lung (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.
lung (L)
lung [lung]
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.
lung (l ng)n. Either of the two saclike organs of respiration that occupy the pulmonary cavity of the thorax and in which aeration of the blood takes place. It is common for the right lung, which is divided into three lobes, to be slightly larger than the left, which has two lobes. |   Top: right and left lungs Bottom: detail showing terminal respiratory units of bronchial tree |
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.
lung [lung]
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.
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.)
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.
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, http://www.cancercare.on.ca. and in the United States they are available at the web site of the National Guideline Clearinghouse, http://www.guideline.gov.
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, http://www.cancercare.on.ca. and in the United States they are available at the web site of the National Guideline Clearinghouse, http://www.guideline.gov.
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.
shock lung acute respiratory distress syndrome.
wet lung
1. pulmonary edema.
lung,
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.
lung
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.
)
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
see consolidation, hepatization.
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
see paragonimus.
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 mites
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 Lungs.
Q. My grandfather died of lung cancer because of smoking. what is the probability of me getting a cancerous tumor? What procedure is done to see if a tumor is malignant? Is a simple MRI enough to make that conclusion?
A. Sad.. my brother in law died from smoking, few years ago.
Regardless of family history, smoking is not exactly helthy and does contribute to lung cancer.
Even though the role of heredity in lung cancer is not as well-known, having a family history of lung cancer does increase our risk to some degree. Hereditary lung cancer is higher in women, nonsmokers and those with early onset lung cancer (lung cancer that occurs before the age of 60). Overall, it has been estimated that 1.7% of lung cancers up to the age of 68 are hereditary.
Regardless of family history, smoking is not exactly helthy and does contribute to lung cancer.
Even though the role of heredity in lung cancer is not as well-known, having a family history of lung cancer does increase our risk to some degree. Hereditary lung cancer is higher in women, nonsmokers and those with early onset lung cancer (lung cancer that occurs before the age of 60). Overall, it has been estimated that 1.7% of lung cancers up to the age of 68 are hereditary.
Q. Does the risk for lung cancer remain the same after I stop smoking? I'm 55 years old woman and have been smoking since age 20 one pack a day. Fortunately, after numerous failures I succeeded to stop smoking 5 years ago. I'm happy and feel much better now, but I'm still worried about the possibility of lung cancer- I know that smoking cause lung cancer, but after I've stopped smoking, am I still at risk to have cancer?
A. The answer is a little complicated: as former smoker, the risk for lung cancer does decrease with time. However, it may never return to the risk of someone similiar to you who never smoke to develop lung cancer.
Q. Is it possible to have lung cancer without smoking? My 89 years-old grandfather was told by his doctor that he has lung cancer, after he had cough for almost two months. I thought that lung cancer happens because people smoke, but my grandfather never smoked or drank alcohol and is still in a very good shape (for his age, of course) – is it possible the doctor was wrong and he doesn’t have lung cancer?
A. There are other things that increase the risk of lung cancer-. He may not be a smoker himself, but maybe he was living with a smoker, maybe he worked in an asbestos building, or exposed to substances that cause lung cancer.
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