From the Research
The thoracic diaphragm moves superiorly during quiet expiration. This is the most appropriate answer because the diaphragm is the primary muscle of respiration that contracts and flattens during inspiration, moving inferiorly to increase thoracic volume and create negative pressure that draws air into the lungs. During quiet expiration, which is a passive process, the diaphragm relaxes and returns to its dome-shaped position, moving superiorly as elastic recoil of the lungs and chest wall pushes air out. The diaphragm does not contract during normal expiration (only during forced expiration). It originates from the lower six ribs, xiphoid process, and lumbar vertebrae (not thoracic vertebrae). The diaphragm's superior surface is lined by parietal pleura (not visceral pleura), and its inferior surface is lined by parietal peritoneum (not pericardium).
Some key points to consider:
- The diaphragm's role in respiration is crucial, and its movement during expiration is an important aspect of this process 1.
- The diaphragm's movement during quiet expiration is a passive process, with the diaphragm relaxing and moving superiorly as the lungs and chest wall recoil 2.
- The diaphragm's function can be affected by various factors, including mechanical ventilation and muscle paralysis 3.
- Diaphragm training and inspiratory muscle training can be effective in improving diaphragmatic function in patients with respiratory problems 4, 5.
In terms of the options provided, the correct answer is the one that states the diaphragm moves superiorly during quiet expiration. The other options are incorrect because:
- The diaphragm does not contract during normal expiration, it only contracts during forced expiration.
- The diaphragm originates from the lower six ribs, xiphoid process, and lumbar vertebrae, not the thoracic vertebrae.
- The diaphragm's superior surface is lined by parietal pleura, not visceral pleura, and its inferior surface is lined by parietal peritoneum, not pericardium.