The lungs

The lungs are part of the body system we use to breathe. This is called 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

The windpipe divides into two 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 two of these on the left side and three on the right. 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.

Each secondary bronchus divides into smaller tubes called bronchioles. They are supported by the surrounding lung tissue.

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

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.

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.

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.

Lymph nodes (also called lymph glands) are small bean shaped glands. You find them throughout the body, 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 and 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 there are cancer cells in the lymph nodes, this is a sign that the cancer may have spread to other parts of the body and this could affect your choice of treatment.

There is more information about the lymphatic system in the about your body section.