The lung – the human respiratory organ: built up out of thousands of air-filled bubbles, the lungs provide a surface about the size of a tennis court for oxygen uptake. But our respiratory system has even more tasks: it releases carbon dioxide, controls the pH of the blood and even has its own blood circulation. A healthy lung has enormous reserve capacity that can be mobilized during exercise.
The human lung anatomically consists of a left and a right lung . Together with the heart they fill the chest ( thorax ). Both the thorax and the lungs are covered by a sheet of the pleura ( pleura ). The name petticoat is misleading, as it is not a hairy coat, but two very thin but extremely firm layers of skin, between which a fine layer of fluid allows the mobility between the lungs and chest when breathing.
The left lung has to divide its thoracic half with the heart and is therefore slightly smaller than the right one. The lung tissue is very light and soft, it would float in the water. Under the microscope, the structure of the lung can be seen: three structures characterize their structure: alveoli , blood vessels and bronchi.
The alveoli allow oxygen uptake
The alveoli are the place of gas exchange. They are air-filled bubbles with a diameter of one third of a millimeter, but together they offer a total surface of 50 to 100 square meters. This is covered by a stabilizing liquid, the surfactant, to German “humidifier”. The surfactant maintains the wall tension of the alveoli comparable to a bubble, without it the bubbles would collapse and shrink the lungs into a small solid chunk.
The wall of the alveoli is so thin that both oxygen, and carbon dioxide can pass through them. In some lung diseases, thickening of the alveolar walls and thus disorders of the oxygen supply occur. Smoking also leads to inflammatory damage to the alveoli.
Vessels take in the oxygen
From the alveoli, the oxygen passes into the blood vessels of the pulmonary circulation. In turn, carbon dioxide migrates, it is produced by the consumption of oxygen in muscles and organs, back into the alveoli. The pulmonary circulation is also called “small circulation” and serves only the admission and release of the blood gases (oxygen and carbon dioxide) in the lung. The heart pumps “used up”, oxygen-poor blood into the lungs.
There, the blood is enriched with oxygen and flows back to the heart, where it is ready to supply the body again. An interesting detail is that the lungs, in addition to small circuit for gas exchange, like any other organ also has vessels to their own supply.
Bronchitis bring the air into the lungs
In order for the gas exchange to begin at all, about 8 liters of fresh air per minute must be inhaled and exhaled into the lungs at rest. The path of the air leads through the mouth or nose through the throat and larynx into the trachea. It divides into the two main bronchi that supply the left and right lungs and branch out into a framework of ever-smaller bronchi.
After 7 to 8 branches the air is at the target: the alveolus. The wall of the bronchi is also perfectly adapted to its tasks: it carries a so-called ciliated epithelium , which means that the lining cells carry tiny, movable brush hairs. The small brushes keep beating ‘up’, towards the larynx and mouth.
Their task is to intercept inhaled dust particles in front of the alveoli and to transport them back to the larynx on a thin layer of mucus like a conveyor belt. If we clear our throat in the morning and some secretions cough up, the work of the flicker hair becomes recognizable. Many diseases, ranging from influenza infections, are associated with high mucus production. The cilia suffer especially from smoking: on the one hand more dirt particles in the bronchial tubes, which must be laboriously removed, on the other hand, the cimmering cells are gradually based on the poisons of tobacco smoke. Smokers know the problem: The lungs are chronically verschleimt, but a coughing will not succeed because the mucus can not solve.
Arteries and veins carry different blood gases
All living things need oxygen, which is ‘burned’ during metabolic processes. The waste product carbon dioxide is produced. The cells of the human body depend on the supply of oxygen-rich blood through the arteries. The chemical binding of oxygen to the red blood cells changes the color of the blood: arterial blood is bright red. When blood is needed for laboratory testing, the doctor usually removes it from a vein. Venous blood is low in oxygen and dark red or bluish. The veins bring it back from consumers to the heart and lungs. It is important for the pulmonologist to determine the arterial oxygen concentration. For this purpose, he must take blood from an artery in the area of the wrist or the groin.
Carbon dioxide is produced in all burns, in the coal furnace, in the gasoline engine or in metabolism . But this gas is also an important part of the acidity of our body. Chemically, carbon dioxide is the anion of carbon dioxide, and the lung can control the pH of the blood, which is how acid or alkaline a liquid is by releasing or retaining carbon dioxide. If you breathe improperly strong and fast, you release too much carbon dioxide. The result is an increase in the pH in the blood, you become dizzy and sometimes unconscious.
The lung volume is measured in spirometry.
With a strong breath, healthy people can inhale and exhale about five and a half liters of air. This value is called Vital capacity and is slightly higher in men than in women. Basically, there is a setpoint dependent on age, gender, height and weight for each person. Lung diseases can significantly reduce the vital capacity. It should be noted that never all air present in the lungs can be exhaled – a remainder of a little more than a liter always remains as a residual volume.
Vital capacity and residual volume add up the total lung capacity . Not only the fixed volumes, but also the respiratory currents are important measurements in spirometry. Peak Flow and Forced Expiratory Volume ( FEV1) give the pulmonary doctor information about the ability of a person to breathe in and out of an efficient manner. The respiratory limit value describes the maximum ventilated air volume per minute, based on 30 breaths per minute men should reach 110 liters and women 100 liters.
Datasheet of the lung
|Total capacity||7.0 liters||6.2 liters|
|Vital capacity||5.6 liters||5.0 liters|
|Residual||1.4 liters||1.2 liters|
|FEV1||4.5 liters||4.0 liters|
The respiratory muscles
Nobody has to think to breathe. Without our conscious perception, the respiratory muscles are in constant motion. A separate respiratory center in the brainstem controls the motor function of the muscles involved in breathing. At rest, the diaphragm , a flat muscle plate that also acts as a border between the rib cage and the abdominal cavity, provides the bulk of the work of breathing. As it contracts, the thoracic cavity becomes larger and air is inhaled into the lungs. The exhale takes place at rest without muscle work – the diaphragmatic tension decreases and the breathing air can escape.
The muscle fibers between the bony ribs are also involved in the respiratory movements. For greater effort, such as in sports, but also when illnesses make breathing difficult, the respiratory aid muscles are used. Muscles of the abdominal wall and neck are especially helpful in increased exhalation. Proper breathing technique is very important for lung patients. Many people breathe ‘wrong’, they lift the shoulders and chest excessively when inhaling deeply, thus reducing their lung capacity. Proper breathing involves the gut: a good example is the observation of opera and concert singers.
They achieve their often unbelievably long breath by skillful breathing technique, with each breath a strong movement of the belly can be recognized, while the shoulders remain calm. Respiratory training for the sick is offered by the physiotherapy , in some cases even with singing exercises that make the learning success for everyone recognizable and audible.
Oxygen means life
Oxygen, called by the chemist O2, is a colorless and odorless gas, it accounts for about 26% of our breathable air. Most of the remainder is nitrogen and the rare noble gases and is not involved in combustion processes. Only a very small proportion, which is growing due to the increase in industrial, household and traffic burns, is carbon dioxide. Pure one hundred percent oxygen is dangerous and harmful to living things.
Its presence causes otherwise moderate burns to explode. Many people with pulmonary disease, on the other hand, depend on a moderate accumulation of oxygen in their breathing air and carry their own breathing masks and gas bottles with them. All living beings, from unicellular organisms to humans and animals, depend on oxygen for their metabolism. Natural history, the ability to absorb oxygen very much limits the size and development of living things.
Only animals with specialized respiratory organs such as gills or lungs can become tall and competitive. Insects do not have powerful respiratory organs, they draw their oxygen through a network of cavities that grows through their bodies. That’s one reason why these otherwise successful creatures always stay so small. If they had lungs like humans, we would have to reckon with man-sized ants like from a science-fiction movie.