Pulmonary Surfactant. The force of surface tension in the lungs is so great that without something to reduce the surface tension, the airways would collapse after exhalation, making re-inflation during inhalation much more difficult and less effective. Collapse of the lungs is called alectasis.
Rules for Using Semicolons. A semicolon is most commonly used to link (in a single sentence) two independent clauses that are closely related in thought. When a semicolon is used to join two or more ideas (parts) in a sentence, those ideas are then given equal position or rank. Some people write with a word processor; others write with a pen or pencil. Use a semicolon between two independent clauses that are connected by conjunctive adverbs or transitional phrases.
In most cases, we mark the end of a main clause (or sentence) with a period. However, a semicolon may be used instead of a period to separate two main clauses that are closely connected in meaning or that express a clear contrast. Examples:  1 I never vote for anyone; I always vote against..