Mechanism of Breathing
The lungs themselves needed draw in air nor push it out the diaphragm abdominal muscle and the intercostal muscles accomplish the expansion and contraction of lungs the diaphragm is a large Dome of skeletal muscle that separates the thoracic cavity from abdominal cavity there are two sets of intercostal muscles between each pair of ribs the external intercostal and the internal intercostal the muscle fibre Run diagonally But in opposite direction in the two sets of muscle breathing takes place in two faces ie inspiration and expiration
Inspiration it is taking in of air it is the active phase of breathing during inspiration the contraction of diaphragm causes its dome shaped to flatten and contraction of the external intercostal and relaxation of the internal intercostal causes the Rib cage to move upward and forward both these events result in increase of inner space of thoracic cavity consequently the pressure in the Thorax and in the lungs is reduced so air enters the lungs and alveoli become inflated
Expiration it is the removal of air out of lungs it is the passive phase of breathing during expiration relaxation of diaphragm causes it to become more dome shaped whereas relaxation of the external intercostal and contraction of the internal intercostal causes the Rib cage to move downward and backward both these event result in degrees of inner space of thoracic cavity pressure inside the Thorax and lungs is increased so air is forced to expelled out of the lungs
The lungs themselves needed draw in air nor push it out the diaphragm abdominal muscle and the intercostal muscles accomplish the expansion and contraction of lungs the diaphragm is a large Dome of skeletal muscle that separates the thoracic cavity from abdominal cavity there are two sets of intercostal muscles between each pair of ribs the external intercostal and the internal intercostal the muscle fibre Run diagonally But in opposite direction in the two sets of muscle breathing takes place in two faces ie inspiration and expiration
Inspiration it is taking in of air it is the active phase of breathing during inspiration the contraction of diaphragm causes its dome shaped to flatten and contraction of the external intercostal and relaxation of the internal intercostal causes the Rib cage to move upward and forward both these events result in increase of inner space of thoracic cavity consequently the pressure in the Thorax and in the lungs is reduced so air enters the lungs and alveoli become inflated
Expiration it is the removal of air out of lungs it is the passive phase of breathing during expiration relaxation of diaphragm causes it to become more dome shaped whereas relaxation of the external intercostal and contraction of the internal intercostal causes the Rib cage to move downward and backward both these event result in degrees of inner space of thoracic cavity pressure inside the Thorax and lungs is increased so air is forced to expelled out of the lungs