Lungs – structure, function, diseases

What are the lungs?

The lungs are one of the most important organs in the human body. It supplies our body with the vital oxygen that all body cells need in order to function. Our respiratory system consists of a right and a left lung. Both lungs are connected to the windpipe (trachea) via the main bronchi. The air we breathe enters the lungs through the mouth, nose and throat. Our physical performance depends largely on the functionality of our lungs and heart.

Where are the lungs located?

The lungs lie – well protected by the ribs and the chest wall – in the rib cage (thorax). The left lung is slightly smaller than the right to make room for the heart, which is slightly shifted to the left. The lower part of the lung borders on the diaphragm, which separates the chest cavity from the abdominal cavity. The upper part extends to just below the collarbone.

Structure of the lungs: Anatomy of the airways

The anatomy of the lungs is reminiscent of an upside-down tree. The trunk is formed by the windpipe (trachea). It branches into two main bronchi, which open into the two lungs. These main bronchi are further subdivided into smaller bronchi and bronchioles, which ultimately end in the alveoli.

The structure of the airways at a glance:

Lungs and lobes distribute air

The two lungs are divided into several lobes. The right lung has three lobes, the left only two due to the position of the heart. These lobes are separated from each other by fine layers of tissue and ensure that the inhaled air is distributed evenly.

Structure of bronchi and bronchioles: the airways of the lungs

The inhaled air enters the two main bronchi via the trachea. They each lead into one of the two lungs. From there, the main bronchi branch out into smaller and smaller bronchi and finally into the fine bronchioles. The bronchial tubes not only distribute the air further, they also trap foreign bodies and pathogens.

Pulmonary alveoli: Function and structure

The alveoli are located at the end of the bronchioles. The tiny air-filled vesicles are surrounded by a dense network of fine blood vessels (capillary network). This is where the actual gas exchange takes place in the lungs. The approximately 300 million alveoli absorb oxygen from the air we breathe in. It migrates through their thin wall into the surrounding blood vessels and thus enters the bloodstream. At the same time, these capillaries release carbon dioxide – a metabolic waste product – from the blood into the alveoli. The superfluous carbon dioxide leaves our body with our exhaled air.

Pleural cavity and pleura function for the lungs

The entire lung is surrounded by a thin, smooth and moist layer of tissue, the pleura visceralis. The rib cage is also lined with such a layer, the parietal pleura. The pleura and pleura form the pleura.

Between the pleura and the pleura is the so-called pleural cavity, in which there is a thin film of fluid. It connects the lungs and chest and at the same time allows them to move. The thin film of fluid in the pleural cavity ensures that the lungs and chest can slide past each other smoothly when breathing. Negative pressure in this area prevents the lungs and chest from separating. Without the pleural cavity, the lungs would not be able to follow the expanding ribcage during inhalation – and breathing would be impossible.

As described above, the main task of the lungs is to absorb oxygen from the air and excrete the waste product carbon dioxide. It also has other important tasks.

Lung tasks: How do the lungs work?

• Function of the alveoli: The main function of the lungs is to absorb oxygen from the air we breathe into the blood and to release carbon dioxide from the blood into the exhaled air.
• Lung function – regulation of the acid-base balance: Carbon dioxide is a waste product of metabolism and acts as an acid in the blood. When the CO₂ content in the blood increases, the blood becomes more acidic (the pH value decreases), and when the CO₂ content decreases, the blood becomes more alkaline (the pH value increases). The lungs help to keep the pH value of the blood in the optimum range by exhaling excess carbon dioxide.
• Bronchial function: The tasks of the bronchi are varied. For example, they filter pollutants, larger dust particles and pathogens from the air. Cells of the lung tissue such as the cilia and special cells of the immune system help to remove dust, bacteria and other particles. We then either cough these up or they are removed from the lungs with the mucus.
• Important lung function – thermoregulation: The lungs help to regulate body temperature by warming or cooling the inhaled air before it enters the body.
• Blood pressure regulation: In the pulmonary vessels, the hormone angiotensin I is converted into angiotensin II, which plays a role in blood pressure regulation.
• The tasks of the diaphragm and the respiratory muscles for the lungs: The diaphragm and the respiratory muscles between the ribs play a central role in breathing. When you inhale, the diaphragm contracts and moves downwards. This expands the chest and the resulting negative pressure draws air into the lungs. The diaphragm relaxes as you exhale. The chest contracts and the air is expelled from the lungs again.

What does the body need oxygen for?

Oxygen ensures that our organs and all cells can perform their tasks. It is the fuel of our body and drives it through so-called cellular respiration, which takes place in the mitochondria, the “power plants” of the cells.

Here are the key points why oxygen is so important:

• Energy production: We need oxygen to convert nutrients such as glucose into energy (in the form of adenosine triphosphate, ATP). This energy boosts all cellular processes such as muscle movement, digestion and the functioning of the nervous system.
• Maintaining vital processes: Organs such as the brain, heart and muscles constantly require oxygen in order to function. Our brain can only survive for a few minutes without oxygen.
• Support of cell functions: Oxygen is essential for the repair and renewal of cells, for the immune defense and the formation of proteins.

Lungs - diseases and infections

There are a variety of lung diseases that have different causes. All lung diseases can vary in their severity and symptoms. If you experience unusual breathing difficulties or prolonged symptoms, it is advisable to consult a doctor.

What lung diseases are there?

Asthma

Bronchial asthma is a disease of the airways that can lead to sudden shortness of breath. In some patients, the airways react sensitively to allergens and other stimuli, which should be avoided if possible. If this is not possible, there are various effective ways to treat this shortness of breath. The disease can usually be controlled well.

• Asthma – Drug treatment

Bronchiectasis

Bronchiectasis are permanent dilatations of the bronchi and small bronchioles. They can be congenital or develop over the course of a lifetime. Frequent triggers are repeated lung infections and chronic lung diseases such as cystic fibrosis. Typical symptoms of bronchiectasis are coughing, often with sputum, shortness of breath, recurrent lung infections and persistent fatigue.

Chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) leads to progressive and permanent damage to the lungs. Non-smokers are much less likely to suffer from this disease than smokers. The trigger is considered to be the inhalation of harmful substances, but above all the smoking of tobacco. Although COPD cannot be cured, various therapies can be used to alleviate the course of the disease, improve quality of life and extend life expectancy. If the disease is detected early, its progression can be slowed down.

• Here you can find out how we treat COPD at the USZ
• Home exercise tips for people with COPD

Long COVID of the lungs (pulmonary long COVID)

Pulmonary long COVID refers to persistent lung symptoms following a COVID-19 infection. Typical symptoms are shortness of breath, chronic coughing, reduced performance and sometimes chest pain. There is no standardized treatment yet. The USZ offers an interdisciplinary Long COVID consultation.

Lung abscess

A lung abscess occurs when pus accumulates in a cavity in the lung. This is often caused by bacteria that enter the lungs from the mouth and throat via the air we breathe. Germs that spread through the bloodstream can also cause an abscess. In most cases, doctors successfully treat a lung abscess with antibiotics so that it usually heals completely.

Lung cancer

Lung cancer is one of the most common forms of cancer and affects millions of people worldwide. There are around 5000 new cases in Switzerland every year. Lung cancer can severely impair quality of life. The earlier lung cancer is detected, the better the treatment options and chances of recovery.

• To the Lung and Thoracic Oncology Center

Pulmonary embolism

Pulmonary emb olism is a potentially life-threatening condition: a blood clot blocks the pulmonary vessels during a pulmonary embolism. The clot is often caused by a thrombosis in the pelvic or leg veins and travels from there to the lungs.

• More on the treatment of pulmonary embolism

Pulmonary emphysema (smoker’s lung)

Pulmonary emphysema is an irreversible destruction of the air sacs (alveoli) in the lungs and leads to agonizing shortness of breath. It usually occurs together with chronic obstructive pulmonary disease (COPD). The main cause of COPD and emphysema is smoking.

• Stop smoking consultation

Pneumonia (lung inflammation)

Pneumonia often begins with a seemingly harmless cough, but can quickly turn into a dangerous illness. Elderly people, babies and people with a weakened immune system are particularly at risk – but healthy people can also fall ill. The most common symptoms are a purulent cough, physical weakness and fever. It is treated with antibiotics and symptomatic, anti-inflammatory therapies. The good news is that in most cases the therapy brings relief, even if recovery requires a few days of patience.

Pulmonary fibrosis

Pulmonary fibrosis occurs when scar tissue forms in the lungs, often as a result of prolonged inflammation. Various diseases and pollutants can promote the development of pulmonary fibrosis. If the cause is unknown, it is referred to as idiopathic pulmonary fibrosis (IPF). Pulmonary fibrosis in the early stages usually begins with shortness of breath during physical exertion: It often develops over years without any other noticeable symptoms and eventually leads to chronic coughing, shortness of breath even at rest, reduced exercise capacity, severe oxygen deficiency and, in the worst case, death. There is hope for drug treatment options that have been approved for certain forms of pulmonary fibrosis.

• More about pulmonary fibrosis treatments

Pleural empyema

Pleural empyema is an accumulation of pus in the pleural cavity between the pleura and the pleura. It often occurs as a result of pneumonia, in which bacteria infect the pleura and penetrate the pleural cavity. Typical symptoms are high fever, shortness of breath and chest pain.

Pulmonary hypertension (PH)

Pulmonary hypertension is elevated blood pressure in the pulmonary circulation. It can occur without a recognizable cause or be associated with various diseases. Typical triggers are also common heart and lung diseases such as chronic heart failure, chronic obstructive pulmonary disease (COPD) or previous pulmonary embolisms.

• More on therapy for pulmonary hypertension

Sarcoidosis (Boeck’s disease)

Sarcoidosis is an inflammatory disease that can be acute or chronic. It can affect almost all organs of the body and impair their function. The disease is characterized by the formation of granulomas, small nodular accumulations of inflammatory cells. The lungs and lymph nodes are particularly frequently affected.

Sleep apnea

Snoring itself is not dangerous. Only when breathing stops at night do doctors speak of sleep apnea. It often occurs in men between the ages of 40 and 70. Five percent of all men suffer from sleep apnea, and three percent of women are also affected. Researchers distinguish between different forms of apnoeic snoring: the most common form is obstructive sleep apnoea (OSA for short). In contrast to “normal” snoring, apneic snoring is not harmless. It increases the risk of other diseases and can severely impair quality of life.

• Snoring and sleep apnea treatments

Tuberculosis

Tuberculosis is still one of the most important infectious diseases that continues to claim lives worldwide. Although it is diagnosed less frequently in Europe, it has by no means been eradicated. The disease usually occurs as pulmonary tuberculosis and can be successfully treated if detected in time. Despite intensive research, there is still no effective vaccination against pulmonary tuberculosis.

• More on the treatment of tuberculosis

Cystic fibrosis

Cystic fibrosis is a congenital metabolic disease and one of the most common hereditary diseases. It is usually diagnosed in the first year of life. Those affected struggle with thick mucus in the lungs and often also suffer from digestive problems. Although cystic fibrosis cannot be cured and shortens life expectancy if left untreated, there are now good treatment options thanks to proven and new therapies that enable those affected to enjoy a significantly higher quality of life and a longer life expectancy.

Here are some tips for laypeople and those affected on keeping the lungs healthy:

• Do not smoke: Avoid cigarettes, e-cigarettes and other tobacco products, as they pose the greatest risk to the lungs. Smoking increases the risk of lung cancer, COPD and other serious respiratory diseases.
• Get some fresh air: spend time outdoors every day to supply your lungs with fresh oxygen. Walks in the countryside or in less polluted areas are particularly beneficial.
• Regular exercise: sports such as jogging, cycling or swimming improve lung function and train the respiratory muscles. Daily exercise such as walking can also help.
• Protection from harmful substances: Avoid contact with fine dust, chemicals, exhaust fumes or polluted air. Wear suitable respiratory masks when working in a contaminated environment.
• Pay attention to indoor air quality: Ventilate regularly to keep the indoor air fresh. Use humidifiers or plants to balance the humidity and avoid pollutants such as smoke or vapors from cleaning agents.
• Healthy diet: Eat plenty of fruit and vegetables that are rich in antioxidants and vitamins, such as apples, berries and leafy vegetables. These support the health of the lungs and strengthen the immune system.
• Sufficient fluids: Drink enough water to keep the mucous membranes in the lungs moist and make it easier to cough up mucus.
• Prevent infections: Get vaccinated against flu, pneumonia and COVID-19 to avoid respiratory infections. Wash your hands regularly and avoid close contact with people who have a cold.
• Early treatment: Take symptoms such as a persistent cough, shortness of breath or chest pain seriously and consult a doctor at an early stage so that possible illnesses can be treated in good time.
• Reduce stress: Chronic stress can also put a strain on the airways.