Question

Which one of the following produces negative pressure within your thoracic cavity:

• A. exhalation
• B. contraction of the diaphragm muscles
• C. relaxation of the muscles between the ribs
• D. relaxation of diaphragm muscles

Answer 1

The correct option is B

contraction of the diaphragm muscles

The correct answer is option (B)

Explanation for the correct option:

1. The diaphragm is present between the thoracic and the abdominal cavity.
2. During inspiration, the diaphragm contracts which leads to an increase in the thoracic cavity volume.
3. This increase in volume results in the production of negative pressure within the thoracic cavity.

Explanation for the incorrect options:

Option (A):

1. Exhalation is caused due to development of positive air pressure within the thoracic cavity as the diaphragm relaxes.

Option (C):

1. The muscles present between the ribs are commonly known as intercostal muscles.
2. The relaxation of intercostal muscles leads to the production of positive air pressure within the thoracic cavity.

Option (D):

1. The relaxation of diaphragm muscles leads to the production of positive air pressure within the thoracic cavity and results in expiration.

Final answer: The contraction of the diaphragm muscles produces negative pressure within the thoracic cavity.