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.
CLEVELAND, Ohio -- The first day of spring 2017 will be March 20, with winter officially ending at 6:28 a.m. that day. Summer 2017 will begin on June 21, fall on Sept. 22 and winter on Dec. 21. The first day of spring and fall each year marks the point when the length of days and nights are approximately equal everywhere on Earth. In Cleveland, day and night will each last very close to 12 hours a little ahead of the start of spring, on March 17, according to the U.S. Naval Observatory.