Briefly differentiate between atmospheric pressure,intrapulmonary pressure, and intrapleural pressure. Which of theseis always negative in a healthy individual during normal breathing?What happens if intrapleural pressure becomes equal to atmosphericpressure? The contraction of the diaphragm and the externalintercostal muscles begins inspiration. Explain exactly whathappens, in terms of volume and pressure changes in the lungs, whenthese muscles contract. What is the functional significance of thepleural fluid during inspiration?
