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What is the primary muscle responsible for ventilation during quiet inspiration?
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Diaphragm.
How do the movements of upper and lower ribs differ during inspiration?
Upper ribs perform 'Pump Handle' movement with motion primarily in the sagittal plane, while lower ribs perform 'Bucket Handle' movement with motion in the frontal plane.
Describe how the thoracic spine moves during forced inspiration.
The thoracic spine moves into extension during forced inspiration.
What role do scalenes play in inspiration, and what potential issue can arise from their hypertrophy?
Scalenes assist in lifting the first two ribs during inspiration. Hypertrophy or spasm can affect the brachial plexus.
What is the significance of the axis of rotation for upper and lower ribs during inspiration?
The axis determines the plane of motion: upper ribs rotate closer to the frontal plane allowing sagittal movement, while lower ribs rotate towards the sagittal plane allowing frontal movement.
Which muscles are primarily involved in forced expiration and what is their function?
Internal intercostal muscles with interosseous fibers, which contract to decrease the intrathoracic volume.
What constitutes quiet expiration and what lacks in its process compared to forced expiration?
Quiet expiration is a passive process with no muscular effort, in contrast to forced expiration which involves active reduction of intrathoracic volume.
What anatomical changes occur in rib motion during inspiration?
The ribs move through elevation, with upper ribs moving in a 'Pump Handle' manner and lower ribs in a 'Bucket Handle' manner, increasing intrathoracic volume.
Contrast the roles of external and internal intercostal muscles.
External intercostals are primary muscles of inspiration, while internal intercostals' parasternal fibers assist in inspiration and interosseous fibers in forced expiration.
Describe the expansion of the diaphragm during quiet versus forced inspiration.
During quiet inspiration, the diaphragm drops about 1.5 cm, whereas in forced inspiration, it can descend 6-10 cm.
What are the attachment points and roles of the scalenes in ventilation?
Scalenes attach to the transverse processes of C3-C6 and the first two ribs, assisting in elevating these ribs during inspiration.
How do changes in intrathoracic volume facilitate ventilation?
Increased intrathoracic volume decreases pressure, drawing air into the lungs, while decreased volume increases pressure, facilitating exhalation.
What role does the costovertebral joint play in the mechanics of inspiration?
The costovertebral joint moves through posterior rotation during inspiration, contributing to rib elevation.
In what directions does the diaphragm increase intrathoracic volume?
It increases intrathoracic volume anterior-posteriorly, medially-laterally, and vertically.
Explain Boyle's Law in the context of ventilation.
Boyle's Law states there is an inverse relationship between volume and pressure of a gas at a constant temperature and mass. In ventilation, increased intrathoracic volume decreases pressure, facilitating air movement.
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