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.
Transmural coronary vasodilator reserve and flow distribution during severe exercise in ponies. Transmural distribution of myocardial blood flow and coronary vasodilator reserve (15-microns-diam radionuclide-labeled microspheres) was studied in 11 adult, healthy ponies at rest and during moderate and severe exercise performed on a treadmill (heart rate 56 +/- 4, 154 +/- 3, and 225 +/- 7 beats . min-1, respectively.). Exercise resulted in a marked increase in cardiac output, mean aortic pressure, right ventricular (RV) systolic and end-diastolic pressure, left ventricular (LV) end-diastolic pressure, and the maximum rate of rise of LV pressure LV (dP/dtmax). Accompanying these changes was...
Extrinsic and intrinsic veins of the equine hoof wall. The extrinsic and intrinsic venous drainage of the equine hoof have previously been poorly described. There is also an absence of information about the venous organisation of both primary and secondary dermal lamellae of the hoof wall. The purpose of this study was to describe the normal venous pattern of the horse hoof, especially that associated with the dermal lamellae of the wall. The venous organisation of 46 pairs of hooves from clinically healthy horses was studied using standard plastic vascular corrosion casts and histological sections. A consistent pattern of venous organisation was ...
Effects of large doses of phenylbutazone administration to horses. The effects of large doses of phenylbutazone were evaluated in clinically normal horses. The drug was given to 4 groups of 2 horses each at the rate of 30 mg/kg of body weight, orally, or 30, 15, or 8 mg/kg IV daily for up to 2 weeks. All horses became anorectic and depressed after 2 to 4 phenylbutazone treatments, and the horses given 15 or 30 mg/kg died on or between days 4 and 7 of treatment. A decrease in total blood neutrophil count occurred in all horses, and was associated with toxic left shift in horses given the 2 larger dosage schedules. The horses also had progressive increases in s...
The equine spleen: an electron microscopic analysis. The capacity of the equine spleen to store and rapidly release as much as half the circulating blood volume after adrenergic stimulation depends upon the size of the spleen, its muscular capsule, and the distinctive structure of its red pulp. The unit, or lobule, of red pulp is a cylinder of pulp spaces organized in a reticular meshwork, supplied by a peripheral ring of arterial capillaries, and drained by a central venule. Reticular cells, which make up the meshwork of the pulp, contain an extraordinarily large complement of microfilaments and intermediate filaments and are richly innervated ...
Structural and functional organization of the suprapatella in two cercopithecines. Gross and microscopic study of Cercopithecus aethiops pygerythrus and Papio cyanocephalus anubis shows that these cercopithecines have a quadriceps tendon the distal portion of which consists mostly of dense collagenous bundles with scattered fine elastic fibres most of which lie in the loose connective tissue planes within and around the tendon and around blood vessels. A distinct fibrovesicular structure, the suprapatella, lies within the tendon of the vastus intermedius above the pony patella. Histologically, this structure is characterised by interwoven bundles of collagenous fibres, among...
Thermographic evaluation of horses with podotrochlosis. The distal forelimbs of 10 clinically normal horses with hair clipped on 1 limb were thermographically scanned before and after exercise. The thermal patterns, temperature distribution, and temperature changes after exercise were determined and compared with those of 8 horses with podotrochlosis. Clipping the hair did not cause changes in the thermal patterns, but the clipped limbs were warmer than the unclipped limbs. The temperature of the limbs of horses with podotrochlosis did not increase as much after exercise as did the limbs of normal horses. The failure of skin temperature increase co...
Microangiographic studies of metaphyseal vessels in young foals. Selective perfusion and microangiographic examination of the radius and metacarpus of 30 foals were performed. Vessels of extraosseous origin supplying the peripheral part of the metaphysis were not demonstrated in young foals, but became more obvious in older animals. The development of this vessel system coincided with the reduction of transphyseal vessels from the epiphysis crossing the growth plate.
Navicular disease in the horse. A microangiographic investigation. Microangiographical investigations of the navicular bone in horses with navicular disease show, compared to similar investigations of normal navicular bones, that, in general, the vascular pattern is preserved but the vessels are dilated with "pooling" of the contrast medium subchondrally under facies flexoria. Similar changes may be observed in cases of human arthrosis. The present investigation therefore supports the view that navicular disease is a disease which resembles arthrosis.
Electron microscopic study of the veins of the dermal lamellae of the equine hoof wall. The venous organisation of the dermal lamellae of the equine hoof wall of 18 pairs of forelimb hooves from clinically healthy horses was studied using plastic vascular corrosion casts, and scanning electron microscopic and histological techniques. A consistent pattern of venous organisation was observed in the dermal lamella of the toe, quarter and heel regions. The lamellar corium had an extensive interconnecting capillary network which drained into axially located veins of the primary dermal lamella. Many of the capillaries had a proximodistal orientation and most of those located at the int...
[Topographico-anatomic data on the testicular artery, ductus deferens artery and cremaster artery in the stallion]. To study the vascularization of the testis of stallions we used 96 testes. We examined its topography and anatomy by roentgenography, stereoroentgenography, by the corosive method, and by means of gel and China ink injections. To make the roentgeno-arteriograms we used minimum emulsified in glycerine as contrast medium. The branching off of the Aa. testiculares from the Aorta abdominalis is variable in stallions. We observed also a peculiar age-dependent arrangement of the loops of the convolution. In the adult stallion, the shape of the convolution is either cylindrical or conical, spindle-sh...
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...