Pulmonary vein Health Dictionary

Relating to the LUNGS.... pulmonary

The condition in which an embolus (see EMBOLISM), or clot, is lodged in the LUNGS. The source of the clot is usually the veins of the lower abdomen or legs, in which clot formation has occurred as a result of the occurrence of DEEP VEIN THROMBOSIS (DVT) – THROMBOPHLEBITIS (see VEINS, DISEASES OF). Thrombophlebitis, with or without pulmonary embolism, is a not uncommon complication of surgical operations, especially in older patients. This is one reason why nowadays such patients are got up out of bed as quickly as possible, or, alternatively, are encouraged to move and exercise their legs regularly in bed. Long periods of sitting, particularly when travelling, can cause DVT with the risk of pulmonary embolism. The severity of a pulmonary embolism, which is characterised by the sudden onset of pain in the chest, with or without the coughing up of blood, and a varying degree of SHOCK, depends upon the size of the clot. If large enough, it may prove immediately fatal; in other cases, immediate operation may be needed to remove the clot; whilst in less severe cases anticoagulant treatment, in the form of HEPARIN, is given to prevent extension of the clot. For some operations, such as hip-joint replacements, with a high risk of deep-vein thrombosis in the leg, heparin is given for several days postoperatively.... pulmonary embolism

In this condition, increased resistance to the blood ?ow through the LUNGS occurs. This is usually the result of lung disease, and the consequence is an increase in pulmonary artery pressure and in the pressure in the right side of the heart and in the veins bringing blood to the heart. Chronic BRONCHITIS or EMPHYSEMA commonly constrict the small arteries in the lungs, thus causing pulmonary HYPERTENSION. (See also EISENMENGER SYNDROME.)... pulmonary hypertension

Fluid in the small air sacs of the lungs, from inefficient pumping by the heart or leakage of fluid from the blood vessels in the lungs (possibly from envenomation). As it prevents air exchange in the lungs it causes hypoxia and may lead to death.... pulmonary oedema

A disorder of the HEART in which obstruction of the out?ow of blood from the right ventricle occurs. Narrowing of the pulmonary valve at the exit of the right ventricle and narrowing of the pulmonary artery may cause obstruction. The condition is usually congenital, although it may be caused by RHEUMATIC FEVER. In the congenital condition, pulmonary stenosis may occur with other heart defects and is then known as Fallot’s tetralogy. Breathlessness and enlargement of the heart and eventual heart failure may be the consequence of pulmonary stenosis. Surgery is usually necessary to remove the obstruction.... pulmonary stenosis

VEINS that have become stretched and dilated. (See VEINS, DISEASES OF.)... varicose veins

The prominent vein which runs from near the bend of the elbow upwards along the inner side of the upper arm.... basilic vein

The vein which carries to the LIVER, blood that has been circulating in many of the abdominal organs. It is peculiar among the veins of the body in that it ends by breaking up into a capillary network instead of carrying the blood directly to the heart – a peculiarity which it shares only with certain small vessels in the kidneys. The PORTAL SYSTEM begins below in the haemorrhoidal plexus of veins around the lower end of the rectum; from this point, along the whole length of the intestines, the blood is collected into an inferior mesenteric vein upon the left, and a superior mesenteric vein upon the right side. The inferior mesenteric vein empties into the splenic vein, and the latter, uniting with the superior mesenteric vein immediately above the pancreas, forms the portal vein. The portal vein is joined by veins from the stomach and gallbladder, and ?nally divides into two branches which sink into the right and left lobes of the liver. (For their further course, see LIVER).

The organs from which the portal vein collects the blood are the large and small intestines, the stomach, spleen, pancreas, and gall-bladder.... portal vein

Tests to assess how the LUNGS are functioning. They range from simple spirometry (measuring breathing capacity) to sophisticated physiological assessments.

Static lung volumes and capacities can be measured: these include vital capacity – the maximum volume of air that can be exhaled slowly and completely after a maximum deep breath; forced vital capacity is a similar manoeuvre using maximal forceful exhalation and can be measured along with expiratory ?ow rates using simple spirometry; total lung capacity is the total volume of air in the chest after a deep breath in; functional residual capacity is the volume of air in the lungs at the end of a normal expiration, with all respiratory muscles relaxed.

Dynamic lung volumes and ?ow rates re?ect the state of the airways. The forced expiratory volume (FEV) is the amount of air forcefully exhaled during the ?rst second after a full breath – it normally accounts for over 75 per cent of the vital capacity. Maximal voluntary ventilation is calculated by asking the patient to breathe as deeply and quickly as possible for 12 seconds; this test can be used to check the internal consistency of other tests and the extent of co-operation by the patient, important when assessing possible neuromuscular weakness affecting respiration. There are several other more sophisticated tests which may not be necessary when assessing most patients. Measurement of arterial blood gases is also an important part of any assessment of lung function.... pulmonary function tests

A condition which may develop in both LUNGS (interstitial pulmonary ?brosis) or part of one lung. Scarring and thickening of lung tissues occur as a consequence of previous lung in?ammation, which may have been caused by PNEUMONIA or TUBERCULOSIS. Symptoms include cough and breathlessness and diagnosis is con?rmed with a chest X-ray. The patient’s underlying condition should be treated, but the damage already done to lung tissue is usually irreversible. (See also ALVEOLITIS.)... pulmonary fibrosis

See pulmonary disease, chronic obstructive.... chronic obstructive pulmonary disease

See thrombosis, deep vein.... deep vein thrombosis

One of 3 veins on each side of the neck that return deoxygenated blood from the head to the heart. The internal jugular, the largest of the 3 (internal, external, and anterior), arises at the base of the skull, travels down the neck alongside the carotid arteries, and passes behind the clavicle, where it joins the subclavian vein (the large vein that drains blood from the arms).... jugular vein

Blockage of a vein carrying blood away from the retina.

It usually results from thrombosis in the affected vein, and is more common in people who have glaucoma.

Retinal vein occlusion may cause visual disturbances, glaucoma, or blindness.... retinal vein occlusion

A major vein that runs the length of the leg just under the skin.

It is sometimes removed and used to bypass a blockage in blood vessels of the heart (see coronary artery bypass).... saphenous vein

A vessel that returns blood towards the heart from the various organs and tissues of the body. The walls of veins, like those of arteries, consist of a smooth inner lining, a muscular middle layer, and a fibrous outer covering. However, blood pressure in veins is lower than in arteries, and the walls of veins are thinner, less elastic, less muscular, and weaker than those of arteries. The linings of many veins contain folds, which act as valves, ensuring that blood flows only towards the heart. Blood is helped on its way through the veins by pressure on the vessel walls from the contraction of surrounding muscles. (See also circulatory system.) A... vein

A combination of mouth to mouth resuscitation (E.A.R.) to oxygenate the blood, and external chest compression (E.C.C.) to compress the heart to help pump this artificially oxygenated blood around the body to maintain tissue oxygen concentration and prevent death.... cardio-pulmonary resuscitation

Naturally produced in the LUNGS by cells called pneumocytes, this substance is a mixture of phospholipids (see PHOSPHOLIPID) and LIPOPROTEINS. Present in ?uid lining the alveoli (see ALVEOLUS) in the lungs, their action helps maintain their patency. Premature babies may have a de?ciency of surfactant, a disorder which causes severe breathing diffculties – RESPIRATORY DISTRESS SYNDROME or hyaline membrane disease – and HYPOXIA. They will need urgent respiratory support, which includes oxygen and the administration (via an endotracheal tube) of a specially prepared surfactant such as beractant (bovine lung extract) or edfosceril palmitate.... pulmonary surfactant

This is a term encompassing chronic BRONCHITIS, EMPHYSEMA, and chronic ASTHMA where the air?ow into the lungs is obstructed.

Chronic bronchitis is typi?ed by chronic productive cough for at least three months in two successive years (provided other causes such as TUBERCULOSIS, lung cancer and chronic heart failure have been excluded). The characteristics of emphysema are abnormal and permanent enlargement of the airspaces (alveoli) at the furthermost parts of the lung tissue. Rupture of alveoli occurs, resulting in the creation of air spaces with a gradual breakdown in the lung’s ability to oxygenate the blood and remove carbon dioxide from it (see LUNGS). Asthma results in in?ammation of the airways with the lining of the BRONCHIOLES becoming hypersensitive, causing them to constrict. The obstruction may spontaneously improve or do so in response to bronchodilator drugs. If an asthmatic patient’s airway-obstruction is characterised by incomplete reversibility, he or she is deemed to have a form of COPD called asthmatic bronchitis; sufferers from this disorder cannot always be readily distinguished from those people who have chronic bronchitis and/ or emphysema. Symptoms and signs of emphysema, chronic bronchitis and asthmatic bronchitis overlap, making it di?cult sometimes to make a precise diagnosis. Patients with completely reversible air?ow obstruction without the features of chronic bronchitis or emphysema, however, are considered to be suffering from asthma but not from COPD.

The incidence of COPD has been increasing, as has the death rate. In the UK around 30,000 people with COPD die annually and the disorder makes up 10 per cent of all admissions to hospital medical wards, making it a serious cause of illness and disability. The prevalence, incidence and mortality rates increase with age, and more men than women have the disorder, which is also more common in those who are socially disadvantaged.

Causes The most important cause of COPD is cigarette smoking, though only 15 per cent of smokers are likely to develop clinically signi?cant symptoms of the disorder. Smoking is believed to cause persistent airway in?ammation and upset the normal metabolic activity in the lung. Exposure to chemical impurities and dust in the atmosphere may also cause COPD.

Signs and symptoms Most patients develop in?ammation of the airways, excessive growth of mucus-secreting glands in the airways, and changes to other cells in the airways. The result is that mucus is transported less e?ectively along the airways to eventual evacuation as sputum. Small airways become obstructed and the alveoli lose their elasticity. COPD usually starts with repeated attacks of productive cough, commonly following winter colds; these attacks progressively worsen and eventually the patient develops a permanent cough. Recurrent respiratory infections, breathlessness on exertion, wheezing and tightness of the chest follow. Bloodstained and/or infected sputum are also indicative of established disease. Among the symptoms and signs of patients with advanced obstruction of air?ow in the lungs are:

RHONCHI (abnormal musical sounds heard through a STETHOSCOPE when the patient breathes out).

marked indrawing of the muscles between the ribs and development of a barrel-shaped chest.

loss of weight.

CYANOSIS in which the skin develops a blue tinge because of reduced oxygenation of blood in the blood vessels in the skin.

bounding pulse with changes in heart rhythm.

OEDEMA of the legs and arms.

decreasing mobility.

Some patients with COPD have increased ventilation of the alveoli in their lungs, but the levels of oxygen and carbon dioxide are normal so their skin colour is normal. They are, however, breathless so are dubbed ‘pink pu?ers’. Other patients have reduced alveolar ventilation which lowers their oxygen levels causing cyanosis; they also develop COR PULMONALE, a form of heart failure, and become oedematous, so are called ‘blue bloaters’.

Investigations include various tests of lung function, including the patient’s response to bronchodilator drugs. Exercise tests may help, but radiological assessment is not usually of great diagnostic value in the early stages of the disorder.

Treatment depends on how far COPD has progressed. Smoking must be stopped – also an essential preventive step in healthy individuals. Early stages are treated with bronchodilator drugs to relieve breathing symptoms. The next stage is to introduce steroids (given by inhalation). If symptoms worsen, physiotherapy – breathing exercises and postural drainage – is valuable and annual vaccination against INFLUENZA is strongly advised. If the patient develops breathlessness on mild exertion, has cyanosis, wheezing and permanent cough and tends to HYPERVENTILATION, then oxygen therapy should be considered. Antibiotic treatment is necessary if overt infection of the lungs develops.

Complications Sometimes rupture of the pulmonary bullae (thin-walled airspaces produced by the breakdown of the walls of the alveoli) may cause PNEUMOTHORAX and also exert pressure on functioning lung tissue. Respiratory failure and failure of the right side of the heart (which controls blood supply to the lungs), known as cor pulmonale, are late complications in patients whose primary problem is emphysema.

Prognosis This is related to age and to the extent of the patient’s response to bronchodilator drugs. Patients with COPD who develop raised pressure in the heart/lung circulation and subsequent heart failure (cor pulmonale) have a bad prognosis.... chronic obstructive pulmonary disease (copd)

When coronary arteries, narrowed by disease, cannot supply the heart muscle with su?cient blood, the cardiac circulation may be improved by grafting a section of vein from the leg to bypass the obstruction. Around 10,000 people in the United Kingdom have this operation annually and the results are usually good. It is a major procedure that lasts several hours and requires the heart to be stopped temporarily, with blood circulation and oxygenation taken over by a HEART-LUNG MACHINE.... coronary artery vein bypass grafting (cavbg)

See THROMBOSIS; VEINS, DISEASES OF.... deep vein thrombosis (dvt)

See LUNGS, DISEASES OF.... pulmonary diseases

The vessels which return the blood to the heart after it has circulated through the tissues; they are both more numerous and more capacious than the ARTERIES.

Structure While of similar structure to an artery, veins have much thinner walls, with much less muscular tissue. Furthermore, most veins have one-way VALVES to ensure that the blood ?ows in the right direction. These are most numerous in the legs, then the arms, with few in the internal organs.

Chief veins Four pulmonary veins open into the left atrium of the heart, two from each lung. The superior vena cava returns the blood from the head, neck, and arms; while the inferior vena cava returns blood from the legs and abdomen. The large basilic vein that runs up the inner side of the upper arm is the vein usually opened in blood-letting (see VENESECTION). The great saphenous vein is of special interest, because of its liability to become distended or varicose. Within the abdomen, the inferior vena cava receives branches corresponding to several branches of the aorta, its largest branches being the hepatic veins, which return not only the blood that has reached the liver in the hepatic arteries, but also blood which comes from the digestive organs in the PORTAL VEIN to undergo a second capillary circulation in the liver.

There are several connections between the superior and inferior cava, the most important being three azygos veins that lie upon the sides of the spinal column, the veins on the front of the abdomen, and some veins that emerge from the abdomen at the navel and connect the portal system with those of the inferior and superior vena cava. (See also CIRCULATORY SYSTEM OF THE BLOOD.)... veins

Veins are the blood vessels that convey blood back from the tissues towards the heart. Two common conditions that affect them are THROMBOSIS and varicosities (see below).

Varicose veins are dilated tortuous veins occurring in about 15 per cent of adults – women more than men. They most commonly occur in the legs but may also occur in the anal canal (HAEMORRHOIDS) and in the oesophagus (due to liver disease).

Normally blood ?ows from the subcutaneous tissues to the super?cial veins which drain via perforating veins into the deep veins of the leg. This ?ow, back towards the heart, is aided by valves within the veins. When these valves fail, increased pressure is exerted on the blood vessels leading to dilatations known as varicose veins.

Treatment is needed to prevent complications such as ulceration and bleeding, or for

cosmetic purposes. Treatment alternatives include injection with sclerosing agents to obliterate the lumen of the veins (sclerotherapy), or surgery; in the elderly or un?t, an elastic stocking may su?ce. One operation is the Trendelenburg operation in which the saphenous vein is disconnected from the femoral vein and individual varicose veins are avulsed. (See also VASCULITIS.)

Thrombosis Thrombosis occurs when blood, which is normally a liquid, clots within the vein to form a semisolid thrombus (clot). This occurs through a combination of reduced blood ?ow and hypercoagulability (a reduced threshold for clotting). The most common site for this to occur is in the deep veins of the leg, where it is known as a deep-vein thrombosis (DVT).

Predisposing factors include immobility (leading to reduced blood ?ow), such as during long journeys (e.g. plane ?ights) where there is little opportunity to stretch one’s legs; surgery (leading to temporary post-operative immobility and hypercoagulability of blood); oestrogen administration (low-dose oestrogen oral contraceptives carry a very low relative risk); and several medical illnesses such as heart failure, stroke and malignancy.

Deep-vein thrombosis presents as a tender, warm, red swelling of the calf. Diagnosis may be con?rmed by venogram (an X-ray taken following injection of contrast medium into the foot veins) or by ultrasound scanning looking for ?ow within the veins.

Prevention is important. This is why patients are mobilised and/or given leg exercises very soon after an operation, even major surgery. People should avoid sitting for long periods, particularly if the edge of the seat is hard, thus impeding venous return from the legs. Car drivers should stop regularly on a long journey and walk around; airline travellers should, where possible, walk round the aisle(s) and also exercise and massage their leg muscles, as well as drinking ample non-alcoholic ?uids.

Diagnosis and treatment are important because there is a risk that the clotted blood within the vein becomes dislodged and travels up the venous system to become lodged in the pulmonary arteries. This is known as PULMONARY EMBOLISM.

Treatment is directed at thinning the blood with ANTICOAGULANTS, initially with heparin and subsequently with WARFARIN for a period of time while the clot resolves.

Blocked super?cial veins are described as super?cial thrombophlebitis, which produces in?ammation over the vein. It responds to antiin?ammatory analgesics. Occasionally heparin and ANTIBIOTICS are required to treat associated thrombosis and infection.... veins, diseases of

One of a large number of tiny, balloon-like sacs at the end of a bronchiole (one of many small air passages in the lungs) where gases are exchanged during respiration.... alveolus, pulmonary

See telangiectasia.... broken veins

Scarring of lung tissue mainly involving the alveoli. There are a number of causes, including occupational exposure to dusts and fibrosing alveolitis, which is an autoimmune disorder.... interstitial pulmonary fibrosis

Cancer of the lung.

By the blood and lymph cancer may be transferred (metastasised) to the lymph nodes under the arm, liver, brain or lungs. An association has been shown between a low intake of Vitamin A and lung cancer. Causes: occupational hazards, environmental pollution, radiation, keeping of pet birds. Cigarette smoking is a strong risk factor. Studies show that a high Vitamin A/carotene intake is protective against the disease in men. Among women, evidence of a similar protective effect has not been found. Vitamin C reduces cancer risk. The increased prevalence of smoking among women results in more female lung cancer. All smokers should drink freely carrot juice (Vitamin A).

Symptoms. Chronic irritative cough, difficult breathing, pain in the chest, recurrent spitting of blood, clubbing of fingers, weight loss.

Alternatives. Only transient benefit is obtainable, yet it may be sufficient to achieve a measure of relief from distressing symptoms. See: CANCER: GENERAL REMARKS. Mullein tea has its supporters. Bugleweed strengthens lung tissue and supports the action of the heart. Blood root is known to arrest bleeding (haemoptysis).

Tea. Equal parts: Red Clover, Gota Kola, Mullein. 2 teaspoons to each cup boiling water; infuse 5-15 minutes. 1 cup three or more times daily.

Formula No 1. Equal parts: Elecampane, Violet, Red Clover, Echinacea. Mix. Dose: Powders: 750mg (three 00 capsules or half a teaspoon). Liquid extracts: 1-2 teaspoons. Tinctures: 1-3 teaspoons. Thrice daily and, if necessary, at bedtime for relief.

Formula No 2. Tincture Blood root 10 drops; Liquid extract Dogwood 20 drops; Liquid extract Elecampane 200 drops (14ml); Liquid extract Bugleweed (Lycopus europ) 30 drops. Flavour with Liquorice if necessary. Dose: 1-2 teaspoons in water 3 or more times daily. (W. Burns-Lingard MNIMH)

Where accompanied by active inflammation, anti-inflammatories are indicated: Mistletoe, Wild Yam, etc.

Diet. A substance in fish oil has been shown to experimentally prevent cancer of the lung. Mackerel, herring and sardines are among fish with the ingredient. See: DIET – CANCER.

Chinese Herbalism. See: CANCER – CHINESE PRESCRIPTION.

Treatment by a general medical practitioner or hospital oncologist. ... cancer – pulmonary

A combination of chronic bronchitis and emphysema, in which there is persistent disruption of air flow into or out of the lungs. Patients are sometimes described as either pink puffers or blue bloaters, depending on their condition. Pink puffers maintain adequate oxygen in their bloodstream through an increase in their breathing rate, and remain “pink” despite damage to the lungs. However, they suffer from almost constant shortness of breath. Blue bloaters are cyanotic (have a bluish discoloration of the skin and mucous membranes) because of obesity, and sometimes oedema, mainly due to heart failure resulting from the lung damage.... pulmonary disease, chronic obstructive

A rare defect of the pulmonary valve at the exit of the heart’s right ventricle. The valve fails to close properly, allowing blood to leak back into the heart. The cause is usually rheumatic fever, endocarditis, or severe pulmonary hypertension.... pulmonary incompetence

The formation of a thrombus within deep-lying veins in the leg. The cause is usually a combination of slow blood flow through 1 part of the body (such as when sitting for long periods or when the tissues are compressed, as occurs in long-haul aircraft flights) and an increase in the clotting tendency of the blood, which occurs with dehydration, after surgery or injury, during pregnancy, and in women taking oral contraceptives. Deep vein thrombosis may also be caused by polycythaemia. Deep vein thrombosis is common in people with heart failure and those who have had a stroke or who have been immobile for long periods. Clots in the leg veins may cause pain, tenderness, swelling, discoloration, and ulceration of the skin, but they can be symptomless. A deep vein thrombosis is not necessarily serious in itself, but part of the clot may break off and travel in the bloodstream to the lungs. This is known as a pulmonary embolism.

A diagnosis is made by doppler ultrasound scanning.

Treatment depends on the site and extent of the clots.

Small clots may not need treatment if they are confined to the calf and the patient is mobile.

Otherwise, anticoagulant drugs or thrombolytic drugs are given.

If there is a high risk of a pulmonary embolism, thrombectomy may be performed.... thrombosis, deep vein

Common disorders affecting veins include varicose veins, deep vein thrombosis (see thrombosis, deep vein), and thrombophlebitis.... veins, disorders of

a congenital abnormality in which the pulmonary veins enter the right atrium or vena cava instead of draining into the left atrium. The clinical features are those of an *atrial septal defect.... anomalous pulmonary venous drainage

an unpaired vein that arises from the inferior vena cava and drains into the superior vena cava, returning blood from the thorax and abdominal cavities.

b... azygos vein

two pairs of veins in the embryo that carry blood from the head (anterior cardinal veins) and trunk (posterior cardinal veins); they unite to form the common cardinal vein, which drains into the sinus venosus of the heart.... cardinal veins

a group of veins within the skull that drain blood from the venous sinuses of the dura mater to veins outside the skull.... emissary veins

one of several short veins originating within the lobes of the liver as small branches, which unite to form the hepatic veins. These lead directly to the inferior vena cava, draining blood from the liver.... hepatic vein

(IPF) a serious interstitial lung disease, formerly called cryptogenic fibrosing alveolitis (see alveolitis). It is characterized by progressive fibrous scarring of the lung and increased numbers of inflammatory cells in the alveoli and surrounding tissues. The disease is usually diagnosed on clinical grounds on a basis of worsening breathlessness, inspiratory crackles at the lung bases on auscultation, clubbing of the fingers or toes, bilateral radiographic shadowing predominantly in the lower zones of the chest X-ray, subpleural *honeycomb change on CT scanning of the chest, and restrictive lung function on spirometry. It is also called usual interstitial pneumonia (UIP; see interstitial pneumonia), a term used by lung pathologists for the most common cellular pattern seen on biopsy. Treatment includes *pirfenidone, corticosteroids, and immunosuppressants.... idiopathic pulmonary fibrosis

the veins draining most of the blood from the lower limbs and pelvic region. The right and left common iliac veins unite to form the inferior vena cava. They are each formed by the union of the internal and external iliac veins.... iliac veins

(brachiocephalic vein) either of two veins, one on each side of the neck, formed by the junction of the external jugular and subclavian veins. The two veins join to form the superior vena cava.... innominate vein

the artery that conveys blood from the heart to the lungs for oxygenation: the only artery in the body containing deoxygenated blood. It leaves the right ventricle and passes upwards for 5 cm before dividing into two, one branch going to each lung. Within the lungs each pulmonary artery divides into many fine branches, which end in capillaries in the alveolar walls. See also pulmonary circulation.... pulmonary artery

(PCWP) an indirect measurement of the pressure of blood in the left atrium of the heart, which indicates the adequacy of left heart function. It is measured using a catheter wedged in the most distal segment of the pulmonary artery. See also Swan-Ganz catheter.... pulmonary capillary wedge pressure

a system of blood vessels effecting transport of blood between the heart and lungs. Deoxygenated blood leaves the right ventricle by the pulmonary artery and is carried to the alveolar capillaries of the lungs. Gaseous exchange occurs, with carbon dioxide leaving the circulation and oxygen entering. The oxygenated blood then passes into small veins leading to the pulmonary veins, which leave the lungs and return blood to the left atrium of the heart. The oxygenated blood can then be pumped around the body via the *systemic circulation.... pulmonary circulation

leakage of the pulmonary valve in the heart. Mild regurgitation is a common normal finding, but severe congenital pulmonary regurgitation may require surgical correction.... pulmonary regurgitation

see tuberculosis.... pulmonary tuberculosis

a valve in the heart lying between the right ventricle and the pulmonary artery. It is a *semilunar valve that prevents blood returning to the ventricle from the pulmonary artery.... pulmonary valve