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Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?
A
One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all
B
The lungs can be made fully empty by forcefully breathing out all air from them
C
One can breathe out air totally without oxygen
D
One can breathe out air through eustachian tubes by closing both the nose and the mouth
Detailed Solution
Breathing is brought about by the diaphragm and the intercostal muscles; contraction of the diaphragm increases the thoracic volume in the antero-posterior axis, and the ribs change it in the dorso-ventral axis.
With conscious effort one can breathe in and out using the diaphragm alone (abdominal breathing) without moving the ribs.
The lungs can never be emptied completely: even after the most forceful expiration about 1100–1200 mL of air (residual volume) remains.
Expired air always contains oxygen (about 16%), so it cannot be made totally free of oxygen.
The Eustachian tubes connect the middle ear to the pharynx and end at the closed ear drum, so air cannot be breathed out through them.
Hence the possibility is breathing by moving the diaphragm alone.
With conscious effort one can breathe in and out using the diaphragm alone (abdominal breathing) without moving the ribs.
The lungs can never be emptied completely: even after the most forceful expiration about 1100–1200 mL of air (residual volume) remains.
Expired air always contains oxygen (about 16%), so it cannot be made totally free of oxygen.
The Eustachian tubes connect the middle ear to the pharynx and end at the closed ear drum, so air cannot be breathed out through them.
Hence the possibility is breathing by moving the diaphragm alone.