The lung (adjectival form In grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun, giving more information about the noun or pronoun's referent. Some examples can be seen in the box to the right. Collectively, adjectives form one of the traditional English eight parts of speech, though linguists today distinguish adjectives from words: pulmonary) is the essential respiration organ Respiratory organs are used by most, or all, animals to exchange the gases necessary for their life function known as respiration. These organs come in many forms, some of them apparently having independently evolved: in all air-breathing animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also, including most tetrapods Tetrapods are vertebrate animals having four feet, legs or leglike appendages. Amphibians, reptiles, dinosaurs, birds, and mammals are all tetrapods, and even the limbless snakes are tetrapods by descent. The earliest tetrapods radiated from the Sarcopterygii, or lobe-finned fish, a few fish A fish is any aquatic vertebrate animal that is covered with scales, and equipped with two sets of paired fins and several unpaired fins. Most fish are "cold-blooded", or ectothermic, allowing their body temperatures to vary as ambient temperatures change. Fish are abundant in most bodies of water. They can be found in nearly all aquatic and a few snails Snail is a common name for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in a general sense, it includes sea snails, land snails and freshwater snails. Otherwise snail-like creatures that lack a shell are called slugs. In mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not and the more complex life forms, the two lungs are located in the chest on either side of the heart The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart.". Their principal function is to transport oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly from the atmosphere The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78% nitrogen, 21% into the bloodstream The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pH to maintain homeostasis, and to release carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere from the bloodstream into the atmosphere. This exchange of gases is accomplished in the mosaic of specialized cells The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans, that form millions of tiny, exceptionally thin-walled air sacs called alveoli An alveolus is an anatomical structure that has the form of a hollow cavity. Found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory sites of gas exchange with the blood. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas-.

To completely explain the anatomy of the lungs, it is necessary to discuss the passage of air through the mouth to the alveoli An alveolus is an anatomical structure that has the form of a hollow cavity. Found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory sites of gas exchange with the blood. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas-. Once air progresses through the mouth or nose, it travels through the oropharynx The Oropharynx reaches from the Uvula to the level of the hyoid bone, nasopharynx The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent (open), the larynx The larynx , commonly called the voice box, is an organ in the neck of mammals involved in protecting the trachea and sound production. It manipulates pitch and volume. The larynx houses the vocal folds, which are an essential component of phonation. The vocal folds are situated just below where the tract of the pharynx splits into the trachea and, the trachea The trachea, or windpipe, is a tube that connects to the pharynx or larynx, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosal goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards, and a progressively subdividing system of bronchi A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. No gas exchange takes place in this part of the lungs and bronchioles The bronchioles or bronchioli are the first airway branches that no longer contain cartilage. They are branches of the bronchi. The bronchioles terminate by entering the circular sacs called alveoli until it finally reaches the alveoli An alveolus is an anatomical structure that has the form of a hollow cavity. Found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory sites of gas exchange with the blood. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas- where the gas exchange of carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere and oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly takes place.^[2]

The drawing and expulsion of air (ventilation In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorised under the following definitions:) is driven by muscular Muscle is the contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause action; in early tetrapods Tetrapods are vertebrate animals having four feet, legs or leglike appendages. Amphibians, reptiles, dinosaurs, birds, and mammals are all tetrapods, and even the limbless snakes are tetrapods by descent. The earliest tetrapods radiated from the Sarcopterygii, or lobe-finned fish, air was driven into the lungs by the pharyngeal The pharynx is the part of the neck and throat situated immediately posterior to (behind) the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea muscles, whereas in reptiles Reptiles are animals in the class Reptilia characterized by breathing air, a "cold-blooded" (poikilothermic) metabolism, laying tough-shelled amniotic eggs (or retaining the same membrane system in species with live birth), and skin with scales or scutes. They are tetrapods (either having four limbs or being descended from four-limbed, birds Birds are winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich and mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not a more complicated musculoskeletal system A musculoskeletal system is an organ system that gives animals (including humans) the ability to move using the muscular and skeletal systems. The musculoskeletal system provides form, support, stability, and movement to the body is used.

Medical terms related to the lung often begin with pulmo-, from the Latin Latin or sometimes Roman is an Italic language originally spoken in Latium and Ancient Rome. Although often considered a dead language, in view of the fact that it has no native, fluent speakers, Latin continues to be taught in schools and has been, and currently is, used in the process of new word production in modern languages from many pulmonarius ("of the lungs"), or with pneumo- (from Greek Ancient Greek is the historical stage in the development of the Greek language spanning the Archaic , Classical (c. 5th–4th centuries BC), and Hellenistic (c. 3rd century BC – 6th century AD) periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek. Its Hellenistic phase is known as Koine (& πνεύμων "lung").

Mammalian lungs

The lungs of mammals have a spongy texture and are honeycombed with epithelium Epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body. Many glands are also formed from epithelial tissue. It lies on top of connective tissue, and the two layers are separated by a basement membrane, having a much larger surface area in total than the outer surface area of the lung itself. The lungs of humans The human lungs are the organs of respiration in humans. Humans have two lungs, with the left being divided into two lobes and the right into three lobes. Together, the lungs contain approximately the same length as 1500 miles of airways and 300 to 500 million alveoli, having a total surface area of about 70 m2 in adults — roughly the same area are a typical example of this type of lung.

Breathing is largely driven by the muscular diaphragm In the anatomy of mammals, the thoracic diaphragm or sometime simply, the diaphragm, is a sheet of internal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration. A diaphragm in anatomy can refer to other flat structures such as at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward, increasing volume and thus decreasing pressure, causing air to flow into the airways. Air enters through the oral and nasal cavities; it flows through the pharynx, then the larynx The larynx , commonly called the voice box, is an organ in the neck of mammals involved in protecting the trachea and sound production. It manipulates pitch and volume. The larynx houses the vocal folds, which are an essential component of phonation. The vocal folds are situated just below where the tract of the pharynx splits into the trachea and and into the trachea The trachea, or windpipe, is a tube that connects to the pharynx or larynx, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosal goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards, which branches out into the main bronchi and then subsequent divisions. During normal breathing Breathing is the process that takes oxygen in and carbon dioxide in and then out of the lungs. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. The medical term for normal relaxed breathing is eupnea, expiration is passive and no muscles are contracted (the diaphragm relaxes). The rib cage The human rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral (shoulder) girdle, forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum, costal cartilages, and the 12 thoracic vertebrae. It, along with the itself is also able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles. As a result, air is transported into or expelled out of the lungs. This type of lung is known as a bellows lung as it resembles a blacksmith's bellows A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location. Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet. A bellows typically has a separate inlet, and valves or flaps to ensure that air enters.^[3]

Anatomy

In humans, the trachea divides into the two main bronchi that enter the roots of the lungs. The bronchi continue to divide within the lung, and after multiple divisions, give rise to bronchioles. The bronchial tree continues branching until it reaches the level of terminal bronchioles, which lead to alveolar sacs. Alveolar sacs are made up of clusters of alveoli An alveolus is an anatomical structure that has the form of a hollow cavity. Found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates, like individual grapes within a bunch. The individual alveoli are tightly wrapped in blood vessels and it is here that gas exchange actually occurs. Deoxygenated blood from the heart The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart." is pumped through the pulmonary artery The pulmonary arteries carry blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood to the lungs, where oxygen diffuses Diffusion describes the spread of particles through random motion from regions of higher concentration to regions of lower concentration. The time dependence of the statistical distribution in space is given by the diffusion equation. The concept of diffusion is tied to notion of mass transfer, driven by a concentration gradient, but diffusion can into blood and is exchanged for carbon dioxide in the hemoglobin Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates. Hemoglobin in the blood is what transports oxygen from the lungs or gills to the rest of the body (i.e. the tissues) where it releases the oxygen for cell use of the erythrocytes Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen (O2) to the body tissues via the blood flow through the circulatory system. They take up oxygen in the lungs or gills and release it while squeezing through the body's capillaries. The oxygen-rich blood returns to the heart via the pulmonary veins to be pumped back into systemic circulation.

Human lungs are located in two cavities on either side of the heart. Though similar in appearance, the two are not identical. Both are separated into lobes In anatomy, a lobe is a clear anatomical division or extension that can be determined without the use of a microscope This is in contrast to a lobule, which is a clear division only visible histologically by fissures, with three lobes on the right and two on the left. The lobes are further divided into segments and then into lobules, hexagonal divisions of the lungs that are the smallest subdivision visible to the naked eye. The connective tissue that divides lobules is often blackened in smokers. The medial border of the right lung is nearly vertical, while the left lung contains a cardiac notch. The cardiac notch is a concave impression molded to accommodate the shape of the heart. Lungs are to a certain extent 'overbuilt' and have a tremendous reserve volume as compared to the oxygen exchange requirements when at rest. Such excess capacity is one of the reasons that individuals can smoke for years without having a noticeable decrease in lung function while still or moving slowly; in situations like these only a small portion of the lungs are actually perfused with blood for gas exchange. As oxygen requirements increase due to exercise, a greater volume of the lungs is perfused, allowing the body to match its CO₂/O₂ exchange requirements. Additionally, due to the excess capacity, it is possible for humans to live with only one lung, with the other compensating for its loss.

The environment of the lung is very moist, which makes it hospitable for bacteria. Many respiratory illnesses are the result of bacterial or viral infection of the lungs. Inflammation of the lungs is known as pneumonia; inflammation of the pleura surrounding the lungs is known as pleurisy.

Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation; it can be measured with a spirometer. In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease.

The lung parenchyma is strictly used to refer solely to alveolar tissue with respiratory bronchioles, alveolar ducts and terminal bronchioles.^[4] However, it often includes any form of lung tissue, also including bronchioles, bronchi, blood vessels and lung interstitium.^[4]

Non respiratory functions

In addition to their function in respiration, the lungs also:

• alter the pH of blood by facilitating alterations in the partial pressure of carbon dioxide
• filter out small blood clots formed in veins
• filter out gas micro-bubbles occurring in the venous blood stream such as those created after scuba diving during decompression.^[5]
• influence the concentration of some biologic substances and drugs used in medicine in blood
• convert angiotensin I to angiotensin II by the action of angiotensin-converting enzyme
• may serve as a layer of soft, shock-absorbent protection for the heart, which the lungs flank and nearly enclose.
• Media:Immunoglobulin-A is secreted in the bronchial secretion and protects against respiratory infections.
• maintain sterility by producing mucus containing antimicrobial compounds.^[6] Mucus contains glycoproteins, e.g. mucins, lactoferrin,^[7] lysozyme, lactoperoxidase.^[8][9] We find also on the epithelium Dual oxidase 2^[10][11][12] proteins generating hydrogen peroxidde, useful for hypothiocyanite endogenous antimicrobial synthesis. Function not in place in cystic fibrosis patient lungs.^[13][14]
• Ciliary escalator action is an important defence system against air-borne infection.The dust particles and bacteria in the inhaled air are caught in the mucous layer present at the mucosal surface of respiratory passages and are moved up towards pharynx by the rhythmic upward beating action of the cilia

Avian lungs

Avian lungs do not have alveoli as mammalian lungs do, they have Faveolar lungs. They contain millions of tiny passages known as para-bronchi, connected at both ends by the dorsobronchi. The airflow through the avian lung always travels in the same direction – posterior to anterior. This is in contrast to the mammalian system, in which the direction of airflow in the lung is tidal, reversing between inhalation and exhalation. By utilizing a unidirectional flow of air, avian lungs are able to extract a greater concentration of oxygen from inhaled air. Birds are thus equipped to fly at altitudes at which mammals would succumb to hypoxia. This also allows them to sustain a higher metabolic rate than an equivalent weight mammal.^[15]

The lungs of birds are relatively small, but are connected to 8-9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones. The air sacs are smooth-walled, and do not themselves contribute much to respiration, but they do help to maintain the airflow through the lungs as air is forced through them by the movement of the ribs and flight muscles.^[16]

Because of the complexity of the system, misunderstanding is common and it is incorrectly believed that that it takes two breathing cycles for air to pass entirely through a bird's respiratory system. A bird's lungs do not store air in either of the sacs between respiration cycles, air moves continuously from the posterior to anterior air sacs throughout respiration. This type of lung construction is called a circulatory lung, as distinct from the bellows lung possessed by other animals.^[15]

Reptilian lungs

Reptilian lungs are typically ventilated by a combination of expansion and contraction of the ribs via axial muscles and buccal pumping. Crocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis), which in turn pulls the bottom of the lungs backward, expanding them. Turtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.^[16]

The lung of most reptiles has a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs. These pockets are similar to, but much larger and fewer in number than, mammalian alveoli, and give the lung a sponge-like texture. In tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.^[16]

Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent. Amphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.^[16]

Amphibian lungs

The lungs of most frogs and other amphibians are simple balloon-like structures, with gas exchange limited to the outer surface area of the lung. This is not a very efficient arrangement, but amphibians have low metabolic demands and also frequently supplement their oxygen supply by diffusion across the moist outer skin of their bodies. Unlike mammals, which use a breathing system driven by negative pressure, amphibians employ positive pressure.^[16] The majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth. The only other known lungless tetrapods are also amphibians; the Bornean Flat-headed Frog (Barbourula kalimantanensis) and Atretochoana eiselti, a caecilian.

The lungs of amphibians typically have a few narrow septa of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honey-comb appearance. In some salamanders, even these are lacking, and the lung has a smooth wall. In caecilians, as in snakes, only the right lung attains any size or development.^[16]

Lungfish

The lungs of lungfish are similar to those of amphibians, with few, if any, internal septa. In Polypterus and the Australian lungfish, there is only a single lung, albeit divided into two lobes in the former case. Other lungfish, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving round and above the esophagus. The blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.^[16]

Invertebrate lungs

Some invertebrates have "lungs" that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs. Some arachnids have structures called "book lungs" used for atmospheric gas exchange. The Coconut crab uses structures called Branchiostegal lungs to breathe air and indeed will drown in water, hence it breathes on land and holds its breath underwater. The Pulmonata are an order of snails and slugs that have developed "lungs".

Origins of the vertebrate lung

The lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs (outpocketings) of the esophagus that allowed early fish to gulp air under oxygen-poor conditions.^[17] These outpocketings first arose in the bony fish; in some of the ray-finned fish the sacs evolved into gas bladders, while in other ray-finned fish (such as the gar, bichir and amia) as well as the lobe-finned fish they evolved into lungs.^[17] The lobe-finned fish gave rise to the land-based tetrapods. Thus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills). This is reflected by the fact that the lungs of a fetus also develop from an outpocketing of the esophagus and in the case of gas bladders, this connection to the gut continues to exist as the pneumatic duct in more "primitive" teleosts, and is lost in the higher orders. (This is an instance of correlation between ontogeny and phylogeny.) No known animals have both a gas bladder and lungs.

See also

• Alveolar-capillary barrier
• American Lung Association
• Asthma
• Borders of the lung
• Bronchitis
• Bronchus
• Cancer
• Cardiothoracic surgery
• Chronic obstructive pulmonary disease
• Drowning
• Dry drowning
• Emphysema
• Gills
• Left lung
• Liquid breathing
• Lung volumes
• Mechanical ventilation
• Pneumothorax
• Pneumonia
• Pulmonary contusion
• Pulmonology
• Right lung
• tuberculosis

Further reading

• Lung Function Fundamentals. http://www.anaesthetist.com/icu/organs/lung/lungfx.htm
• Dr D.R. Johnson: Introductory anatomy, respiratory system
• Franlink Institute Online: The Respiratory System
• Lungs 'best in late afternoon'
• Chronic Respiratory Disease - leading research and articles on respiratory disease.
• Avian lungs and respiration

Footnotes

1. ^ ^{a b} Gray's Anatomy of the Human Body, 20th ed. 1918.
2. ^ Wienberger, Cockrill, Mandel. Principles of Pulmonary Medicine. Elsevier Science.^{[verification needed]}
3. ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright1 (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1. OCLC 32308337. ^{[page needed]}
4. ^ ^{a b} medilexicon.com > Medical Dictionary - 'Parenchyma Of Lung' In turn citing: Stedman's Medical Dictionary. 2006
5. ^ Wienke B.R. : "Decompression theory"^{[verification needed]}
6. ^ Travis SM, Conway BA, Zabner J, et al. (May 1999). "Activity of abundant antimicrobials of the human airway". American Journal of Respiratory Cell and Molecular Biology 20 (5): 872–9. PMID 10226057. http://ajrcmb.atsjournals.org/cgi/pmidlookup?view=long&pmid=10226057.
7. ^ Rogan MP, Taggart CC, Greene CM, Murphy PG, O'Neill SJ, McElvaney NG (October 2004). "Loss of microbicidal activity and increased formation of biofilm due to decreased lactoferrin activity in patients with cystic fibrosis". The Journal of Infectious Diseases 190 (7): 1245–53. doi:10.1086/423821. PMID 15346334.
8. ^ Wijkstrom-Frei C, El-Chemaly S, Ali-Rachedi R, et al. (August 2003). "Lactoperoxidase and human airway host defense". American Journal of Respiratory Cell and Molecular Biology 29 (2): 206–12. doi:10.1165/rcmb.2002-0152OC. PMID 12626341.
9. ^ Conner GE, Salathe M, Forteza R (December 2002). "Lactoperoxidase and hydrogen peroxide metabolism in the airway". American Journal of Respiratory and Critical Care Medicine 166 (12 Pt 2): S57–61. doi:10.1164/rccm.2206018. PMID 12471090.
10. ^ Fischer H (October 2009). "Mechanisms and function of DUOX in epithelia of the lung". Antioxidants & Redox Signaling 11 (10): 2453–65. doi:10.1089/ARS.2009.2558. PMID 19358684.
11. ^ Rada B, Leto TL (2008). "Oxidative innate immune defenses by Nox/Duox family NADPH oxidases". Contributions to Microbiology 15: 164–87. doi:10.1159/000136357. PMID 18511861.
12. ^ Rada B, Lekstrom K, Damian S, Dupuy C, Leto TL (October 2008). "The Pseudomonas toxin pyocyanin inhibits the dual oxidase-based antimicrobial system as it imposes oxidative stress on airway epithelial cells". Journal of Immunology 181 (7): 4883–93. PMID 18802092. PMC 2776642. http://www.jimmunol.org/cgi/pmidlookup?view=long&pmid=18802092.
13. ^ Moskwa P, Lorentzen D, Excoffon KJ, et al. (January 2007). "A novel host defense system of airways is defective in cystic fibrosis". American Journal of Respiratory and Critical Care Medicine 175 (2): 174–83. doi:10.1164/rccm.200607-1029OC. PMID 17082494.
14. ^ Conner GE, Wijkstrom-Frei C, Randell SH, Fernandez VE, Salathe M (January 2007). "The lactoperoxidase system links anion transport to host defense in cystic fibrosis". FEBS Letters 581 (2): 271–8. doi:10.1016/j.febslet.2006.12.025. PMID 17204267.
15. ^ ^{a b} Ritchson, G. "BIO 554/754 - Ornithology: Avian respiration". Department of Biological Sciences, Eastern Kentucky University. http://www.people.eku.edu/ritchisong/birdrespiration.html. Retrieved 2009-04-23.
16. ^ ^{a b c d e f g} Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 330–334. ISBN 0-03-910284-X.
17. ^ ^{a b} Colleen Farmer (1997). "Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates". http://www.biology.utah.edu/farmer/publications%20pdf/1997%20Paleobiology23.pdf.

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