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The lungs

The lungs are the main organs for breathing, and are part of the respiratory system. As well as the lungs, the respiratory system 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.

Lobes – The lungs are two large, spongy organs. Each lung is made up of sections called lobes – the left lung has two lobes and the right lung has three.

Diaphragm – The lungs rest on the diaphragm, which is a wide, thin muscle that helps with breathing.

Mediastinum – The space between the two lungs is called the mediastinum. Several 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 two layers of a thin sheet of tissue called the pleura, which is about as thick as plastic cling wrap. The inner layer (the visceral pleura) lines the lung surface and the outer layer (the parietal pleura) lines the chest wall and diaphragm. The layers are separated by a film of fluid that lets them slide over each other. This fluid helps the lungs move smoothly against the chest wall when you breathe. The pleural cavity is the potential space between the two layers, but there is no space between them 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). Inhaled oxygen passes through the alveoli into the blood, while the waste gas (carbon dioxide) moves from the blood into the alveoli. When you breathe out (exhale), carbon dioxide is removed from the body and released back into the air.

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This information is reviewed by

This information was last reviewed in October 2020 by the following expert content reviewers: A/Prof Nick Pavlakis, President, Australasian Lung Cancer Trials Group, President, Clinical Oncology Society of Australia, and Senior Staff Specialist, Department of Medical Oncology, Royal North Shore Hospital, NSW; Dr Naveed Alam, Thoracic Surgeon, St Vincent’s Private Hospital Melbourne, VIC; Prof Kwun Fong, Thoracic and Sleep Physician and Director, UQ Thoracic Research Centre, The Prince Charles Hospital, and Professor of Medicine, The University of Queensland, QLD; Renae Grundy, Clinical Nurse Consultant – Lung, Royal Hobart Hospital, TAS; A/Prof Brian Le, Director, Palliative Care, Victorian Comprehensive Cancer Centre – Peter MacCallum Cancer Centre and The Royal Melbourne Hospital, and The University Of Melbourne, VIC; A/Prof Margot Lehman, Senior Radiation Oncologist and Director, Radiation Oncology, Princess Alexandra Hospital, QLD; Susana Lloyd, Consumer; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Nicole Parkinson, Lung Cancer Support Nurse, Lung Foundation Australia.