Editing Lung (section)

== Clinical significance ==
{{Main|Respiratory disease|Pulmonology}}
Lungs can be affected by a number of diseases and disorders. [[Pulmonology]] is the [[specialty (medicine)|medical speciality]] that deals with [[respiratory disease]]s involving the lungs and [[respiratory system]].<ref name="ACP">{{cite web|author1=American College of Physicians|title=Pulmonology|url=https://www.acponline.org/patients_families/about_internal_medicine/subspecialties/pulmonology/|publisher=ACP|access-date=9 February 2016|archive-url=https://web.archive.org/web/20150909203508/https://www.acponline.org/patients_families/about_internal_medicine/subspecialties/pulmonology/|archive-date=9 September 2015|author1-link=American College of Physicians}}</ref> [[Cardiothoracic surgery]] deals with [[surgery]] of the lungs including [[lung volume reduction surgery]], [[lobectomy]], [[pneumectomy]] and [[lung transplantation]].<ref>{{cite web|title=The Surgical Specialties: 8 – Cardiothoracic Surgery|url=https://www.rcseng.ac.uk/media/media-background-briefings-and-statistics/the-surgical-specialties-8-2013-cardiothoracic-surgery|website=Royal College of Surgeons|access-date=9 February 2016}}</ref>

===Inflammation and infection===
{{See also|Ghon focus}}
[[Inflammation|Inflammatory]] conditions of the lung tissue are [[pneumonia]], of the respiratory tract are [[bronchitis]] and [[bronchiolitis]], and of the [[pulmonary pleurae|pleurae]] surrounding the lungs [[pleurisy]]. Inflammation is usually caused by [[infection]]s due to [[bacteria]] or [[virus]]es. When the lung tissue is inflamed due to other causes it is called [[pneumonitis]]. One major cause of [[bacterial pneumonia]] is [[tuberculosis]].<ref name=DAVIDSONS2014 /> [[Chronic condition|Chronic]] infections often occur in those with [[immunodeficiency]] and can include a [[fungal infection]] by ''[[Aspergillus fumigatus]]'' that can lead to an [[aspergilloma]] forming in the lung.<ref name=DAVIDSONS2014 /><ref>{{cite web|title=Aspergilloma|website=Medical Dictionary|publisher=TheFreeDictionary|url=http://medical-dictionary.thefreedictionary.com/Aspergilloma}}</ref> In the US certain species of rat can transmit a [[hantavirus]] to humans that can cause untreatable [[hantavirus pulmonary syndrome]] with a similar presentation to that of [[acute respiratory distress syndrome]] (ARDS).<ref name="CDC1">{{cite web |title=Clinical Manifestation {{!}} Hantavirus {{!}} DHCPP {{!}} CDC |url=https://www.cdc.gov/hantavirus/technical/hps/clinical-manifestation.html |website=www.cdc.gov |access-date=7 January 2023 |language=en-us |date=21 February 2019}}</ref>

Alcohol affects the lungs and can cause inflammatory [[alcoholic lung disease]]. Acute exposure to alcohol stimulates the beating of [[cilia]] in the respiratory epithelium. However, chronic exposure has the effect of desensitising the ciliary response which reduces [[mucociliary clearance]] (MCC). MCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of [[alveolar macrophage]]s are decreased. A subsequent inflammatory response is the release of [[cytokine]]s. Another consequence is the susceptibility to infection.<ref name="Arvers">{{cite journal |last1=Arvers |first1=P |title=[Alcohol consumption and lung damage: Dangerous relationships]. |journal=Revue des maladies respiratoires |date=December 2018 |volume=35 |issue=10 |pages=1039–1049 |doi=10.1016/j.rmr.2018.02.009 |pmid=29941207|s2cid=239523761 }}</ref><ref name="Slovinsky">{{cite journal |last1=Slovinsky |first1=WS |last2=Romero |first2=F |last3=Sales |first3=D |last4=Shaghaghi |first4=H |last5=Summer |first5=R |title=The involvement of GM-CSF deficiencies in parallel pathways of pulmonary alveolar proteinosis and the alcoholic lung. |journal=Alcohol (Fayetteville, N.Y.) |date=November 2019 |volume=80 |pages=73–79 |doi=10.1016/j.alcohol.2018.07.006 |pmid=31229291|pmc=6592783 }}</ref>

===Blood-supply changes===
[[File:InfarctPandLbasilarsegmentsPE.PNG|thumb|[[Infarction|Tissue death]] of the lung due to a [[pulmonary embolism]]]]
<!-- Blood supply -->A [[pulmonary embolism]] is a blood clot that becomes lodged in the [[pulmonary arteries]]. The majority of emboli arise because of [[deep vein thrombosis]] in the legs. Pulmonary emboli may be investigated using a [[ventilation/perfusion scan]], [[CT pulmonary angiography|a CT scan of the arteries of the lung]], or blood tests such as the [[D-dimer]].<ref name=DAVIDSONS2014 /> [[Pulmonary hypertension]] describes an increased pressure at the beginning of the [[pulmonary artery]] that has a large number of differing causes.<ref name=DAVIDSONS2014 /> Other rarer conditions may also affect the blood supply of the lung, such as [[granulomatosis with polyangiitis]], which causes inflammation of the small blood vessels of the lungs and kidneys.<ref name=DAVIDSONS2014 />

A [[pulmonary contusion|lung contusion]] is a bruise caused by chest trauma. It results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.
<!-- Intrapleural collections -->The function of the lungs can also be affected by compression from fluid in the pleural cavity [[pleural effusion]], or other substances such as air ([[pneumothorax]]), blood ([[hemothorax]]), or rarer causes. These may be investigated using a [[chest X-ray]] or [[CT scan]], and may require the insertion of a [[surgical drain]] until the underlying cause is identified and treated.<ref name=DAVIDSONS2014>{{cite book|editor1=Brian R. Walker|editor2=Nicki R. Colledge|editor3=Stuart H. Ralston|editor4=Ian D. Penman|others=Illustrations by Robert Britton|title=Davidson's principles and practice of medicine|date=2014|publisher=Churchill Livingstone/Elsevier |isbn=978-0-7020-5035-0|edition=22nd}}</ref>

===Obstructive lung diseases===
[[File: Respiratory tract.jpg|thumb|3D still image of constricted airways as in bronchial asthma]]
[[File:Emphysema H and E.jpg|thumb|Lung tissue affected by emphysema using [[H&E stain]]]]
<!-- Obstructive lung disease-->[[Asthma]], [[bronchiectasis]], and [[chronic obstructive pulmonary disease]] (COPD) that includes [[Bronchitis#Chronic bronchitis|chronic bronchitis]], and [[emphysema]], are all [[obstructive lung disease]]s characterised by [[airway obstruction]]. This limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation. Obstructive lung diseases are often identified because of symptoms and diagnosed with [[pulmonary function tests]] such as [[spirometry]]. 

Many obstructive lung diseases are managed by avoiding triggers (such as [[dust mite]]s or [[smoking]]), with symptom control such as [[bronchodilator]]s, and with suppression of inflammation (such as through [[corticosteroid]]s) in severe cases. A common cause of chronic bronchitis, and emphysema, is smoking; and common causes of [[bronchiectasis]] include severe infections and [[cystic fibrosis]]. The definitive cause of [[asthma]] is not yet known, but it has been linked to other atopic diseases.<ref name=DAVIDSONS2014 /><ref>{{Cite journal |last1=Galli |first1=Elena |last2=Gianni |first2=Simona |last3=Auricchio |first3=Giovanni |last4=Brunetti |first4=Ercole |last5=Mancino |first5=Giorgio |last6=Rossi |first6=Paolo |date=2007-09-01 |title=Atopic dermatitis and asthma |url=http://www.ingentaconnect.com/content/10.2500/aap2007.28.3048 |journal=Allergy and Asthma Proceedings |language=en |volume=28 |issue=5 |pages=540–543 |doi=10.2500/aap2007.28.3048 |pmid=18034972 |issn=1088-5412}}</ref>

The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD. [[Elastase]] breaks down the [[elastin]] in the lung's connective tissue that can also result in emphysema. Elastase is inhibited by the [[acute-phase protein]], [[alpha-1 antitrypsin]], and when there is a [[Alpha-1 antitrypsin deficiency|deficiency]] in this, emphysema can develop. With persistent stress from smoking, the [[airway basal cell]]s become disarranged and lose their regenerative ability needed to repair the epithelial barrier. The disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of [[COPD]], and with continued stress can undergo a malignant transformation. Studies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.<ref name="Crystal" /> Basal cells become further deranged in a smoker's transition to clinically defined COPD.<ref name="Crystal">{{cite journal |last1=Crystal |first1=RG |title=Airway basal cells. The "smoking gun" of chronic obstructive pulmonary disease. |journal=American Journal of Respiratory and Critical Care Medicine |date=15 December 2014 |volume=190 |issue=12 |pages=1355–62 |doi=10.1164/rccm.201408-1492PP |pmid=25354273|pmc=4299651 }}</ref>

===Restrictive lung diseases===
<!-- Restrictive lung disease-->Some types of chronic lung diseases are classified as [[restrictive lung disease]], because of a restriction in the amount of lung tissue involved in respiration. These include [[pulmonary fibrosis]] which can occur when the lung is inflamed for a long period of time. [[Fibrosis]] in the lung replaces functioning lung tissue with [[fibrous connective tissue]]. This can be due to a large variety of [[occupational lung disease]]s such as [[Coalworker's pneumoconiosis]], [[autoimmune disease]]s or more rarely to a reaction to [[medication]].<ref name=DAVIDSONS2014 /> Severe respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of [[mechanical ventilation]] to ensure an adequate supply of air.

===Cancers===
<!-- Cancer-->[[Lung cancer]] can either arise directly from lung tissue or as a result of [[metastasis]] from another part of the body. There are two main types of primary tumour described as either [[small-cell lung carcinoma|small-cell]] or [[non-small-cell lung carcinoma]]s. The major risk factor for cancer is [[tobacco smoking|smoking]]. Once a cancer is identified it is [[tumour staging|staged]] using scans such as a [[CT scan]] and a sample of tissue from a [[biopsy]] is taken. Cancers may be treated surgically by removing the tumour, the use of [[radiotherapy]], [[chemotherapy]] or a combination, or with the aim of [[palliative care|symptom control]].<ref name=DAVIDSONS2014 /> [[Lung cancer screening]] is being recommended in the United States for high-risk populations.<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspslung.htm |title=Lung Cancer Screening |year=2013 |publisher=[[United States Preventive Services Task Force|U.S. Preventative Services Task Force]] |access-date=2016-07-10 |archive-url=https://web.archive.org/web/20101104055403/http://www.uspreventiveservicestaskforce.org/uspstf/uspslung.htm |archive-date=2010-11-04 |url-status=dead }}</ref>

===Congenital disorders===
[[Congenital disorder]]s include [[cystic fibrosis]], [[pulmonary hypoplasia]] (an incomplete development of the lungs)<ref name=Cadichon>{{citation
|last=Cadichon
|first=Sandra B.
|contribution=Chapter 22: Pulmonary hypoplasia
|title=Congenital malformations: evidence-based evaluation and management
|editor1-last= Kumar
|editor1-first=Praveen
|editor2-last=Burton
|editor2-first=Barbara K.
|year=2007
|contribution-url=https://books.google.com/books?id=n2M9tfQQN9cC&pg=PA143}}</ref>[[congenital diaphragmatic hernia]], and [[infant respiratory distress syndrome]] caused by a deficiency in lung surfactant. An [[azygos lobe]] is a congenital [[anatomical variation]] which though usually without effect can cause problems in [[thoracoscopy|thoracoscopic]] procedures.<ref>{{cite journal|last1=Sieunarine|first1=K.|last2=May|first2=J.|last3=White|first3=G.H.|last4=Harris|first4=J.P.|title=Anomalous azygos vein: a potential danger during endoscopic thoracic sypathectomy|journal=ANZ Journal of Surgery|date=August 1997|volume=67|issue=8|pages=578–579|doi=10.1111/j.1445-2197.1997.tb02046.x|pmid=9287933}}</ref>

===Pleural space pressure===
A [[pneumothorax]] (collapsed lung) is an abnormal collection of air in the [[pleural space]] that causes an uncoupling of the lung from the [[chest wall]].<ref name="BMJ2014">{{Cite journal |last1=Bintcliffe |first1=Oliver |last2=Maskell |first2=Nick |date=8 May 2014 |title=Spontaneous pneumothorax |journal=[[BMJ]] |volume=348 |pages=g2928 |doi=10.1136/bmj.g2928 |pmid=24812003|s2cid=32575512 |url=http://www.bmj.com/content/bmj/348/bmj.g3302.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.bmj.com/content/bmj/348/bmj.g3302.full.pdf |archive-date=2022-10-09 |url-status=live }}</ref> The lung cannot expand against the air pressure inside the pleural space. An easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall. Similarly, [[scuba diver]]s ascending while holding their breath with their lungs fully inflated can cause air sacs ([[Pulmonary alveolus|alveoli]]) to burst and leak high pressure air into the pleural space.

===Examination===
{{Main|Respiratory examination|Respiratory sounds}}
As part of a [[physical examination]] in response to respiratory symptoms of [[dyspnea|shortness of breath]], and [[cough]], a [[respiratory examination|lung examination]] may be carried out. This exam includes [[palpation]] and [[auscultation]].<ref>{{Cite book|title=Principles of Pulmonary Pathology|last1=Weinberger|first1=Steven|last2=Cockrill|first2=Barbara|last3=Mandell|first3=J|year=2019|isbn=9780323523714|pages=30|publisher=Elsevier }}</ref> The areas of the lungs that can be [[auscultation|listened to]] using a stethoscope are called the [[lung fields]], and these are the posterior, lateral, and anterior lung fields. The posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the [[axilla]]e, the left axilla for the lingual, the right axilla for the middle right lobe. The anterior fields can also be auscultated from the front.<ref>{{Cite web|url=https://meded.ucsd.edu/clinicalmed/lung.htm|title=Lung examination|website=meded.ucsd.edu|access-date=31 August 2019}}</ref> An area known as the [[triangle of auscultation]] is an area of thinner musculature on the back which allows improved listening.<ref name="Malik">{{cite book|last1=Malik |first1=N |last2=Tedder |first2=BL |last3=Zemaitis |first3=MR |title=Anatomy, Thorax, Triangle of Auscultation |date=January 2021 |pmid=30969656}}</ref> Abnormal [[respiratory sounds|breathing sounds]] heard during a lung exam can indicate the presence of a lung condition; [[wheezing]] for example is commonly associated with [[asthma]] and [[COPD]].

=== Function testing ===
{{Main|Pulmonary function testing|Lung volumes}}
{{multiple image
| total_width       = 600
| align             = right
| direction         = horizontal
| image1            = LungVolume.jpg
| caption1          = [[Lung volumes]] as described in the text
| image2            = DoingSpirometry.JPG
| caption2          = A person doing a [[spirometry]] test
}}

[[Pulmonary function testing|Lung function testing]] is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.<ref name="Ganong2012_34">{{cite book|last1=Kim E.|first1=Barrett|title=Ganong's review of medical physiology|date=2012|publisher=McGraw-Hill Medical|location=New York|isbn=978-0-07-178003-2|chapter=Chapter 34. Introduction to Pulmonary Structure and Mechanics|edition=24th}}</ref> The volume of air inhaled and exhaled by a person at rest is the [[tidal volume]] (normally 500–750&nbsp;mL); the [[inspiratory reserve volume]] and [[expiratory reserve volume]] are the additional amounts a person is able to forcibly inhale and exhale respectively. The summed total of forced inspiration and expiration is a person's [[vital capacity]]. Not all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the [[Lung volumes|residual volume]]. Together these terms are referred to as [[lung volumes]].<ref name="Ganong2012_34" />

Pulmonary [[plethysmograph]]s are used to measure [[functional residual capacity]].<ref>{{cite journal|last1=Criée|first1=C.P.|last2=Sorichter|first2=S.|last3=Smith|first3=H.J.|last4=Kardos|first4=P.|last5=Merget|first5=R.|last6=Heise|first6=D.|last7=Berdel|first7=D.|last8=Köhler|first8=D.|last9=Magnussen|first9=H.|last10=Marek|first10=W.|last11=Mitfessel|first11=H.|last12=Rasche|first12=K.|last13=Rolke|first13=M.|last14=Worth|first14=H.|last15=Jörres|first15=R.A.|title=Body plethysmography – Its principles and clinical use|journal=Respiratory Medicine|date=July 2011|volume=105|issue=7|pages=959–971|doi=10.1016/j.rmed.2011.02.006|pmid=21356587|doi-access=free}}</ref> Functional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.<ref name=Applegate2014 /> The total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between four and six litres.<ref name=Ganong2012_34 /> Females tend to have a 20–25% lower capacity than males. Tall people tend to have a larger total lung capacity than shorter people. [[tobacco smoking|Smokers]] have a lower capacity than nonsmokers. Thinner persons tend to have a larger capacity. Lung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.<ref name=Applegate2014>{{cite book|last1=Applegate|first1=Edith|title=The Anatomy and Physiology Learning System|date=2014|publisher=Elsevier Health Sciences|isbn=978-0-323-29082-1|page=335|url=https://books.google.com/books?id=c8nsAwAAQBAJ&q=factors+that+influence+total+lung+capacity&pg=PA335}}</ref><ref name="Laeremans et al. 2018">{{cite journal  | last = Laeremans  | first = M  | title = Black Carbon Reduces the Beneficial Effect of Physical Activity on Lung Function  | journal = Medicine and Science in Sports and Exercise  | volume =   50| issue = 9  | pages = 1875–1881  | year = 2018  | doi = 10.1249/MSS.0000000000001632| pmid = 29634643  | hdl = 10044/1/63478 | s2cid = 207183760 | hdl-access = free  }}</ref>

Other lung function tests include [[spirometry]], measuring the amount (volume) and flow of air that can be inhaled and exhaled. The maximum volume of breath that can be exhaled is called the [[vital capacity]]. In particular, how much a person is able to exhale in one second (called [[Spirometry#Parameters|forced expiratory volume]] (FEV1)) as a proportion of how much they are able to exhale in total (FEV). This ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is [[restrictive lung disease|restrictive]] or [[obstructive lung disease|obstructive]].<ref name=DAVIDSONS2014 /><ref name=Ganong2012_34 /> Another test is that of the lung's  [[diffusing capacity]] – this is a measure of the transfer of gas from air to the blood in the lung capillaries.