The main function of the lungs is to inhale oxygen and discharge carbon dioxide. Our lungs are not a whole, but are divided into the left lung and the right lung, and the left and right lungs are composed of relatively independent lung lobes (the left lung includes 2 lung lobes,

The main function of the lungs is to inhale oxygen and discharge carbon dioxide . Our lungs are not a whole, but are divided into the left lung and the right lung, and the left and right lungs are composed of relatively independent lung lobes (the left lung includes 2 lung lobes, and the right lung includes 3 lung lobes). As we breathe, air enters the trachea from the nose. The trachea gradually breaks out and becomes thinner, and eventually becomes a small balloon-like alveolar . oxygen in the air enters the blood in the alveoli.

Just like building a building requires different materials such as bricks, cement, and steel bars, our lungs are also composed of different cells, most of which are called " epithelial cell ". The cells that make up the lungs have specific growth and death cycles, thus keeping the number of cells in the lungs stable. However, harmful environmental factors and their own genetic factors sometimes affect the normal growth of cells and induce oncogenic gene mutations.

If a normal cell undergoes gene mutation, causing abnormal changes in the growth and death cycle of the cell, then normal cells will become cancer cells, and then uncontrolled division and proliferation will occur, forming a larger number of cancer cells. It's like a car's brake failure or the accelerator keeps pressing on it, cancer cells continue to divide and proliferate without anything stopping them. After years of proliferation, these cancer cells will form a clump in the lungs, which will appear as nodules or block shadows during chest CT examination.

Cancer cells usually do not have normal cellular functions, they are not regulated and will proliferate infinitely. Unlimited proliferation of cancer cells not only consume a large amount of human resources, but also when the cancer cells proliferate to a certain number, they will infiltrate and migrate to other normal tissues and cause damage everywhere. The same is true for lung cancer cells. In addition to proliferation in the lungs, they will also spread to other parts of the body. This is what is called "metastasis" in clinical practice. Lung cancer often first metastasizes to lymph nodes , and may also be transferred to other organs through blood flow, such as bone, brain, liver, etc. It should be noted that although these metastases are no longer on the lungs, treatment is still the solution for lung cancer because the source of the cancer cells is still the lungs.