Pulmonary alveoli, also called alveoli or alveoli, are an essential part of the respiratory system that plays an important role in the breathing process.
Here are more details about it:
What are the pulmonary alveoli?
The alveoli are very small air sacs found in the lower respiratory tract, a group of sacs that form together into grape-like structures that are inflatable, and can expand and contract during inhalation and exhalation.
In general, the lower respiratory system consists of the trachea , which branches into two tubes known as the bronchi, where one of these tubes connects to the right lung and the other to the left lung.
Inside the lungs, the bronchi branch into smaller tubes called bronchioles, where the ends of these bronchioles are connected to hundreds of millions of lung alveoli by alveolar ducts.
Installation of the walls of the alveoli of the lungs
The alveoli are surrounded by a network of small blood vessels called pulmonary capillaries, which have a thin, flexible wall.
In general, the walls of the pulmonary alveoli consist of two main types of very thin epithelial cells , which include the following:
1. Type I pneumocytes
They are flat cells that cover most of the outer surface of the pulmonary alveoli, which is the barrier responsible for the process of gas exchange between the alveoli and the capillaries.
2. Type II granular pneumocytes
They are smaller than type I lung cells and are responsible for secreting fatty substances that help reduce the surface tension of the alveolar wall to facilitate gas exchange.
It is worth noting that the inner cavity of the pulmonary alveoli contains another type of cells called alveolar macrophage, which are movable phagocytic cells, and their function is to swallow foreign bodies that enter the lungs, such as: bacteria, carbon particles, damaged blood cells, and dust.
pulmonary alveolar function
The alveoli are the last part of the lower respiratory tract in which inspiratory air settles, and in which the exchange of oxygen and carbon dioxide between the air and the bloodstream takes place.
Thus, the process of gaseous exchange between blood and air is the primary function of the alveoli, where the alveoli give the blood oxygen and take carbon dioxide from it.
gas exchange process
When a person breathes, during the inhalation process, the air moves from the upper respiratory tract, which is the nose or mouth, through the trachea, then to the bronchi, and then reaches the alveoli in the lungs.
Alveoli and capillaries both have a common membrane called the air-blood barrier, which allows gases to pass freely from the alveoli to the capillaries and vice versa.
When the inhaled air reaches the alveoli, the capillaries take oxygen from the air in the alveoli and combine it with red blood cells, then transport it to the bloodstream and then distribute it to all body tissues.
In turn, the alveoli collect carbon dioxide from the capillaries, and excrete it outside the body during the exhalation process.
Normally, about 0.3 liters of oxygen is transferred from the alveoli into the blood, and a similar amount of carbon dioxide is excreted from the blood into the alveoli per minute.
Diseases affecting the pulmonary alveoli الرئوي
Like all other organs of the body, the alveoli can be exposed to some kind of damage, and this damage can affect their vital function, which in turn may lead to the occurrence of multiple respiratory problems, the most prominent of which are:
1. النفاخ (Emphysema)
It is an irreversible damage to the walls of the alveoli, which leads to a decrease in the efficiency of the gas exchange process and thus difficulty in breathing, and this disease usually results from many reasons, including: smoking, environmental pollutants, or as a result of some genetic factors.
2. Pulmonary Alveolar Proteinosis
It is a rare lung disease that causes blockage of the alveoli due to the accumulation of some fluids containing fatty and protein substances, and this disease usually causes difficulty breathing.
3. Pulmonary alveolar microlithiasis
It is a lung disorder that occurs as a result of the deposition of small stones consisting of the accumulation of a compound called calcium phosphate, which causes damage to the alveoli, causing multiple respiratory problems, including: persistent cough and shortness of breath.
4. Other diseases
There are other diseases that can affect the function of the alveoli, including the following:
- Pneumoconiosis is a group of problems caused by inhaling coal dust.
- acute respiratory distress syndrome ;
- Pulmonary edema.
- Lung cancer .
- Chronic obstructive pulmonary disease.