This system is concerned with breathing and gas exchange. It is composed of the following:
The nose, larynx and trachea
These are the upper airways. As air is inhaled, it is filtered in the nose, heated to body temperature and fully saturated with water vapour. Partial recovery of this heat and moisture occurs on expiration.
The lungs and bronchi
These constitute the lower airways.
There are two lungs, each situated in its own side of the chest cavity. The trachea divides into the right main bronchus and left main bronchus which enter the right and left lungs respectively. Each lung also has one major artery (pulmonary artery) and two major veins (pulmonary veins), all of which undergo subdivisions within the lung substance, together with the bronchi and bronchial vessels and nerves. These divisions eventually terminate as the alveoli where exchange of gases takes place.
The surface of the lung is mottled, and is either pink or grey in colour according to the atmosphere in which the owner has lived. It is crepitant to the touch, like a sponge.
Symptoms of Respiratory Diseases
Diseases of the respiratory system account for up to a third of deaths in most countries and for a major proportion of visits to the doctor and time away from work or school.
The symptoms that may point to a problem with the respiratory system are:
- Breathlessness inappropriate to the level of physical exertion, or even at rest
- Production of excessive sputum
- Presence of blood in coughed-up sputum
- Chest pain
- Noisy breathing
- Change in voice, hoarseness or weakness of voice
- Ear pain
- Nasal discharge
- Sore throat
Cough of short duration is most commonly caused by viral infections, inflammation of the nose or inhalation of a foreign body.
Long-standing cough may be caused by chronic infections like tuberculosis and pertussis. Lung cancers and occupational lung diseases like coal-miner’s lung disease may also cause chronic cough. Asthma may present with cough as the only constant feature. Chronic cough can also occur with back-flow of stomach contents through the oesophagus into the lungs. Some antihypertensive drugs can cause a chronic dry cough.
Everyone becomes breathless on strenuous exertion. But, breathlessness inappropriate to the level of physical exertion, or even occurring at rest, can be a symptom of respiratory disease. Problems with other systems can also cause breathlessness.
Respiratory causes of breathlessness include severe asthma, air in the chest cavity, pneumonia, inhaled foreign body, obstructive airway disease, and lung cancers.
The presence, appearance and quantity of sputum can give an idea of the cause of a respiratory problem. Pink or white frothy sputum may be a sign of congestion of the lungs. Rusty-coloured sputum points to a type of pneumonia. Blood in sputum may suggest lung cancer or tuberculosis, among other possible causes. The causes of copious amounts of sputum are now rare.
Noisy breathing may be noticed on expiration (wheezing) or on inspiration (stridor). The former is usually due to obstruction in the lower airways and may be caused by such conditions like asthma. Stridor is a serious finding which indicates narrowing of the larger upper airways such as the trachea or main bronchi.
Apart from musculoskeletal aches and pains consequent upon prolonged bouts of coughing, chest pain caused by lung disease usually arises from the lung coverings (pleura).
Pleuritic pain is sharp and stabbing, and is made worse by deep breathing or coughing. It occurs when the pleura is inflamed, most commonly by infection in the lung.
More constant pain, unrelated to breathing, may be caused by invasion of the chest wall by a lung or pleural tumour.
Air in the chest cavity causes pain which is worse on breathing but which may have more of an aching character.
Diseases in the ear, nose and throat may cause respiratory problems and vice versa. An inflammation of the nose can cause cough. Change in voice may be due to a lung cancer that has affected the vocal cords. Some treatments for asthma may cause a fungal infection called candidiasis to develop in the mouth and throat.