Diaphragm

In the syllabus and the exam

The diaphragm is central to the mechanism of breathing content standard, where candidates must explain inhalation and exhalation as a chain of pressure and volume changes rather than describing the diaphragm in isolation. A full answer states that the diaphragm contracts and moves downward while the external intercostal muscles contract to lift the ribcage, together increasing thoracic volume, decreasing pressure inside the thorax below atmospheric pressure, and drawing air in; exhalation reverses each of these steps. SPM structured questions often present this as a fill-in-the-blank or sequencing task covering both diaphragm and rib movement, and candidates lose marks by mentioning only the diaphragm while omitting the intercostal muscles, or by stating direction of movement without linking it to the resulting pressure and volume change. Some candidates also incorrectly describe the diaphragm as part of the lungs rather than as a separate sheet of muscle beneath them.

Example

When the diaphragm contracts and flattens, the volume of the thorax increases and air is drawn into the lungs.

Related terms

TracheaGaseous exchangeAlveolus

Source:SRC-DSKP-EN