Topic:Blood Vessels
Blood vessels in horses are integral components of the circulatory system, responsible for the transportation of blood throughout the body. They consist of arteries, veins, and capillaries, each serving distinct functions in maintaining circulatory efficiency. Arteries carry oxygen-rich blood away from the heart to various tissues, while veins return deoxygenated blood back to the heart. Capillaries facilitate the exchange of nutrients, gases, and waste products between blood and tissues. The structure and function of equine blood vessels are subjects of study due to their role in health and disease, including conditions such as laminitis and equine metabolic syndrome. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of blood vessels in horses.
Use of computed tomography angiography to evaluate the vascular anatomy of the distal portion of the forelimb of horses. To provide a detailed description of the vascular anatomy of the distal portion of the forelimbs of horses by use of computed tomography angiography (CTA). Methods: 6 forelimbs of 5 horses and 1 forelimb from an equine cadaver; none of the horses had orthopedic or vascular disease. Methods: Horses were anesthetized and CTA was conducted on the dependent forelimb. A catheter was inserted in the median artery, and contrast medium was infused at a rate of 3 mL/s. A computed tomography (CT) scanner was used to obtain contiguous slices from the region of the proximal sesamoid bones to the toe. All ...
Characteristics of the in vitro hypoxic pulmonary vasoconstrictor response in isolated equine and bovine pulmonary arterial rings. Hypoxaemia accompanies dorsal recumbency in the horse and frequently complicates general anaesthesia. The physiology associated with this phenomenon is poorly understood. One possible cause of poor tolerance to dorsal recumbency is an absent or reduced response to hypoxic pulmonary vasoconstriction (HPV). This study compared the HPV response in isolated pulmonary artery vessels from equivalent regions of equine and bovine lung. Methods: Equine and bovine, in vitro study. Methods: Equine and bovine pulmonary arteries were removed from the lungs of euthanased horses and cattle. Measurements of i...
Influence of weight bearing and hoof position on Doppler evaluation of lateral palmar digital arteries in healthy horses. To describe the pulsed-wave Doppler tracing of the equine lateral palmar digital artery and its modification in relation to standardized changes in posture. Methods: 17 healthy Saddlebred horses. Methods: Pulsed-wave Doppler examinations of left and right lateral palmar digital arteries of the horses were performed. The baseline examination was performed on each forelimb while horses were standing squarely with the body weight equally distributed among the 4 limbs (BED position). For each forelimb, the examination was repeated during 3 standardized modifications of the horse's posture (non-wei...
Clinical anatomy of the equine sphenopalatine sinus. Disorders of the equine sphenopalatine sinus, including empyema and neoplasia, have been reported to cause damage to cranial nerves II and V. However, the clinical anatomy of these sinuses is not well described in horses. Objective: To examine the anatomy of the sphenopalatine sinuses in a range of equidae and, in particular, to examine the relationship of these sinuses to adjacent major nerves and vessels. Methods: The anatomy of the sphenoidal and palatine paranasal sinuses was examined in 16 equidae, primarily using transverse skull sections. Relevant structures were documented and photogra...
Structure of long bones in mammals. Techniques for staining (silver, osmium, metal sulfides, ink) and microphotography (epi-illumination) of polished bone surfaces have been developed to visualize the three-dimensional structure of the shafts of mammalian long bones. Bone is a two-compartment system with capillaries and some kinds of connective tissue in one compartment separated from fibers of bone collagen, often forming lamellae, in the other. Laminar bone consists of stacks of lamellae separated by vascular spaces containing capillary network sheets. It is deposited at the periosteal and endosteal surfaces. Osteonic bone, we...
Parainguinal laparocystotomy for urolith removal in geldings. To describe parainguinal laparocystotomy for urolith removal and to report outcome. Methods: Prospective clinical study. Methods: Ten geldings with uroliths. Methods: Signalment, number, size, type of uroliths, surgical technique, and complications were recorded. Long-term follow-up was obtained by telephone interviews with the client and/or examination by the referring veterinarian. Results: Cystic calculi, 3-9 cm in diameter, were removed by parainguinal laparocystotomy. Mean surgical time was 59 minutes (range, 40-100 minutes). With this approach, ligation of the pudendal or superficial epi...
The mystery of fungal infection in the guttural pouches. Advances in the understanding of guttural pouch physiology and novel therapeutic approaches to mycotic infections in the horse are reviewed. It is suggested that the guttural pouches may contribute to the regulation of arterial blood temperature, cooling the circulation to the brain to below body temperature. Aspergillus spp. is the major organism found in a guttural pouch affected with mycosis but it is unclear why this agent becomes aggressive. Conventional therapy aims to prevent fatal haemorrhage and to treat any neurological lesions but it is desirable to try to prevent the disease. A tec...
Endotoxin-induced digital vasoconstriction in horses: associated changes in plasma concentrations of vasoconstrictor mediators. Lipopolysaccharide (LPS) infusion reduces digital perfusion, but the mediators responsible remain undetermined. Objective: To identify vasoconstrictor mediators released following LPS infusion and relate their appearance in plasma to digital blood flow alterations. Methods: Blood flow in the lateral digital vessels of 6 Thoroughbred horses, following a 30 min infusion of LPS (E. coli 055:B5; 30 ng/kg), was measured using Doppler ultrasonography. Concomitant measurements of hoof wall and coronary band surface temperatures (HWST and CBST) were made. Serial blood samples were collected and plasma...
The effects of vasoactive amines found in the equine hindgut on digital blood flow in the normal horse. Disturbances of digital blood flow are thought to be fundamental to the pathophysiology of acute laminitis. However, factors linking the initiating events in the equine hindgut with these disturbances in the foot remain to be determined. Objective: Amine compounds, formed by bacteria in the equine hindgut, have digital vasoconstrictor effects in vivo. Methods: Tryptamine (1.6 microg/kg/min) and phenylethylamine (2.13 microg/kg/min) were infused i.v. into standing nonsedated horses. Digital blood flow was measured by Doppler ultrasound and foot surface temperature was monitored. Plasma 5-hydrox...
Desmoplakin and Plakoglobin–specific markers of lymphatic vessels in the skin? Monoclonal antibodies against Desmoplakin and Plakoglobin were tested for their suitability as specific markers of lymphatic vessels. The tissue samples were taken from horse skin in an attempt to establish the horse as a model for human lymphatic diseases. To obtain a clear, positive identification of blood and lymphatic vessels, immunohistochemical staining with antibodies against vascular endothelial growth factor receptor 3 (VEGFR-3) and platelet endothelial adhesion molecule (PECAM-1, CD31), was compared with Desmoplakin and Plakoglobin. Because anti-VEGFR-3 is specific for lymphatic vess...
Aberrant blood flow area and plasma gonadotropin concentrations during the development of dominant-sized transitional anovulatory follicles in mares. Color Doppler transrectal ultrasound was used to evaluate blood flow area in the wall of dominant anovulatory follicles versus ovulatory follicles in mares during the transition between anovulatory and ovulatory seasons. Daily examinations were done in 11 control mares toward the end of the anovulatory season. In 13 separate mares, follicular fluid was collected from 30-mm follicles, and blood flow areas from control mares were used as a basis for designating the sampled follicle as either anovulatory or ovulatory. Blood flow area in the controls ranged from 0.18 to 0.35 cm(2) in six mares on ...
Differential blood flow changes between the future dominant and subordinate follicles precede diameter changes during follicle selection in mares. Diameter deviation during a follicular wave is characterized by the continued growth of the developing dominant follicle and reduced growth and regression of the subordinate follicles. This study considered the hypothesis that reduced blood flow in the future largest subordinate follicle precedes the beginning of diameter deviation. The hypothesis was tested by quantifying the daily changes in blood-flow velocities and blood-flow area within the wall of follicles before and during diameter deviation in mares (n = 7). The blood-flow end points were quantified daily by transrectal color Doppler ...
The coagulation system in horses with colic. Colic in horses very often induces changes in the coagulation system causing the development of disseminated intravascular clotting. It is promoted by blood concentration and an increase in exposition of coagulation activators with a simultaneous decrease in coagulation inhibitors activity, mainly antithrombin III. Progressing blood platelets aggregation supports production of microthromboses and plugging capillary vessels. The progression of this processes causes complications in basic disease and becomes the reason for therapeutic failure. Determination of coagulation system indexes such as ...
Oxytalan fibres in the periodontal ligament of equine molar cheek teeth. The distribution and arrangement of oxytalan fibres were examined in periodontal specimens of cheek teeth from seven horses. Oxidation prior to aldehyde fuchsin exposition permitted a selective staining of the oxytalan fibres, which are a distinct component of the elastic fibre system. On three horizontal levels of the periodontium--(a) subgingival, (b) middle third and (c) apical--two oxytalan fibre groups were shown histologically: 'blood vessel-related' and 'independent' oxytalan fibres. In levels a and b, both groups were arranged in a typical occluso-apical alignment along the reserve cro...
Quantitative effect of tenorrhaphy on intrinsic vasculature of the equine superficial digital flexor tendon. To compare effects of the locking-loop suture pattern (LLP) and 3-loop pulley (3LP) suture pattern for tenorrhaphy on the intrinsic vasculature of the superficial digital flexor tendon (SDFT) of horses in vitro after surgery. Methods: 16 forelimbs obtained from 8 mature horses. Methods: Tenotomy and subsequent tenorrhaphy was performed in anesthetized horses. Following systemic administration of heparin, horses were euthanatized and the limbs were removed and placed under tension to load the flexor tendons. The intrinsic vasculature was then perfused with a mixture of barium sulfate and water....
In situ coagulation and transection of the ovarian pedicle: an alternative to laparoscopic ovariectomy in juvenile horses. The feasibility of leaving the ovaries within the peritoneal cavity after laparoscopic coagulation and transection of the ovarian pedicle was assessed in the juvenile horse. Elective ovariectomy was performed on 10 quarter horses, aged 4 to 5 mo, with the fillies in a Trendelenburg position. The mesovarium was isolated, and multiple coagulation and transection cycles were performed until all ovarian attachments had been severed. The ovaries were dropped within the abdomen, and hemostasis of the transected mesovarium was evaluated before closure. The mean surgical time was 33 min (range, 23 to ...
Color Doppler ultrasound evaluation of testicular blood flow in stallions. The objectives of this study were to evaluate the potential use of color Doppler ultrasound to characterize blood flow to the stallion testis, and to establish reference values for Doppler measures of blood flow in the testicular artery of the stallion. Both testes from each of 52 horses were examined using a pulsed-wave color Doppler ultrasound with a sector array 5/7.5 MHz transducer with a 1mm gate setting. Peak systolic velocity (PSV), end diastolic velocity (EDV), resistive index (RI), and pulsatility index (PI) of the testicular artery were measured in each of two locations, the convolut...
Arterionecrosis of the equine mesentery in naturally occurring endotoxaemia. This report describes the mesenteric arteriolar lesions in a Thoroughbred racehorse with endotoxaemia due to colic. The vascular lesions consisted of a striking loss of medial smooth muscle cells, associated with granular cell debris derived from necrosed muscle cells, plasma insudation, erythrocyte infiltration and the deposition of a fibrinoid substance (fibrinoid degeneration) in the entire arterial wall, possibly produced by the infiltration of blood components through endothelial cell junctions into the arterial wall. The morphology of the mesenteric arteriolar necrosis closely resembled ...
Transrectal Doppler sonography of uterine and umbilical blood flow during pregnancy in mares. Transrectal color Doppler sonography was used to investigate uterine and umbilical blood flow during pregnancy (duration, 46-48 weeks) in four mares. The resistance index (RI) and blood flow volume (VOL) of the uterine arteries ipsilateral and contralateral to the conceptus, and the presence of an early diastolic notch in the Doppler wave, were evaluated every 4 week throughout pregnancy. Fetal blood flow was calculated semiquantitatively every 2 week (from 20 to 40 weeks), using the RI of the umbilical arteries. During the entire period of investigation, there were no significant individual v...
The effect of acetylsalicylic acid and captopril on uterine and ovarian blood flow during the estrous cycle in mares. In previous studies, transrectal color Doppler sonography was used to demonstrate an increase in genital blood flow resistance in subfertile mares. The objectives of the present study were to determine the effects of an anticoagulant (acetylsalicylic acid) and a vasodilator (captopril) on uterine and ovarian perfusion and plasma progesterone concentrations in cycling mares. From Day 1 to 11 of an estrous cycle (Day 0=day of ovulation following prostaglandin-induced luteolysis), five Trotter mares were given 2500 mg lactose, 2500 mg ASA, or 50 mg captopril twice daily in their feed (one compoun...
Evaluation of a vessel-sealing device for small intestinal resection and anastomosis in normal horses. To compare arterial bursting pressure after vessel closure using a vessel-sealing device (LigaSure Atlas Laparoscopic Sealer/Divider Instrument; Valleylab, Boulder, CO), a ligate-and-divide stapling device (LDS), and 2-0 polydioxanone suture. To evaluate the LigaSure Atlas as a method for ligation of the mesenteric vasculature during small intestinal resection in normal horses. Methods: Experimental study. Methods: Part A: jejunal segments from 19 horses. Part B: 6 horses, aged 1 to 18 years, weighing 330 to 509 kg. Methods: Part A: Jejunal segments with mesenteric vessels were collected from ...
Characterisation of the response of equine digital arteries and veins to substance P. Substance P (SP), a potent vasodilator, has been detected in equine digital sensory-motor nerves. The aim of the study was to characterise the functional responses of equine digital blood vessels to exogenous SP. Pre-constricted equine digital arteries (EDA) and veins (EDV) vasodilated in a biphasic, endothelium- and concentration-dependent manner to SP. A nitric oxide (NO) synthase inhibitor Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME; 300 microm) inhibited both phases of the relaxation response curve of EDAs to SP by >70%. In EDVs, the first relaxant phase to SP was largely...
Do Thoroughbred and Standardbred horses have similar increases in pulmonary vascular pressures during exertion? To test the hypothesis that the pulmonary vascular pressures of Thoroughbred and Standardbred horses behave similarly during exertion. Measurements were made on 5 Thoroughbred and 5 Standardbred horses on a treadmill at rest and during 3-minute exercise intervals at speeds predicted to produce 75%, 90%, and 100% maximal heart rate. Left forelimb acceleration, heart rate, esophageal pressure, and pulmonary artery pressure were measured continuously. Pulmonary capillary and wedge pressures were measured during intermittent occlusion of the pulmonary artery. Breathing rate and gait frequency were...
Characterization and comparison of the responses of equine digital arteries and veins to endothelin-1. To compare the responses of equine digital arteries (EDAs) and equine digital veins (EDVs) to endothelin-1 (ET-1) and determine the role of the endothelium and type of receptors involved in the modulation and mediation of those responses, respectively. Methods: 5 to 9 palmar digital vessels/experiment from 28 healthy horses. Methods: Rings of dissected vessels were mounted under tension between force transducer wires in organ baths containing Krebs-Henseleit solution at 30 degrees C. Responses of EDAs and EDVs (with intact [+e] or denuded [-e] endothelium) to cumulative concentrations of ET-1 ...
Comparative histology of the laminar bone between young calves and foals. Laminar bone or primary plexiform tissue, not Haversian bone, shows an alternative concentric pattern of laminar-bone units or plates around the bone marrow periphery of long bones, although the laminar bone is gradually replaced by osteons during the growth period. One laminar-bone unit is constructed with a hypercalcified line in the center, woven bone on both sides of the line, and lamellar bone with laminated appositional lines. Such a laminar bone showing a homogeneous calcification has been reported in young calves and some young large animals, but it has not been reported in foals altho...
Immunohistochemical study of equine endometrial extracellular matrix during the oestrous cycle. This study was designed to identify the distribution of type IV collagen, laminin, and fibronectin with an avidin-biotin method in sections of equine endometrial samples, fixed in Bouin's solution and embedded in paraffin wax. Thirty endometrial biopsies were collected at three different stages of the oestrous cycle. The basement membrane of luminal epithelium reacted positively with antibody against type IV collagen. Both type IV collagen and laminin were found in the basement membranes of endometrial glands, and fibronectin occurred diffusely in the interstitial tissue. Blood vessels express...
Inclined running increases pulmonary haemorrhage in the Thoroughbred horse. Capillary stress failure-induced (exercise-induced) pulmonary haemorrhage (EIPH) during intense running in horses is thought to involve both intravascular (i.e. mean pulmonary arterial pressure [Ppa] > 100 mmHg) and extravascular (e.g. negative inspiratory pressure swings) mechanisms. Objective: That inclined running would reduce breathing frequency (coupled to stride frequency) and increase tidal volume thus increasing lung volume changes and intrapleural pressure swings resulting in more pronounced EIPH. Methods: Six Thoroughbred horses were run to volitional fatigue (incremental step tes...
The cardiopulmonary effects of severe blood loss in anesthetized horses. To characterize the acute cardiopulmonary effects of severe hemorrhage in anesthetized horses. Methods: Prospective experimental study. Methods: Three geldings and six mares, aged 14.4 +/- 2.7 years, weighing 486 +/- 41 kg (range: 425-550 kg). Methods: Horses were anesthetized using xylazine, guaifenesin, ketamine and halothane or isoflurane. Cardiovascular variables, hematocrit, total solids, capillary refill time (CRT) and color of mucous membranes were measured as blood was collected from the carotid artery into sterile plastic bags. Arterial blood gas analysis was also performed. Results: ...
Effects of monoamines formed in the cecum of horses on equine digital blood vessels and platelets. To determine in vitro vasoactive potency of monoamines formed in the cecum and found in the systemic circulation of horses. Methods: Segments of digital blood vessels obtained from 6 healthy mixed-breed horses and ponies euthanatized at an abattoir and platelets isolated from 4 healthy ponies. Methods: Paired rings of digital artery and vein from the same horse were examined, and isometric tension was recorded. Concentration-response curves for tryptamine (TRP), tyramine (TYR), phenylethylamine (PEA), isoamylamine (IAA), and isobutylamine (IBA) were obtained. Vasoconstrictor mechanisms were in...