ANIMAL PHYSIOLOGY
GAS EXCHANGE IN HUMANS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Pressure increases and volume decreases.
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Pressure and volume both increase.
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Pressure and volume both decrease.
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Pressure decreases and volume increases.
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Detailed explanation-1: -When the lungs inhale, the diaphragm contracts and pulls downward. At the same time, the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs.
Detailed explanation-2: -Contraction of these muscles raises the rib cage upward and outward, thereby contributing to the expansion of the thoracic cavity and reduction of pressure within the lung, causing air to move from the air into the lungs (see Figure 6.1.
Detailed explanation-3: -During inspiration, the diaphragm and external intercostal muscles contract, increasing the volume of the thoracic cavity. This causes the intrapleural pressure to become more negative, which increases the transpulmonary pressure, causing the lungs to expand.
Detailed explanation-4: -Breathing out (expiration) the intercostal muscles relax pulling the ribcage downwards and inwards. the diaphragm relaxes, doming upwards. volume of the thorax decreases and the pressure inside increases. air is pushed out of the lungs.
Detailed explanation-5: -Diaphragm’s Role in Breathing When the diaphragm contracts and moves lower, the chest cavity enlarges, reducing the pressure inside the lungs. To equalize the pressure, air enters the lungs. When the diaphragm relaxes and moves back up, the elasticity of the lungs and chest wall pushes air out of the lungs.