Lung Health Dictionary

Lung: From 2 Different Sources


One of the 2 main organs of the respiratory system. The lungs supply the body with the oxygen needed for aerobic metabolism and eliminate the waste product carbon dioxide. Air is delivered to the lungs via the trachea (windpipe); this branches into 2 main bronchi (air passages), with 1 bronchus supplying each lung. The main bronchi divide again into smaller bronchi and then into bronchioles, which lead to air passages that open out into grape-like air sacs called alveoli (see alveolus, pulmonary). Oxygen and carbon dioxide diffuse into or out of the blood through the thin walls of the alveoli. Each lung is enclosed in a double membrane called the pleura; thetwo layers of the pleura secrete a lubricating fluid that enables the lungs to move freely as they expand and contract during breathing. (See also respiration.) lung cancer The most common form of cancer in the. Tobacco-smoking is the main cause. Passive smoking (the inhalation of tobacco smoke by nonsmokers) and environmental pollution (for example, with radioactive minerals or asbestos) are also risk factors.

The first and most common symptom is a cough. Other symptoms include coughing up blood, shortness of breath, and chest pain. Lung cancer can spread to other parts of the body, especially the liver, brain, and bones. In most cases, the cancer is revealed in a chest X-ray. To confirm the diagnosis, tissue must be examined microscopically for the presence of cancerous cells (see cytology). If lung cancer is diagnosed at an early stage, pneumonectomy (removal of the lung) or lobectomy (removal of part of the lung) may be possible. Anticancer drugs and radiotherapy may also be used. lung, collapse of See atelectasis; pneumothorax.

Health Source: BMA Medical Dictionary
Author: The British Medical Association
n. one of the pair of organs of *respiration, situated in the chest cavity on either side of the heart and enclosed by a serous membrane (see pleura). The lungs are fibrous elastic sacs that are expanded and compressed by movements of the rib cage and diaphragm during *breathing. They communicate with the atmosphere through the *trachea, which opens into the pharynx. The trachea divides into two bronchi (see bronchus), which enter the lungs and branch into *bronchioles. These divide further and terminate in minute air sacs (see alveolus), the sites of gaseous exchange. (See illustration.) Atmospheric oxygen is absorbed and carbon dioxide from the blood of the pulmonary capillaries is released into the lungs; in each case down a concentration gradient (see pulmonary circulation). The total capacity of the lungs in an adult male is about 5.5 litres, but during normal breathing only about 500 ml of air is exchanged (see also residual volume). Other functions of the lung include water evaporation: an important factor in the fluid balance and heat regulation of the body.

British Lung Foundation: basic information on the lungs and some common lung conditions

Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Farmer’s Lung

Allergic alveolitis. An occupational lung disease due to inhaling dust and mouldy grain, hay or other mouldy vegetable produce. Usually affects farm workers and those exposed to its wide range of allergens.

Symptoms: Influenza-like fever, breathlessness, cough.

Prognosis: Chronic lung damage and progressive disability.

Indicated: antifungals, antibiotics.

Alternatives. Teas. Marigold, Ground Ivy, Scarlet Pimpernel, Yarrow. 1 heaped teaspoon to each cup boiling water; infuse 5-15 minutes; 1 cup freely.

Tablets/capsules. Garlic, Echinacea, Goldenseal, Thuja.

Powders. Combine, parts, Echinacea 3; Goldenseal 1; Thuja 1. Dose: 500mg, (two 00 capsules or one- third teaspoon) thrice daily.

Decoction. Irish Moss, to promote expectoration and eliminate debris.

Tinctures. Alternatives. (1) Echinacea 2; Lobelia 1; Liquorice 1. (2) Equal parts: Wild Indigo, Thuja and Pleurisy root. (3) Echinacea 2; Marigold 1; Thuja half; Liquorice half. Dosage: two 5ml teaspoons in water thrice daily. Acute cases: every 2 hours.

Topical. Inhalation of Eucalyptus or Tea Tree oils.

Diet. See: DIET – GENERAL. Yoghurt in place of milk.

Note: Bronchodilators of little value. Those at risk should have an X-ray at regular intervals. ... farmer’s lung

Heart-lung Machine

A device that temporarily takes over the function of the heart and lungs. It is used in certain operations in the chest, giving the surgeon more time for operations such as open-heart surgery, heart transplants and heart-lung transplants. The machine also ensures an operating area largely free of blood, which helps the surgeon to work more quickly. A pump replaces the heart and an oxygenator replaces the lungs. When connected up, the machine in e?ect bypasses normal cardiopulmonary activity. It also contains a heat exchanger to warm or cool the patient’s blood according to the requirements of the operation. The patient is given an anticoagulant (HEPARIN) to counteract clotting which may occur when blood cells get damaged during the machine’s use. Patients are on the machine for a few hours only, because blood supply to vital organs begins to be reduced.... heart-lung machine

Iron Lung

A large machine formerly used to maintain breathing, especially in people paralysed by poliomyelitis. The iron lung has been replaced by more efficient means of maintaining breathing (see ventilation).... iron lung

Artificial Ventilation Of The Lungs

When we breathe in, the outward movement of the chest increases the volume of the lungs and the pressure in them falls below that of the outside world. Therefore, air is drawn in automatically. When we breathe out, some air exits because of the normal elastic recoil of the lungs, but we also force air out by using the muscles of the chest and the DIAPHRAGM. Replicating this arti?cially involves using a device to produce intermittent positive or negative pressure ventilation as described below.... artificial ventilation of the lungs

Bird Fancier’s Lung

Also known as pigeon breeder’s lung, this is a form of extrinsic allergic ALVEOLITIS resulting from sensitisation to birds. In bird fanciers, skin tests sometimes show sensitisation to birds’ droppings, eggs, protein and serum, even through there has been no evidence of any illness.... bird fancier’s lung

Budgerigar-fancier’s Lung

Budgerigar-fancier’s lung is a form of extrinsic allergic ALVEOLITIS, resulting from sensitisation to budgerigars, or parakeets as they are known in North America. Skin tests have revealed sensitisation to the birds’ droppings and/or serum. As it is estimated that budgerigars are kept in 5– 6 million homes in Britain, current ?gures suggest that anything up to 900 per 100,000 of the population are exposed to the risk of developing this condition.... budgerigar-fancier’s lung

Farmer’s Lung

A form of external allergic ALVEOLITIS caused by the inhalation of dust from mouldy hay or straw.... farmer’s lung

Heart-lung Transplant

An operation in which a patient’s diseased lungs and heart are removed and replaced with donor organs from someone who has been certi?ed as ‘brain dead’ (see BRAIN-STEM DEATH). As well as the technical diffculties of such an operation, rejection by the recipient’s tissues of donated heart and lungs has proved hard to overcome. Since the early 1990s, however, immunosuppressant drug therapy (see CICLOSPORIN; TRANSPLANTATION) has facilitated the regular use of this type of surgery. Even so, patients receiving transplanted hearts and lungs face substantial risks such as lung infection and airway obstruction as well as the long-term problems of transplant rejection.... heart-lung transplant

Lung Flukes

Trematode worms infecting the lungs of humans and other crab-eating mammals. Belong to the genusParagonimus and are found in parts of Africa, Latin America, Asia and SE Asia.... lung flukes

Lung Volumes

The volume of air within the LUNGS changes with the respiratory cycle (see RESPIRATION). The volumes de?ned in the following table can be measured, and may be useful indicators of some pulmonary diseases.

Normal values for a 60 kg man are (in ml):

Total lung capacity (TLC) The volume of air that can be held in the lungs at maximum inspiration.

Tidal volume (TV) The volume of air taken into and expelled from the lungs with each breath.

Inspiratory reserve volume (IRV) The volume of air that can still be inspired at the end of a normal quiet inspiration.

Expiratory reserve volume (ERV) The volume of air that can still be expired at the end of a normal quiet expiration.

Residual volume (RV) The volume of air remaining in the lungs after a maximal expiration.

Vital capacity (VC) The maximum amount of air that can be expired after a maximal inspiration.

Functional residual capacity (FRC) The volume of air left in the lungs at the end of a normal quiet expiration.... lung volumes

Shock Lung

See ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS).... shock lung

Lobectomy, Lung

An operation to cut out one of the lobes of a lung, usually to remove a cancerous tumour.... lobectomy, lung

Lung Disease, Chronic Obstructive

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

Lung Function Tests

See pulmonary function tests.... lung function tests

Lung Imaging

Techniques that provide images of the lungs to aid in the diagnosis of disease.

Most lung disorders can be detected by chest X-ray.

CT scanning and MRI play an important role in detecting the presence and spread of lung tumours.

Ultrasound scanning is sometimes used to reveal pleural effusion.

Radioisotope scanning is used to detect evidence of pulmonary embolism.... lung imaging

Lung Tumours

Growths in the lungs. These tumours may be either cancerous (see lung cancer) or noncancerous.Cancerous lung tumours are usually associated with tobacco-smoking.

Noncancerous tumours occur less frequently than cancers.

The most common form of noncancerous tumour is a bronchial adenoma, which arises in the lining of a bronchus.

Adenomas often cause bronchial obstruction; affected people may also cough up blood.

Treatment involves surgical removal of the tumour.

Other rare noncancerous tumours include fibromas (which consist of fibrous tissue) and lipomas (which consist of fatty tissue).

No treatment is necessary unless the tumours are causing problems.... lung tumours

Lungs

Positioned in the chest, the lungs serve primarily as respiratory organs (see RESPIRATION), also acting as a ?lter for the blood.

Form and position Each lung is a sponge-like cone, pink in children and grey in adults. Its apex projects into the neck, with the base resting on the DIAPHRAGM. Each lung is enveloped by a closed cavity, the pleural cavity, consisting of two layers of pleural membrane separated by a thin layer of ?uid. In healthy states this allows expansion and retraction as breathing occurs.

Heart/lung connections The HEART lies in contact with the two lungs, so that changes in lung volume inevitably affect the pumping action of the heart. Furthermore, both lungs are connected by blood vessels to the heart. The pulmonary artery passes from the right ventricle and divides into two branches, one of which runs straight outwards to each lung, entering its substance along with the bronchial tube at the hilum or root of the lung. From this point also emerge the pulmonary veins, which carry the blood oxygenated in the lungs back to the left atrium.

Fine structure of lungs Each main bronchial tube, entering the lung at the root, divides into branches. These subdivide again and again, to be distributed all through the substance of the lung until the ?nest tubes, known as respiratory bronchioles, have a width of only 0·25 mm (1/100 inch). All these tubes consist of a mucous membrane surrounded by a ?brous sheath. The surface of the mucous membrane comprises columnar cells provided with cilia (hair-like structures) which sweep mucus and unwanted matter such as bacteria to the exterior.

The smallest divisions of the bronchial tubes, or bronchioles, divide into a number of tortuous tubes known as alveolar ducts terminating eventually in minute sacs, known as alveoli, of which there are around 300 million.

The branches of the pulmonary artery accompany the bronchial tubes to the furthest recesses of the lung, dividing like the latter into ?ner and ?ner branches, and ending in a dense network of capillaries. The air in the air-vesicles is separated therefore from the blood only by two delicate membranes: the wall of the air-vesicle, and the capillary wall, through which exchange of gases (oxygen and carbon dioxide) readily takes place. The essential oxygenated blood from the capillaries is collected by the pulmonary veins, which also accompany the bronchi to the root of the lung.

The lungs also contain an important system of lymph vessels, which start in spaces situated between the air-vesicles and eventually leave the lung along with the blood vessels, and are connected with a chain of bronchial glands lying near the end of the TRACHEA.... lungs

Oedema Of The Lungs

This occurs as a result of left ventricular failure (see HEART, DISEASES OF). There is an abrupt increase in the venous and capillary pressure in the pulmonary vessels, followed by ?ooding of ?uid into the interstitial spaces and alveoli. The commonest cause of acute pulmonary oedema is myocardial infarction (see HEART, DISEASES OF) which reduces the ability of the left ventricular myocardial muscle to handle the blood delivered to it. Pulmonary oedema may result from other causes of left ventricular failure such as HYPERTENSION or valvular disease of the mitral and aortic valves. The initial symptoms are cough with breathlessness and occasionally with wheezing (once called ‘cardiac asthma’). The patient becomes extremely short of breath and in a severe attack the patient is pale, sweating and cyanosed and obviously gasping for breath. Frequently, frothy sputum is produced which may be blood-stained. Treatment is with DIURETICS and measures to deal with the myocardial infarction or other underlying cause.... oedema of the lungs

Tea For Lungs

Lung affections consist of mucus accumulations, water retention, upper chest inflammations and other problems of the respiratory system. If you have trouble breathing, you feel a back pain or it seems like there’s something pressing on your chest, it’s possible that you have a lung problem. However, schedule an appointment with your doctor to find out which disease you suffer from. How a Tea for Lungs Works A Tea for Lungs’ main goal is to clear out all the unwanted accumulations and improve your respiration. Many other diseases are linked to lungs affections, such as heart conditions (low or increased blood pressure, arrhythmia, cardiovascular problems). A Tea for Lungs can treat your localized affections and not only: a tea rich in enzymes and tannins will also improve your heartbeat and blood pressure. Efficient Tea for Lungs In order to be effective, a Tea for Lungs needs to be both one hundred percent safe and contain the right amount of active constituents. You may not know this, but their proportion determines which tea is good for which affection, so not any tea found in the kitchen can treat your lung problems. If you don’t know which teas to choose from, here’s a list to guide you on: - Elecampane Tea – the main active constituents are mucilage, essential oils and a substance called camphor, which is a natural antibiotic with expectorant action. This tea can flush out of your system all infection triggers and reduce inflammation while calming the affected areas. However, you may want to talk to your doctor before starting a treatment based on this Tea for Lungs. - Hawthorn Tea – good for a number of affections, such as pleurisy, pulmonary edema or even mild cancer cases, this tea contains an important level of flavonoids and procyanidis which can treat your arrhythmia and stabilize your blood pressure. Don’t drink more than two cups per day for a short amount of time (one or two weeks) in order to avoid further complications. - Thyme Tea – contains thymol, which is a powerful antibiotic and polymethoxyflavones which have anti-coughing and anti-inflammatory properties. Thanks to its great expectorant properties, this Tea for Lungs is recommended by practitioners around the world as a great bronchitis treatment. Tea for Lungs Side Effects When taken according to medical specifications, these teas are one hundred percent safe. However, talk to your doctor before starting any kind of medical treatment and remember that self medication may cause even more damages. Don’t take any of these teas if you’re pregnant, breastfeeding, on anti-coagulants or blood thinners. The same advice for patients who are preparing for a surgery: these teas contain substances that may interfere with the anesthetic. If you have the green light from your doctor, choose a Tea for Lungs that fits you best and enjoy its wonderful health benefits!... tea for lungs

Bird-fancier’s Lung

a form of extrinsic allergic *alveolitis caused by the inhalation of avian proteins present in the droppings and feathers of certain birds, especially pigeons and caged birds (such as budgerigars). As in *farmer’s lung, there is an acute and a chronic form.... bird-fancier’s lung

Lungs, Diseases Of

Various conditions affecting the LUNGS are dealt with under the following headings: ASTHMA; BRONCHIECTASIS; CHEST, DEFORMITIES OF; CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD); COLD, COMMON; EMPHYSEMA; EXPECTORATION; HAEMOPTYSIS; HAEMORRHAGE; OCCUPATIONAL HEALTH, MEDICINE AND DISEASES; PLEURISY; PNEUMONIA; PULMONARY EMBOLISM; TUBERCULOSIS.

In?ammation of the lungs is generally known as PNEUMONIA, when it is due to infection; as ALVEOLITIS when the in?ammation is immunological; and as PNEUMONITIS when it is due to physical or chemical agents.

Abscess of the lung consists of a collection of PUS within the lung tissue. Causes include inadequate treatment of pneumonia, inhalation of vomit, obstruction of the bronchial tubes by tumours and foreign bodies, pulmonary emboli (see EMBOLISM) and septic emboli. The patient becomes generally unwell with cough and fever. BRONCHOSCOPY is frequently performed to detect any obstruction to the bronchi. Treatment is with a prolonged course of antibiotics. Rarely, surgery is necessary.

Pulmonary oedema is the accumulation of ?uid in the pulmonary tissues and air spaces. This may be caused by cardiac disease (heart failure or disease of heart valves – see below, and HEART, DISEASES OF) or by an increase in the permeability of the pulmonary capillaries allowing leakage of ?uid into the lung tissue (see ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS)).

Heart failure (left ventricular failure) can be caused by a weakness in the pumping action of the HEART leading to an increase in back pressure which forces ?uid out of the blood vessels into the lung tissue. Causes include heart attacks and HYPERTENSION (high blood pressure). Narrowed or leaking heart valves hinder the ?ow of blood through the heart; again, this produces an increase in back pressure which raises the capillary pressure in the pulmonary vessels and causes ?ooding of ?uid into the interstitial spaces and alveoli. Accumulation of ?uid in lung tissue produces breathlessness. Treatments include DIURETICS and other drugs to aid the pumping action of the heart. Surgical valve replacement may help when heart failure is due to valvular heart disease.

Acute respiratory distress syndrome Formerly known as adult respiratory distress syndrome (ARDS), this produces pulmonary congestion because of leakage of ?uid through pulmonary capillaries. It complicates a variety of illnesses such as sepsis, trauma, aspiration of gastric contents and di?use pneumonia. Treatment involves treating the cause and supporting the patient by providing oxygen.

Collapse of the lung may occur due to blockage of a bronchial tube by tumour, foreign body or a plug of mucus which may occur in bronchitis or pneumonia. Air beyond the blockage is absorbed into the circulation, causing the affected area of lung to collapse. Collapse may also occur when air is allowed into the pleural space – the space between the lining of the lung and the lining of the inside of the chest wall. This is called a pneumothorax and may occur following trauma, or spontaneously

– for example, when there is a rupture of a subpleural air pocket (such as a cyst) allowing a communication between the airways and the pleural space. Lung collapse by compression may occur when ?uid collects in the pleural space (pleural e?usion): when this ?uid is blood, it is known as a haemothorax; if it is due to pus it is known as an empyema. Collections of air, blood, pus or other ?uid can be removed from the pleural space by insertion of a chest drain, thus allowing the lung to re-expand.

Tumours of the lung are the most common cause of cancer in men and, along with breast cancer, are a major cause of cancer in women. Several types of lung cancer occur, the most common being squamous cell carcinoma, small- (or oat-) cell carcinoma, adenocarcinoma, and large-cell carcinoma. All but the adenocarcinoma have a strong link with smoking. Each type has a di?erent pattern of growth and responds di?erently to treatment. More than 30,000 men and women die of cancer of the trachea, bronchus and lung annually in England and Wales.

The most common presenting symptom is cough; others include haemoptisis (coughing up blood), breathlessness, chest pain, wheezing and weight loss. As well as spreading locally in the lung – the rate of spread varies – lung cancer commonly spawns secondary growths in the liver, bones or brain. Diagnosis is con?rmed by X-rays and bronchoscopy with biopsy.

Treatment Treatment for the two main categories of lung cancer – small-cell and nonsmall-cell cancer – is di?erent. Surgery is the only curative treatment for the latter and should be considered in all cases, even though fewer than half undergoing surgery will survive ?ve years. In those patients unsuitable for surgery, radical RADIOTHERAPY should be considered. For other patients the aim should be the control of symptoms and the maintenance of quality of life, with palliative radiotherapy one of the options.

Small-cell lung cancer progresses rapidly, and untreated patients survive for only a few months. Because the disease is often widespread by the time of diagnosis, surgery is rarely an option. All patients should be considered for CHEMOTHERAPY which improves symptoms and prolongs survival.

Wounds of the lung may cause damage to the lung and, by admitting air into the pleural cavity, cause the lung to collapse with air in the pleural space (pneumothorax). This may require the insertion of a chest drain to remove the air from the pleural space and allow the lung to re-expand. The lung may be wounded by the end of a fractured rib or by some sharp object such as a knife pushed between the ribs.... lungs, diseases of

Honeycomb Lung

the honeycomb pattern seen on X-ray at the later stages of chronic lung conditions, in which the lungs become less elastic and more fibrotic. Once the honeycomb appearance is visible on the X-ray, the lungs are likely to progress to respiratory failure.... honeycomb lung

Lung Cancer

cancer arising in the epithelium of the air passages (bronchial cancer) or lung (see also non-small-cell lung cancer; small-cell lung cancer). It is a very common form of cancer, particularly in Britain, and is strongly associated with cigarette smoking and exposure to industrial air pollutants (including asbestos). There are often no symptoms in the early stages of the disease, when diagnosis is made on X-ray examination. Treatment includes surgical removal of the affected lobe or lung (less than 20% of cases are suitable for surgery), radiotherapy, and chemotherapy.... lung cancer

Malt-worker’s Lung

a form of extrinsic allergic *alveolitis seen in people who work with barley.... malt-worker’s lung

Non-small-cell Lung Cancer

(NSCLC) any type of lung cancer other than *small-cell lung cancer. Such cancers include *adenocarcinoma of the lung, large-cell carcinomas, and squamous-cell carcinoma of the lung.... non-small-cell lung cancer

Canary Fancier’s Lung

Bird fancier’s lung. Allergic alveolitis following antigens from pet birds: pigeons, budgerigars, canaries, chickens.

Symptoms: dry cough, difficult breathing usually at night. Loss of weight, tiredness, feverishness with rise of temperature. (Clinical Allergy, 1984. 14,429)

Tea. Yarrow, Elderflowers, Comfrey herb: equal parts.

Tablets/capsules. Garlic. Lobelia. Iceland Moss.

Powders. Formula. Pleurisy root 2; Hyssop 1; Iceland Moss 1. Dose: 500mg (two 00 capsules or one- third teaspoon) thrice daily.

Liquid Extracts. Formula. Pleurisy root 2; Liquorice 1; Hyssop 1. 1 teaspoon in water thrice daily, and when necessary. ... canary fancier’s lung

Lung Weakness

There is no reason why lung weakness of childhood should not, in later life, resolve into vigorous respiration. However, some cases present a life-long hazard, arresting full development and reducing the body’s ability to defend itself. To strengthen alveolar tissue, allay infection and enhance respiratory function a good pectoral may ensure against future disorders of lungs, trachea, bronchi and bronchioles.

Tablets/capsules. Iceland Moss.

Decoction. Irish Moss.

Tea. Combine equal parts, Comfrey, White Horehound, Liquorice. 1 heaped teaspoon to each cup water simmered gently 1 minute. Dose: half-1 cup morning and evening. Pinch Cayenne improves.

Potential benefits of Comfrey for this condition outweigh risk. ... lung weakness

Lungwort

Pulmonaria officinalis L. Lobaria pulmonaria L. Lichen. Leaves bear a resemblance to the human lung – see: DOCTRINE OF SIGNATURES. So-named because of its traditional use for tuberculosis. Keynote: upper respiratory organs.

Constituents: palmitic acid, linoleic acid, tannins, ergosterol, saponin.

Action: expectorant, demulcent astringent, haemostatic, orexigenic, antibiotic (mild).

Uses: asthma, laryngitis, sore throat, children’s dry cough, whooping cough, haemoptysis, nasal catarrh, bronchitis.

External: open wounds – to avoid infection.

Combinations. With Coltsfoot and White Horehound for TB cough. With Ephedra for difficult breathing. Preparations. Average dose: 2-4g. Thrice daily. Tea: 1 teaspoon to each cup boiling water; infuse 15 minutes; dose: one-third-1 cup. Or may be boiled in milk.

Liquid Extract BHP (1983): 1:1 in 25 per cent alcohol. Dose: 2-4ml.

Balm of Gilead Cough Mixture. ... lungwort

Heart–lung Machine

A machine that temporarily takes over the function of the heart and lungs to facilitate operations such as open heart surgery, heart transplants, and heart–lung transplants.

A heart–lung machine consists of a pump (to replace the heart’s function) and an oxygenator (to replace the lung’s function). It bypasses the heart and lungs, and the heart can be stopped.

Use of a heart–lung machine tends to damage red blood cells and to cause blood clotting. These problems can be minimized, however, by the administration of heparin, an anticoagulant drug, beforehand.heart–lung transplant A procedure in which the heart and lungs of a patient are removed, and replaced with donor organs. This surgery is used to treat diseases in which the lung damage has affected the heart, or vice versa. Such diseases include cystic fibrosis, fibrosing alveolitis, and some severe congenital heart defects (see heart disease, congenital). A heart–lung machine is used to take over the function of the patient’s heart and lungs during the operation, which is no more dangerous than a heart transplant.

heart-rate The rate at which the heart contracts to pump blood around the body. Most people have a heart-rate of between 60 and 100 beats per minute at rest. This rate tends to be faster in childhood and to slow slightly with age. Very fit people may have a resting rate below 60 beats per minute.

The heart muscle responds automatically to any increase in the amount of blood returned to it from active muscles by increasing its output. During extreme exercise, heart-rate may increase to 200 contractions per minute and the output to almost 250 ml per beat.

The heart-rate is also regulated by the autonomic nervous system. The parts of this system concerned with heart action are a nucleus of nerve cells, called the cardiac centre, in the brainstem, and 2 sets of nerves (the parasympathetic and sympathetic).

At rest, the parasympathetic nerves – particularly the vagus nerve – act on the sinoatrial node to maintain a slow heart-rate. During or in anticipation of muscular activity, this inhibition lessens and the heart-rate speeds up.

Sympathetic nerves release noradrenaline, which further increases the heart-rate and force of contraction. Sympathetic activity can be triggered by fear or anger, low blood pressure, or a reduction of oxygen in the blood.

Release of adrenaline and noradrenaline by the adrenal glands also acts to increase heart-rate.

The rate and rhythm of the heart can be measured by feeling the pulse or by listening with a stethoscope; a more accurate record is provided by an ECG.

A resting heart-rate above 100 beats per minute is termed a tachycardia, and a rate below 60 beats per minute a bradycardia. (See also arrhythmia, cardiac.)... heart–lung machine

Small-cell Lung Cancer

(SCLC) a type of bronchial carcinoma characterized by small cells (or oat cells), small round or oval cells with darkly staining nuclei and scanty indistinct cytoplasm. Small-cell carcinoma is usually related to smoking and accounts for about one-quarter of bronchial carcinomas; it carries a poor prognosis due to early distant spread, typically to bones, liver, and brain. Treatment is primarily with chemotherapy and radiotherapy and paraneoplastic symptoms (see paraneoplastic syndrome) from *ectopic hormone production are common. Compare non-small-cell lung cancer.... small-cell lung cancer

Lung, Disorders Of

The most common lung disorders are infections. These diseases include pneumonia, tracheitis, and croup. Bronchitis and bronchiolitis, which are inflammatory disorders affecting the airways within the lungs, can be complications of colds or influenza. The disorder bronchiectasis may occur as a complication of severe bacterial pneumonia o.

cystic fibrosis. The lungs can also be affected by allergic disorders. The most important of these is asthma. Another such disorder is allergic alveolitis, which is usually a reaction to dust of plant or animal origin. Irritation of the airways, usually by tobacco-smoking, can cause diseases characterized by damage to lung tissue and narrowing of the airways (see pulmonary disease, chronic obstructive). The lungs can also be affected by cancerous tumours; lung cancer is one of the most common cancers. Noncancerous lung tumours are uncommon.

Injury to a lung, usually resulting from penetration of the chest wall, can cause the lung to collapse (see pneumothorax; haemothorax). Damage to the interior of the lungs can be caused by inhalation of toxic substances (see asbestosis; silicosis). Blood supply to the lungs may be reduced by pulmonary embolism.

Lung disorders can be investigated in various ways, such as chest X-ray, bronchoscopy, and pulmonary function tests.... lung, disorders of




Recent Searches