuscles were found in cattle and horses. A hypothesis on the...
Functional significance of the morphology and micromechanics of collagen fibres in relation to partial rupture of the superficial digital flexor tendon in racehorses. The high incidence of partial rupture of the superficial digital flexor tendor in the equine athlete represents a major cause for concern in the racing industry. Frequently, the lesion is localised to the central core of the tendon. This study tested the hypothesis that the site specific structural failure results from differences in the collagen fibre morphology and associated micromechanics between central and peripheral regions of the tendon. Bundles of collagen fibres were dissected from central and peripheral sites in the mid-metacarpal region of the tendon. Crimp morphology was quantifie...
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.
Radiographic/morphologic investigation of a radiolucent crescent within the flexor central eminence of the navicular bone in thoroughbreds. The source of a previously described radiolucent crescent in the flexor cortex of the distal sesamoid (navicular) bone on the palmaro45 degrees proximal-palmarodistal oblique (Pa45 degrees Pr-PaDio) clinical radiographic projection was investigated in 48 forelimb navicular bones from 24 Thoroughbreds by use of high-detail radiography and x-ray computed tomography (CT). Twenty-five of these bones also were evaluated, using microradiography and histologic examinations. Of these 25 bones, 5 had been labeled in vivo with fluorochrome markers. Tetrachrome-stained 100-microns-thick nondecalcified se...
Variability of muscle fibre composition and fibre size in the horse gluteus medius: an enzyme-histochemical and morphometric study. To determine the variability in fibre types and fibre sizes in the equine gluteus medius muscle, biopsy specimens were removed from 5 sites, at 4 different depths, within the right and left muscles of 3 Andalusian stallions. The percentage, lesser fibre diameter and cross-sectional area of the various fibre types were measured systematically in myosin ATPase and NADH-tetrazolium reductase-stained, serial cryostat sections of these multiple samples. Significant differences in muscle fibre type composition were recorded, with a lower percentage of type I fibres (high myosin ATPase activity at pH...
Effects of intra-articular administration of methylprednisolone acetate on normal articular cartilage and on healing of experimentally induced osteochondral defects in horses. The effects of intra-articular administration of methylprednisolone acetate (MPA) on the healing of full-thickness osteochondral defects and on normal cartilage were evaluated in 8 horses. In group-1 horses (n = 4), a 1-cm-diameter, full-thickness defect was created bilaterally in the articular cartilage on the dorsal distal surface of the radial carpal bone. Cartilage defects were not created in group-2 horses (n = 4). One middle carpal joint was randomly selected in each horse (groups 1 and 2), and treated with an intra-articular injection of 100 mg of MPA, once a week for 4 treatments. Inje...
High-resolution computed tomography of the mammalian lung. High-resolution computed tomography (HRCT) was performed in 21 isolated animal lungs, from 4 mammalian species (pigs, rabbits, dogs, sheep). Gross and subgross central and peripheral lung morphology was determined by HRCT. Three distinct types of lungs can be identified, principally based on the extent of interlobular septal development; the relationship of major vessels to airways; and the thickness of the visceral pleura. Type-I lung is found in pigs, sheep, and cattle; type-II lung is found in rabbits, dogs, cats, and monkeys; and type-III lung is found in human beings and horses. These mam...
[Scanning electron microscopic findings of the navicular bone and deep flexor tendon in podotrochlosis of horses]. In 25 adult horses the podotrochlea of 49 forelimbs was examined by means of light and electron microscopy in order to correlate clinical and morphological findings. According to the clinical diagnosis the animals were divided into three groups: lameness due to syndrome of podotrochlosis (group 1) or due to tendopathy (group 2) and horses without lameness (group 3). The most striking pathological findings of the navicular bone and the opposite surface of the deep flexor tendon were found in horses with podotrochlosis, consisting of loss of cartilage and tendon matrix with denudation of collage...
Morphologic and biochemical study of sternal cartilage autografts for resurfacing induced osteochondral defects in horses. Using biodegradable pins, sternal cartilage autografts were fixed into osteochondral defects of the distal radial carpal bone in ten 2 to 3-year-old horses. The defects measured 1 cm2 at the surface and were 4 mm deep. Control osteochondral defects of contralateral carpi were not grafted. After confinement for 7 weeks, horses were walked 1 hour daily on a walker for an additional 9 weeks. Horses were euthanatized at 16 weeks. Half of the repair tissue was processed for histologic and histochemical (H&E and safranin-O fast green) examinations. The other half was used for the following bioch...
Loss of absorptive capacity for sodium and chloride in the colon causes diarrhoea in Potomac horse fever. Ehrlichia risticii, an obligate intracellular bacterium in the family Rickettsiaceae, causes Potomac horse fever which is often associated with severe watery diarrhoea. The mechanism of the diarrhoea is unknown. The aim of this study was to determine whether sodium and chloride transport, morphology and cyclic adenosine 3', 5'-monophosphate (cyclic AMP) content of colonic mucosa was altered in E risticii-infected horses. Mucosa-submucosa sheets from the large and small colon of nine infected and seven to nine uninfected horses were set up in Ussing chambers for measurement of short-circuit cur...
Comparison of spermatozoal movement and semen characteristics with fertility in stallions: 64 cases (1987-1988). Information pertaining to evaluation of single ejaculates of semen and records for 2 consecutive breeding seasons were obtained. In all, data for 99 individual breeding seasons (n = 43 Standardbreds and 56 Thoroughbreds) were evaluated. Included in each semen evaluation was examination of semen characteristics and computer-aided analysis of spermatozoal movement characteristics. On the basis of the analysis of breeding records for 4,175 mares (7,017 estrous cycles), a per-estrous cycle fertility rate was calculated from data for 96 of the breeding seasons. Stallions with lower fertility than t...
Evaluation of stallion semen. This article outlines a basic method for conducting a stallion semen evaluation. After the removal of the gel fraction of the ejaculate, semen gel-free volume is determined, and any abnormality in appearance is noted. Concentration of sperm cells in semen can be determined with the use of either a hemacytometer or spectrophotometer after appropriate dilution of raw semen. The percentage of progressively motile sperm is evaluated promptly after collection of semen with the use of a phase-contrast microscope. The total numbers of sperm and progressively motile sperm in the ejaculate are calculat...
Villous hypoplasia of the small intestine in neonatal foals. To elucidate the pathomorphogenesis of extremely shortened small-intestinal villi, occurring spontaneously in neonatal foals, the morphology of the small intestine with stunted villi was studied in eight cases. All intestinal wall elements and the villi were poorly developed. Most villi were found to be extremely short throughout the entire length of the small intestine. The villous core consisted of undifferentiated, fibroblast-like cells held loosely together by ground substance which was rich in glycosaminoglycan. Development of the villous lamina propria was poor with respect to capillarie...
Allometric relationships of cell numbers and size in the mammalian lung. Allometric studies have shown that lung volume, alveolar surface area, and diffusing capacity increase proportionally with body weight across a broad range of mammalian species. Changes in the number of cells and in average cell size and surface areas with increasing body weight have not been defined. We speculated that cell size is determined more by cell function than by species and body weight. To test this hypothesis, nine species ranging in size from shrew (2 to 3 g) to horse (510 kg) were studied. Random sites from the distal alveolar region of each species were analyzed using morphometr...
Characterization of Sarcocystis neurona from a thoroughbred with equine protozoal myeloencephalitis. Morphological information is presented for syntype material of the etiologic agent of equine protozoal myeloencephalitis, Sarcocystis neurona. A clinical description of the horse from which the organism was isolated and the methodology used to immunosuppress the horse in an attempt to increase parasite numbers are also given. The description includes microscopic details observed both with light and transmission electron microscopy. Mainly stages from tissue are illustrated, but information is also presented on the development of the organism after inoculation onto monolayers of bovine monocyte...
Elbow extensor muscles of the horse: postural and dynamic implications. Based on histochemical and immunohistochemical evidence, horse elbow extensor muscles are composed of two morphologically distinct muscle groups. The long and lateral heads of the triceps brachii are large, predominantly type II (presumed fast) muscles. The long and lateral heads of the triceps together account for 96% of the weight of the elbow extensors (long head of triceps is 81%). The long and lateral heads contain three histochemical fiber types: types I, IIa and IIb. Type I muscle fibers account for approximately 18 and 27% of the fibers in the long and lateral heads of the triceps, res...
Spermatozoal head defect as a cause of infertility in a stallion. A 9-year-old Arabian stallion with a 3-year history of infertility was evaluated for breeding soundness. Both testes were small. Ultrasonography revealed a small amount of free fluid between the tunics of both testes. Results of cytologic examination of the fluid were unremarkable. On semen examination, progressive motility was 10%, and total number of spermatozoa in the ejaculate was 6.6 x 10(9), of which 92% were abnormal. Predominant abnormalities were head defects (75%): 57% of the heads had single or multiple vacuoles, and 60% also had midpiece swelling or bending.
Possible importance for laminitis research of recent studies on substances influencing the differentiation of cultured keratinocytes. After a survey of the state of laminitis research the authors conclude that none of the present concepts of the pathogenesis of laminitis unequivocally explains the basic clinical and morphological observations in this disease. There is therefore reason to consider the advances that have been made during the last decades in respect to the influence of various substances on the differentiation of cultured skin keratinocytes. The technique is available for studying hoof keratinocytes in a comparable way. Relevant literature on cultured skin keratinocytes is surveyed. Some of the results from exp...
Co-culture of day-5 to day-7 equine embryos in medium with oviductal tissue. Oviductal and uterine embryos were collected from mares at 5 to 7 days following ovulation 1) to evaluate the effects of oviductal tissue explants on in vitro growth and development of equine embryos and 2) to study the morphologic development of equine embryos in culture. Embryos were incubated for 5 days in a medium (control group) or in medium supplemented with oviductal tissue explants (co-culture group). Embryos were evaluated and the media changed daily. Following 5 days in culture, 10 10 (100%) control embryos and 27 29 (93%) co-cultured embryos had doubled in diameter. All embryos that...
Small intestinal malabsorption in the horse: an assessment of the specificity of the oral glucose tolerance test. Specificity of the oral glucose tolerance test (OGTT) for the diagnosis of small intestinal malabsorption in the horse was assessed by comparing the results of OGTT with the results of a histopathological examination of the small intestine in 42 adult horses affected by chronic weight loss. The horses were assigned to three groups on the basis of the results of the test. Five horses were considered to have a normal OGTT absorption result (Group 1); all the horses had a histologically normal small intestine. Twenty-five horses had a partial malabsorption result (Group 2) seven of which had norm...
Pulmonary gas exchange correlated to clinical signs and lung pathology in horses with chronic bronchiolitis. Eight horses (mean weight 438 kg) with chronic obstructive pulmonary disease (COPD) were studied for clinical signs, ventilation/perfusion relationships (VA/Q) and lung morphology. Four horses were killed and necropsied after the study. In horses with COPD, minute ventilation was almost twice as high as normal, whereas PaO2 was significantly decreased. Cardiac output was normal, but pulmonary artery pressure and pulmonary vascular resistance were significantly increased. The VA/Q distribution was abnormal with an increased scatter of VA/Q ratios. However, shunt (VA/Q = 0) was increased in one ...
Morphological examination of epididymal epithelium in the mule (E. hinnus) in comparison with parental species (E. asinus and E. caballus). Following previous studies about the ultrastructure of male genital tract in parental species, a comparative study of epididymis of one of the possible hybrids, the mule, has been undertaken. Apart from small differences, general features of epididymal epithelium in the mule are similar to those of parental species. However, extension of our studies from the donkey to the horse to the hybrid permits a deeper insight into the morphology of this tract of excurrent duct. In the meantime, it is possible to evidence some features, sometimes shared with other species if taken separately, which in th...
Fertility of a stallion with low sperm motility and a high incidence of an unusual sperm tail defect. At the beginning of the breeding season an eight-year-old standardbred stallion had semen with virtually zero sperm motility and an approximately 90 per cent incidence of midpiece and tail defects. The motility of the sperm improved to 7 per cent when semen was collected daily but its morphology did not improve. Electron microscopy revealed that the defects consisted mainly of a loss of microtubules in the axoneme and of disorganised midpieces. A pregnancy rate of 24 per cent per cycle and 44 per cent for the season was achieved in 32 mares after the insemination of whole ejaculates collected ...
Pulsed carbon dioxide laser for cartilage vaporization and subchondral bone perforation in horses. Part II: Morphologic and histochemical reactions. A pulsed carbon dioxide laser was used to vaporize articular cartilage in four horses, and perforate the cartilage and subchondral bone in four horses. Both intercarpal joints were examined arthroscopically and either a 1 cm cartilage crater or a series of holes was created in the third carpal bone of one joint. The contralateral carpus served as a control. After euthanasia at week 8, the treated and control joints were examined for gross changes, and samples of cartilage and subchondral bone, synovial membrane, and peripheral lymph nodes were examined histologically. Depletion of cartilage ma...
