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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.
Defining cytochemical markers for different cell types in the equine retina. The major cell types in the mammalian retina are photoreceptors, amacrine, horizontal, bipolar, ganglion and Mueller glial cells. Most of the specific cell types are conserved, but cytochemical markers vary between species. The aim of our study was to characterize cytochemically distinctive markers for different cell types in the equine retina. We were able to define specific markers for equine Mueller glial cells and photoreceptor cells. Furthermore, we describe markers for large ganglion cells, horizontal and amacrine cells and a subpopulation of bipolar cells. Additionally, discrimination b...
Guttural pouches, brain temperature and exercise in horses. Selective brain cooling (SBC) is defined as the lowering of brain temperature below arterial blood temperature. Artiodactyls employ a carotid rete, an anatomical heat exchanger, to cool arterial blood shortly before it enters the brain. The survival advantage of this anatomy traditionally is believed to be a protection of brain tissue from heat injury, especially during exercise. Perissodactyls such as horses do not possess a carotid rete, and it has been proposed that their guttural pouches serve the heat-exchange function of the carotid rete by cooling the blood that traverses them, thus pro...
Evaluation of changes in architecture of the stratum internum of the hoof wall from fetal, newborn, and yearling horses. To evaluate morphologic changes of the stratum internum of hooves from near-term fetal, newborn, and yearling horses. Methods: Feet from 27 near-term equine fetuses, 19 newborn foals, and 8 yearlings. Methods: Primary epidermal laminae (PEL) of the stratum internum were examined for evidence of architectural changes. Results: In near-term fetuses, the PEL had a homogeneous appearance and symmetric distribution around the hoof wall with no significant differences in PEL density between the toe and quarters. However after birth, branched laminae at the toe formed within the first few weeks, whic...
Subchondral bone failure in overload arthrosis: a scanning electron microscopic study in horses. Mechanical overload leads to a common arthrosis in the metacarpal condyle of the fetlock joint of racehorses. This is usually asymptomatic but severe forms can cause lameness. Subchondral bone failure is often present and the predictability of the site provided an opportunity to study of the progression of bone failure from microcracks to actual collapse of subchondral bone. Twenty-five fetlock condyles from racehorses with various stages of disease were selected. Stages ranged from mild through severe subchondral bone sclerosis, to the collapse of bone and indentation or loss of cartilage kno...
The blood vessel system in the periodontal ligament of the equine cheek teeth–part I: The spatial arrangement in layers. Corrosion casts of blood vessels in the periodontium of cheek teeth from eight horses were observed three-dimensionally with a dissection microscope. Selected specimens were examined in a scanning electron microscope. Periodontal blood vessels communicated with those from the gingiva, the alveolar bone, and the apical region. In the upper jaw, there were anastomoses with the blood vessels of the mucosa of the maxillary sinus. The periodontal vascular system was organized in two or three layers. The peripheral layer was mainly composed of large venules, the inner one consisted of capillaries. I...
The blood vessel system in the periodontal ligament of the equine cheek teeth–part II: The micro-architecture and its functional implications in a constantly remodelling system. The micro-vasculature of the equine periodontal ligament (PDL) was investigated using corrosion casts for scanning electron microscopy. Specimens from eight healthy warm-blooded horses were examined. Specific vascular features such as large ampullae with a diameter of up to 300 microm and blind vascular casts were found in the specimens of the equine PDL. The ampullae-shaped venules occurred only in the peripheral layer, where they were formed at the confluence of several vessels. Two types of blind stumps were identified. The first was developed in all three layers, while the second was found...
Laparoscopic cryptorchidectomy and ovariectomy in horses. Laparoscopic surgery has become commonplace in the field of equine urogenital surgery. As with most surgical procedures, the limiting factors in developing new surgical techniques are limited to the patient size and demeanor, the skills of the surgeon, and the available equipment. Some of the greatest benefits of laparoscopic surgery in the horse include better visualization of the important structures; tension-free amputation of the testes or ovaries,which generally leads to less postoperative pain; and the ability to evaluate the transected stump carefully to make sure there is no hemorrhage...
Laparoscopic cryptorchidectomy and ovariectomy in horses. Laparoscopic surgery has become commonplace in the field of equine urogenital surgery. As with most surgical procedures, the limiting factors in developing new surgical techniques are limited to the patient size and demeanor, the skills of the surgeon, and the available equipment. Some of the greatest benefits of laparoscopic surgery in the horse include better visualization of the important structures; tension-free amputation of the testes or ovaries,which generally leads to less postoperative pain; and the ability to evaluate the transected stump carefully to make sure there is no hemorrhage...
Magnetic resonance imaging, ultrasonography and histology of the suspensory ligament origin: a comparative study of normal anatomy of warmblood horses. The diagnosis of lameness caused by proximal metacarpal and metatarsal pain can be challenging. Magnetic resonance imaging (MRI) offers the possibility for further diagnosis but there have been no studies on the normal MRI appearance of the origin of the suspensory ligament (OSL) in conjunction with ultrasonography and histology. Objective: To describe the MRI appearance of the OSL in fore- and hindlimbs of sound horses and compare it to the ultrasonographic and histological appearance. The findings can be used as reference values to recognise pathology in the OSL. Methods: The OSL in the fore...
Myosin heavy chain composition in normal and atrophic equine laryngeal muscle. The myosin heavy chain (MHC) composition of a given muscle determines the contractile properties and, therefore, the fiber type distribution of the muscle. MHC isoform expression in the laryngeal muscle is modulated by neural input and function, and it represents the cellular level changes that occur with denervation and reinnervation of skeletal muscle. The objective of this study was to evaluate the pattern of MHC isoform expression in laryngeal muscle harvested from normal cadavers and cadavers with naturally occurring left laryngeal hemiplegia secondary to recurrent laryngeal neuropathy. L...
Technetium-99m-HDP uptake characteristics in equine fractures: a retrospective study. Bone scintigraphy is a very sensitive diagnostic tool to detect elevated bone metabolism. In cases of fractures and fissure fractures, the radiopharmaceutical uptake in the bone is said to be increased within a few hours after the injury. In this retrospective study, the scintigraphic uptake characteristics at the fracture site of 36 horses with radiographically confirmed fractures or fissure fractures were evaluated. Uptake ratios between the fracture region and adjacent normal bone or soft tissue activity respectively were calculated and compared to different anamnestic and radiographic data...
Cartilage T2 assessment: differentiation of normal hyaline cartilage and reparative tissue after arthroscopic cartilage repair in equine subjects. To prospectively assess T2 mapping characteristics of normal articular cartilage and of cartilage at sites of arthroscopic repair, including comparison with histologic results and collagen organization assessed at polarized light microscopy (PLM). Methods: Study protocol was compliant with the Canadian Council on Animal Care Guidelines and approved by the institutional animal care committee. Arthroscopic osteochondral autograft transplantation (OAT) and microfracture arthroplasty (MFx) were performed in knees of 10 equine subjects (seven female, three male; age range, 3-5 years). A site of art...
In vitro heterogeneity of osteogenic cell populations at various equine skeletal sites. Bone cell cultures were evaluated to determine if osteogenic cell populations at different skeletal sites in the horse are heterogeneous. Osteogenic cells were isolated from cortical and cancellous bone in vitro by an explant culture method. Subcultured cells were induced to differentiate into bone-forming osteoblasts. The osteoblast phenotype was confirmed by immunohistochemical testing for osteocalcin and substantiated by positive staining of cells for alkaline phosphatase and the matrix materials collagen and glycosaminoglycans. Bone nodules were stained by the von Kossa method and counted....
Alobar holoprosencephaly, mobile proboscis and trisomy 13 in a fetus with maternal gestational diabetes mellitus: a 2D ultrasound diagnosis and review of the literature. Alobar holoprosencephaly is a rare and severe brain malformation due to early arrest in brain cleavage and rotation. Methods: We report a congenital anomalous fetus with alobar holoprosencephaly, prenatally diagnosed by two-dimensional (2D) sonography at the 40 weeks of gestation. The mother was affected by gestational diabetes mellitus and was obese (BMI > 30 kg/m(2)). 2D Ultrasound depicted the cerebral malformation, cyclopy, proboscis, cardiac defects (atrial septal defect, hypoplastic left heart, anomalous communication between right ventricle and aorta) and extremities defects. The new...
In vitro evaluation of a closed-bowel technique for one-layer hand-sewn inverting end-to-end jejunojejunosotomy in the horse. To report a technique for closed-bowel 1-layer inverting end-to-end jejunojejunal anastomosis in horses. Methods: Experimental study. Methods: Fresh cadaveric jejunal segments from 12 horses. Methods: For each bowel segment a 1-layer closed and a 2-layer inverting end-to-end jejunojejunosotomy was created. Anastomosis construction time and anastomotic bursting pressure were measured and compared. Results: Closed-bowel anastomosis was significantly faster to create than a 2-layer technique. Luminal narrowing (<30%) was similar with both techniques and comparable with other inverting techniques....
Comparison of one-layer (continuous Lembert) versus two-layer (simple continuous/Cushing) hand-sewn end-to-end anastomosis in equine jejunum. To evaluate single and double layer end-to-end anastomosis in equine jejunum. Methods: Experimental in vitro study. Methods: Mid-jejunal sections from 12 adult horses without gastrointestinal disease. Methods: Jejunal end-to-end anastomoses were performed by a continuous Lembert pattern or a simple continuous pattern oversewn with a Cushing pattern. Jejunal segments were distended with fluid at 1 L/min, and intraluminal pressure at failure, and mode of failure were recorded. Bursting pressure and bursting wall tension were calculated. Anastomosis construction time and degree of luminal reducti...
Computed tomographic documentation of a comminuted fourth carpal bone fracture associated with carpal instability treated by partial carpal arthrodesis in an Arabian filly. To report treatment of a unilateral comminuted fourth carpal bone (C4) fracture associated with carpal instability by partial carpal arthrodesis (PCA) of the middle carpal joint (MCJ) and carpometacarpal joint (CMCJ). Methods: Case Report. Methods: An 8-month-old Arabian filly. Methods: A C4 slab fracture was diagnosed radiographically; however, fracture comminution was conclusively diagnosed after computed tomographic (CT) imaging. PCA of the MCJ and CMCJ was performed with 2 narrow dynamic compression plates. Results: PCA provided appropriate carpal stability and correct limb alignment immed...
Levator labii superioris muscle transposition to treat oromaxillary sinus fistula in three horses. To describe surgical transposition of the levator labii superioris muscle to treat oromaxillary sinus fistula in horses. Methods: Clinical study. Methods: Three horses with chronic oromaxillary sinus fistula. Methods: After severing its tendinous insertion, the muscle belly of the levator labii superioris muscle was retracted and transposed through the oromaxillary sinus fistula. The tendon exited the oral cavity through a full-thickness buccal incision created adjacent to the oral end of the fistula and was then tunneled subcutaneously in a ventral direction before being anchored by sutures t...
In vitro evaluation of an inverted end-to-end equine jejunojejunal anastomosis using skin staples. To compare functional indices of end-to-end (EEA) jejunojejunal anastomosis using skin staples in horses with a 2-layer inverting hand-sewn technique. Methods: Experimental study. Methods: Jejunal segments from 8 fresh equine cadavers. Methods: For each bowel segment, 2 EEA anastomoses were created: one 2-layer hand-sewn and one 1-layer using skin staples. Time for anastomosis creation was recorded and compared. Lumen diameter of each anastomosis was measured on digital radiographs after intraluminal instillation of contrast medium and inflation of the jejunal segments to 14 mm Hg. Anastomotic...
Initial evaluation of a technique for complete cecal bypass in the horse. To describe a novel stapling technique for creation of a complete cecal bypass, without ileal transection in horses. Methods: Experimental study. Methods: Four adult horses. Methods: Through a ventral median celiotomy, jejunocolostomy was made with an intraluminal anastomosis device (ILA-100) and oversewn with a Cushing pattern to reinforce the staple line. Immediately distal to the anastomosis, 4 rows of staples were applied using a thoracoabdominal stapling device (TA-90) to occlude the lumen of the distal jejunum and proximal ileum. Necropsy exams were performed at least 60 days after surge...
Computer-assisted surgery for screw insertion into the distal sesamoid bone in horses: an in vitro study. To compare the precision of computer-assisted surgery with a conventional technique (CV) using a special guiding device for screw insertion into the distal sesamoid bone in horses. Methods: In vitro experimental study. Methods: Cadaveric forelimb specimens. Methods: Insertion of a 3.5 mm cortex screw in lag fashion along the longitudinal axis of intact (non-fractured) distal sesamoid bones was evaluated in 2 groups (8 limbs each): CV and computer-assisted surgery (CAS). For CV, the screw was inserted using a special guiding device and fluoroscopy, whereas for CAS, the screw was inserted using ...
Comparison of radiography and computed tomography to evaluate metacarpo/metatarsophalangeal joint pathology of paired limbs of thoroughbred racehorses with severe condylar fracture. To compare the orthogonal radiographic (OR) and computed tomographic (CT) appearance of paired Thoroughbred racehorse limbs with severe condylar fracture. Methods: In vitro study. Methods: Cadaveric paired limbs with severe condylar fracture (n=11 horses). Methods: Four standard radiographic and multiple transverse CT images were obtained of the fractured and contralateral limbs centering on the metacarpo/metatarsophalangeal (fetlock) joints. Radiographs and CT images were graded by 4 raters, and interobserver agreement was calculated. Imaging evaluations were supplemented by fetlock joint dis...
Collagen fiber architecture of the periodontal ligament in equine cheek teeth. The objective of this study was to examine the spatial arrangement of the fiber apparatus of the equine periodontium which is supposed to meet two contrary requirements: (1) to attach the tooth firmly and elastically to the alveolar bone; and, to be appropriately remodeled and reconstructed in order to facilitate the prolonged eruption of the tooth. Specimens of periodontal ligament were obtained from the buccal and lingual/palatal aspects of the first molars from the maxilla and mandible of 12 horses. The animals were assigned to three age groups. Histological sections were prepared from thre...
Fatty acid transport in articular cartilage. Articular cartilage extracellular matrix imposes a significant transport barrier to albumin, the principal carrier of fatty acids. It has not been previously established whether it also influences the transport of fatty acids important for chondrocyte metabolism. Albumin was labelled with rhodamine-maleimide and bound to NBD-labelled lauric acid. Plugs of fresh equine metacarpal-phalangeal cartilage and subchondral bone were incubated with the complex at 4 degrees C for 2-160 h. The fluorophore distribution was quantified using quantitative microscopy in histological sections. The fluorescence...
Ultrasonography of the equine larynx. Nasopharyngeal and laryngeal evaluation is important when examining horses with upper airway signs for poor performance. Currently endoscopy is the most common method to evaluate the equine upper airway. Ultrasonography of the equine larynx has not previously been described. Using six cadaveric specimens and four standing horses, the ultrasonographic appearance of the equine larynx was established. A scanning technique, including useful acoustic windows and the normal ultrasonographic appearance at each site, is described. Ultrasound allowed visualization of portions of the hyoid apparatus, la...
Magnetic resonance microscopy of the equine hoof wall: a study of resolution and potential. Obtaining magnetic resonance images of the inner hoof wall tissue at the microscopic level would enable early accurate diagnosis of laminitis and therefore more effective therapy. Objective: To optimise magnetic resonance imaging (MRI) parameters in order to obtain the highest possible resolution of the structures beneath the equine hoof wall. Methods: Magnetic resonance microscopy (MRM) was performed in front feet from 6 cadaver horses using T2-weighted fast spin echo (FSE-T2), and T1-weighted gradient echo (GRE-T1) sequences. Results: In T2 weighted FSE images most of the stratum medium show...
