Question

At the time of expiration, diaphragm becomes

• A. Oblique
• B. Normal
• C. Flattened
• D. Dome-shaped

Answer 1

Answer: (D)

Dome-shaped

Expiration or exhalation involves relaxation of both phrenic and external intercoastal muscles. The diaphragm bends upwards and this reduces the vertical length of thoracic cavity. The relaxation of external intercoastal muscles leads ribs and rib cage downwards and inwards respectively and this results in reduction in thoracic volume in anteroposterior direction.

Hence, diaphragm becomes dome shaped during expiration as shown in the figure.

So, the correct answer is 'Dome-shaped'.