The lungs and respiratory system

About the lungs

The lungs are the parts of the body that we use to breathe. We have 2 lungs. One on the right side of our body and one on the left side. They supply oxygen to the organs and tissues of the body. The lungs are divided into areas called lobes. The right lung has 3 lobes, and the left lung has 2 lobes.

The lungs are covered by a lining called the pleura, which has 2 layers. The inner layer covers the lungs. The outer layer lines the ribcage and the diaphragm. The diaphragm is a sheet of muscle that separates the chest from the upper tummy (abdomen).

Related pages

Lung cancer

The respiratory system

The lungs are part of our breathing system. This system is also called our respiratory system. It includes the:

nose and mouth
windpipe (trachea)
two tubes called the left bronchus and right bronchus – they branch from the windpipe going into each lung
lungs.

Diagram of the respiratory system

The respiratory system shows an airway going in through the mouth and one through the nose. — Image: The illustration shows the respiratory system. It shows an airway going in through the mouth and one through the nose. They meet and go down into the windpipe, also called the trachea. This extends down from the neck area. It divides into two tubes, the right and left bronchus, each of which goes into the respective right and left lungs. These divide into smaller tubes called bronchioles. At the end of the bronchioles are air sacs called alveoli.

How the respiratory system works

When we breathe in, air passes from our nose or mouth through to the windpipe. The windpipe is also called the trachea. The trachea divides into 2 tubes that go to each lung. These tubes are called the right and left bronchus.

Air passes through each bronchus into the lungs through smaller tubes called bronchioles. At the end of the bronchioles, there are tiny air sacs called alveoli. This is where oxygen from the air we have breathed in passes into the blood. The oxygen is then circulated through the blood around the body.

A waste gas called carbon dioxide passes from the blood into the alveoli. We get rid of carbon dioxide when we breathe out.

The lymphatic system

The lymphatic system helps protect us from infection and disease. It drains lymph fluid from the tissues of the body and then returns it to the blood.

The lymphatic system is made up of fine tubes called lymphatic vessels that connect to groups of lymph nodes throughout the body. Lymph nodes are sometimes called lymph glands. They are small and bean-shaped. They filter bacteria (germs) and disease from the lymph fluid. When you have an infection, lymph nodes often swell as they fight it.

Sometimes, cancer can spread through the lymphatic system. If the cancer cells spread outside the lungs, they are most likely to go to lymph nodes nearby in the chest.

The lungs in the chest with the windpipe, also called the trachea, coming down from the neck. The trachea divides into 2 tubes called the left and right bronchus. — Image: The illustration shows the lungs in the chest with the windpipe, also called the trachea, coming down from the neck. The trachea divides into two tubes called the left and right bronchus. They go into each lung. The illustration shows groups of pea-sized lymph nodes connected to each other by fine tubes. There are lymph nodes close to the trachea and in the middle of the chest near the right and left bronchi. There are also lymph nodes on each side of the neck going along the bones that connect with each shoulder called the collarbones and also extending down to the underarm area.

References

Below is a sample of the sources used in our lung cancer information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk

National Institute for Health and Care Excellence (NICE). Lung cancer – Diagnosis and management. Clinical guideline 2019. Last updated 2023. (accessed Nov 2023) Available at: https://www.nice.org.uk/guidance/ng122

European Society for Medical Oncology (ESMO). Small-cell lung cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. 2021. (accessed Nov 2023). Available at: https://www.esmo.org/guidelines/guidelines-by-topic/esmo-clinical-practice-guidelines-lung-and-chest-tumours/small-cell-lung-cancer

European Society for Medical Oncology (ESMO). Early and locally advanced non-small-cell lung cancer (NSCLC): ESMO clinical practice guidelines for diagnosis, treatment and follow-up. 2017. eUpdate 01 September 2021: New Locally Advanced NSCLC Treatment Recommendations (accessed Nov 2023) Available at: https://www.esmo.org/guidelines/esmo-clinical-practice-guideline-early-stage-and-locally-advanced-non-small-cell-lung-cancer

European Society for Medical Oncology (ESMO). ESMO expert consensus statements on the management of EGFR mutant non-small-cell lung cancer. 2022 (accessed Nov 2023). Available at: https://pubmed.ncbi.nlm.nih.gov/35176458/

Cancer Information Development team

Author

Dr David Gilligan

Reviewer

Consultant Clinical Oncologist

Addenbrookes Hospital, Cambridge

Date reviewed

Reviewed: 31 January 2025

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Next review: 31 January 2028

The language we use

We want everyone affected by cancer to feel our information is written for them.

We want our information to be as clear as possible. To do this, we try to:

use plain English
explain medical words
use short sentences
use illustrations to explain text
structure the information clearly
make sure important points are clear.

We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.

You can read more about how we produce our information here.