The diaphragm is a dome-shaped muscular partition that separates the chest cavity from the abdominal cavity. It is present below the lungs in the thoracic region.
Function: When the diaphragm contracts, it flattens and moves downward, increasing the volume of the chest cavity. This causes air to rush into the lungs (inhalation). When it relaxes, it moves upward, decreasing chest volume, forcing air out (exhalation). Thus, it plays a key role in the breathing mechanism.
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The diaphragm is not explicitly detailed in the source passages provided, but it is a standard part of the CBSE Class 10 Chapter 5 (Life Processes) curriculum on human respiration. Examiners expect students to mention two things: (1) its location (below the lungs / between thoracic and abdominal cavity) and (2) its function in breathing (contraction → inhalation; relaxation → exhalation). Both points carry 1 mark each. Avoid writing only one aspect.