BIOL 221 Lecture 7: TOPIC 7 -17
3 Mar 2020
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Document Summary
Surfactant (lipoprotein secreted by type ii pneumocytes) Production begins around 24 weeks in utero, not enough until 27 weeks. Respiratory distress syndrome (rds; a. k. a. hyaline membrane disease of the newborn) Alveolar surface tension is due to the presence of a thin film of water in the alveoli. This surface tension tends to cause collapse of the alveoli. Surfactant is a lipid secreted by type ii pneumocytes. Production begins around the 24th week in utero (in the uterus during fetal development). Not enough is produced until about the 27th week. A fetus born before that time will often suffer from respiratory distress syndrome (rds), also called hyaline membrane disease of the newborn. Diaphragm and external intercostal muscles relax; lungs recoil. Expiration during eupnea results from relaxation of the inspiratory muscles, which is a passive process. The lungs recoil as does the thoracic wall. Thoracic volume decreases and intrapleural pressure increases. The lungs are compressed and the intrapulmonary pressure increases.
