Arteriole Health Dictionary

Tube through which blood is conducted from or to the heart. Blood from the heart is conducted via arteries and arterioles through capillaries and back to the heart via venules and then veins. (See ARTERIES and VEINS.)... blood vessel

Hardening of the arterioles and arteries of the kidney.... nephrosclerosis

Any of the vessels that carry blood between the smallest arteries, or arterioles, and the smallest veins, or venules (see circulatory system). Capillaries form a fine network throughout the body’s organs and tissues. Their thin walls are permeable and allow blood and cells to exchange constituents such as oxygen, glucose, carbon dioxide, and water (see respiration). Capillaries open and close to blood flow according to the requirements of different organs. The opening and closing of skin capillaries helps to regulate temperature.

A direct blow to the body may rupture the thin capillary walls, causing bleeding under the surface of the skin, which in turn causes swelling and bruising. Increasing age, high doses of corticosteroid drugs, and scurvy (vitamin C deficiency) make capillaries more fragile; a tendency to purpura (small areas of bleeding under the skin) may develop.... capillary

Arteries are vessels which convey oxygenated blood away from the heart to the tissues of the body, limbs and internal organs. In the case of most arteries the blood has been puri?ed by passing through the lungs, and is consequently bright red in colour; but in the pulmonary arteries, which convey the blood to the lungs, it is deoxygenated, dark, and like the blood in veins.

The arterial system begins at the left ventricle of the heart with the AORTA, which gives o? branches that subdivide into smaller and smaller vessels. The ?nal divisions, called arterioles, are microscopic and end in a network of capillaries which perforate the tissues like the pores of a sponge and bathe them in blood that is collected and brought back to the heart by veins. (See CIRCULATORY SYSTEM OF THE BLOOD.)

The chief arteries after the aorta and its branches are:

(1) the common carotid, running up each side of the neck and dividing into the internal carotid to the brain, and external carotid to the neck and face;

(2) the subclavian to each arm, continued by the axillary in the armpit, and the brachial along the inner side of the arm, dividing at the elbow into the radial and the ulnar,

which unite across the palm of the hand in arches that give branches to the ?ngers;

(3) the two common iliacs, in which the aorta ends, each of which divides into the internal iliac to the organs in the pelvis, and the external iliac to the lower limb, continued by the femoral in the thigh, and the popliteal behind the knee, dividing into the anterior and posterior tibial arteries to the front and back of the leg. The latter passes behind the inner ankle to the sole of the foot, where it forms arches similar to those in the hand, and supplies the foot and toes by plantar branches.

Structure The arteries are highly elastic, dilating at each heartbeat as blood is driven into them, and forcing it on by their resiliency (see PULSE). Every artery has three coats: (a) the outer or adventitia, consisting of ordinary strong ?brous tissue; (b) the middle or media, consisting of muscular ?bres supported by elastic ?bres, which in some of the larger arteries form distinct membranes; and (c) the inner or intima, consisting of a layer of yellow elastic tissue on whose inner surface rests a layer of smooth plate-like endothelial cells, over which ?ows the blood. In the larger arteries the muscle of the middle coat is largely replaced by elastic ?bres, which render the artery still more expansile and elastic. When an artery is cut across, the muscular coat instantly shrinks, drawing the cut end within the ?brous sheath that surrounds the artery, and bunching it up, so that a very small hole is left to be closed by blood-clot. (See HAEMORRHAGE.)... arteries

Redness of the skin due to dilatation of dermal blood vessels. It may be transient or chronic, localised or widespread, and it can be blanched by pressure. Erythema may be caused by excessive exposure to heat or ultraviolet light, or by in?ammation of the skin due to infection, DERMATITIS, and various allergic reactions – for example, to drugs. It may be emotional (e.g. as in ?ushing), mediated by the autonomic nervous system.

Erythema ab igne is a ?xed redness of the skin caused by chronic exposure to heat from a domestic ?re or radiator.

Erythema pernio (See CHILBLAIN.) Redness induced by spasm of the skin arterioles due to cold. It affects the hands, feet or calves in winter. The red swollen areas are cooler than normal.

Erythema nodosum A singular pattern of red, tender nodules occurring on the shins, often lasting several weeks. It may be caused by a streptococcal throat infection, primary tuberculosis, SARCOIDOSIS, or may be drug-induced.

Erythema multiforme is an acute allergic eruption of the extremities characterised by circular areas of erythema, purpura and blistering, which resolve over two or three weeks, caused by infections or drugs. In severe forms the mucous membranes of the eyes, mouth and genitalia may be involved.

Erythema infectiosum is an acute contagious disease of children caused by a parvo-virus (see PARVOVIRUSES). In young children a bright erythema of the face gives a ‘slapped cheek’ appearance.

... erythema

A disease of children resulting in acute RENAL failure. A febrile illness of the gastrointestinal or respiratory tracts is followed by intravascular COAGULATION of blood which results in HAEMOLYSIS, ANAEMIA, THROMBOCYTOPAENIA and renal failure (resulting from ?brin deposition in renal arterioles and glomerular capillaries).

The death rate is 2–10 per cent and the majority of patients survive without renal failure. The longer the period of OLIGURIA, the greater the risk of chronic renal failure.

Treatment is supportive, with replacement of blood and clotting factors, control of HYPERTENSION, and careful observation of ?uid balance.... haemolytic uraemic syndrome

An amine (see AMINES) derived from HISTIDINE. It is widely distributed in the tissues of plants and animals, including humans. It is a powerful stimulant of gastric juice, a constrictor of smooth muscle including that of the bronchi, and a dilator of arterioles and capillaries. It is this last action which is responsible for the eruption of URTICARIA.... histamine

Tissue material that has a glass-like appearance when stained and viewed under the microscope. It occurs in a variety of tissues and diseases, particularly ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS), hyaline degeneration of arterioles, and alcoholic liver disease.... hyaline

Labetalol is an alpha- and beta-adrenoceptor blocker (see ADRENERGIC RECEPTORS) used to treat HYPERTENSION. Beta blockers block the beta-adrenoceptors in the heart, peripheral blood vessels and bronchi. Many drugs belonging to this group are now available, and all are equally e?ective – but with di?erences that may make them suitable for a particular patient. Labetalol has the added property of dilating arterioles (small arteries), thus lowering resistance in the small peripheral blood vessels and helping to reduce blood pressure.... labetalol

Abnormal dilatation of ARTERIOLES and venules (see VENULE). In the skin it is seen in spider NAEVUS and ROSACEA particularly.... telangiectasis

A congenitally determined tissue abnormality. In the SKIN, naevi of blood vessels are best known, but a MOLE is a MELANOCYTE naevus, and warty streaked and linear naevi of the epidermis occasionally occur. There are several patterns of vascular naevi:

Naevus simplex Also known as ‘salmon patch’. About one-third of white children are born with macular pink areas of ERYTHEMA on the nape, brow or eyelids which usually disappear after a few months, but patches on the nape may persist.

Naevus ?ammeus Also known as ‘portwine stain’ and present at birth. It is unilateral, usually on the face, and may be extensive. It tends to darken with age and is permanent. Laser treatment is e?ective.

Strawberry naevus (cavernous haemangioma) is usually not present at birth but appears within a few weeks and grows rapidly, reaching a peak in size after 6–12 months, when the lobulated red nodule may resemble a ripe strawberry. Untreated, the naevus disappears spontaneously over several years. It may occur anywhere and may be very troublesome when occurring around an eye or on the ‘nappy’ area. If possible it should be left alone, but where it is causing problems other than simply cosmetic ones it is best treated by an expert. This may involve medical treatment with steroids or interferon or laser therapy.

Spider naevus is due to a dilated ARTERIOLE causing a minute red papule in the skin, the small branching vessels resembling spider legs. A few spider naevi are common in young people, but multiple naevi are common in pregnancy and may also be a warning sign of chronic liver disease.... naevus

So called after Maurice Raynaud (1834–81), the Paris physician who published a thesis on the subject in 1862. This is a condition in which the circulation (see CIRCULATORY SYSTEM OF THE BLOOD) becomes suddenly obstructed in outlying parts of the body. It is supposed to be due to spasm of the smaller arteries in the affected part, as the result of them responding abnormally to impuilses from the SYMPATHETIC NERVOUS SYSTEM. Its effects are increased both by cold and by various diseases involving the blood vessels.

Symptoms The condition is most commonly con?ned to the occurrence of ‘dead ?ngers’ – the ?ngers (or the toes, ears, or nose) becoming white, numb, and waxy-looking. This condition may last for some minutes, or may not pass o? for several hours, or even for a day or two.

Treatment People who are subject to these attacks should be careful in winter to protect the feet and hands from cold, and should always use warm water when washing the hands. In addition, the whole body should be kept warm, as spasm of the arterioles in the feet and hands may be induced by chilling of the body. Su?erers should not smoke. VASODILATORS are helpful, especially the calcium antagonists. In all patients who do not respond to such medical treatment, surgery should be considered in the form of sympathectomy: i.e. cutting of the sympathetic nerves to the affected part. This results in dilatation of the arterioles and hence an improved blood supply. This operation is more successful in the case of the feet than in the case of the hands.... raynaud’s disease

Another word for fainting – a loss of consciousness due to a fall in BLOOD PRESSURE. This may result because the cardiac output has become reduced, or because the peripheral resistance provided by the arterioles has decreased. The simple faint or vaso-vagal attack is a result of a failure to maintain an adequate venous return of blood to the heart. This is likely to occur after prolonged periods of standing, particularly if one is standing still or if the climatic conditions are hot. It can also result from an unpleasant or painful experience. Pallor, sweating and a slow pulse are characteristic. Recovery is immediate when the venous return is restored by lying ?at.

Syncope can also result when the venous return to the heart is impaired as a result of a rise in intrathoracic pressure. This may happen after prolonged vigorous coughing – the so-called COUGH SYNCOPE – or when elderly men with prostatic hypertrophy strain to empty their bladder. This is known as micturition syncope. Syncope is particularly likely to occur when the arterial blood pressure is unusually low. This may result from overtreatment of HYPERTENSION with drugs or it may be the result of diseases, such as ADDISON’S DISEASE, which are associated with low blood pressures. It is important that syncope be distinguished from EPILEPSY.... syncope

The increase of blood into the skin, resulting from the relaxation of the small arterioles that lead into the capillary beads at the edges of the body. This is a gentle way to lessen early high blood pressure, decreasing the difficulty of pushing columns of arterial blood through miles of capillaries.... vasodilation, peripheral

Networks of extremely fine blood vessels that allow exchange of oxygen, CO2, minerals, water, etc between the tissues and the blood. Their contents are fed by the arterioles and drained by the venules. ... capillaries

n. inflammation of the arterioles (the smallest arteries), which may complicate severe hypertension. This produces necrotizing arteriolitis, which may result in kidney failure. A similar condition may affect the lung in pulmonary hypertension.... arteriolitis

a thick-walled blood vessel that connects an arteriole directly with a venule, thus bypassing the capillaries. Arteriovenous anastomoses are commonly found in the skin of the lips, nose, ears, hands and feet; their muscular walls can constrict to reduce blood flow or dilate to allow blood through to these areas.... arteriovenous anastomosis

n. a blood vessel carrying blood away from the heart. All arteries except the *pulmonary artery carry oxygenated blood. The walls of arteries contain smooth muscle fibres, which contract or relax under the control of the sympathetic nervous system. See illustrations. See also aorta; arteriole.... artery

a disease associated with diffuse atherosclerosis and sloughing of atheromatous plaques in the aorta and main renal arteries. This results in occlusion of smaller arteries and arterioles downstream within the kidney, with ischaemic and inflammatory reactions. This leads to the onset of renal impairment. Precipitating factors include invasive procedures with aortic cannulae, vascular surgery, and therapy with thrombolytics or anticoagulants. Less commonly the condition can occur spontaneously.... atheroembolic renal disease

Poor circulation may be due to a number of disorders including varicose veins, high or low blood pressure, arterio-sclerosis, thrombosis, phlebitis, chilblains, anaemia, weak heart. A common cause is auto-toxaemia, calling for blood tonics and agents to assist elimination of wastes and poisons via the kidneys, skin and bowels.

Other causes requiring specific treatment are: thickening and narrowing of blood vessels, diabetes, Buerger’s disease, Raynaud’s disease (spasm of the arterioles and veins), arteritis. See appropriate entries.

As a protection against these diseases Garlic becomes increasingly popular. Control of blood fats through diet and exercise necessary.

Alternatives. Cayenne, Ginger, Hawthorn berries, Horseradish, Mustard, Prickly Ash bark, Buckwheat, Dandelion, Lime flowers, Mistletoe, Rosemary, Yarrow, Ginkgo.

Tea: Lime flowers, Hawthorn berries, Yarrow. Equal parts. Mix. Ginger, quarter part (or pinch of Red Pepper). Mix. 1-2 teaspoons to each cup water. Bring to boil. Remove vessel when boiling point is reached. Dose: 1 cup 2-3 times daily.

Tablets or capsules: Prickly Ash, Hawthorn, Mistletoe, Ginkgo.

Formula. Hawthorn 2; Yarrow 2; Prickly Ash 1; Ginger quarter. Dose: Powders: 500mg (two 00 capsules or one-third teaspoon). Liquid extracts: 1 teaspoon. Tinctures 2 teaspoons 2-3 times daily.

Practitioner. Liquid extracts: Hawthorn 2; Lily of the Valley 2; Prickly Ash 1; Tincture Capsicum (one- tenth part). Dose: 30-60 drops in water or honey, 2-3 times daily.

Diet and Supplements. See: DIET – HEART AND CIRCULATION. ... circulatory disorders

Pre-eclampsia. Toxaemia of last 3 months of pregnancy. Due to a number of causes, one of which is calcium deficiency. Calcium controls muscular spasms that are a feature of the condition. Eclampsia is due, in part, to a traffic jam of blood through the placenta causing a compensatory rise in blood pressure. Black women run 12 times the risk of developing pre-eclampsia during their first pregnancy as non-black women. (American researchers)

Women who use barrier contraceptives are more than twice as likely to develop pre-eclampsia in pregnancy than those using non-barrier methods. (North Carolina Memorial Hospital)

Symptoms. Headache, dizziness, nausea, upper abdominal pain, twitching of face and limbs, albumin in the urine. Extreme cases: high blood pressure, rigidity, congestive heart failure.

Treatment. Hospitalisation. To be treated by qualified obstetrician.

Formula. Cramp bark 2; Motherwort 1; Black Cohosh 1. Dose: Powders: 750mg (three 00 capsules or half a teaspoon). Liquid extracts: one to two 5ml teaspoons. Tinctures: 1-3 teaspoons. Hourly, or more frequently as tolerated; in water or honey. Magnesium sulphate for fits.

Suppression of urine. Dilation of kidney arterioles to increase flow of blood and to re-start kidney function.

Bearberry (Uva Ursi) tea. 1-2 teaspoon to each cup boiling water; infuse 15 minutes; 1 cup freely. Bearberry Liquid extract. 2-4ml hourly, or as tolerated, in water or honey.

White Willow. Conventional treatment places high-risk women on low-dose aspirin therapy. As White Willow is a source of natural aspirin, it would appear to offer some benefit. White Willow reduces platelet aggregation, and encourages placental blood flow. Aspirin of pharmacy cuts the risk of pregnancy-induced high blood pressure by two-thirds.

Diet. Pre-eclampsia: oily fish or fish oil supplements. (Journal of Obstetrics and Gynaecology 1990, 97 (12) 1077-79)

Supplements. Calcium. Magnesium.

Note: A serious condition which can be fatal but which can be prevented by regular antenatal examinations by a qualified obstetrician. ... eclampsia

n. the presence of excess blood in the vessels supplying a part of the body. In active hyperaemia (arterial hyperaemia) the arterioles are relaxed and there is an increased blood flow. In passive hyperaemia the blood flow from the affected part is obstructed.... hyperaemia

dangerously high blood pressure (diastolic pressure >130 mmHg) associated with necrosis of small arteries and arterioles. Retinal haemorrhage and *papilloedema are present. Untreated, malignant hypertension causes severe organ damage, targeting the central nervous and cardiovascular systems and the kidneys (malignant *nephrosclerosis). Causes include complications of essential and secondary *hypertension and pregnancy and the use of certain drugs (e.g. MAO inhibitors).... malignant hypertension

a dilated arteriole forming a red papule from which radiate prominent capillaries, so that it resembles a spider. Excessive numbers of spider naevi are a sign of liver cirrhosis, hepatitis, thyrotoxicosis, and rheumatoid arthritis; they are also a feature of normal pregnancy. See also telangiectasis.... spider naevus

the formation of thrombi in arterioles and capillaries, leading to haemolytic anaemia and *thrombocytopenia. The term encompasses primary *haemolytic uraemic syndrome and *thrombotic thrombocytopenic purpura, as well as the microangiopathies that can complicate pregnancy (pregnancy-related haemolytic uraemic syndrome, *HELLP syndrome), *malignant hypertension, *scleroderma, *antiphospholipid antibody syndrome, organ transplantation, and cancer.... thrombotic microangiopathy

The heart and blood vessels, which together maintain a continuous flow of blood throughout the body. The system provides tissues with oxygen and nutrients, and carries away waste products. The circulatory system consists of 2 main parts: the systemic circulation, which supplies blood to the whole body apart from the lungs; and the pulmonary circulation to the lungs. Within the systemic circulation, there is a bypass (the portal circulation), which carries nutrient-rich blood from the stomach, intestine, and other digestive organs to the liver for processing, storage, or re-entry into general circulation.

In the systemic circulation, oxygen-rich blood from the pulmonary circulation is pumped under high pressure from the left ventricle of the heart into the aorta, from where it travels through arteries and smaller arterioles to all parts of the body. Within body tissues, the arterioles branch into networks of fine blood vessels called capillaries. Oxygen and other nutrients pass from the blood through the capillaries’ thin walls into body tissues; carbon dioxide and other wastes pass in the opposite direction. Deoxygenated blood is returned to the heart via venules, veins, and the venae cavae.

Venous blood returns to the right atrium of the heart to enter the pulmonary circulation. It is pumped from the right ventricle through the pulmonary artery

to the lungs, where carbon dioxide is exchanged for oxygen. The reoxygenated blood then returns through the pulmonary veins to the heart and re-enters the systemic circulation.... circulatory system

(JGA) a microscopic structure within the kidney that is important in regulating blood pressure, body fluid, and electrolytes. It is situated in each nephron, between the afferent arteriole of the glomerulus and the returning distal convoluted tubule of the same nephron. The JGA consists of specialized cells within the distal tubule (the macula densa), which detect the amount of sodium chloride passing through the tubule and can secrete locally acting vasoconstrictor substances that act on the associated afferent arteriole to induce a reduction in filtration pressure (tubuloglomerular feedback). Modified cells within the afferent arterioles secrete *renin in response to a fall in perfusion pressure or feedback from the macula densa and form a central role in the renin-*angiotensin-aldosterone axis. Mesangial cells support and connect the macula densa and the specialized cells in the afferent arteriole and have sympathetic innervation, facilitating the renin response to sympathetic nervous stimulation.... juxtaglomerular apparatus