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Topic:Arteries
Arteries in horses are blood vessels responsible for carrying oxygenated blood away from the heart to various tissues and organs throughout the body. These vessels are integral to the circulatory system, facilitating the delivery of essential nutrients and oxygen to maintain cellular function and overall health. The structure of equine arteries includes a thick muscular wall that accommodates the high pressure of blood flow, allowing for efficient transport. Research on equine arteries often focuses on their anatomical characteristics, physiological functions, and potential disorders that may affect them, such as atherosclerosis or aneurysms. This page compiles peer-reviewed research studies and scholarly articles that examine the anatomy, physiology, and pathophysiology of arteries in horses.
Effect of chronic hypoxia on breathing and EMGs of respiratory muscles in awake ponies. Breathing, diaphragmatic and transversus abdominis electromyograms (EMGdi and EMGta, respectively), and arterial blood gases were studied during normoxia (arterial PO2 = 95 Torr) and 48 h of hypoxia (arterial PO2 = 40-50 Torr) in intact (n = 11) and carotid body-denervated (CBD, n = 9) awake ponies. In intact ponies, arterial PCO2 was 7, 5, 9, and 11 Torr below control (P less than 0.01) at 1 and 10 min and 5 and 24-48 h of hypoxia, respectively. In CBD ponies, arterial PCO2 was 3-4 Torr below control (P less than 0.01) at 4, 5, 6, and 24 h of hypoxia. In intact ponies, pulmonary ventilation, ...
Participation of H1-receptors in histamine-induced contraction and relaxation of horse coronary artery in vitro. The mechanisms of histamine-induced contraction and relaxation were investigated in rings isolated from a middle part of the left descending coronary arteries of horses. Intact and endothelium-denuded preparations were compared. Rings of horse coronary arteries contracted in response to histamine in a concentration dependent manner, but some of them relaxed with lower concentrations and contracted with higher concentrations. Removal of the endothelium abolished the relaxation and potentiated the contraction. The pD2 values were 4.70 +/- 0.08 in the rings with intact endothelium and 4.95 +/- 0....
Microvascular circulation of the cecum in horses. The microvascular circulation of the cecum was studied in 15 adult horses, using microangiography and light microscopy combined with gross studies and scanning electron microscopy of vascular replicas. After heparinization, the horses were euthanatized and the cecum was transected at the cecocolic junction. Blood was flushed free of the circulation with isotonic NaCl and the cecal lumen was slightly distended. In 6 horses, the vascular system was injected with a modified radiopaque medium and evaluated radiographically. Sections evaluated radiographically were also prepared for histologic exam...
Effects of xylazine butorphanol on cecal arterial blood flow, cecal mechanical activity, and systemic hemodynamics in horses. A chronic model with an ultrasonic transit time blood flow probe and strain gauge force transducers implanted on the cecum was used to evaluate cecal mechanical activity and cecal arterial blood flow in 4 conscious adult horses. Intravenous administration of xylazine (1.1 mg/kg of body weight) significantly decreased heart rate and cardiac output, but significantly increased diastolic pulmonary arterial pressure, mean pulmonary arterial pressure, carotid arterial pressure, and central venous pressure. Lateral cecal arterial blood flow after xylazine administration was decreased substantially m...
Haemodynamic effects of change in position and respiration mode during a standard halothane anaesthesia in ponies. The effects of change in position and respiration modes were studied in 5 experimental ponies during a standard halothane anaesthesia. A marked cardiovascular depression (decrease in mean arterial blood pressure, cardiac output, stroke volume and left ventricle work) occurred in recumbent, spontaneously breathing ponies. No significant differences were found between right and left lateral recumbency. The most pronounced cardiovascular depression was observed in the dorsal position. Sternal recumbency appeared to be slightly beneficial (higher systemic blood pressure and arterial oxygenation). ...
Palliative repair of aortic atresia associated with tricuspid atresia and transposition of the great arteries. Successful palliative repair of aortic atresia and hypoplastic aortic arch associated with tricuspid atresia in a neonate is described. The repair consisted of reconstruction of the hypoplastic aortic arch with an equine pericardial patch, division of the patient ductus arteriosus, connection of the pulmonary artery to the aorta, implantation of the proximal part of the ascending aorta into the main pulmonary artery, and anastomosis of a polytetrafluoroethylene graft 5 mm in diameter between the right ventricular outflow tract and the central pulmonary artery, which was transferred anteriorly ...
Action of sympathomimetic drugs on the bronchial circulation of the horse. In the quietly standing horse I.V. administration of adrenaline decreased, and of dobutamine increased, bronchial artery flow. These changes paralleled changes in arterial pressure. With phenylephrine and noradrenaline bronchial artery flow decreased while arterial pressure increased, indicating active vasoconstriction in the bronchial circulation. With clenbuterol an increase in bronchial artery flow was accompanied by a decrease in systemic blood pressure, indicating bronchial arterial vasodilatation. We conclude that alpha-constrictor and beta 2-dilator receptors are present in the bronchia...
An investigation of the incidence of chronic obstructive pulmonary disease (COPD) in random populations of Swiss horses. The incidence of Chronic Obstructive Pulmonary Disease (COPD) in Switzerland was determined in three groups of horses selected at random. Group A (97 horses) and Group B (93 horses) had no history of respiratory disease, but Group C (113 horses) had a history of lower respiratory tract disease. All horses were examined by auscultation of the respiratory tract under forced breathing, endoscopic examination of the upper and lower respiratory tract, arterial blood gas analysis at rest and cytological examination of respiratory secretions (RS). Fifty-four per cent of the horses in Group A and 54.8...
Histology and morphometry of Strongylus vulgaris-mediated equine mesenteric arteritis. Histological and morphometric evaluation of equine cranial mesenteric arteries was performed on 239 and 89 arteries, respectively. Histological examination revealed that thrombosis and the severity of inflammation varied on a seasonal basis and were directly associated with larval presence. Intimal and adventitial fibrosis were generally of greater severity than medial fibrosis. Fibrosis of the vasa vasorum was less frequent than fibrosis of the artery itself. Morphometry revealed a significant increase in intimal, adventitial and, to a lesser extent, medial area in affected as compared with n...
In vitro responses of equine digital vessels to dopamine and fenoldopam. The in vitro responses of isolated vascular preparations of digital arteries and veins obtained from healthy anaesthetised horses were determined for dopamine and fenoldopam. The digital vessels were harvested, cut into 4 mm vascular segments, suspended in tissue baths and attached to force-displacement transducers. Dose-response studies between 10(-8) and 10(-4)M concentrations were performed for all drugs. The change in tension of each vascular ring was measured in grams of force. The reactivity between palmar and plantar digital vessels and baseline vascular responses were determined for do...
Cardiorespiratory responses to electrical stimulation of the buccal mucosa in ponies. The cardiovascular and respiratory responses to electrical stimulation of the buccal mucosa under general anaesthesia in ponies were measured in order to provide some insight into the cardiorespiratory effects of anaesthesia in equidae. This knowledge may be useful for reducing morbidity during clinical anaesthesia in horses. Anaesthesia was induced with intravenous thiopentone and maintained with 1.3 per cent inspired halothane in oxygen. Arterial blood pressure, heart rate, minute volume, tidal volume, respiratory rate, arterial blood gas tensions and clinical signs of anaesthetic depth were...
Effect of endotoxin administration on equine digital hemodynamics and starling forces. Using a pump-perfused extracorporeal isolated digital preparation, the effects of a 30-minute infusion of either saline solution (control) or endotoxin on equine digital hemodynamics and microvascular function were determined. Digital blood flow and arterial, venous, and capillary pressures were recorded at 15-minute intervals for 150 minutes. From these data, total vascular resistance and pre- and postcapillary resistances were calculated. Isogravimetric capillary filtration coefficient, vascular compliance, and the osmotic reflection coefficient were determined after the last hemodynamic mea...
Effect of partial spinal cord ablation on exercise hyperpnea in ponies. We addressed the role of spinal afferent information in the exercise hyperpnea. Arterial PCO2 (PaCO2) was assessed in 10 normal ponies during low (1.8 mph 7% or 17% grade) or moderate (6 mph 7% grade) treadmill exercise. After control studies, bilateral spinal ablation (SA) of the dorsolateral sulcus and dorsolateral funiculus at L2 was performed in seven ponies. In normal ponies within the first 90 s of exercise, PaCO2 initially decreased 2.7, 4.1, and 5.2 Torr below rest at the three work loads, respectively (P less than 0.05). PaCO2 thereafter increased toward resting levels but remained 1....
Doxapram infusion during halothane anaesthesia in ponies. Doxapram, 0.05 mg/kg bodyweight/min, was infused during the second hour of 2 h halothane anaesthesia in six ponies. Two of the ponies were anaesthetised on a second occasion as controls and given 5 per cent dextrose in place of the doxapram. Respiratory depression typical of halothane anaesthesia in ponies developed in the first hour of anaesthesia and continued during the second hour in the control animals. During doxapram infusion arterial carbon dioxide tension decreased and pH increased. Arterial blood pressure increased but there was no change in pulse rate, the electrocardiogram or arter...
Vascular response of the equine radius to cerclage devices. The arterial blood supply to the diaphysis of the radius, and the vascular reaction when three cerclage devices (cerclage wire, Parham-Martin band, and a partially contacting band) were applied 2 cm apart, were studied in six adult ponies. The opposite radial diaphysis served as the control. Ponies were euthanatized at weeks 4 and 8. A centrifugal blood flow pattern was demonstrated by microangiography. Larger numbers of medullary arteries exist in equine than in canine and human long bones. Changes in centrifugal blood supply were not identified beneath any of the cerclage devices.
Pulmonary artery, aortic and oesophageal pressure changes during high intensity treadmill exercise in the horse: a possible relation to exercise-induced pulmonary haemorrhage. This study investigated changes in packed cell volume (PCV), pulmonary artery and aortic pressures, and the interaction between oesophageal pressure and pulmonary artery and aortic pressures during strenuous exercise in the horse. It was hypothesised that oesophageal pressure changes summate with pulmonary artery and aortic pressures during exercise and contribute to exercise-induced pulmonary haemorrhage (EIPH). Acute treadmill exercise (10 m/sec, 3 degrees incline) produced increases in heart rate (HR) from 50 to 202 beats/min; mean pulmonary artery pressure (PAP) from 28 to 80 mmHg; mean ao...
Ischemic optic neuropathy and blindness after arterial occlusion for treatment of guttural pouch mycosis in two horses. Ischemic optic neuropathy accompanied by blindness was induced in 2 horses after surgical occlusion of the external and internal carotid and greater palatine arteries, performed as part of the management of guttural pouch mycosis. The blindness was acute and unilateral and may have been caused by ischemic retinal damage. Vascular occlusion is a recommended procedure for treatment of guttural pouch mycosis. Retinal damage and blindness are a possible complication if all possible sources of hemorrhage are occluded.
Hemodynamic responses of the equine digit to intravenous and digital arterial infusion of dopamine. In 6 adult horses anesthetized with pentobarbital, the hemodynamic responses of the equine digit to infusion of dopamine were evaluated by use of an isolated extra corporeal pump perfused digital preparation. Digital blood flow was maintained at a constant rate that was independent of systemic hemodynamic changes. Three sequential experiments were performed on each horse. In the first experiment (n = 6), dopamine was infused IV at rates of 1.0, 2.5, and 5.0 micrograms/kg/min. For the second experiment (n = 5), dopamine (400 micrograms/ml) was infused into the digital artery at the rates of 0.0...
Effects of repeated Strongylus vulgaris inoculations and concurrent ivermectin treatments on mesenteric arterial lesions in pony foals. Eight of 10 pony foals reared under helminth-free conditions were inoculated PO with 50 Strongylus vulgaris infective larvae/week for 4 weeks, at which time 1 foal died of acute verminous arteritis. Inoculation of 7 remaining foals continued at 2-week intervals for 20 weeks. Of the 7 foals, 3 were treated with ivermectin (0.2 mg/kg of body weight) in an oral paste formulation at experiment weeks 8, 16, 24; 4 foals were not treated. Two foals were not inoculated or treated and served as controls. After the first ivermectin treatment, ivermectin-treated foals had fewer days (12 +/- 2.9) with rec...
Hypoperfusion of the small intestine during slow infusion of a low dosage of endotoxin in anesthetized horses. The effects of intravenous infusion of endotoxin for 30 minutes at a cumulative dosage of 0.03 micrograms/kg on average carotid arterial pressure, and on average arterial pressure, capillary pressure, venous pressure, total vascular resistance, precapillary resistance, postcapillary resistance, and capillary filtration coefficient in the jejunum were compared to the effects of intravenous infusion of 0.9% sodium chloride solution in 6 anesthetized horses. Endotoxin significantly reduced intestinal venous blood flow by inducing vasoconstriction. Increased vascular resistance resulted from incre...
Sequential mesenteric arteriography in pony foals during repeated inoculations of Strongylus vulgaris and treatments with ivermectin. Semiselective mesenteric arteriography was performed at regular intervals (inoculation weeks [IW] 0, 11, 18, and 24) in 9 of 10 pony foals raised to be free of parasites. Fifty infective larvae (L3) of Strongylus vulgaris were administered weekly for 4 weeks, then every 2 weeks through the 20th week. Three ponies were given ivermectin (oral paste, 0.2 mg/kg of body weight) treatment at IW 8, 16 and 24. Four ponies were inoculated, but did not receive ivermectin, and a third group of 2 ponies acted as uninoculated controls. Control ponies did not have gross or arteriographic lesions, whereas th...
Arterial blood supply to the ileocaecal junction in the horse. The arteries supplying the ileocaecal junctions of 7 horses were injected with latex via the A. ileocolica and dissected macroscopically. The same basic pattern emerged whereby a single papillary artery arising from the R. ilei mesenterialis, supplied all aspects of the ileocaecal papilla. In one instance, the papillary artery arose directly from the ileocolic artery. No collateral arterial supply to the ileocaecal junction was present in any of the specimens dissected.
A scanning electron microscopical study of the dermal microcirculation of the equine foot. The microcirculation of the dermal laminae and papillae of the equine foot from seven clinically normal Australian ponies was studied using an improved microvascular casting corrosion technique and scanning electron microscopy. Casts of veins, arteries, capillaries and arteriovenous anastomoses (AVAs) were readily identified by their characteristic surface morphology. Arteries entered the laminar circulation axially, between pairs of axial veins, and were connected to each other by smaller calibre interconnecting arteries. Short abaxial branches of the axial interconnecting arteries gave rise ...
In vivo regulation of plasma [H+] in ponies during acute changes in PCO2. The major objective of this study was to test the hypothesis that in ponies the change in plasma [H+] resulting from a change in PCO2 (delta H+/delta PCO2) is less under acute in vivo conditions than under in vitro conditions. Elevation of inspired CO2 and lowering of inspired O2 (causing hyperventilation) were used to respectively increase and decrease arterial PCO2 (Paco2) by 5-8 Torr from normal. Arterial and mixed venous blood were simultaneously sampled in 12 ponies during eucapnia and 5-60 min after Paco2 had changed. In vitro data were obtained by equilibrating blood in a tonometer at f...
The ultrastructure of Strongylus vulgaris-mediated equine chronic mesenteric arteritis. Cells found in the intima and media of the cranial mesenteric artery of a mature mare with chronic arteritis were identified as smooth muscle cells and occurred in association with collagen and elastin fibres. As no fibroblasts were demonstrable within these regions, the smooth muscle cells were the likely source of the extracellular matrix. In contrast, the abnormal adventitis from the same artery contained abundant fibroblasts which are considered to be the source of the adventitial collagen.
Pulmonary shunting by the bronchial artery in the anaesthetized horse. In the quietly standing horse the bronchial arterial blood flow is low, 0.1-0.2% of the pulmonary arterial flow. In horses anaesthetized with halothane, the bronchial arterial flow is reduced by a greater fraction than that in the pulmonary artery. Thus the shunting through the bronchial circulation is decreased about 3-fold by anaesthesia, and cannot, therefore, contribute significantly to the increased alveolar-arterial gradient seen in dorsal recumbency. The results indicate bronchial vasoconstriction under anaesthesia.
Antagonism in isolated equine digital vessels of contraction induced by epinephrine in the presence of hydrocortisone and an aqueous extract of black walnut (Juglans nigra). Prazosin, isoxsuprine, and nifedipine were screened for ability to reverse contraction of isolated equine digital vascular strips produced by epinephrine (Epi) in the presence of hydrocortisone (Hc) and an aqueous extract of black walnut (Juglans nigra) (BW). Two arteries and two veins from each of three horses for each drug (n = 9) were maintained in isolated tissue baths in Krebs' bicarbonate buffer with 95% oxygen at 37 degrees C. Six-point Epi concentration-response (C-R) curves were obtained for each vessel in the presence of Hc, BW, and the appropriate vehicle. This was repeated for each...
