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.
Distribution of internal carotid artery blood flow in the pony. This study determined whether blood flow through the internal carotid artery (ICA) could be used to sample total cerebral blood flow in the pony. To answer this question we considered both the anatomic arrangement of the ICA in cadavers and the relative distribution of ICA blood flow to cerebral and extracerebral tissue using radioactive microspheres. Acrylic corrosion casts of the ICA indicated that this vessel traveled directly to the base of the brain, contributing to the formation of the circle of Willis, and did not send any significant branches to other tissues. Two vessels (internal eth...
Sir Frederick Smith Memorial Lecture. A superb transport system–the circulation. This paper discusses certain aspects of circulatory physiology, including foetal circulation and the role of the thorax, and gives parameters for total blood volume, cardiac output, stroke volume and the distribution of blood between the pulmonary and peripheral circulation within the horse. The reader is taken on a journey around the circulatory system, beginning in the left atrium, into which richly oxygenated blood runs from the pulmonary veins. From here the blood is squeezed via the mitral valve into the left ventricular pump, where it is forced under high pressure through the peripheral ...
Occlusion of the digital arteries — A model for pathogenesis of navicular disease. The digital arteries of 10 horses suffering from navicular disease, and 7 horses from a control group, were examined angiographically. The horses from the disease group showed complete or partial occlusion of the digital arteries in all cases. In the control group of 7 healthy horses, isolated vessel obstructions were also found but these were limited to narrowing of part of an artery only. Histological investigations showed that total occlusion of a vessel involved an organised thrombus but that partial occlusion generally involved changes to the vascular wall, similar to those caused by enda...
Acute vitamin D2 (ergocalciferol) toxicosis in horses: case report and experimental studies. Acute accidental vitamin D2 (ergocalciferol) toxicosis was diagnosed in a 6-month-old foal with extensive lesions of soft tissue mineralization. In an experimental study, three 18-month-old horses were given ergocalciferol per os at a rate of 9,300, 22,200, or 47,200 IU/kg of body weight/day for 21 days. Clinical signs or lesions were not seen in horses given the low and intermediate doses, whereas the horse receiving the highest dose developed clinical signs and lesions similar to those noted in the foal. Signs included depression, loss of appetite, weakness, limb stiffness with impaired mobi...
Renal dysfunction in a case of purpura haemorrhagica. A four-year-old thoroughbred was presented with clinical manifestations of purpura haemorrhagica. Evidence of renal involvement consistent with glomerulopathy and nephrotic syndrome, characterized by heavy proteinuria and azotaemia, became apparent and may have been exacerbated by diuretic therapy. Autopsy revealed membrano- and mesangial proliferative glomerulonephritis and chronic pleuritis. Circulating immune complexes may have been responsible for the renal diseases and the purpura.
Isolation and identification of steroids from gonadal vein blood of the fetal horse. Direct connection of the artery of a fetal ovary to the carotid artery of the mare allowed collection of a large volume of blood over a 30-min period. Extraction of steroids and their fractionation was followed by separation of the steroids by alumina adsorption chromatography, and Sephadex LH-20 and Celite partition chromatography. Further resolution of the material by HPLC led to the identification of dehydroepiandrosterone (DHA) by nuclear magnetic resonance and mass spectrometry. Other compounds were isolated, which remain to be identified fully, but in the 8th month of pregnancy the princ...
Ultrastructural study of the development of the pars distalis (anterior pituitary) in the foal. The pituitary glands of 4 horse embryos (41-55 days of gestation) were examined by light microscopy, and the pars distalis from 10 fetal foals (75-300 days) was examined by electron microscopy. At Day 41 the development of Rathke's pouch and the saccus infundibuli was advanced; the former had almost lost its connection with the stomodaeum and the latter had started to differentiate into infundibular process and infundibular stalk. By Day 43 Rathke's pouch was completely dissociated from the stomodaeum and its walls were beginning to show uneven growth. The ventral wall of the pouch, the future...
A random walk model for the migration of Strongylus vulgaris in the intestinal arteries of the horse. A study of the migration of fourth stage larvae of the parasite Strongylus vulgaris in the intestinal arteries of the horse is presented. It is established, that the larvae migrate along the arteries in almost straight lines. It is suggested that this is primarily due to their ability to sense the curvature of the vessel wall, and not, as might have been expected, because of an ability to sense the direction of blood flow. A larva will sometimes alter its direction of motion when encountering a small off-branching artery. This behaviour suggests, that the migration of S. vulgaris larvae can be...
[Structure and vascularization of the dental pulp in horse incisors]. The dental pulp of 34 horses aged between 4 months and 20 years has been studied on India ink injected and on paraffin embedded specimens. The pulp dimensions of the first and especially of the second dentition decrease with age. This reduction is accompanied by pronounced changes of structure; the mucous connective tissue becomes a dense, irregular connective tissue. The vessels are numerous and make a network particularly rich at the margins of the pulp; they diminish with advancing age. The reduction of the pulp volume and the regression of its vascular network are particularly pronounced a...
Distribution of 5′-nucleotidase and gamma glutamyl transferase activities in the tissues of the horse. In the horse, 5'-nucleotidase (5'-NT) activity is found mainly in homogenates of lung, kidney, small intestine, mammary gland, liver and pancreas. Lower activities are present in brain and muscle. Activity can be demonstrated histochemically in the glomeruli and tubules of the kidney, in the sinusoidal borders of the hepatocytes and the bile duct epithelium as well as in the blood vessels of all organs. There is no significant difference between the 5'-NT activity in serum and plasma of normal horses and of horses suffering from a range of orthopaedic conditions. Previous findings that gamma g...
Experimental evidence of reciprocal temperature relationship between the parietofrontal region and the orbital emissary vein in the pony. The heads of 5 ponies were embalmed and the vessels were double injected with latex. Dissection of these specimens revealed venous pathways (1) from the nasal area to the cavernous sinus and (2) from the parietofrontal region to the ventral petrosal sinus. Thermistors were chronically implanted near the orbital emissary veins of 3 additional ponies. Hot and cold packs were applied alternately to the parietofrontal regions. The temperature near the orbital emissary veins increased during the 5 trials with cold application and decreased during the 5 trials with hot application. The authors were ...
Blood flow in the hypertrophied right ventricular myocardium of unanesthetized ponies. To examine the effects of right ventricular (RV) hypertrophy on regional myocardial blood flow and coronary vascular reserve, hemodynamics and myocardial blood flow (15-micrometers radio-nuclide-labeled microspheres) were studied in 12 unanesthetized adult ponies before and during intravenous isoproterenol HCl infusion (1 microgram.kg-1.min-1). Six ponies served as controls, whereas in each of the others the main pulmonary artery (PA) had been banded 35-90 days prior to the study. Marked RV hypertrophy was present in PA-banded animals. In these ponies, there was a significant increase in RV sy...
Surgical technique and considerations for implantation of electromagnetic blood flow transducer and occluder onto the coronary arteries. A technique was developed for the implantation of an electromagnetic flow probe and vascular occluder onto the right and left coronary arteries in the calf and pony. Surgical manipulation was well tolerated in the animals. The subcutaneous housing on the peripheral ends of these devices of the lateral thoracic wall served as a maintenance-free technique for chronic exteriorization of these devices. Implantation onto the coronary arteries required a surgical technique which accomplished the prerequisites for proper flow probe function. A reactive hyperemic response was elicited in each animal b...
Intravascular neutrophilic granulocyte kinetics in horses. Intravascular granulocyte kinetics in 4 healthy horses were determined with chromium-51 as the cell label. The disappearance rate of labeled granulocytes was an exponential function. Mean total blood granulocyte pool (+/- 1 SD) was 5.65 +/- 1.514 X 10(8) granulocytes/kg of body weight, of which 2.71 +/- 0.715 X 10(8) granulocytes/kg were circulating and 2.94 +/- 0.876 X 10(8) granulocytes/kg were marginated along blood vessel walls. The mean disappearance half-life (T1/2) was 10.5 +/- 1.33 hours and the mean granulocyte turnover rate was 8.84 +/- 1.495 X 10(8) granulocytes/kg/day. A granulokin...
Potential blood supply to muscles in horses and dogs and its relation to athletic ability. A modification of the histochemical reaction to demonstrate myosin adenosine triphosphatase activity in skeletal (striated) muscle was used to define the density of capillaries in transverse sections of 3 muscles (semitendinosus, diaphragm, and pectoralis transversus) of horses and dogs. Thoroughbred horses and Greyhound dogs, breeds noted for their speed in running, were compared with other members of their respective species. Thoroughbred cross horses were grouped with non-Thoroughbreds for comparison with Thoroughbreds. The area of muscle supplied by a capillary was remarkably similar in mu...
Systemic and digital vascular effects of intravenous histamine in the pony. The effects of a 60-minute IV infusion of histamine (0.5 mg of histamine base/minute) on the systemic, pulmonary, and digital vasculature were investigated in mature ponies. Immediately after the start of histamine infusion, there were a transient decrease in systemic pressure lasting less than 1 minute and then a brief period of systemic hypertension. Systemic pressure then returned to preinfusion levels for the remainder of the infusion period. Pulmonary arterial pressure increased transiently coincident with systemic hypotension. Histamine increased cardiac output and decreased both total p...
Warfarin anticoagulation in the horse. The hematologic and clinical effects of anticoagulation with warfarin were documented in 4 horses. All of the animals had thrombophlebitis (external jugular vein). Measures of coagulation were monitored, with a prothrombin time of 1.5 to 2.5 x base-line value being used as the effective range of anticoagulation. Recanalization was achieved in 2 of 4 cases. Hemorrhage, both subcutaneous and through a surgical incision, was a complication. Vitamin K1, an antidote to warfarin toxicosis, was administered intravenously to reverse anticoagulation and to control hemorrhage.
Vascular supply of the equine stifle joint. The vascular supply of the equine stifle joint was investigated, using latex vascular injections of pelvic limbs from 3 adult horses and 6 ponies. Vessels were grossly dissected to the small arteriole level. The primary source of blood supply was the femoral artery and its branches which entered the joint on the caudal and medial surfaces. The superficial vasculature arose from the caudal branch of the deep circumflex iliac artery cranially and laterally, and from the saphenous and descending genicular arteries medially. The deep vasculature arose from the popliteal artery and its branches on ...
Influence of head height on arterial blood pressure in standing horses. Eighteen horses were used to investigate the influence of head position on arterial blood pressure, measured indirectly at the coccygeal artery. Head height significantly altered systolic pressure, diastolic pressure, pulse pressure, and mean arterial pressure, such that head-lowering decreased and head-raising increased all variables.
Assessment of wall shear stress in arteries, applied to the coronary circulation. Time dependent wall shear rates cannot be directly or accurately measured in arteries using presently available techniques. Here a simple method is presented for calculating them from a single measured velocity waveform (either centreline or cross-sectionally averaged velocity). The method involves only Fourier analysis and the application of given formulae, and it is expected to be approximately valid in any segment of artery which has no branches or sharp curves for a distance of several diameters. It is shown, however, that a frequency response of 30 Hz is required in the velocity measuring...