Answer: The correct answer to the question is option D
THE VOLUME OF THE THORAX DECREASES.
Explanation: Ventilation is required to maintain a concentration gradient so that gaseous exchange can occur, it involves the exchange of air between the atmosphere and the lungs which is achieved by the physical act of breathing.
INHALATION;
- The internal intercoastal muscles relax and the external intercoastal muscles contract, pulling the ribcage upward and outwards.
- The diaphram contracts pulling downwards.
- Both of these muscle contractions results in an increase in the volume of thorax which in turn results in a drop in pressure inside the thorax
- Pressure eventually drops below atmospheric pressure.
- Air then flows inside the lungs from outside the body through the mouth or nose,trachea,bronchi and bronchioles.
- Air continues to enter the lungs until the pressure inside the lungs rises to the atmospheric pressure.
EXHALATION;
- The internal intercoastal muscles contract,this moves the ribcage down and in.
- The abdominal muscles contract. this pushes the diaphragm up,back into a done shape.
- Both of these muscle contractions result in a decrease in the volume of the thorax.
- As a result of the decrease in volume,the pressure inside the thorax increases.
- Eventually the pressure rises above atmospheric pressure.
- Air then flows out of the lungs to outside of the body through the nose or mouth.
- Air continues to flow out of the lungs until the pressure in the lungs has fallen back to atmospheric pressure.
