Surfactant is produced in the developing babies lungs. In week 35 most babies have enough to have fully functional lungs. It consists of fosfolipids and proteins. The proteins have antibacterial properties. The fosfolipids reduce the surface tension in the alveoli. When we exhale, the surfactant concentrates which decreases surface tension and prevents the alveoli from collapsing. When we inhale, the surfactant dilutes which increases the surface tension. This mechanism helps even out alveoli size during breathing, which allows for maximum oxygenation.
