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.
Three-dimensional anatomical description of the microarchitecture of the distal sesamoid bone in healthy and navicular syndrome-affected horses by computed microtomography. Navicular syndrome (NS) is a chronic, degenerative condition of the equine thoracic limb that compromises the distal sesamoid bone (DSB) and associated structures responsible for stabilization and load absorption during locomotion. Although historically attributed to vascular alterations, its etiology is now recognized as biomechanical, characterized by chronic overload of the deep digital flexor tendon. Conventional diagnostic techniques-radiography, scintigraphy, and ultrasonography-lack the sensitivity and precision required to detect early microarchitectural alterations. This study aimed t...
Histomorphometric Analysis of the Endometrium of Jennies (Equus asinus) and Mares (Equus caballus) in Estrus: Anatomical Differences and Possible Reproductive Implications. Assisted reproductive techniques are often extrapolated from horses to donkeys, despite poorer fertility outcomes in jennies. This issue has been attributed to unknown uterine species-specific differences. This study compared, through histomorphometry, the endometrium of jennies and mares. Endometrial biopsies (N = 12) were taken from reproductively sound jennies (n = 6) and mares (n = 6) in estrus. Histomorphometric analysis evaluated luminal (LE, µm) and glandular epithelium height (GE, µm), glandular lumen diameter (LD, µm), glandular area (GA, µm), the number of glands (#G), and glandu...
Motion Coupling at the Cervical Vertebral Joints in the Horse-An Ex Vivo Study Using Bone-Anchored Markers. The influence of soft tissue structures, including ligaments spanning one or more intervertebral junctions and the nuchal ligament, on motion of the equine cervical joints remains unclear. The present study addressed this using four post-mortem horse specimens extending from head to withers with all ligaments intact. Three-dimensional kinematics was obtained from markers on the head and bone-anchored markers on each cervical and the first thoracic vertebra during rotation, lateral bending, flexion and extension of the whole head, and neck segment. Yaw, pitch, and roll angles in 8 cervical join...
Morphological and morphometric characterization of the aorta of Brazilian horses (Equus ferus caballus, Linnaeus-1758): Comparative analysis of the aortic bulb and ascending aorta. We examined 52 horse aortas to characterize the morphological aspects of the aortic bulb wall and the ascending aorta. The morphometric data were analyzed using ImageJ®-Fiji 1.5 software. The Tunica intima was composed of endotheliocytes with scarce cytoplasm and ellipsoid nuclei, supported by a collagenous subendothelial stratum. The Tunica media was composed entirely of fascicles of vascular smooth muscle cells interspersed with bundles of collagen fibers and elastic lamellae, characterizing the aortic medial lamellar unit. The Tunica adventitia consisted of two distinct sub-layers: the ext...
Histological Study of the Normal Proximal Third Interosseus Muscle Enthesis in the Equine Pelvic Limb. In human medicine, the enthesis, or tendon-to-bone insertion, is generally considered a linked entity or 'enthesis organ' and plays a crucial biomechanical role. This study aimed to histologically assess the equine proximal third interosseus muscle (suspensory ligament) enthesis in 10 pelvic limbs from 7 horses. The area of the proximal third interosseus muscle enthesis was divided into 6 compartments based on post-mortem computed tomography and prepared for histology using haematoxylin/eosin and trichrome staining. The proximal third interosseus muscle enthesis showed a fibrocartilaginous nat...
Tendon/Ligaments: Structure and Composition. The mid-metacarpal SDFT, intrasynovial DDFT and suspensory ligament are frequently injured soft tissues in the equine athlete. The mid-metacarpal SDFT exhibits a hierarchical structure and encounters repetitive strains at its functional limit. The intrasynovial DDFT possesses fibrocartilage where opposing bony surfaces to facilitate resistance-free gliding and contains chondrocyte-like cells embedded in a proteoglycan-rich ECM. While suspensory ligament enthesis injuries are common, collagen and non-collagen ECM structure-function specializations at the bone-ligament interface are understudied...
Pathophysiology of penetrating captive-bolt stunning of horses. There has been limited research into the effectiveness of penetrating captive bolt (PCB) for stunning horses () at slaughter. This study observed 100 horses at a commercial abattoir in Mexico, stunned using pneumatic PCB. Animals were assessed at the time of stunning and immediately after for signs of effective/ineffective stunning and shot positioning, with macroscopic gross brain pathology conducted to determine brain trauma. Twenty-five percent (25/100) received more than one shot and 28% (28/100) displayed behavioural signs of ineffective stunning. Of these 28 animals, all had deviations o...
Inspiratory and expiratory tracheal pressures during high-intensity exercise in harness racehorses. Exercise-related upper respiratory tract (URT) disorders are common in racehorses. Objective assessment of URT mechanics is essential to quantify degrees of obstruction caused by URT disorders identified upon dynamic endoscopy. Objective: To establish reference values for inspiratory and expiratory tracheal pressures (cmHO) during high-speed treadmill endoscopy in harness racehorses with clinically normal URTs. Methods: Prospective observational study. Methods: Tracheal pressures were measured in harness racehorses (Standardbreds and Norwegian-Swedish coldblooded trotters) in which no URT abno...
Normal MRI features of the manica flexoria in horses and evaluation of the anatomic variability between forelimbs and hindlimbs. Manica flexoria tears are increasingly recognized as a cause of lameness in horses resulting in a need for improved pre-operative diagnosis. Partial tears are difficult to pre-operatively diagnose and thus research for diagnostics of manica flexoria tears has been seen in increasing frequency over the past decade, though a deficit of information exists for the features of this structure on MRI, which is best suited for evaluation of soft tissues. The goal is to perform an observational study on the morphometry of the normal manica flexoria prospectively and describe it retrospectively on MRI. ...
Non-contrast enhanced visualization of the equine foot vasculature in a cadaver model using time-of-flight sequence. The objective of this study was to establish a non-contrast enhanced MR angiography (NC-MRA) sequence for the equine foot (EF) using a post-mortem angiography model. Unassigned: Time-of-flight (TOF) sequences were tested using variable parameter settings and 3 slice orientations during vascular perfusion of frozen-thawed cadaver EF with paraffine oil. Transverse and dorsal orientations were planned perpendicular or parallel to the sublamellar vascular plexus at the dorsal aspect of P3, or approximately perpendicular to the coronary plexus. Visibility of the coronary plexus, sublamellar plexus,...
Equestrian-related maxillofacial injuries-a five-year retrospective review. Equestrian-related activities inherently involve the risk of serious injury. There are few reports of maxillofacial injury patterns and management arising from equestrian activities in the literature. Objective: To investigate maxillofacial fracture presentations at a tertiary trauma centre to identify injury profiles of patients who have sustained equine-based injuries over 5 years. Methods: This work involved a retrospective review of all trauma presentations to our unit over 5 years. The data collected included patient demographics, injury mechanisms and patterns, and management of fractu...
Usefulness of a Computer-Aided Learning Module for Teaching Radiology of the Equine Foot to Clinical Veterinary Students. Lameness in horses resulting from foot pathology is very common. When investigating the cause of a lameness localised to the foot, the first step is most frequently radiographic imaging. Therefore, being able to identify normal anatomy and recognise pathology on radiographs is important for a veterinary medicine student to learn. Computer-aided learning (CAL) is becoming increasingly utilised in the teaching of students on medicine-related courses, especially post-COVID where online learning has been continued in hybridisation with in-person teaching.In this study, a low-cost CAL module was cr...
Computed tomographic myelography of the cranial cervical spine in Warmblood horses with no spinal pathology-Inter- and intravertebral ratios and distribution of contrast columns in neutral and flexed cervical spine. Computed tomographic myelography (CTM) and radiographic myelography (RxM) are diagnostic for extradural spinal cord compression, but knowledge about the contrast distribution in flexion and normal position of nonaffected horses is lacking. Objective: (1) To determine the inter- and intravertebral ratios at C3-C4 of CTM in neutral and flexed positions in Warmbloods. (2) To compare the diameters of the spinal cord and the contrast columns at C3-C4 between neutral and flexed positions in CTM and RxM. (3) To evaluate the variability of measurements. Methods: Terminal in vivo method-comparison stud...
Physiological response to weight carrying and associations with conformation traits in Icelandic horses used for tour riding. Weight carrying capacity is an important trait in riding horses and it may be associated with conformation. This study examined the physiological response to a ridden incremental weight carrying test in 16 adult Icelandic horses used for tour riding. Horses carried 20% (BWR20%), 25% (BWR25%), 30% (BWR30%) and 35% (BWR35%) of their body weight (BW) in tölt (~ 5.7 m/seconds, 640 m/step), and associations with body measurements and back conformation (score) were examined. Horses were divided into two groups (narrow or broad back) and body measurements were collected. Plasma lactate was analy...
Computed Tomography of the Hyoid Apparatus in Equine Headshaking Syndrome. Headshaking is a common condition in horses, most cases are presumed idiopathic/trigeminal-nerve mediated. Diagnostic work-up of a headshaking horse may involve computed tomography (CT) of the head to exclude causative structural pathology. The relevance of the presence and severity of hyoid apparatus findings at CT to headshaking is unknown. A retrospective analysis of CT changes in the hyoid apparatus in horses was carried out. Comparisons were performed between horses with signs of headshaking and a control population and a subgroup of horses with signs of headshaking and no other 'likely...
Complementary Radiographic Projection for Evaluation of the Conchal Sinuses and Bullae in Horses. Radiographic examination of the skull is a well-established and indispensable procedure for the diagnostic evaluation of dental and paranasal sinus disorders in horses. Complementary projections make significant contributions to radiographic diagnosis in nasal conchae disorders. This article describes a complementary radiographic projection designed for the evaluation of the conchal sinuses and bullae in horses. Six equine cadaveric heads were used. Specimens were dissected, and openings were created in the ventral and dorsal nasal conchae for the introduction of radiopaque material. The new r...
Sinonasal angiofibroma in a horse. A 34-year-old Haflinger gelding presented with a unilateral, expansile, intranasal mass that regrew after partial excision. After euthanasia, a large pedunculated mass that originated from the left caudal maxillary sinus and obliterated the left nasal cavity was seen by radiological and macroscopic examination. Histopathology revealed a poorly cellular, expansile, well-vascularized neoplasm composed of a loosely arranged meshwork of spindle cells and collagen fibres. Spindle cells were immunopositive for alpha-smooth muscle actin and occasionally for vimentin, whereas endothelial cells immunol...
Morphological variations of the interatrial septum and potential implications in equine cardiology. The interatrial septum morphology, shaped by the septum primum and secundum fusion, results in the formation of the fossa ovalis (FO) and its limbus. Incomplete fusion can lead to a patent foramen ovale (PFO), while complete fusion may produce septal ridges and pouches (SPs), with SPs in humans linked to ischemic stroke and atrial arrhythmias. In horses, atrial tachycardia and fibrillation often originate near the FO. This study examines adult equine interatrial septum morphology to enhance understanding the region and guide electrophysiological interventions for equine cardiac arrhythmias. Po...
Analysis of different techniques for injection of the interspinal space in horses. Impingement of spinous processes (SPs) is commonly diagnosed in the equine athlete. For diagnostic and therapeutic purposes, local injections are performed at the level of the space between adjacent spinous processes in affected horses. Objective: To assess the accuracy of different techniques for the local injection of the interspinal space in the equine thoracolumbar spine. Methods: Ex vivo experimental study. Methods: Equine thoracolumbar spine specimens were used to compare three techniques for needle insertion (midline; bilateral abaxial; unilateral oblique), two needles (20G-1½″; 20G-...
INJECTION OF THE INSERTION OF THE COLLARAL LIGAMENT OF THE DISTAL INTERPHALANGEAL JOINT IN STANDING HORSES USING THE PALMAR RADIOGRAPHIC-GUIDED APPROACH. Injury to the collateral ligament (CL) of the distal interphalangeal joint (DIPJ) is recognized as a source of lameness in horses. Intralesional injection has been advocated to increase return to performance. This study was a proof-of-concept study in standing horses to evaluate success of a palmar radiographic-guided approach for injecting insertions of the DIPJ CLs previously described in cadaver limbs. Horses were sedated, nerve blocked, and placed on wooden blocks with the limb to be injected staggered approximately 20cm cranially to the other limb. The DIPJ CL insertion was injected, usin...
Internal carotid artery dolichoarteriopathies in the horse: An endoscopic and anatomic study. Endoscopy of the guttural pouches in neonatal foals occasionally reveals atypical aspects in the course of the extracranial internal carotid arteries (ICAs) that are hardly seen in adult horses. While in veterinary medicine the data available on the presence of these anomalies in domestic mammals are limited and incomplete, in human medicine the morphological aspects of the ICAs have been the subject of extensive studies. Anomalies in the course and geometry of ICAs are commonly defined as dolichoarteriopathies, and should be classified as tortuous, kinked or coiled. To document whether the an...
A dorsal ultrasound-guided approach to perineural injection of the sixth and seventh cervical spinal nerves in horses is accurate and does not result in epidural placement. To determine the accuracy of a dorsal ultrasound-guided approach for perineural injection of the sixth and seventh cervical spinal nerves (CSNs) with the use of a clinically relevant volume of injectate (2 mL). We hypothesized that the majority of injections would result in identification of contrast solution in the intervertebral foramen (IVF) on CT and corresponding methylene blue dye staining of the CSN on postmortem evaluation, and distribution of injectate into the epidural space would not occur. Unassigned: 7 horses donated to the University of Pennsylvania New Bolton Center for euthanas...
Computed tomographic measurements in 110 front hooves of non-lame Thoroughbred racehorses and Warmblood showjumpers. There are no published reference ranges on computed tomographic (CT) hoof wall and sole measurements. Objective: To establish reference ranges for CT measurements of the hoof wall and sole in non-lame horses, and to investigate associations between measurements and signalment, laterality, and medial or lateral sides. Methods: Retrospective, cross-sectional study. Methods: Soft tissue reconstructions of fan-beam CT studies of 110 front feet of 56 non-lame horses (30 Thoroughbred racehorses, 26 Warmblood showjumpers), performed in non- to semi-weightbearing positions, were analysed. Hoof wall th...
Gross anatomy, computed tomographic contrast tenography, and needle endoscopy of the equine medial digital flexor tendon sheath. To investigate the computed tomography (CT) and gross anatomy of the equine medial digital flexor tendon sheath (MDFTS), and the endoscopic anatomy and approach to the MDFTS. Methods: Ex vivo experimental study and one clinical case. Methods: Twelve clinically normal cadaveric hindlimbs. Methods: Dissection, native and contrast CT scans were conducted to evaluate the anatomy of the MDFTS. Based on these findings, the portal locations for the endoscopic approaches were determined. Six hindlimbs were used in the pilot phase and another six limbs were selected for the main study. Endoscopic image...
Major Salivary Gland Examinations of the Donkey (Equus asinus) Using Sectional Anatomy, Computed Tomography and Magnetic Resonance Imaging. Visualizing the major salivary glands (MSGs) in domestic mammals using plain radiology and identifying damaged their structures is impossible. To accurately display MSGs, the knowledge of normal sectional imaging anatomy is essential for veterinarians, aiding them significantly in identifying the exact relations and position of MSGs; however, no reports on the MSGs sectional imaging anatomy in this species have been made. Objective: This study aimed to evaluate computed tomography (CT), magnetic resonance imaging (MRI) and gross sections of MSGs. Methods: Seven healthy adult donkeys were used ...
Equine cadaveric study suggests tibial and fibular nerve block is feasible with a single ultrasound-guided injection via a caudocranial midfemoral approach. To describe anatomical references and sonoanatomy of an echo-guided injection for blocking the tibial and common fibular nerves with the use of a caudocranial midfemoral approach and to evaluate dye spreading in horse cadavers. Unassigned: 1 horse cadaver preserved in glycerin was used for the anatomical study, and 14 fresh horse cadavers were used for the dye spreading study. The experimental procedures were conducted on the first cadaver on March 25, 2021, and on the last cadaver on October 5, 2022. A glycerin-preserved horse cadaver's pelvic limb was dissected to identify anatomical landmar...
Resistivity and Pulsatility Indexes Renal Values Do Not Differ When Obtained from Abdominal or Transrectal Approaches in Healthy Horses. Early detection of renal deficient function is imperative for the success of treatments and determining prognosis. In horses, a renal ultrasound can be performed through the abdominal wall (TA) or transrectally (TR), being an important tool for the evaluation of the kidneys. Besides renal morphology, resistivity (RI) and pulsatility indexes (PI) may be early tools to detect renal injury as they reflect arterial compliance. Twenty-nine healthy adult horses were sonographically evaluated by TA and TR approaches, measuring RI and PI on both kidneys. The mean values from the TA for RI and PI in th...
Comparison of a dorsolateral approach and a dorsomedial approach to access the medial malleolus of the distal tibia in horses. To determine the utility of a dorsolateral arthroscopic approach to the tarsocrural joint (TCJ) to examine and surgically access the medial malleolus (MM) and compare this to the standard dorsomedial approach to the MM. Methods: Experimental cadaver study. Methods: Six pelvic limbs from four adult horses. Methods: Arthroscopic examination of the dorsal aspect of the TCJ was performed followed by the dorsomedial and dorsolateral surgical approaches to the MM, in randomized order on cadaver limbs (n = 6). The dorsomedial approach involved placing the arthroscope and instrument in the dorsome...
Computed Tomographic Tenography of the Equine Carpal Flexor Tendon Sheath. Exploratory tenoscopy is considered the gold standard technique to identify intrathecal pathology of the equine carpal flexor tendon sheath (CFTS). Preoperative diagnosis allows for more precise prognostication and surgical planning, potentially associated with improved surgical outcomes. This prospective, descriptive, anatomical study aimed to describe the anatomy of the equine CFTS using noncontrast and contrast CT in clinically normal cadaver limbs. Ten pairs of equine forelimbs free of gross external abnormalities were examined from mid-antebrachium to distal metacarpus. Specimens initiall...
Preoperative computed tomography imaging for accurate diagnosis and surgical planning in equine cranial disorders: two case reports of congenital malformations. Computed tomography (CT) offers high-resolution, three-dimensional imaging, making it particularly valuable for assessing complex structures, such as the head, especially when conventional radiography and endoscopy are insufficient for a definitive diagnosis. Herein, we present two cases of equine cranial disorders resulting from congenital malformations. In case 1, which had a dentigerous cyst, CT images confirmed the location of the ectopic tooth within the skull and a detailed fistula tube. In case 2, which had temporohyoid osteoarthropathy, CT examination revealed that the stylohyoid bone ...