2 also called pulmonary surfactant. one of certain lipoproteins that reduce the surface tension of pulmonary fluids, allowing the exchange of gases in the alveoli of the lungs and contributing to the elasticity of pulmonary tissue.or example, if a drop of detergent is added to a drop of water, the detergent reduces the surface tension and the drop of water flattens out. In the lungs, surfactant reduces the surface tension and helps to maximize the surface area available for gas exchange.
The First Day of Summer 2016 (Summer Solstice) is on Monday, June 20. The First Day of Summer 2017 (Summer Solstice) is on Wednesday, June 21. The First Day of Summer 2018 (Summer Solstice) is on Thursday, June 21. The First Day of Summer 2019 (Summer Solstice) is on Friday, June 21. The First Day of Summer 2020 (Summer Solstice) is on Saturday, June 20.
The official start of summer in Australia is December 1st. It  finishes on 28 February or 29 February in a leap year. Australian summer starts on the 1st December and goes til 28th/29th Februrary. December,January,And Feburary The summer months in Australia are December, January, and February.