ANIMAL PHYSIOLOGY
GAS EXCHANGE IN HUMANS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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ribs and sternum move up and out
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diaphragm moves down/ flattens
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External intercoastal muscles relax
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diaphragm contracts
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width of thorax increases
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Detailed explanation-1: -Expiration is a process in which air is drawn out of the lungs. During expiration, the external intercostal muscles relax, and the ribs move downwards and inwards.
Detailed explanation-2: -During normal expiration, the external intercostals together with the diaphragm relax. Everything happens in reverse compared to inspiration. The intrathoracic volume decreases, intrapulmonary pressure increases and air is expelled from the lungs.
Detailed explanation-3: -During expiration, the diaphragm and intercostals relax, causing the thorax and lungs to recoil. 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-4: -The intercostal muscles relax while the lungs are expanding, allowing them to fill up with air. When an organism breathes out, the intercostal muscles contract to put pressure on the lungs and help drive the air out.
Detailed explanation-5: -The diaphragm is drawn down and the ribs flared by the external intercostal muscles to increase the thoracic volume. The negative pressure created draws air into the lungs through the upper respiratory tract. In expiration the relaxing muscles allow the ribs to fall back and the diaphragm rises.