Difference between inspiration and expiration according to pulmonary pressure,thorasic chamber,sternum,ribs,diaphargm
Answers
The processes of inspiration (breathing in) and expiration (breathing out) are vital for providing oxygen to tissues and removing carbon dioxide from the body. Inspiration occurs via active contraction of muscles – such as the diaphragm – whereas expiration tends to be passive, unless it is forced.Process of Inspiration
Inspiration is the phase of ventilation in which air enters the lungs. It is initiated by contraction of the inspiratory muscles:
Diaphragm – flattens, extending the superior/inferior dimension of the thoracic cavity.
External intercostal muscles – elevates the ribs and sternum, extending the anterior/posterior dimension of the thoracic cavity.
The action of the inspiratory muscles results in an increase in the volume of the thoracic cavity. As the lungs are held against the inner thoracic wall by the pleural seal, they also undergo an increase in volume.
Fig 2 – Diagram showing the process of inspiration and expiration at rest.Forced Breathing
Forced breathing is an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise.
Active Inspiration
Active inspiration involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity:
Scalenes – elevates the upper ribs.
Sternocleidomastoid – elevates the sternum.
Pectoralis major and minor – pulls ribs outwards.
Serratus anterior – elevates the ribs (when the scapulae are fixed).
Latissimus dorsi – elevates the lower ribs.
Active Expiration
Active expiration utilises the contraction of several thoracic and abdominal muscles. These muscles act to decrease the volume of the thoracic cavity:
Anterolateral abdominal wall – increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity.
Internal intercostal – depresses the ribs.
Innermost intercostal – depresses the ribs.
By TeachMeSeries Ltd (2020)
Fig 3 – The muscles of the anterolateral wall are utilised in forced expiration.Forced Breathing
Forced breathing is an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise.
Active Inspiration
Active inspiration involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity:
Scalenes – elevates the upper ribs.
Sternocleidomastoid – elevates the sternum.
Pectoralis major and minor – pulls ribs outwards.
Serratus anterior – elevates the ribs (when the scapulae are fixed).
Latissimus dorsi – elevates the lower ribs.
Active Expiration
Active expiration utilises the contraction of several thoracic and abdominal muscles. These muscles act to decrease the volume of the thoracic cavity:
Anterolateral abdominal wall – increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity.
Internal intercostal – depresses the ribs.
Innermost intercostal – depresses the ribs.
By TeachMeSeries Ltd (2020)
Active Inspiration
Active inspiration involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity:
Forced Breathing
Forced breathing is an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise.