Question

Which of the following is true regarding negative pressure breathing to pull air into the lungs of mammals? (more than one answer may apply) The diaphragm relaxes to increase lung volume Rib muscles contract to increase lung volume The diaphragm contracts to increase lung volume

Answer 1

Ans:-Rib muscles contract to increase lung volume , The diaphragm contracts to increase the lung volume.

Explanation:-Mammals use negetive pressure breathing that means they use their diaphragm to create low pressure within their lungs.during negetive pressure breathing diaphragm and rib muscles contract.contraction of diaphragm made it to move down and contraction of rib muscles made it to move up this causes lungs to expand which in result create a low pressure inside the lungs.At last Air is pull into the lungs.so,the last 2 options are correct.

During expiration the diaphragm relaxes and there is decrease in volume of thoracic cavity . there is increase in pressure which result in contraction of lungs ,the the contraction of lungs force the air to expire.so,option 1(The diaphragm relaxes to increase lung volume) is incorrect as it occur during expiration not in inspiration.