The base of each lung rests on which muscle?

• A. Abdominal
• B. Intercostal
• C. Serratus anterior
• D. Diaphragm

Answer: (D)

The base of each lung rests on the diaphragm, which is a dome-shaped muscle that plays a crucial role in respiration. The diaphragm separates the thoracic cavity, which houses the lungs, from the abdominal cavity. During inhalation, the diaphragm contracts and moves downward, creating a vacuum that pulls air into the lungs. When it relaxes during exhalation, the air is pushed out. The diaphragm's position and function are essential for effective breathing and overall respiratory mechanics, making it the correct answer to this question.

In contrast, the abdominal muscles assist in forced exhalation but do not directly support the lungs. Intercostal muscles are also involved in breathing by aiding in the movement of the rib cage, but they do not form the base of the lungs. The serratus anterior muscle has different functions, primarily related to arm movement and stability of the scapula, and does not have a direct role in supporting the lungs.