Which Muscle Separates the Thoracic and Abdominal Cavities and Is

Question

Which muscle separates the thoracic and abdominal cavities and is also the chief breathing muscle?
A) Serratus anterior
B) Intercostal muscle
C) Sternocleidomastoid
D) Diaphragm

Accepted Answer

The diaphragm is a dome-shaped muscle that separates the thoracic and abdominal cavities. It is also the main muscle responsible for breathing, contracting downward during inhalation and relaxing upward during exhalation. The other muscles listed do not play a significant role in separating the thoracic and abdominal cavities, nor are they the primary muscle for breathing.