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.
Morphometric estimation of pulmonary diffusion capacity in two horse lungs. The lungs of two half-bred geldings were fixed in situ by instillation of a glutaraldehyde solution into the airways during deep anaesthesia. The body weight of both animals was 510 kg and their average lung volume about 38 l. Stratified random samples from 22 regions were morphometrically analysed from electron microscopic films. Eighty-six per cent of the total lung volume was gas exchange parenchyma. It contained 26.9 l air space and 5.6 l interalveolar septa which were composed of equal parts of capillaries and tissue. The average alveolar and capillary surface areas were 2457 m2 and 1663 ...
Electromagnetic measurements of metacarpal blood flow in nonanesthetized horses. Blood flow (milliliter/minute) was measured in the medial palmar artery of 12 horses, using electromagnetic flow equipment. Extraluminal flow probes were surgically placed around the artery and base-line blood flows were recorded during surgical manipulation. After horses had recovered from anesthesia, blood flows were recorded each day for 11 days. According to mean average blood flows, horses were allotted to two groups: group 1--those with predominately normal flow characteristics, and group 2--those horses with predominately abnormal flow features. Average daily mean blood flows in the med...
Pathological observations on an outbreak of paralysis in broodmares. A description is given of the pathological changes present in 8 mares which died or were euthanased in the course of an outbreak of paralysis on a Thoroughbred studfarm. In all cases the principal changes were in the central nervous system (CNS) and consisted of a severe and widespread vaculitis in the brain, cord, sheaths of nerves, capsules of ganglia and occasionally elsewhere in the body. Associated with the damage to vessel walls there was haemorrhage and exudation of plasma into the perivascular tissues. Involvement of neurones was minimal and no neuronophagia was present. Six cases had ...
Vascular anatomy and surgical technique for bilateral adrenalectomy in the equid. The vascular anatomy of the adrenal glands and a surgical technique for bilateral adrenalectomy in the equid are described. Bilateral adrenalectomy was performed in six ponies and one horse via bilateral transcostal retroperitoneal approaches through the 18th rib during a single anesthetic period. Complications included hemorrhage from the right side only and pneumothorax which usually occurred on the right side. One pony died as a result of the surgical technique. Maintenance of adrenal function was accomplished with desoxycorticosterone pivilate and prednisolone.
Cell morphology and collagen types in equine tendon scar. The histological appearance of cells and tissues in the reparative scar tissue which forms in the equine superficial flexor tendon following partial rupture was compared to that of normal tendon. The repair fibroblasts were found to be larger and more basophilic than the tenocytes of normal tendon, to have large vesicular nuclei and to resemble the 'myofibroblasts' described in scar tissue elsewhere. The cell to matrix ratio in scarred zones of tendon was found to be increased and the concentration of collagen in these areas was less than in normal tendon. However, the scar tissue collagen was...
Electromagnetic measurement of cardiac output during exercise in the horse. Aortic root blood flow was measured with an electromagnetic (EM) flow meter in unanesthetized horses during rest and exercise. The cardiac output response to exercise, as determined by the EM technique, was compared with the response reported by others who used indicator dilution techniques with good agreement. The EM method will allow making measurement of cardiovascular responses to exercise in the horse, not obtainable with other techniques.
Vascular responses in equine thoracic limb during and after pneumatic tourniquet application. Vascular responses occurring with pneumatic tourniquet application were evaluated in the equine thoracic limb. Recordings of pressure (arterial and venous) and flow (arterial) distal to the tourniquet were made for 60 minutes. Reactive hyperemia was observed; however the increased flow was neither of a sufficient duration nor of a great enough volume for total repayment of flow loss.
Effects of trimetaquinol on equine pulmonary vascular and airway smooth muscle. Trimetaquinol [TMQ: 1-(3’,4‘,5’-trimethoxybenzyl)6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride] a potential p-sympathomimetic bronchodilator (Iwasawa & Kiyomoto 1967), has been shown to be an effective tracheal smooth muscle relaxant in guineapigs (Iwasawa & Kiyomoto 1967; Brittain 1972; Brittain et a1 1970, 1976) and an inhibitor of experimental bronchospasm in guinea-pigs and cats (Brittain et a1 1970; Brittain 1972). In addition, clinical studies with TMQ indicated that the drug was an effective bronchodilator in mild to moderate asthma (Yamamura & Kishimoto 1968). It may...
Effect of pneumatic tourniquet application to the distal extremities of the horse: blood gas, serum electrolyte, osmolality, and hematologic alterations. With 120 minutes of pneumatic tourniquet application to the distal extremity in the horse, the following effects were noted in the tourniqueted limb vein (TLV): (i) local venous acidemia, (ii) increase in serum K+ concentrations, (iii) minimal changes in plasma total solids, Na+, or osmolality, and (iv) apparent reduction in hematocrit values when compared with the same measurements in the control leg. Tourniquet release after 120 minutes produced a prompt return to base line for PCV and PO2 in the TLV; however, pH, PCO2 and K+ values in the TLV required 10 to 15 minutes to reach base line (TL...
A precursor role for DHA in a feto-placental unit for oestrogen formation in the mare. Plasma levels of total oestrogens and dehydroepiandrosterone (DHA) were measured by radioimmunossay in samples taken from various blood vessels in both maternal and fetal compartments in 11 Pony mates. High concentrations of oestrogens (greater than 100 ng/ml of plasma), expressed as oestrone equivalents, were found in the fetal circulation. On both the fetal and maternal sides, oestrogen concentrations were lower in blood going to than from the placenta. DHA concentrations, on the other hand, were higher in blood flowing to the placenta from the fetus. The fetal gonads were seen as the source...
Corticosteroid-potentiated vascular responses of the equine digit: a possible pharmacologic basis for laminitis. Spirally cut digital arteries and veins were mounted isotonically in organ baths containing oxygenated Krebs' Q-Henseleit solution. Twelve arterial and 12 venous preparations all contracted dose dependently when epinephrine, norepinephrine, serotonin, or histamine were added to the bathing fluid. Addition of hydrocortisone or betamethasone alone did not cause contractions in any of the tissues tested. However, when hydrocortisone or betamethasone was added to vessel strips that were partially contracted (40% to 60% maximal) by epinephrine, norepinephrine, or serotonin, each vessel strip invari...
[Architectonics of the blood vessels in the wall of the allantoamnion of the mare]. Alantoamnion vascularization was studied on clarified preparations from three mares in advanced pregnancy. Two large blood vessels (artery and vein) beginning from the umbilical vessels were found in the alantoamnion wall. Numerous anastomoses were observed at the passage between the arterial and the vein section. The large arteries had a thick, jely-like vascular wall and snake-like folded lumen. In separate sections of the alantoamnion wall a well developed capillary net was observed consisting of individual particles, polygonal in shape. Vast avascular zones surrounded by numerous vascular ...
Shunting in intracranial microvasculature demonstrated by SEM of corrosion-casts. The use of methyl methacrylate corrosion-casts has made it possible to examine the intracranial microvasculature on a three-dimensional scale with the scanning electron microscope. By this means we have compared regions of four cerebral and cerebellar arteries among three domestic animal species. The results of this study suggest that there are from one to three different levels of interarteriolar anastomosis between branches of the same or adjacent vessels. In the horse and ox anastomoses were demonstrated (1) at the level of the precapillary arterioles, (2) along the arterioles, and (3) betw...
Haemodynamics in the horse: 2. Intracardiac, pulmonary arterial and aortic pressures. The paper reports the changing pressure values during the cardiac cycle recorded from various chambers of the heart and great vessels using 2 catheter-mounted transducers, 9 cm apart. Pulse pressures are calculated. Transvalval pressure differences are determined taking account of the effect of hydrostatic pressure between the 2 sensors. The effects of some valvular lesions and arrhythmias and of changes in intrathoracic pressure are also described.
A report on clinical aspects and histopathology of sweet itch. Sweet itch is an intensely pruritic dermatitis of horses recurring annually in Ireland from April to November. The tissue changes of sweet itch have similarities to immediate-type hypersensitivity reactions which occur in skin sensitised to the saliva of bloodsucking insects. There was subepidermal oedema, and marked eosinophilia; the blood vessels were tortuous and enlarged. Microfilaria were not found in serial sections of lesions of 5 affected horses. The histopathology of the immediate dermal remal reaction to the intradermal injection of Culicoides extract shows dermal vasodilation and eo...
Electromagnetic blood flowmeters and flow probes: theoretic and practical considerations. Electromagnetic blood flowmeters and flow probes are used to measure blood flow in blood vessels throughout the circulatory system. The principle of this measuring device is based on laws of electromagnetic induction discovered in the 19th century. The instrument has been predominantly used in research, but is presently used in human cardiovascular units to measure blood flow in blood vessels, and in prosthesis in conjection with cardiovascular surgical procedures. Electromagnetic flow equipment provides the most accurate measurement (in vivo) of blood flow available, both for acute and chroni...
Haemodynamics in the horse: 1. Pressure pulse contours. Using a catheter with 2 transducers, one mounted at the tip and one 9 cm proximal to it, enabled transvalval pressure waveforms to be recorded in 8 horses. A simultaneous electrocardiogram acted as a time base. The changing waveforms produced in the chambers of the heart and great vessels are described and related to the events of the cardiac cycle. The effect of second degree AV block, ectopic beats, a pan diastolic murmur and chronic obstructive pulmonary disease are described.
A case of spermatic arteriovenous anastomosis in the horse. A large anastomosis of the spermatic artery and vein is described. This was found while surgically removing an abdominal testis. Before surgery the animal wanted to rear after exercise and could not stand on 3 legs for any length of time while being shod. This unusual behaviour disappeared after removal of the mass. The performance and conformation of the horse has also greatly improved.