Respiratory System and Pulmonology

The respiratory system is a branch of medicine that specializes in diagnosing and treating diseases of the lungs and other parts of the respiratory system.
The process of exchange of gases is called respiration, which is an involuntary activity involving inhalation and exhalation of oxygen and carbon dioxide respectively.
The respiratory system consists of two major units: the respiratory passage and the respiratory organ.

The respiratory passage takes air from the atmosphere through the nostrils, nasal cavity, pair of internal nares, nasopharynx, larynx, trachea, bronchi, and branches of bronchi on the lung surface (alveoli).
The upper respiratory tract consists of:
- External nostrils: for the intake of air
- Nasal chamber: lined with hair and mucus to filter air from dust and dirt
- Pharynx: a common passageway for both air and food
- Internal nares: posterior opening of nasal cavity that leads to nasopharynx
- Nasopharynx: contains pharyngeal tonsils, or adenoids, which are collections of lymphatic tissue
The lower respiratory tract consists of:
- Larynx: contains the vocal cords and is surrounded by pieces of cartilage for support
- Epiglottis: a flap of cartilage attached to the root of the tongue, prevents choking or aspiration of food
- Trachea: a long tube passing through the mid-thoracic cavity
- Bronchi: the trachea divides into left and right bronchi
- Bronchioles: each bronchus leads to a separate lung where it divides and subdivides into smaller and finer tubes

The functions of the human respiratory system are:
- Inhalation and exhalation: the respiratory system helps in breathing (also known as pulmonary ventilation)
- Exchange of gases between lungs and bloodstream: inside the lungs, oxygen and carbon dioxide enter and exit respectively through millions of microscopic sacs called alveoli

Asthma: a condition where airways are constantly inflamed and may spasm, causing wheezing and shortness of breath
Chronic obstructive pulmonary disease (COPD): a lung condition where you can’t exhale the way you usually would, causing trouble breathing
Emphysema: a form of COPD where lung damage allows air to be trapped in your lungs
Acute bronchitis: a sudden infection of your airways, usually caused by a virus
Cystic fibrosis: a condition where you have trouble clearing mucus out of your bronchi, leading to repeated lung infections

Air sacs (alveoli): tiny sacs where gas exchange occurs between the lungs and bloodstream
Lung diseases affecting the alveoli include:
- Pneumonia: an infection of the alveoli, usually by bacteria or viruses
- Tuberculosis: a type of pneumonia that slowly gets worse, caused by the bacteria Mycobacterium tuberculosis

Interstitium: the thin, delicate lining between the alveoli where tiny blood vessels run through, allowing gas transfer between the alveoli and the blood
Lung diseases affecting the interstitium include:
- Interstitial lung disease (ILD): a group of lung conditions that includes sarcoidosis, idiopathic pulmonary fibrosis, and autoimmune disease
- Pulmonary embolism: a blood clot that breaks off, travels to the heart, and gets pumped into the lungs, causing shortness of breath and low blood oxygen levels

Pleura: the thin lining that surrounds the lung and lines the inside of the chest wall
Lung diseases of the pleura include:
- Pleural effusion: fluid collects in the space between the lung and the chest wall
- Pneumothorax: air gets into the space between the chest wall and the lung, collapsing the lung

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