What is lung cancer?
Lung cancer is cancer that usually starts in the lining of the bronchi (the main airways of the lungs), but also can begin in other areas of the respiratory system, including the trachea, bronchioles or alveoli. It is the leading cause of cancer death in both men and women.
Lung cancers are believed to develop over a period of many years.
Nearly all lung cancers are carcinomas, cancers that begin in the lining or covering tissues of an organ. The tumor cells of each type of lung cancer grow and spread differently, and each type requires different treatment. More than 95 percent of lung cancers belong to the group called bronchogenic carcinoma.
Lung cancers are generally divided into two types:
Non-small cell lung cancer – more common than small cell lung cancer. There are several types of non-small cell lung cancer, named for the type of cells found in the tumor:
- Squamous cell carcinoma – also called epidermoid carcinoma, is the most common type of lung cancer in men. It often begins in the bronchi and usually does not spread as quickly as other types of lung cancer.
- Adenocarcinoma – usually begins along the outer edges of the lungs and under the lining of the bronchi. This type of non-small cell lung cancer begins in cells that have secretory (glandular) characteristics. It is the most common type of lung cancer in women and in people who have never smoked.
- Large cell carcinomas – are a group of cancers with large, abnormal-looking cells. These tumors usually begin along the outer edges of the lungs.
- Adenosquamous carcinoma – begins in flattened cells when viewed under a microscope. These cells also have secretory characteristics
- Undifferentiated carcinoma – involves abnormal-looking cancer cells that tend to multiply quickly.
- Small cell lung cancer – sometimes called oat cell cancer because the cancer cells may look like oats when viewed under a microscope, grows rapidly and quickly spreads to other organs.
It is important to find out what kind of lung cancer a person has. The different types of carcinomas, involving different regions of the lung, may cause different symptoms and are treated differently.
What is respiration?
Respiration is the act of breathing:
- Inhaling (inspiration) – taking in oxygen.
- Exhaling (expiration) – giving off carbon dioxide.
What makes up the respiratory system?
The respiratory system is made up of the organs involved in the interchanges of gases and consists of the:
The upper respiratory tract includes the:
- Nasal cavity
- Ethmoidal air cells
- Frontal sinuses
- Maxillary sinus
The lower respiratory tract includes the:
What are the functions of the lungs?
The lungs take in oxygen, which cells need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the body’s cells.
The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the chest or the thorax (the part of the body between the base of the neck and diaphragm).
The lungs are enveloped in a membrane called the pleura.
The lungs are separated from each other by the mediastinum, an area that contains:
- Heart and its large vessels
- Trachea (windpipe)
- Lymph nodes
The right lung has three sections called lobes. The left lung has two lobes. When you breathe, the air:
- Enters the body through the nose or the mouth.
- Travels down the throat through the larynx (voice box) and trachea (windpipe).
- Goes into the lungs through tubes called main-stem bronchi:
- One main-stem bronchus leads to the right lung and one to the left lung.
- In the lungs, the main-stem bronchi divide into smaller bronchi.
- Then divide into even smaller tubes called bronchioles.
- Bronchioles end in tiny air sacs called alveoli.