ANIMAL PHYSIOLOGY
GAS EXCHANGE IN HUMANS
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
Contraction of external intercostal muscles raises the ribcage.
|
|
|
Relaxation of the abdominal muscles decreases the air volume in the lungs.
|
|
|
Contraction of internal intercostal muscles raises the ribcage.
|
|
|
Relaxation of the diaphragm decreases the air pressure in the lungs.
|
Detailed explanation-1: -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-2: -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-3: -The external intercostals contract during inhalation after the scalene muscles have raised the first rib. They contract sequentially from a rostral to caudal position, lifting the ribs, increasing the intrathoracic space and creating a negative intrathoracic pressure.