<unk> s can be affected by a number of diseases and disorders. Pulmonology is the medical speciality that deals with respiratory diseases involving the<unk> s and respiratory system. Cardiothoracic surgery deals with surgery of the<unk> s including<unk>  volume reduction surgery, lobectomy, pneumectomy and<unk>  transplantation. Inflammation and infection Inflammatory conditions of the<unk>  tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the<unk> s pleurisy. Inflammation is usually caused by infections due to bacteria or viruses. When the<unk>  tissue is inflamed due to other causes it is called pneumonitis. One major cause of bacterial pneumonia is tuberculosis. 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<unk> . Alcohol affects the<unk> s and can cause inflammatory alcoholic<unk>  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 macrophages are decreased. A subsequent inflammatory response is the release of cytokines. Another consequence is the susceptibility to infection. Blood-supply changes Tissue death of the<unk>  due to a pulmonary embolism 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, a CT scan of the arteries of the<unk> , or blood tests such as the D-dimer. Pulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes. Other rarer conditions may also affect the blood supply of the<unk> , such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the<unk> s and kidneys. A<unk>  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. The function of the<unk> s 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. Obstructive<unk>  diseases 3D still image of constricted airways as in bronchial asthma.<unk>  tissue affected by emphysema using H&E stain. Asthma, bronchiectasis, and chronic obstructive pulmonary disease (COPD) that includes chronic bronchitis, and emphysema, are all obstructive<unk>  diseases 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<unk>  diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry. Many obstructive<unk>  diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) 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. 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<unk> '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 deficiency in this, emphysema can develop. With persistent stress from smoking, the airway basal cells 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. Basal cells become further deranged in a smoker's transition to clinically defined COPD. Restrictive<unk>  diseases Some types of chronic<unk>  diseases are classified as restrictive<unk>  disease, because of a restriction in the amount of<unk>  tissue involved in respiration. These include pulmonary fibrosis which can occur when the<unk>  is inflamed for a long period of time. Fibrosis in the<unk>  replaces functioning<unk>  tissue with fibrous connective tissue. This can be due to a large variety of occupational<unk>  diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication. 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<unk>  cancer can either arise directly from<unk>  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 or non-small-cell<unk>  carcinomas. The major risk factor for cancer is smoking. Once a cancer is identified it is 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 symptom control.<unk>  cancer screening is being recommended in the United States for high-risk populations. Congenital disorders Congenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the<unk> s)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in<unk>  surfactant. An azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures. Pleural space pressure A pneumothorax (collapsed<unk>  is an abnormal collection of air in the pleural space that causes an uncoupling of the<unk>  from the chest wall. The<unk>  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 divers ascending while holding their breath with their<unk> s fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space. Examination As part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a<unk>  examination may be carried out. This exam includes palpation and auscultation. The areas of the<unk> s that can be listened to using a stethoscope are called the<unk>  fields, and these are the posterior, lateral, and anterior<unk>  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 axillae, the left axilla for the lingual, the right axilla for the middle right lobe. The anterior fields can also be auscultated from the front. An area known as the triangle of auscultation is an area of thinner musculature on the back which allows improved listening. Abnormal breathing sounds heard during a<unk>  exam can indicate the presence of a<unk>  condition; wheezing for example is commonly associated with asthma and COPD. Function testing<unk>  function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances. The volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); 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<unk> s even after a forced breath out; the remainder of the air is called the residual volume. Together these terms are referred to as<unk>  volumes. Pulmonary plethysmographs are used to measure functional residual capacity. 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. The total<unk>  capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres. Females tend to have a 20–25% lower capacity than males. Tall people tend to have a larger total<unk>  capacity than shorter people. Smokers have a lower capacity than nonsmokers. Thinner persons tend to have a larger capacity.<unk>  capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution. Other<unk>  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
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Central nervous system
Peripheral nervous system