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Related to lung: lung cancer, Lung Disease, lung pain


either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration. Other functions include filtration of blood, serving as reservoirs to store blood, and playing a role in metabolic activities. See also color plates.

The lungs are made of elastic tissue filled with interlacing networks of tubes and sacs carrying air, and with blood vessels carrying blood. The bronchi, which bring air to the lungs, branch out within the lungs into many smaller tubes, the bronchioles, which culminate in clusters of tiny air sacs called alveoli, whose total runs into millions. The alveoli are surrounded by a network of capillaries. Through the thin membranes of the capillaries, the air and blood make their exchange of oxygen and carbon dioxide.

The lungs are divided into lobes, the left lung having two (the left upper lobe and the left lower lobe) and the right having three (the right upper lobe, the right middle lobe, and the right lower lobe); these are further subdivided into bronchopulmonary segments, of which there are about 20. Protecting each lung is the pleura, a two-layered membrane that envelops the lung and contains lubricating fluid between its inner and outer layers.
Mechanics of Inflation and Deflation. The lungs are inflated by action of the diaphragm and the intercostal muscles. The diaphragm, a large dome-shaped muscle, forms the bottom of the thoracic cage. As it contracts it flattens, increasing the diameter of the thorax and elevating the lower ribs. Both of these actions increase the space for expansion of the lungs. The external intercostal muscles provide flexibility to the thoracic cage and allow more room for lung expansion by elevating the anterior end of each rib, thereby increasing the anterior-posterior diameter of the chest wall.

Deflation of the lungs is chiefly a passive maneuver. The major muscles involved in exhalation are the abdominal muscle group. As these muscles contract, they depress the lower ribs, and, through an increase in abdominal pressure, move the diaphragm upward.

As the lungs are compressed and distended by the respiratory muscles, the pressure within the alveoli (intra-alveolar pressure) rises and falls. During inhalation the pressure becomes slightly negative (−3 mm Hg) in relation to atmospheric pressure. During exhalation the intra-alveolar pressure rises to approximately +3 mm Hg. The effect of negative pressure within the alveoli is to cause air under atmospheric pressure to flow into the lungs (inhalation). The condition of positive pressure creates the opposite effect, causing air to flow outward (exhalation).

The lungs are surrounded by an airtight compartment, the pleural space within the pleural membrane. The intrapleural pressure is less than atmospheric pressure and is expressed as negative pressure. Normally the intrapleural pressure is about −4 mm Hg. When the lungs are fully expanded this pressure may be as great as −9 mm Hg. Under normal conditions, however, the intrapleural pressure fluctuates between −4 and −6 mm Hg.

If anything should penetrate the walls of the pleura, the negative pressure is lost as air rushes into the pleural cavity in response to atmospheric pressure. This condition is called pneumothorax. The walls of the alveoli also must remain intact in order to maintain normal intrapleural pressure. If a lesion causes a break in the alveolar membranes, air enters the pleural cavity through the break and produces pneumothorax. Relief of pneumothorax and collapse of the lung from accumulations of either air or fluids within the pleural space may be provided by aspiration of the air or fluid from the thoracic cavity (thoracentesis) or by insertion of chest tubes to provide for a gradual reexpansion of the lung. (Specific tests to determine pulmonary volume and capacities are discussed under pulmonary function tests.)
Disorders of the Lungs. The air brought to the lungs is filtered, moistened, and warmed on its way along the respiratory tract but it can nevertheless bring irritants and infectious organisms, and when the body resistance is low for any reason the lungs may suffer diseases of some seriousness. Such diseases include tuberculosis and pneumonia. Other disorders of the lungs include pulmonary edema, pleurisy, asthma, bronchiectasis, atelectasis, emphysema, and pneumoconiosis. Still other diseases enter the lungs via pathogens in the circulation, and the lungs may also be affected by pulmonary embolism and chronic obstructive pulmonary disease.
Structure of the lung. From Applegate, 2000.
lung abscess an infection of the lung, characterized by a localized accumulation of pus and destruction of tissue. It may be a complication of pneumonia or tuberculosis. A lung abscess may also follow a period of excessive drinking by an alcoholic. Infected matter that has been aspirated (usually in a drunken stupor) may lodge in a bronchiole and produce inflammation. Lung cancer may also be responsible for formation of an abscess.

The first symptoms include a dry cough and chest pain. Later these may be followed by fever, chills, productive cough, headache, perspiration, foul-smelling sputum, and sometimes dyspnea. If the abscess is a complication of pneumonia, the symptoms tend to be moderated to an exaggeration of the pneumonia symptoms.

When a lung abscess forms, it is in the acute stage and treatment with antibiotics usually is effective. postural drainage may be prescribed to assist in drainage of exudate from lungs and bronchioles. In most cases, this treatment produces a cure. If the abscess becomes chronic, surgery may be necessary and usually involves removal of the portion of the lung containing the abscess.
accessory lung pulmonary sequestration.
bird breeder's lung pigeon breeder's lung.
black lung coal workers' pneumoconiosis.
brown lung byssinosis.
lung cancer malignant growths of the lung. Although the exact cause of lung cancer is not known, inhaled carcinogens are known to be important predisposing causes. Cancer in the lungs may also be a metastasis of malignancy elsewhere in the body. Many years ago it was realized that miners of certain ores who inhaled the mine dust developed lung cancer much more often than workers in other occupations. Later, other carcinogens of lung tissue, such as air polluted by fumes from burning fuels or motor exhausts, were singled out as probable causes of the increasing number of cases of the disease in urban and industrial areas. The most obvious carcinogen, however, and the one most widely encountered, is tobacco smoke, especially cigarette smoke, which is much more frequently and deeply inhaled than the smoke of pipes or cigars.

A study based on autopsies of the lungs of individuals who had died from many varied causes, but whose smoking history was known, showed that unrecognized cancer and precancerous changes in tissue were numerous among smokers and rare among nonsmokers. These findings led the Surgeon General of the United States to appoint an investigative committee, which ultimately issued a report stating that “cigarette smoking is a health hazard of sufficient importance in the United States to warrant appropriate action.”

Since the factors causing lung cancer act slowly and may produce a tumor near the periphery of the lung, early symptoms are vague or may not appear at all, and nearly a third of the cases are in an advanced stage when they are discovered. The earliest and most common symptom is a cough. Dry at first, this cough later produces sputum, which eventually becomes blood-streaked. An isolated persistent wheeze in the chest is frequently a symptom and indicates a partial obstruction in a bronchus. Chest pains, weakness, and loss of weight are later symptoms, as is dyspnea.

Diagnosis depends on a careful physical examination, including a chest x-ray. If a suspicious density is seen on the x-ray, samples of sputum will be examined microscopically for the presence of malignant cells. bronchoscopy is also done, and at the same time a specimen for biopsy can be obtained or the bronchial secretions can be washed out and the cells stained and examined.

When examination indicates lung cancer, prompt treatment is essential. This may involve the surgical removal of the lobe of the lung containing the cancer or of an entire lung if the malignant cells have spread. A significant number of persons affected by lung cancer can be cured by such operations if the surgery is performed in time. In some cases of widespread involvement surgery is not possible; these patients are treated with radiation therapy and antineoplastic drugs.

Carcinogens that can trigger lung cancer must be avoided and, when possible, eliminated. Mine workers should take adequate precautions to avoid inhaling harmful dusts. Public health authorities and industry must act more effectively to control air pollution. The most important step toward protection against lung cancer is elimination of cigarette smoking. State and local units of the American Lung Association are excellent sources of information about lung disease and its prevention.

Lung cancer clinical guidelines have been published in both the United States and Canada. In Canada they are available at the web site of Cancer Care Ontario, and in the United States they are available at the web site of the National Guideline Clearinghouse,
coal miner's lung coal workers' pneumoconiosis.
farmer's lung hypersensitivity pneumonitis caused by inhalation of moldy hay dust.
iron lung popular name for Drinker respirator.
pigeon breeder's lung hypersensitivity pneumonitis caused by inhalation of particles of bird feces, seen in those who work closely with pigeons or other birds; it may eventually result in pulmonary fibrosis.


(lŭng), [TA]
One of a pair of viscera occupying the pulmonary cavities of the thorax, the organs of respiration in which blood is aerated. In humans, the right lung is slightly larger than the left and is divided into three lobes (an upper, a middle, and a lower or basal), whereas the left has but two lobes (an upper and a lower or basal). Each lung is irregularly conic, presenting a blunt upper extremity (the apex), a concave base following the curve of the diaphragm, an outer convex surface (costal surface), a generally concave inner or medial surface (mediastinal surface), a thin and sharp anterior border, and a rounded posterior border.
Synonym(s): pulmo [TA]
[A.S. lungen]


(lung) the organ of respiration; either of the pair of organs that effect aeration of blood, lying on either side of the heart within the chest cavity.
black lung  pneumoconiosis of coal workers.
brown lung  byssinosis.
farmer's lung  hypersensitivity pneumonitis from inhalation of moldy hay dust.
humidifier lung  hypersensitivity pneumonitis caused by breathing air that has passed through humidifiers, dehumidifiers, or air conditioners contaminated by certain fungi, amebas, or thermophilic actinomycetes.
iron lung  popular name for Drinker respirator.
pigeon breeder's lung  hypersensitivity pneumonitis from inhalation of particles of bird feces by those who work closely with pigeons or other birds; it may eventually result in pulmonary fibrosis.
white lung  pneumonia alba.


1. Either of two spongy, saclike respiratory organs in air-breathing vertebrates, occupying the chest cavity together with the heart and functioning to provide oxygen to the blood while removing carbon dioxide.
2. A similar organ in some invertebrates, including spiders and terrestrial snails.

lung (L)

Etymology: AS, lungen
one of a pair of light, spongy organs in the thorax, constituting the main component of the respiratory system. The two highly elastic lungs are the main mechanisms in the body for inhaling (inspiring) air, from which oxygen is extracted for the arterial blood system, and for exhaling (expiring) carbon dioxide dispersed from the venous system. The right lung is divided into three lobes; the left lung, two lobes. Each lung is conical and has an apex, a base, three borders, and two surfaces. The apex is rounded and extends into the root of the neck about 4 cm above the first rib. The base of the lung is broad and concave, rests on the convex surface of the diaphragm, and with the diaphragm moves up during expiration and down during inspiration. Each lung is composed of an external serous coat, a subserous layer of areolar tissue, and the parenchyma. The serous coat comprises the thin, visceral pleura. The subserous areolar tissue contains many elastic fibers and invests the entire surface of the organ. The parenchyma is composed of secondary lobules divided into primary lobules, each of which consists of blood vessels, lymphatics, nerves, and an alveolar duct connecting with air spaces. The surfaces of the lungs are partially concave, with a cardiac impression that cradles the heart. The bronchial arteries supply blood to nourish the lungs and are derived from the ventral side of the thoracic aorta or from the aortic intercostal arteries. The bronchial vein is formed at the root of the lung. Most of the blood supplied by the bronchial arteries is returned by the pulmonary veins to the left atrium of the heart. The lungs are pinkish white at birth and darken in later life. The coloring is from carbon granules deposited in the areolar tissue near the surface of the lung. The carbon deposits increase with age. The lungs of men are usually heavier than those of women and usually have a greater capacity. The quantity of air that can be exhaled from the lungs after the deepest inspiration, the vital capacity, averages 3700 cc.


One of the 2—right and left—organs of respiration located in the thoracic cavity on either side of the mediastinum, and protected laterally by the ribs, anteriorly by the sternum and posteriorly by the vertebral column. The lungs are the site of respiration/gas exchange, allowing O2 in, and expelling CO2. At birth, the lungs are pinkish-white, but with age and exposure to air-borne pollutants, the lungs become grey and mottled black due to carbon and particulate deposition.

Each lung extends into the lower neck, just above the level of the first rib.

Each lung extends to the diaphragm, the primary respiratory muscle, which separates the thoracic and abdominal cavities.

Each lung is divided into upper and lower lobes. The upper lobe of the right lung usually has triangular subdivision, the middle lobe. The right lung is larger and heavier than the left lung, which is smaller because of the left position of the heart. Each hilum (root) connects the lungs to the heart and the trachea, and is comprised of a main stem bronchus, pulmonary artery (the main artery that returns O2-poor blood to the right or left lungs), pulmonary vein (the main vein ports O2-rich blood from the lungs to the left heart), bronchial arteries and veins, nerves and lymphatic vessels. The lungs are covered by a thin serosal layer called the visceral pleura, which is continuous with the pleura that covers the inner face of the thoracic cavity, the parietal pleura. The flattened layer of tissue is known as the mesothelium. Under the pleura is a layer of elastic fibres that span the lung surface and extend down into its subdivisions. The trachea splits into right and left main stem bronchi, which are similar to the trachea in composition and progressively branch into ever-smaller subdivisions—the “tracheobronchial tree,” which conducts, humidifies, and heats inspired air.

The lungs are innervated by the anterior and posterior pulmonary plexi, arising from sympathetic and vagal nerves.

The tracheobronchial tree is lined by columnar epithelium and glands that produce mucus and serous fluid. Cilia in the lining move in a constant, beating motion to cleanse the airways of foreign bodies and pathogens, a process facilitated by a watery mucous layer. In lungs damaged by smoking, the cilia may be defective or even absent and replaced by squamous metaplasia. Coughing triggers a high-speed flow of air, and mobilises mucus (sputum), which also contains nasal secretions, and saliva.

The bronchial passage of the lung, the pulmonary parenchyma, is made up of roughly 130,000 clusters of spongy air sacs called primary lobules, each measuring 3.5 mm in diameter, containing about 2,200 alveoli/air sacs and ducts. Bronchial branches larger than 1 mm in diameter have cartilage and are called segmental bronchi. Smaller sub-divisions, bronchioles, lack cartilage and divide into terminal bronchioles, ending in irregular, swollen projections, alveolar ducts and alveolar sacs, which exchange gas. The alveolar regions contain a detergent-like substance, surfactant, which reduces surface tension within the alveoli and keeps them from collapsing during breathing.

O2-poor blood is ported to the lungs via the pulmonary artery, which divides into branches paralleling the bronchial tree, ending in a network of pulmonary capillaries within the walls/interstitium of the small air passages and alveoli of the lungs. The pulmonary veins carry O2-rich blood away from the lungs. They begin in the pulmonary capillaries, unite to form larger branches—e.g., the left and right superior and inferior pulmonary veins—and eventually lead into the left atrium of the heart. The heart then pumps oxygenated blood out to the body via the aorta.

occult primary malignancy

Occult cancer, unknown primary A malignancy of unknown 1º site or origin that is symptomless, which first manifests itself as metastases or secondary–paraneoplastic phenomena, and usually has a poor prognosis; OPMs are problematic as appropriate therapy requires that the primary malignancy be eradicated, and many remain obscure despite aggressive diagnostic work-up; certain malignancies metastasize to certain sites with greater than expected frequency; in OPMs affecting the brain, the primary arises in the lungs in up to 85% Treatment Up to 30% of Pts with metastases from an occult primary adenoCA may respond to chemotherapy–mitomycin C, adriamycin, vincristine; poor response is more common in ♂ and in Pts with liver and/or infradiaphragmatic metastases
Occult primary malignancies
Bone Breast, bronchus, prostate, thyroid, kidney
CNS Breast, bronchus, kidney, colon
Head & neck Oropharynx, nasopharynx–most are squamous cell carcinoma;  also adenocarcinoma, melanoma, rhabdomyosarcoma, oat cell, salivary  gland, thyroid carcinomas
Liver CA of stomach, colon, breast, pancreas, or bronchus
Lung Breast, colon, kidney, melanoma, sarcoma, stomach, testis, thyroid
Lymph nodes
• Cervix  Naso– and oropharynx, thyroid, larynx, lymphoma
• Supraclavicular  Bronchi, breast, stomach, esophagus, pancreas, colorectal,
• Axillary  Breast, melanoma, lymphoma
• Inguinal  Urogenital tract, anus, melanoma, lymphoma
Ovary Stomach, colon
Serosal surfaces Bronchi, breast, ovary, lymphoma
Skin Melanoma, breast, bronchus, stomach, kidney  


(lŭng) [TA]
One of a pair of viscera occupying the pulmonary cavities of the thorax, the organs of respiration in which aeration of the blood takes place. As a rule, the right lung is slightly larger than the left and is divided into three lobes (an upper, a middle, and a lower or basal), whereas the left has but two lobes (an upper and a lower or basal). Each lung is irregularly conic, presenting a blunt upper extremity (the apex), a concave base following the curve of the diaphragm, an outer convex surface (costal surface), an inner or mediastinal surface, a thin and sharp anterior border, and a thick and rounded posterior border.
Synonym(s): pulmo [TA] .
[A.S. lungen]


Enlarge picture
Either of two cone-shaped spongy organs of respiration contained within the pleural cavity of the thorax. See: illustration; alveolus for illus.


The lungs are connected with the pharynx through the trachea and larynx. The base of each lung rests on the diaphragm, and each lung apex rises from 2.5 to 5 cm above the sternal end of the first rib, the collarbone, supported by its attachment to the hilum or root structures. The lungs include the lobes, lobules, bronchi, bronchioles, alveoli or air sacs, and pleural covering.

The right lung has three lobes and the left two. In men, the right lung weighs approx. 625 g, the left 570 g. The lungs contain 300,000,000 alveoli and their respiratory surface is about 70 sq m. Respirations per minute are 12 to 20 in an adult. The total capacity of the lung varies from 3.6 to 9.4 L in men and 2.5 to 6.9 L in women.

The left lung has an indentation, called the cardiac depression, for the normal placement of the heart. Behind this is the hilum, through which the blood vessels, lymphatics, and bronchi enter and leave the lung.

Air travels from the nasal passages to the pharynx, larynx, and trachea. Two primary bronchi, one on each side, extend from the trachea. The primary bronchi divide into secondary bronchi, one for each of five lobes. These further divide into a great number of smaller bronchioles. The pattern of distribution of these into the segments of each lobe is important in pulmonary and thoracic surgery. There are about 10 bronchopulmonary segments in the right lung and eight in the left, the actual number varying. There are 50 to 80 terminal bronchioles in each lobe. Each of these divides into two respiratory bronchioles, which in turn divide to form two to 11 alveolar ducts. The alveolar sacs and alveoli arise from these ducts. The spaces between the alveolar sacs and alveoli are called atria.

In the alveolus, blood and inspired air are separated only by the cell of the alveolus and that of the pulmonary capillary. This respiratory membrane is thin (0.07 to 2.0 µm) and permits oxygen to diffuse into the blood and carbon dioxide to diffuse from the blood to the air.

Nerve Supply

The lungs are innervated by parasympathetic fibers via the vagus nerve and sympathetic fibers from the anterior and posterior pulmonary plexuses to the smooth muscle in the walls of the bronchial tree.

Blood Vessels

The bronchial arteries and veins circulate blood to the bronchial tree. The pulmonary arteries and veins circulate the blood involved in gas exchange.


The primary purpose of the lung is to bring air and blood into intimate contact so that oxygen can be added to the blood and carbon dioxide removed from it. This is achieved by two pumping systems, one moving a gas and the other a liquid. The blood and air are brought together so closely that only approx. 1 µm (10-6 m) of tissue separates them. The volume of the pulmonary capillary circulation is 150 ml, but this is spread out over a surface area of approx. 750 sq ft (69.68 sq m). This capillary surface area surrounds 300 million air sacs called alveoli. The blood that is low in oxygen but high in carbon dioxide is in contact with the air that is high in oxygen and low in carbon dioxide for less than 1 second. See: respiratory defense mechanism

Physical Examination

Inspection: The examiner determines the respiratory rate by unobtrusively watching the patient's chest rise and fall and counting the number of breaths per minute. In adults a normal respiratory rate at rest is about 12 breaths per minute. While counting the respiratory rate, the examiner can observe other breathing characteristics. Dyspneic patients breathe rapidly, often laboring to draw breath even when at rest. Retractions of the intercostal and supraclavicular spaces are visible during inspiration. Sleep apnea is characterized by episodes of stalled breathing followed by periods of respiratory compensation. Regular slow breathing is normal.

Palpation: In health, the chest and lung transmit a vibration, called fremitus, during speech. Fremitus abnormalities may be felt in chronic obstructive lung diseases or obesity, in which the vibration is diminished, and in pneumonia, in which it is increased over the infected lobe.

Percussion: Tapping on the chest wall over healthy lung results in a hollow resonant sound. The hollow character of the resonance sometimes is exaggerated in emphysematous lungs or in pneumothorax, and muffled by pleural effusions or pulmonary consolidation.


Normal breath sounds: In the healthy person, breath sounds are low-pitched and have a frequency of 200 to 400 cycles per second (cps); frequency rarely exceeds 500 cps. These sounds are called vesicular breath sounds when heard over the lungs. They are produced by air passing in and out of the airways.

Bronchial and tracheal breath sounds: These are higher-pitched and louder than vesicular sounds, and are produced by air passing over the walls of the bronchi and trachea. These sounds are normally heard only over the bronchi and trachea.

Amphoric and cavernous breathing:These two nearly identical sounds are loud, with a prolonged, hollow expiration. The pitch of amphoric breathing is slightly higher than that of the cavernous type, and may be imitated by blowing over the mouth of an empty jar. It is heard in bronchiectatic cavities or pneumothorax when the opening to the lung is patulous; in the consolidation area near a large bronchus; and sometimes over a lung compressed by a moderate effusion.

Harsh inspiratory sounds are typical of stridor, a medical emergency. Expirations that are prolonged and musical are characteristic of wheezing.

Friction: This sound is produced by the rubbing together of roughened pleural surfaces. It may be heard in both inspiration and expiration. Friction often resembles crackle, but is more superficial and localized than the latter and is not modified by cough or deep inspiration.

Metallic tinkling: A silvery bell-like sound heard at intervals over a hydropneumothorax or large cavity. Speaking, coughing, and deep breathing usually induce this sound. It must not be confused with a similar sound produced by liquids in the stomach.

Crackles: Abnormal bubbling sounds heard in air cells or bronchi.

Succussion-splash or hippocratic succussion: A splashing sound produced by the presence of air and liquid in the chest. It may be elicited by gently shaking the patient during auscultation. This sound nearly always indicates either a hydropneumothorax or a pyopneumothorax, although it has also been detected over very large cavities. The presence of air and liquid in the stomach produces similar sounds.

bird breeder's lung

An allergic inflammation of the lung due to exposure to bird excreta. In some patients the onset is slow rather than acute. Symptoms include chills, fever, cough, and shortness of breath and usually subside when exposure to the antigen ceases.
Synonym: pigeon breeder's disease See: psittacosis

black lung

Lay term for a form of pneumoconiosis in which carbon and silica deposits accumulate in the lungs due to coal dust inhalation Synonym: anthracosilicosis; coal worker's pneumoconiosis

blast lung

The shredding-type effect that takes place in the alveolar surfaces of the lung caused by the shock of an explosion or blast, which can cause alveolar contusion.

brewer's lung

An allergic respiratory condition caused by the mold Aspergillus.

cobalt lung

Hard metal disease.

dirty lung

A colloquial term for a lung with increased markings in its interstitial tissues, usually identified in smokers.

farmer's lung

A form of hypersensitivity alveolitis caused by exposure to moldy hay that has fermented. Actinomyces micropolyspora faeni and Thermoactinomyces vulgaris are the causative microorganisms.
See: alveolitis; bagassosis; hypersensitivity

flock worker's lung

Interstitial lung disease that results from the inhalation of airborne nylon fibers at work. Nylon fibers are used in making products for upholstery, automobiles, carpet, and apparel.

granite worker's lung

A type of silicosis found in granite miners after exposure to and inhalation of dusts.

honeycomb lung

An abnormal appearance of the lungs seen on chest x-ray exam, in which small cystic spaces alternate with coarsely increased interstitial markings. This pattern is typical of pulmonary injury caused by inhalation of dusts, minerals, toxic gases, or fibers; rheumatological diseases; and interstitial pneumonitis.

humidifier lung

Humidifier fever.

iron lung

Drinker respirator.

malt worker's lung

A hypersensitivity pneumonitis typically found in agricultural workers exposed to Aspergillus clavatus spores in barley and other grains.

shock lung

A diffuse lung injury, causing reduced perfusion, pulmonary edema, and alveolar collapse, associated with acute respiratory distress syndrome. Synonym: wet lung

trapped lung

Lung that cannot expand and contract during respiration because it is restricted by the visceral pleura.

wet lung

Shock lung.


the organ that allows an animal to breath air (see AERIAL RESPIRATION). In mammals the paired lungs are each supplied by a bronchus which divides, tree-like, into bronchioles. Each bronchiole ends in an atrium from which arise numerous alveoli which contact a vast capillary system. The 300 million alveoli in man give a large surface area of about 70 m2 over which gaseous exchange can take place. see BREATHING.


(lŭng) [TA]
One of a pair of viscera occupying thoracic pulmonary cavities; organs of respiration in which blood is aerated.
[A.S. lungen]


n the light, spongy organs in the thorax, constituting the main component of the respiratory system. They provide the tissue surface necessary for the exchange of gases between the environment and the blood. Oxygen is extracted from inspired air, and carbon dioxide is dispersed from the venous system back into the environment.
lung abscess,
n a complication of an inflammation and infection of the lung, often caused by aspiration of infected material from the oral cavity.


either of the two main organs of respiration, lying on either side of the heart, within the chest cavity. The lungs supply the blood with oxygen inhaled from the outside air, and they dispose of waste carbon dioxide in the exhaled air, as a part of the process of respiration. They are usually divided into lobes, the left lung has up to three (cranial, middle and caudal), while the right lung has up to four (cranial, middle, caudal and accessory). Horse lungs are least subdivided; cat and dog lungs are deeply fissured into lobes.
The lungs are made of elastic tissue filled with interlacing networks of tubes and sacs carrying air, and with blood vessels carrying blood. The bronchi, which bring air to the lungs, branch out within the lungs into many smaller tubes, the bronchioles, which culminate in clusters of tiny air sacs called alveoli, whose total runs into millions. The alveoli are surrounded by a network of capillaries. Through the thin membranes of the capillaries, the air and blood make their exchange of oxygen and carbon dioxide. See also pulmonary, respiratory.
Enlarge picture
Lung lobes. By permission from Aspinall V, O'Reilly M, Introduction to Veterinary Anatomy and Physiology, Butterworth Heinemann, 2004

accessory lung
develop from an embryonic lung bud in an abnormal site, e.g. neck, abdomen.
lung birth changes
include dilation of the alveoli and the bronchial tree, marked pulmonary vasodilation, decreased resistance to blood flow through the lungs, constriction of the ductus arteriosus, removal of fluid from the fetal bronchial tree.
lung breath sounds
see breath sounds.
lung bud
blunt end of the respiratory diverticulum which grows ventrally out of the proximal end of the foregut, then extends caudally and divides into two, forming the origins of the bronchial tree.
lung consolidation
lung-digit syndrome
an uncommon condition in cats in which a primary lung tumor metastasizes to, usually multiple, digits as well as other sites.
ectopic lung
edematous, lobulated masses of lung tissue in the abdominal or thoracic cavities or in subcutaneous sites.
lung factor
closely related ipomeanols produced in rotting sweet potatoes by the catabolic activities of the fungus Perilla frutescens and other fungi of phytoalexins in the tubers. The factor is not toxic until it is activated by pulmonary microsomal enzymes.
lung fluke
lung hilus
that part of the lung that is not covered by pleura and through which blood vessels, bronchi, nerves and lymphatics enter and leave the lung.
lung lobe torsion
occurs uncommonly in dogs and cats, most often of the right middle lobe. May occur spontaneously, following trauma, or in association with pleural effusion. Impaired venous return causes engorgement and rapid necrosis. Clinical signs include coughing and hemoptysis.
lung meridian points
acupuncture points on the lung meridian.
lung perforation
may cause lung hemorrhage, emphysema, hemothorax or pneumothorax, or any combination of these conditions.
lung puller
appliance for pulling the pluck, the heart and lungs on the trachea, out of the thorax at the abattoir.
lung puncture
see lung perforation (above).
lung Qi deficiency
in acupuncture terminology is a deficiency of Qi or energy in the lungs manifested by recurrent illness, weak cough, rapid shallow respiration, dry cracked muzzle.
lung reflexes
hering-breuer reflexes.
lung resonance
resonant sound achieved on percussion of the chest wall over normal lung.
shock lung
see shock lung.
lung sounds absent
breath sounds audible on auscultation over normal lung are absent over consolidated, neoplastic and collapsed lung.
stiff lung
one with decreased compliance.
total lung capacity
the sum of the potential air spaces in the bronchioles and the alveoli.
lung volume
see total lung capacity (above), volume.

Patient discussion about lung

Q. LUNG CANCER how do you get it?

A. Lung cancer is one of the most common cancers in the world. It is a leading cause of cancer death in men and women in the United States.

Cigarette smoking causes most lung cancers. The more cigarettes you smoke per day and the earlier you started smoking, the greater your risk of lung cancer. High levels of pollution, radiation and asbestos exposure may also increase risk. Lately researchers connect this lung cancer with genetic factors.

for more information please check this link :

Q. How much do I have to smoke to get lung cancer? If I only smoke 1 cigarette a day will I get cancer?

A. some people dont even have to smoke to get lung cancer,just being around someone who smokes can give you lung cancer.

Q. Heart serious, Lungs swollen. My brother Bennet, seventeen, and it is birthday tomorrow. But I guess he already got his seventeenth birthday present: lupus. He is recently diagnosed with lupus, yet some complications are still under-diagnosed. He have always had huge aspirations. Now, as my health deterioates at a weird rate, he can't walk around. His heart is in serious condition, his lungs are swollen, so are his joints. His voice is almost not there and he is, thinking about his eighteenth birthday. His face is swollen, as some gland in his neck has bloated and somehow he don't enjoy what he see in the mirror he says. He is very sensitive to sunlight and so he stay in for all day and when he decide to go out, it is after 8 or 9 p.m. He is despondent, yes. Because he see his dreams shattering, his family life is breaking apart and he feels as if he is getting more useless EVERY single day. How long will he continue? Maybe another thirty years...maybe not another day. Could anyone help him to SURV

A. Sorry to hear about your brother being so miserable with his symptoms, and the apparent distress it understandably is causing you.

With sunlight bothering him, that is called photophobia and is a symptom of certain types of lupus, or can be an effect from a medication he may be taking. The swelling on his neck may be due to hyperthyroidism, asthma, or an allergic reaction perhaps to prednisone, which is given to lupus patients.

You should get your bother to see a doctor soon, if you have not already. You don't want him to stop breathing or anything.


More discussions about lung
References in classic literature ?
Seeing how important an organ of locomotion the tail is in most aquatic animals, its general presence and use for many purposes in so many land animals, which in their lungs or modified swim-bladders betray their aquatic origin, may perhaps be thus accounted for.
Weakly I rose for the last time--my tortured lungs gasped for the breath that would fill them with a strange and numbing element, but instead I felt the revivifying breath of life-giving air surge through my starving nostrils into my dying lungs.
To the others men and women were only cases, good if they were complicated, tiresome if obvious; they heard murmurs and were astonished at abnormal livers; an unexpected sound in the lungs gave them something to talk about.
I felt no particular distress until I suddenly started upward at ever-increasing velocity; then my lungs seemed about to burst, and I must have lost consciousness, for I remember nothing more until I opened my eyes after listening to a torrent of invective against Germany and Germans.
His endurance was faltering, but he compelled his arms and legs to drive him deeper until his will snapped and the air drove from his lungs in a great explosive rush.
He gargled his mouth and throat, took a suck at a divided lemon, and all the while the towels worked like mad, driving oxygen into his lungs to purge the pounding blood and send it back revivified for the struggle yet to come.
600,000,000 air cells in one pair of lungs, and 2,000 pores to a square inch of surface; so you see what quantities of air we must have, and what care we should take of our skin so all the little doors will open and shut right.
He breathes heavily, taking into his lungs the frost itself.
The lungs absorb the oxygen, which is indispensable for the support of life, and reject the nitrogen.
When he came to himself, he began to cry and shriek at the top of his lungs, stamping his feet on the ground and wailing all the while:
I gasped with the anguish and shock of it, filling my lungs before the life-preserver popped me to the surface.
The medical man who examined him, being informed of this circumstance, considered the post-mortem appearances as being perfectly compatible with murder by smothering--that is to say, with murder committed by some person, or persons, pressing the pillow over the nose and mouth of the deceased, until death resulted from congestion of the lungs.