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The lungs

Men and women discussing lung cancer

This page tells you about the lungs and how they work. There is information about

 

A quick guide to what's on this page

The lungs

These bring oxygen into our bodies and pass it into the bloodstream so that it can circulate to every body cell. They are part of the body system we use to breathe - the respiratory system.

The parts of the breathing system

The windpipe (trachea) divides into 2 airways, called the right main bronchus and the left main bronchus. One goes to each lung. Within the lungs, they divide into smaller tubes called the secondary bronchi. There are 2 of these on the left side and 3 on the right. Each secondary bronchus divides into smaller tubes called bronchioles. At the end of the bronchioles are tiny air sacs called alveoli. In the alveoli oxygen passes into the bloodstream to be carried round the body. Carbon dioxide passes into the alveoli from the bloodstream to be breathed out.

The right lung is divided into 3 sections called the upper, middle and lower lobes. The left lung is divided into 2 sections called the upper and lower lobes.

Lymph nodes

Close to the lungs and airways are lymph nodes (also called lymph glands). They are small bean shaped glands that filter fluid from the lung tissues. Cancer cells may be released from a tumour in the lung and then may get trapped in nearby lymph nodes. 

The covering of the lungs (pleura)

There are 2 fibrous sheets of tissue that cover the lungs. These are called the pleura or pleural membranes. The gap between the pleura is called the pleural space. The pleural membranes produce a lubricating fluid that moistens them. The fluid helps the pleural membranes to move smoothly over each other as we breathe.

Lung cancer cells can sometimes spread to the pleura. The cells irritate the pleura and they make too much fluid, which collects and presses in on the lung. This is called a pleural effusion. You can't breathe in so well and may feel breathless. 


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The lungs and breathing system

These are part of the body system we use to breathe - the respiratory system. It is made up of the

  • Nose and mouth
  • Windpipe (trachea)
  • Airways to each lung (the right main bronchus and left main bronchus)
  • The lungs

Diagram showing the parts of the respiratory system

The windpipe divides into 2 airways. These are called the right main bronchus and left main bronchus. One goes to each lung.

Within the lungs, the left and right bronchus divide into smaller tubes called the secondary bronchi. There are 2 of these on the left side and 3 on the right. Each secondary bronchus divides into smaller tubes called bronchioles. They are supported by the surrounding lung tissue.

The lungs are slightly different on each side. The right lung is divided into 3 sections called the upper, middle and lower lobes. The left lung is divided into 2 sections called the upper and lower lobes.

 

How the lungs work

The lungs bring oxygen into our bodies and pass it into the bloodstream so that it can circulate to every body cell. We use the muscles of our chest and a large flat muscle under the lungs (the diaphragm – pronounced di-a-fram) to draw air into the lungs. The diaphragm is at the base of the chest cavity, just above the stomach. The chest cavity is sealed so that when you breathe in and the muscles make it bigger, this creates a vacuum inside, which draws air in through your nose and down into the lungs.

At the end of the smallest airways in the lungs (the secondary bronchii) are the smallest tubes, the bronchioles. These carry air throughout the lungs. At the end of the bronchioles are air sacs called alveoli. There are millions of these tiny sacs. This is where oxygen is absorbed into the bloodstream from the air that we breathe in. Once in the blood, the oxygen can travel throughout the body and reach every body cell.

As oxygen is being absorbed, carbon dioxide passes back into the alveoli from the bloodstream. This waste gas is removed from the body as we breathe out.

 

The lymph nodes

Close to the lungs and airways are lymph nodes (also called lymph glands). They are small bean shaped glands found throughout the body. They are connected by a network of tubes called lymphatics or lymphatic vessels. This network carries a fluid that leaks out of the blood vessels and bathes the body tissues and cells. The lymph nodes help to filter this fluid and the lymphatic vessels channel it back into the bloodstream.

Lymph fluid circulates through body tissues. So the lymphatic system is one of the ways that cancer can spread from one part of the body to another. Cancer cells may be released from a tumour in the lung and then get trapped in nearby lymph nodes. Cancer surgeons and medical cancer specialists (oncologists) check your lymph nodes for cancer cells when you are diagnosed. If cancer cells are in the lymph nodes, this is a sign that the cancer may have spread to other parts of the body. This could affect your choice of treatment.

We have detailed information about the lymphatic system on this website.

 

The pleura (the covering of the lungs)

There are 2 fibrous sheets of tissue that cover the lungs and help to protect them. These are callled the pleura or pleural membranes. Doctors usually call these the lining of the lungs, although this can be a bit confusing as they are on the outside.

The gap between the pleura is called the pleural space. The pleura produce a lubricating fluid that moistens the gap between them. This helps the pleural membranes to move smoothly over each other when the lungs get bigger and smaller as we breathe.

Lung cancer can spread to the pleura. The cancer cells irritate the pleural membranes and they then make too much fluid.

Diagram showing a build up of fluid in the lining of the lungs (pleural effusion)

The fluid collects and reduces the space available for the lung. So your lung can't expand as much as it should and this can make you feel breathless. Build up of fluid between the pleura is called a pleural effusion.

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Updated: 25 March 2014