Question

describe the process of inhalation and exhalation with regard to the contraction of the diaphragm – which is an active process and which is passive?

Answer 1

Inhalation is the process of taking air into the lungs. For this to occur, the air pressure inside the lungs must be lower than that of the external atmosphere as air flows from areas of higher pressure to lower pressure. This is achieved by the contraction of the external intercostal muscles and the relaxation of the internal intercostals which acts to pull the ribcage upwards and outwards, hence, increasing the volume of the thoracic cavity. The diaphragm also contracts to extend the cavity further downwards. Due to the function of the pleural membrane, the size of the lungs is increased which, in turn, creates an area of lower air pressure inside the lungs; hence, air is drawn into the lungs.

Exhalation is the process of expelling air out of the lungs. For this to occur, the air pressure inside the lungs must be higher than that of the external atmosphere as air flows from areas of higher pressure to ones of lower pressure. This is achieved by the relaxation of the external intercostal muscles which bring the rib cage inwards and the diaphragm bulges upwards (recoiling to its original shape) respectively. The internal intercostal muscles contract so as to pull the rib cage further inwards, hence, decreasing the volume of the thoracic cavity and that of the lungs which, in turn, creates high pressure in the lungs; hence air is pushed out of lungs. In passive breathing, the movements of the diaphragm are responsible - the ribs aren't needed.


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Answer 2

exhalation is generally passive, while inhalation is active.