Unless intra-alveolar pressure changes as shown in Fig 9-4, air cannot move into the alveoli of the lungs and oxygen and carbon dioxide cannot be exchanged between the air and blood. Specifically, alveolar pressure must (increase or decrease) to a level (Higher or Lower) than (atmospheric or intrathoracic) pressure in order to cause inspiration.

PULMONARY PHYSIOLOGY

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

A	decrease lower atmospheric
B	increase higher atmospheric
C	decrease higher intrathoracic
D	None of the above

Explanation:

Detailed explanation-1: -The air pressure within the lungs increases to above the pressure of the atmosphere, causing air to be forced out of the lungs.

Detailed explanation-2: -Contraction and relaxation of the diaphragm and intercostals muscles (found between the ribs) cause most of the pressure changes that result in inspiration and expiration. These muscle movements and subsequent pressure changes cause air to either rush in or be forced out of the lungs.

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