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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.
Comparative anatomy of the accessory ciliary ganglion in mammals. The orbits of 13 mammalian species (pig, sika deer, domestic sheep, horse, cat, fox, racoon dog, marten, rat, rabbit, crab-eating macaque, japanese macaque and man) were stained with silver nitrate and dissected under a dissecting microscope with special attention to the presence and location of the accessory ciliary ganglion. Some preparations were stained with thionin and examined as whole-mounts in a transmission microscope. The accessory ciliary ganglion was present in all 13 species, although the number and degree of development varied greatly from species to species. The accessory ciliar...
Effects of season and lower ambient temperature on the structure of the sweat glands in anhidrotic horses. Histological studies of the sweat glands of anhidrotic horses in the Hong Kong summer and under conditions of reduced thermal stress, both natural and controlled, were undertaken to determine if glandular regeneration occurs. Clinical data were collected for comparison with the histological results in each instance. Horses were assigned to one of three categories on the basis of the resulting change in the number of thin glandular profiles in a cooler environment. Group 1, which was classed as normal, had a low initial value, which was maintained. Group 2, typical of mild and moderately affect...
Radiographic measurement from the lateromedial projection of the equine foot with navicular disease. Radiographic measurements from the lateromedial projection of the equine foot were compared in three groups of horses. Group 1 consisted of 143 normal horses, group 2 were 60 horses with clinical navicular disease and group 3 were 161 horses with clinical and radiographic navicular disease. Several measurements tended to be larger in group 3 than group 1. An enlargement of the navicular bone was observed in proximodistal and dorsopalmar directions. Partial enlargement of the pedal bone was observed in groups 2 and 3. Few differences were observed between age classes. All horses aged four years...
Fat cell size in various body region. A statistical analysis in Equus caballus. In 13 horses from both sexes, between 5 months and 18 years of age, in good nutritional state, statistical evaluations of fat cell sizes were performed in 16 body regions. From direct and indirect measurements referred to the cell diameter and cell number in equivalent areas, carried out on sections from paraffin embedded material and on preparations of dissociated whole cells, it emerged that the adipose cells of the subserous fat of the abdominal floor are consistently the largest, whereas those of the orbital fat body and supraorbital fossa are the smallest. In the other regions the cells h...
Use of high-speed cinematography and computer generated gait diagrams for the study of equine hindlimb kinematics. High-speed cinematography with computer aided analysis was used to study equine hindlimb kinematics. Eight horses were filmed at the trot or the pace. Filming was done from the side (lateral) and the back (caudal). Parameters measured from the lateral filming included the heights of the tuber coxae and tailhead, protraction and retraction of the hoof and angular changes of the tarsus and stifle. Abduction and adduction of the limb and tarsal height changes were measured from the caudal filming. The maximum and minimum values plus the standard deviations and coefficients of variations are prese...
[Diagnostic sonography of the limb of the horse]. The ultrasonic examination of tendons and ligaments of the distal limb of the horse improves the diagnostic possibilities of these frequently injured structures. The successful application is based upon a reliable knowledge of the normal sonographic anatomy and upon a standardized, flawless technic of the examination. Practice and experience allow the recognition of minor alterations which enables a more precise diagnosis, a more reliable prognosis, and in follow-up examinations also more specific information about the further use of the horse.
Cytochemical and ultrastructural characteristics of the stallion epididymis (Equus caballus). The epididymis of stallion castrated during the breeding and non breeding seasons were subdivided into six regions and their ultrastructural and cytochemical characteristics were studied in order to provide a better understanding of the structure-function relationship of this androgen target organ. Even when the stallion has been postulated to be a seasonal breeder, our results do not show significant ultrastructural or cytochemical differences in both seasons. The pseudostratified epithelium is composed mainly of principal and basal cells and intraepithelial lymphocytes. The principal cells s...
Spinal hyperostosis in comparative pathology. A useful approach to the concept. Spinal hyperostosis, an anatomical and radiological concept primarily described in man, is characterized by enthesopathic bony overgrowth on vertebral bodies in the form of spurs or intervertebral bridges. It can also be part of a more diffuse enthesopathic condition, including the appendicular skeleton. These changes are distinct from those of osteoarthrosis. Similar changes can be observed in all kinds of mammals, independent of their type of locomotion (bipodic, quadrumanous, quadrupedic, or aquatic). An anatomical and radiological study is presented of six cases (with histological examinat...
Urogenital paraneurons in several mammals. Amines and/or peptide-producing cells, deserving to be called paraneurons, were demonstrated in the urethro-prostatic complex of the man, rabbit, buffalo and sheep and in the uterine horns of the pig, horse and mouse, by means of histochemical, immunohistochemical, immunofluorescent and double labeling immunofluorescent techniques. In particular, the urethro-prostatic complex of the sheep contains cells producing serotonin, chromogranin A and somatostatin. Often the amine and the "marker"-protein were colocalized in the same cells. Chromogranin A- and somatostatin-containing cells were found i...
Evolution of tooth structure in the Equoidea. During the evolution of the Equoidea, the histological structures of the teeth have become more complex as the molars have become hypsodont in form. The straight Hunter-Schreger bands of Hiracotherium have evolved into a more complex pattern in Equus. The enamel prisms changed from an arched form (about 5μm in diameter) with an alternating pattern in Hiracotherium to an oval form (about 2 μm width) arranged in straight rows in Equus. In Equus the rows of prisms are separated by interprismatic sheets. This pattern may have increased the architectural strength of the enamel, and is related to ...
Ultrasonography of umbilical structures in clinically normal foals. The umbilical arteries, urachus, and umbilical vein were scanned ultrasonographically in 13 clinically normal foals that ranged in age from 6 hours to 4 weeks. Sonograms were obtained using a 7.5-MHz sector scanner transducer placed across the midline of the ventral portion of the foal's abdominal wall. The umbilical vein was scanned from the umbilical stalk to its entrance into the hepatic parenchyma. The mean (+/- SD) diameter of the umbilical vein was 0.61 +/- 0.20 cm immediately cranial to the umbilical stalk, 0.52 +/- 0.19 cm midway between the umbilicus and liver, and 0.6 +/- 0.19 cm at ...
Displacements, malpositions, and miscellaneous injuries of the mare’s urogenital tract. Although they are pivotal events in the continued production of new generations of horses, breeding and foaling are not without risk to the mare. This article reviews the accidents that can occur and result in injury, displacement, and malpositions of the urogenital tract of the mare.
Adjunctive methods of examination of the urogenital tract. Included in this article are descriptions of adjunctive methods of examination of the urogenital tract, including ultrasonography of the kidneys, urinary bladder, ovaries and uterus; endoscopy of the urethra, urinary bladder, and uterus; contrast radiography of the urinary tract; kidney biopsy; and laparoscopy of the abdomen, emphasizing examination of the mare's reproductive tract.
Communications and boundaries of the middle carpal and carpometacarpal joints in horses. To study communications and boundaries of the middle carpal and carpometacarpal joints of the horse, 50 forelimbs were obtained from fresh cadaver specimens. Blue latex solution (20 +/- 2.5 ml) was injected into the middle carpal joint, and the specimens were frozen in extension. Frozen specimens were cut into 1-cm sagittal sections from the middle of the radius to the middle of the metacarpus. The communications between the middle carpal and carpometacarpal joints and the presence, length, and position of the distopalmar outpouchings of the carpometacarpal joint were recorded. The middle carp...
Normal and cryptorchid castration. Surgical exploration of the horse that has presumably had a normal castration or a previously successful cryptorchid surgery remains a distinct challenge. No hard and fast rules dictate a proper course of action for each case. If a horse was anesthetized for routine castration, discovered to have only one scrotal testis, had a brief exploratory on the nondescended side and was recovered, trauma to the inguinal region would probably be sufficiently minimal that an inguinal approach could be used at subsequent exploratory surgery. If the inguinal canal was extensively manipulated and the tail of...
Mitochondrial size and shape in equine skeletal muscle: a three-dimensional reconstruction study. Individual mitochondria were reconstructed from ultrathin serial sections of selected muscle fibers in the M. semitendinosus of a horse, over a length of nearly two sarcomeres. Mitochondria were found to be highly variable, with size and complexity of single mitochondria increasing with the fractional part of a fiber occupied by mitochondria. In fibers with a mitochondrial volume density of less than 4%, corresponding to the mitochondrial content of fast-twitch glycolytic fibers, mitochondria were generally rather simple cylindrical shapes, oriented parallel to the myofibrils. In fibers with a...
Surgical management of congenital and perinatal abnormalities of the urogenital tract. Surgical management of various congenital and perinatal abnormalities of the urogenital tract are discussed, including ruptured bladder, ruptured urachus, ureteral defect, patent urachus and umbilical remnant infection, ureteral ectopia, congenital inguinal hernia, and atresia ani and rectourethral or rectovaginal fistula.
Sternothyrohyoideus myectomy in horses: 17 cases (1984-1985). Review of medical records of 78 horses admitted to the George D. Widener Hospital for Large Animals with dorsal displacement of the soft palate revealed 94% of these horses to have evidence of an intermittent abnormal "gurgling" respiratory noise at the time of exercise. Sternothyrohyoideus myectomy was used as a primary treatment for 17 of these horses, with a success rate of 58%. Anatomic dissection of 30 horses indicated that the midcervical region is the optimal site for sternothyrohyoideus myectomy to alleviate dorsal displacement of the soft palate.
Hematochezia attributable to cranial mesenteric arterial aneurysm with connecting tracts to cecum and ileum in a horse. A cranial mesenteric arterial aneurysm with fistulous tracts to the cecum and ileum was discovered in a Missouri Fox Trotter stallion. The principal clinical sign was hematochezia, observed at 7- and 10-day intervals. The lesion may have been attributable to arteritis caused by fourth-stage larvae of Strongylus vulgaris.
A comparison of enterotomies through the antimesenteric band and the sacculation of the small (descending) colon of ponies. Three pairs of longitudinal enterotomies were performed in the small colon of 10 ponies. Each pair consisted of one enterotomy through the antimesenteric band and one through the sacculation. The ponies were destroyed 96 h after surgery. The enterotomies in the two sites were compared for: speed of surgery, adhesions, bursting wall tension, neovascularisation by micro-angiography, and histological reaction. Enterotomies made through the antimesenteric band were superior because they were quicker to perform, stronger, more accurately apposed, and had less inflammation than those made through th...
Cortical somatosensory-evoked potentials in the horse. Cortical somatosensory-evoked potentials (SEP) were recorded from thoracic and pelvic limbs in 15 horses (13 Thoroughbreds and 2 Quarter Horses). Ulnar nerve SEP were evoked by electrical stimulation of the lateral palmar branch of the ulnar nerve at the level of the metacarpophalangeal joint. Recordings were taken between electrodes at 2 cm lateral to the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were found in all recordings: N1, P1, N2, and P2. Latencies to the peaks were 39.0 +/- 2.7, 45.5 +/- 5.3, 50.4 +/- 5.2, and 62.3 +/- 3.7 ms (...
Surgical repair of urethral transection in a horse. A recently castrated horse was examined because of preputial and ventral abdominal swelling, prolapse of the preputial fold, and serosanguinous fluid dripping from the external urethral orifice. After a poor response to initial medical management, a urethral laceration was found during exploratory surgery. Half of the ventral portion of the corpus cavernosum penis had been transected. Primary closure was followed by healing without complications.
Subchondral cyst-like lesions in the distal portion of the radius of four horses. Four horses with subchondral cyst-like lesions in the medial radial facet of the distal portion of the radius were examined. Joint effusion and signs of pain from flexion of the antebrachiocarpal joint were not observed, but lameness was observed in 3 of the 4 horses. Regional nerve blocks and intra-articular anesthesia were used to localize the lesions, and conservative treatment resulted in soundness for performance.
Ultrastructure of junctional epidermolysis bullosa in Belgian foals. Ultrastructural examination of a mechanobullous disease of probable hereditary nature in Belgian foals, confirmed light microscopic findings that separation of the dermo-epidermal junction occurred through the lamina lucida of the basement membrane, leaving the intact lamina densa adherent to the dermis and the plasmalemma of the basal epithelial cells intact. The location of the cleft and the presence of small hemidesmosomes in adjacent intact skin are additional characteristics which make this condition similar to junctional epidermolysis bullosa of man.
Micronema deletrix-induced granulomatous osteoarthritis in a lame horse. Necropsy of a chronically lame 16-year-old thoroughbred gelding revealed granulomatous osteomyelitis and polyarthritis due to a widely disseminated infection by Micronema deletrix. Diagnosis was based upon the nematode's morphology with its characteristic rhabditiform oesophagus. Granulomata, often containing one or more centrally located M. deletrix, were observed histologically in sections prepared from femur, kidney, stomach, lung, adrenal gland and sublumbar lymph nodes. Neither verminous meningo-encephalitis nor cephalic granulomata, which are the more commonly described lesions, was foun...
Gastric hyperplastic polyp in a horse. An unusually large, pedunculated (20 cm long) mass arising the gastric pylorus which produced complete obstruction of the proximal duodenum and severe gastric distension was found in a 13-year old castrated male Arabian horse. The histological diagnosis was gastric hyperplastic polyp, which has not been reported previously in the horse. The clinico-pathological findings in this horse are compared with hyperplastic (inflammatory) gastric polyps of man.
