Questions: The diaphragm separates the: mediastinum from the abdominal cavity. pelvic cavity from the abdominal cavity. pericardial cavity from the pleural cavity. mediastinum from the pleural cavity.

The answer is the first one: the original text in the question...

Explanation for each option:

1. Mediastinum from the abdominal cavity: This is correct. The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity (which includes the mediastinum) from the abdominal cavity.

2. Pelvic cavity from the abdominal cavity: This is incorrect. The diaphragm does not separate the pelvic cavity from the abdominal cavity. The pelvic cavity is located below the abdominal cavity, and there is no diaphragm between them.

3. Pericardial cavity from the pleural cavity: This is incorrect. The pericardial cavity (which contains the heart) and the pleural cavities (which contain the lungs) are both within the thoracic cavity, and the diaphragm does not separate them. Instead, they are separated by the mediastinum.

4. Mediastinum from the pleural cavity: This is incorrect. The diaphragm does not separate the mediastinum from the pleural cavities. The mediastinum is the central compartment of the thoracic cavity, and the pleural cavities are on either side of it.

Summary: The diaphragm separates the mediastinum from the abdominal cavity.