Surfactant: The primary key to life

The Surfactant is a surface-acting complex material or component that is in charge of bringing down the surface tension of a fluid. The complex is amphiphilic (i.e. it contains both hydrophobic and hydrophilic groups), making it preferably suited as a surface-active material to diminish surface tension at the air-liquid interface in the alveoli during the respiratory cycle. It is emitted via the lung alveoli.
The Surfactant turns away alveolar fall at low lung volume and moderates bronchiolar patency in the midst of typical and constrained breaths.  Likewise, it is associated with the protection of the lungs from injuries and diseases caused by breathed in particles and micro-organisms (immunological, non-biophysical capacities. The nearness of such iotas with surface activity had been suspected since the mid-1900s and was finally asserted in the mid-1900s. From the point forward, the chemical, physical and biological properties of the surfactant blend have been uncovering because of crafted by a few gatherings of agents.

Sources :

It is radiated by exceptional surfactant-discharging epithelial cells called type-II alveolar epithelial cells, which constitute around 10% of the surface zone of the alveoli. These cells are granular, containing lipid inclusions that are emitted by the surfactant into the alveoli.

Generation of lung surfactant:
1. Typical lamellar bodies, membrane bound-organelles containing phospholipid are formed in type-II alveolar epithelial cells.

2. Lamellar body is emitted into the alveolar lumen by exocytosis.

3. Tubes of lipid called tubular myelin(TM) are formed from the lamellar body.

4. Tubular myelin, thusly, forms the phospholipid film.

5. Some of the protein-lipid complexes in surfactant are taken by type-II alveolar cells & reused.

6. Formation of the phospholipid film is greatly facilitated by the proteins in the surfactant. This material contains four unique proteins: SP-A, SP-B, SP-C, and SP-D.

7. Maturation of surfactant in the lung is quickened by glucocorticoid hormones.

Composition:

The Surfactant is a mind boggling blend of a couple phospholipids, proteins, and ions. The most important components are the phospholipid dipalmitoylphosphatidylcholine, surfactant apoproteins, and calcium ions. In quantitative terms, the surface tension of different water fluids is approximately the following:

* Pure water: 72 dynes/cm

* Normal fluid lining the alveoli but without surfactant: 50 dynes/cm

* Normal fluids lining the alveoli and with the normal amount of surfactant included: 5 to 30 dynes/cm.

Biochemical compounds:

1. Dipalmitoylphosphatidylcholine: 62%P
2. Phosphatidylglycerol 5%O
3. Otherphospholipids: 10%N
4. Neutrallipids: 13%P
5. Protein 8%C
6. Carbohydrate 2%

Functions:

The surfactant lessens the surface tension in the alveoli of lung and prevents the collapsing tendency of the lung. It stabilizes the alveoli. Lungs remain collapsed until the birth, the infant makes several strong inspiratory efforts by crying loudly just after birth and the lung expand. Environmental air enters the lung and alveoli start to exchange gases; lung becomes functional. Surfactant prevents the recoil tendency of the lung alveoli and prevents lung collapse again. Surfactant deficiency leads to infant respiratory distress syndrome (IRDS, also known as hyaline membrane disease), the serious pulmonary disease that develops in the infant before their surfactant system is functional.

So having a great role in starting a life; surfactant is called as the primary key to the life.