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.
In the astronomical calendar, summer begins on the June equinox â the point at which the Northern Hemisphere is tilted closest to the sun and the days are at their longest during the year. The summer solstice falls on June 21 this year, but the date varies from year to year, falling as early as June 20 or as late as 22 June. Since summer (and other seasons) can begin and end on different days each year on the astronomical calendar, it can be hard to compare seasons from year to year in this way. To standardize the length and start of the seasons, in meteorology, the 12 months of the year have been split up into four, 3-month periods. Therefore, in the meteorological calendar, summer includes the months of June, July and August - always starting on 1 June and ending on 31 August.