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The lungs

The lungs are 2 sponge-like organs that are used for breathing. They are part of the respiratory system, which also includes the nose, mouth, trachea (windpipe) and airways (tubes) to each lung. There are large airways known as bronchi (singular: bronchus) and small airways called bronchioles. The lungs sit in the chest and are protected by the rib cage.

Lobes – Each lung is made up of sections called lobes – the left lung has 2 lobes, and the right lung has 3 lobes.

Diaphragm – The lungs rest on the diaphragm, which is a wide, thin muscle that helps with breathing, and separates the chest from the abdomen (belly).

Mediastinum – The space between the lungs is called the mediastinum. A number of important structures lie in this space, including:

  • the heart and large blood vessels
  • the trachea – the tube that carries air into the lungs
  • the oesophagus – the tube that carries food to the stomach
  • lymph nodes – small, bean-shaped structures that collect and destroy bacteria and viruses.

Pleura – The lungs are covered by 2 thin layers of tissue called the pleura. The inner layer (visceral pleura) lines the lung surface, and the outer layer (parietal pleura) lines the chest wall, mediastinum and diaphragm. The layers are separated by a small amount of fluid that lets them smoothly slide over each other when you breathe. The pleural cavity is the potential space between the 2 layers; there is no space between the layers when the lungs are healthy.

How breathing works

When you breathe in (inhale), air goes into the nose or mouth, down the trachea and into the bronchi and bronchioles. At the end of the bronchioles, tiny air sacs  called alveoli are surrounded by small blood vessels (capillaries). When the inhaled air reaches the alveoli, oxygen passes into the blood in the capillaries, and waste gas (carbon dioxide) passes out. When you breathe out (exhale), carbon dioxide is removed from the body and released into the air.

Image of the respiratory system with lung highlighted

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This information is reviewed by

This information was last reviewed in October 2022 by the following expert content reviewers: A/Prof Brett Hughes, Senior Staff Specialist Medical Oncologist, Royal Brisbane and Women’s Hospital, The Prince Charles Hospital and The University of Queensland, QLD; Dr Brendan Dougherty, Respiratory and Sleep Medicine Specialist, Flinders Medical Centre, SA; Kim Greco, Nurse Consultant – Lung Cancer, Flinders Medical Centre, SA; Dr Susan Harden, Radiation Oncologist, Peter MacCallum Cancer Centre, VIC; A/Prof Rohit Joshi, Medical Oncologist, GenesisCare and Lyell McEwin Hospital, Director, Cancer Research SA; Kathlene Robson, 13 11 20 Consultant, Cancer Council ACT; Peter Spolc, Consumer; Nicole Taylor, Lung Cancer and Mesothelioma Cancer Specialist Nurse, Canberra Hospital, ACT; Rosemary Taylor, Consumer; A/Prof Gavin M Wright, Director of Surgical Oncology, St Vincent’s Hospital and Research and Education Lead – Lung Cancer, Victorian Comprehensive Cancer Centre, VIC.