Alveolar epithelium which is present in adult lungs represents a physical barrier that provides protection from environmental insults. This is done by the segregation of inhaled foreign agents and the regulation of ions and water transport. So, Alveolar epithelium contributes to the maintenance of the fluid balance on the alveolar surface. It is made up of two main types of cells, and they are:
- Alveolar Type I
- Alveolar Type II
And, the answer to the question of which type of alveolar cells can secrete or produce Surfactant is Alveolar Type II.
A brief expansion of the question and the answer mentioned above have been provided next. So, read on to know more.
About Surfactant
Surfactant, not to be confused with a biodegradable surfactant, is also known as Pulmonary Surfactant. It can be defined as a lipoprotein material secreted from Alveolar Type II cells and mainly consists of some glycoprotein components and dipalmitoylphosphatidylcholine. The first and foremost function of it is the reduction of surface tension in the alveoli of the lungs. Some other major functions of it are as follows:
- It is responsible for keeping the alveoli dry
- It can help by reducing the work of breathing
- The size of the alveolar is stabilized by it
- In the lung volume-pressure curve it can cause the hysteresis
Alveolar Type II Cells Producing Surfactant
Alveolar Type I and II cover the alveolar surface area, and the ratio is 95% and 5% respectively. Even though Type II cells are fewer in comparison, they contain 15% of peripheral lung cells. Besides producing Surfactant, Type II cells are responsible for the reformation of the alveolar epithelium if the very sensitive Alveolar Type I cells are damaged somehow. From the apical surface, the cells are also known for transporting fluid and sodium into the interstitium. They also play a key player in innate immunity.
The Function Of Lipogenesis
When the Type II cells produce pulmonary surfactant, the secreted surfactant offers low surface tension in the lung’s distal Amine Gas Treating exchange units. Because of this, it is also capable of decreasing the work of breathing. According to many studies, it has anti-inflammatory and antimicrobial properties along with the capability of preventing pulmonary edema.
After Synthesis Of Surfactant Produced By Alveolar Type II Cells
Surfactant is synthesized in different compartments of the Alveolar Type II cells’ endoplasmic reticulum. After the synthesis, it gets assembled into lamellar bodies in the cytosol. When the lamellar bodies are secreted into the alveolar lumen, they get transformed into the surfactant’s extracellular form known for having tubular myelin which is a quadratic lattice structure. The tubulin myelin at the air-liquid crossing point spreads in a monolayer and this leads to the reduction of the surface tension. The endocytosis and uptake seen in the Alveolar Type II cells are responsible for recycling surfactant.
The synthesis of surfactants is dependent on several factors which include thyroid hormones, catecholamine (functioning through β-adrenergic receptors and cAMP), glucocorticoids, androgens, estrogens, cytokines, and growth factors.
The Role of Surfactants in Host defense against Pulmonary Infection and Lung Disease is a major one. It is highly necessary as during breathing it can prevent atelectasis. Thus, its proper production by Alveolar Type II cells is required to achieve optimal conditions.
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