A key process in surfactant secretion is exocytosis of LB, and there have been several ultrastructural observations of lamellar material passing from AT II cells into alveoli (reviewed in ref.
In one general practice sample, costochondritis, also known as costosternal syndrome and anterior chest wall syndrome, was the most common specific cause of anterior musculoskeletal chest pain, with a prevalence of 13%.
1 Injury to the chest wall. You can have a crushing injury to your chest wall from a motor vehicle accident or a fall. This can set up sharp pain under left breast that may mean you have fractured a rib or sprained the muscles of the chest wall itself.  Chest wall inflammation.