How does the lung work?
The lungs are one of the big vital organs. It ensures that the oxygen from the breathing air gets into the blood. It is then transported via the bloodstream to all body cells. The lungs are well protected from the ribs in the upper thorax. The structure of the lung resembles that of a tree that is upside down: two branches, the main bronchi, descend from the trachea to the right and left of the two lungs. They ramify in the lungs in ever thinner branches and end in the alveoli.
How does the pulmonary circulation work?
With every breath, oxygen-containing air flows through the trachea and bronchi into the alveoli. These so-called alveoli are crucial for the gas exchange: they are grape-like on the bronchial branches. A healthy lung contains about 300 million alveoli. They are all surrounded by fine blood vessels (capillaries).
Through the thin envelope of the alveoli , the oxygen from the inhaled air passes into the blood vessels. This process is also called diffusion. Through the bloodstream, the oxygen is distributed in the body and reaches every cell . At the same time that the blood takes in oxygen, it also releases carbon dioxide. Carbon dioxide (C O 2 ) is produced as a by-product of cell metabolism and is disposed of with exhalation. It takes the opposite route as oxygen: from the blood through the walls of the alveoli and the airways to the outside.
What happens during breathing?
As you inhale, the ribcage expands and the lungs expand. As you exhale, the lungs contract again. Both are controlled by movements of the diaphragm and the intercostal muscles. The breathing is unconscious.
Adults breathe calmly 14-16 times a minute. With every calm breath about half a liter of air is inhaled. When exerted, the breathing becomes faster and deeper, so that more oxygen gets into the blood .
A person’s performance depends heavily on how the lungs and heart work. Pulmonary function can be measured using various breath tests.
How is the lung structured?
The trachea is about ten centimeters long in adults and divides at its end into the main bronchi (right and left main bronchus). These main bronchi branch into smaller lobar bronchi – three in the right lung, two in the left lung. There is less space because the left lung partially encloses the heart.
The lobar bronchi, in turn, branch out into several segmental bronchi. The right lung is divided into ten, the left lung into nine lung segments. Each segment is supplied by a segment bronchus and a branch of the pulmonary artery. In case of severe lung disease or injury, a segment can therefore be removed individually if necessary.
The trachea and bronchi are lined with mucus-producing cells and millions of tiny cilia . Together, they ensure that inhaled pollutants such as dust or other particles do not accumulate in the lungs: The mucus binds the foreign particles, is continuously transported out of the lungs by the movement of the cilia and finally swallowed or coughed up in the pharynx. When larger foreign bodies enter the trachea, the respiratory tract responds with a reflex-like coughing sensation.