Lecture on Surface Tension

Introduction to Surface Tension

• Surface tension is a force produced by water molecules.
• It can prevent objects like coins from sinking.
• Water forms a domed or droplet shape due to surface tension.

Water Molecules and Polarity

• Water molecules have a slight negative charge on one side and a slight positive charge on the other.
• These charges make water molecules polar.
• Polar covalent bonds form between water molecules, characterized by partial sharing of electrons.

Surface Tension in the Respiratory System

• Surface tension plays a role in the lungs, specifically in the alveoli.
• Alveoli are tiny sacs in the lungs that exchange oxygen and carbon dioxide with the blood.
• They are spherical and form clusters, lined with mucus.
• The curved surface of alveoli produces surface tension.

LaPlace's Law

• Describes the relationship between gas pressure needed to balance surface tension and the radius of a sphere.
• Gas pressure must balance the collapsing force of surface tension.
• Smaller alveoli radius results in larger balancing pressure, which works to collapse the alveoli.

Role of Surfactant

• Surfactant is secreted by type 2 cells lining the alveoli.
• It reduces surface tension, preventing alveoli collapse.
• As long as surfactant-secreting cells are healthy, alveoli remain inflated.

Conclusion

• Surface tension is crucial in various natural phenomena, including respiratory function.