Raylan was riding his horse across in the back woods of kentucky. his horse was startled by a harmless garter snake on the path and raylan was thrown off his horse. he hit his thoracic cage hard on a fallen limb. his ribs hurt but he thought he could make it home. as he continued his ride, breathing became more and more difficult. once home, he experienced sharp chest pains, with great difficulty breathing. he was rushed to the hospital and the doctors suspected a pneumothorax. what is a pneumothorax? why is the fluid bond between the parietal pleura and visceral pleura so important in ventilation? explain what pressures are involved.