To know about the types of lung cells, one must first know about the functioning of the lungs.Our lungs are vital respiratory organs. They help in transporting the oxygen which has been taken in by us from our atmosphere and help in releasing the carbon dioxide with the help of various types of lung cells called alveoli. Alveoli, is a word which is taken from Latin and it means ‘little cavity’. Thus, in lungs it has a structure which appears to be like cavity, so that the exchange can take place easily.
There are mainly three types of lung cells in alveoli which help in performing this function and they are: Type 1 Epithelial Cells, Type 2 Epithelial Cells and
Alveolar Macrophage. Apart from this, there even exists Capillary Endothelial Cells which are placed between where the gasses are exchanged in the lungs. Their primary function is to prevent the formation of air bubbles in the blood, and also prevent blood from entering into the alveoli.
Type 1 Epithelial Cells are also known as squamous alveolar Cells and these types of lung cells make for the alveolar wall. These cells form almost 95% of the surface occupied by alveoli. These cells are devoid of organelles like Golgi Apparatus, Mitochondria, and thus the cytoplasmic plates around these cells help in providing an easy exchange for the oxygen and carbon dioxide gasses to pass through. The wall formed by them is so thin and is of just 25nm that most of the time, you will require a microscope to see this thin wall of epithelial cells. Since, these cells are not able to replicate and are prone to damage, Type 2 cells provide support to Type 1 cells.
Type 2 Epithelia Cells are also known as great alveolar cells and occupies the rest of the space in alveoli. Since, these cells are in the shape of cuboid, they are even called cuboidal cells. They are those types of lung cells which are generally found in the blood-air barrier. The main function performed by these cells is to form a lipoprotein complex which is generally known as, pulmonary surfactant. This surfactant helps in differentiating air and water and thus with the help of adsorption of this, it reduces surface tension, and thereby, helps in increasing the capability and process of the exchange between gasses. Apart from this, the surfactant helps in replacing the damaged Type 1 cells as well, and keeps them moist too.
Alveolar Macrophage is also known as dust cells. These types of lung cells provide a defensive mechanism against the toxic or foreign substances. The air which we inhale may contain harmful substances and these may enter through trachea, larynx, or bronchioles, and may harm the epithelial cells which cover the whole passage. When these toxic substances are able to pass through these as well, then macrophage tends to neutralize their effect and tends to kill them. They , then, release into our body, various types of secretary products with the help of surface receptors. Since, our lungs and even the Type 1 as well Type 2 are prone to damage, these macrophages are kept in an inactive state and try to prevent the inflammation which is uncontrolled.