The alveoli are very small air sacs in the lungs that are vital to the breathing process. In this article, we will learn about it in some detail, its definition, function, the most important diseases that affect it, and the most important advice to avoid harm.

Definition of alveoli

Alveoli are very small air sacs at the end of the bronchioles, where the exchange of oxygen and carbon dioxide occurs during the process of breathing with inhalation and exhalation.

The shape and composition of the alveoli

The alveolus is similar to a small balloon, and it is considered the smallest part of the respiratory system, and it is found in all parts of the lungs in groups, as it is the last part of the branches of the respiratory tree (a term that describes the branches of the respiratory system that transport air from the nose and mouth to the lungs, and includes the trachea, Bronchioles, bronchi, and bronchioles) have very thin walls that allow gas exchange between them and the capillaries.

Alveolar cells

The alveolus consists of two types of cells, each with its own functions, namely:

• Type I pneumocytes: They are the cells responsible for the gas exchange process.
• Type II pneumocytes: They produce a surfactant that prevents collapse of the alveoli, and they switch to Type I to repair any damage, one source notes.
• A type of immune cell called alveolar macrophages: It is responsible for cleaning particles that are inhaled, and getting rid of bacteria and dead cells.

How many alveoli are in the lungs?

The number of alveoli varies from person to person, and their number is estimated at millions. According to one source, their number ranges between 274-790 million, with an average of 480 million.

What is the function of the alveoli?

The alveoli is an important part of the respiration process, which includes:

• Exit and entry of air into and out of the lungs.
• Gas exchange between oxygen and carbon dioxide.
• blood flow to the lungs.

When you breathe, air flows from the nose and mouth into the trachea and then into the bronchi and then into smaller and smaller branches until it reaches the alveoli, where oxygen molecules travel through one layer of lung cells, then through one cell layer in the capillary to enter the bloodstream

As for carbon dioxide – which is a by-product of the process that takes place in cells using oxygen to produce energy – and once oxygen enters the bloodstream, it travels from the capillaries to the alveoli and is then expelled out of the body from the nose and mouth during the exhalation process.

The explanation of the process of gas exchange in the respiratory system is that the concentration of oxygen in the alveoli is higher than that of the capillaries, and the opposite is true for carbon dioxide, as molecules move from the medium of higher concentration to the medium of lower concentration.

How are the alveoli affected?

The alveoli are affected by many factors, of which we mention three main factors: natural aging, diseases, pollution and smoking.

getting old

Aging may affect the respiratory system, as the capacity of the lungs decreases due to the weakness of the chest muscles, and the elderly are at greater risk of developing pneumonia, whether from bacteria or viruses.

Smoking and pollutants

Many sources confirm that smoking harms the lungs and results in many lung diseases such as chronic obstructive pulmonary disease and chronic bronchitis, as smoking causes irritation of the alveoli and bronchioles and damages the lining of the lungs. Over the years, smoke scars the lungs, affecting gas exchange, and this damage is considered permanent.

Follicles may also be affected by pollutants such as secondhand smoke, dust, chemicals, vehicle exhaust, industrial emissions and other pollutants.

diseases

There are many diseases that may affect the alveoli, including:

• Pneumonia: It is caused by infections of all kinds, as the vesicles become inflamed in one or both lungs, and are filled with pus, making breathing difficult.
• Emphysema: It is a chronic disease, and it usually affects those who have a history of smoking, as the patient suffers from lung infections that cause the destruction of the alveoli, which leads to their failure to perform their function properly, as they lose their ability to expand or contract during exhalation, and this results in air confinement.
• Lung cancer: Lung cancer may originate from the alveoli.
• Idiopathic pulmonary fibrosis: The walls around the follicles become scarred and thickened.
• Acute Respiratory Distress Syndrome: It is a life-threatening condition in which fluid builds up in the alveoli, preventing gas exchange.
• Respiratory Distress Syndrome: This condition may appear in premature babies, as they do not have enough surfactants, which means there are fewer spaces for gas exchange to occur.
• Pulmonary edema: It is a condition caused by the accumulation of too much fluid in the lungs where it accumulates in the alveoli, resulting in respiratory failure, a condition in which the oxygen level in the blood becomes low.

How to keep the alveoli healthy

To maintain the health of the alveoli and the respiratory system in general, it is recommended to follow the following tips:

• Try to stay away from sources of pollution by using an air purifier, and wearing a face mask on days when pollutants such as pollen or dusty winds spread.
• Stay away from smoking.
• Doing exercise.
• Eat healthy meals rich in vitamins and minerals.
• Make sure to visit the doctor to check up on general health on a regular basis.
• Maintaining a healthy immune system.