The respiratory system is the collection of organs that are responsible for gas exchange. Gas exchange is the process by which oxygen, which is needed for cellular respiration, is absorbed, and carbon dioxide, a waste product of cellular respiration, is released. The human respiratory system consists of two main sections: the upper respiratory tract, consisting of the nasal cavity, pharynx, and larynx, and the lower respiratory tract, which includes the trachea, primary bronchi, and lungs. Both tracts are colonized by symbiotic microbial communities, and each possesses special barriers and mechanisms that help to protect from potential pathogens such as mucus and coughing. Many common respiratory infections, like influenza and the common cold, are caused by viruses. Bacteria can also contribute to disease, such as tuberculosis and pneumonia. Some fungi also cause respiratory diseases like pneumonia when the common oral-cavity fungus Candida albicans invades the lungs.
At A Glance
- The respiratory system is made up of the upper respiratory tract, contained in the head and neck and consisting of the nasal passages, sinus cavities, pharynx, and larynx, and the lower respiratory tract, contained entirely within the thorax and made up of the lungs, bronchi, bronchioles, and alveoli. Each part of the system contains unique means of protecting against infection.
- The respiratory system is colonized by hundreds of bacterial species, which form the native microbiota. These bacteria can either protect from or contribute to infection.
- Many common respiratory infections with diverse causative agents present with similar symptoms that are classified based on what areas are inflamed.
Vaccines protect against infection by causing the immune system to proactively develop antibodies against a pathogen before it is ever encountered. Several vaccines are available to prevent respiratory infections.
- Several species of bacteria cause diseases of the respiratory system, including pneumonia and tuberculosis.
Viruses cause the common cold, the flu, and several more rare but serious diseases, such as hantavirus pulmonary syndrome.
Influenza is a common seasonal respiratory tract infection caused by strains of the influenza virus, which evolves so quickly that new vaccines must be developed every year to prevent the spread of infection.
- Several fungal species will opportunistically cause secondary infections or infect the respiratory system of patients with compromised immune systems.