Mechanism Of Breathing

Question 1

Explain relaxed inhalation and exhalation

Answer 1

During relaxed inhalation the diaphragm contracts and pushes down to the abdominal viscera causing an increase vertical dimension of the thoracic cavity, this decreases the pressure in the thoracic cavity allowing oxygen to enter via inhalation. The diaphragm contracts and the intercostals elevate the thoracic cavity.
During exhalation the diaphragm relaxes, causing the vertical dimension of the thoracic cavity to decrease causing an increase in pressure expelling the air out via exhalation. The diaphragm relaxes causing the intercostals to lower the thoracic cavity.

Question 2

Explain forced inhalation and exhalation

Answer 2

Similar to relaxed inhalation the diaphragm contracts and the intercostals elevate the thoracic cavity. 3 muscles (written on notes) elavate the sternum and ribs
Forced exhalation works by allowing the muscles mentioned above to relax causing the lungs to recoil and expel air which depress the ribs and cause depression or ribs and sternum.
The internal and innermost intercostals muscle contract reducing the transverse dimension of the thoracic cavity allowing an increase in the vertical dimension of the thoraci cavity.