Changing concepts of the mechanism of pulmonary atelectasis. A study of smooth muscle elements in the human lung.
This study is an attempt to challenge the generally accepted concept that the human lung is merely an elastic sponge with no musculature existing beyond the terminal bronchioles. Photomicrographs of human lung tissue taken in situ, and specifically stained, reveal minute smooth muscle fibers in the most distally located portion of the air passage including alveolar sacs. While such smooth muscle elements are present in the normal lung tissue, a marked increase of these structures is noted in the lungs of individuals with bronchitis, emphysema, and, particularly, pulmonary hypertension. The existence of alveolar musculature can explain the ability of the human lung to contract actively, as may be the case in nonobstructive pulmonary collapse or "contraction atelectasis."
By the methods of literature study and interview,the paper analyzes the characteristics and defects of the courses PE Health and PE Fitness in the first and second curriculum reforms in Shanghai and looks into the future tendencies of the school PE curriculum reforms in Shanghai.