During inhalation, which changes occur?

During inhalation, which changes occur?

• A. Diaphragm relaxes and moves up; intercostals contract decreasing chest cavity.
• B. Diaphragm flattens and moves down; intercostals move rib cage up and out.
• C. The diaphragm contracts upward; intercostals move ribs inward.
• D. Pressure inside lungs increases during inhalation.

Answer: (B)

During inhalation the chest cavity expands, not contracts. The diaphragm contracts and moves downward, flattening to increase vertical space. At the same time, the external intercostal muscles lift the ribs outward and upward, expanding the rib cage. This increased thoracic volume lowers the pressure inside the lungs below atmospheric pressure, drawing air in. That’s why the best description is the diaphragm moving down and flattening and the rib cage being lifted outward. The other options imply the chest cavity would become smaller or the pressure would rise, which would not produce inhalation.

During inhalation the chest cavity expands, not contracts. The diaphragm contracts and moves downward, flattening to increase vertical space. At the same time, the external intercostal muscles lift the ribs outward and upward, expanding the rib cage. This increased thoracic volume lowers the pressure inside the lungs below atmospheric pressure, drawing air in. That’s why the best description is the diaphragm moving down and flattening and the rib cage being lifted outward. The other options imply the chest cavity would become smaller or the pressure would rise, which would not produce inhalation.