Which muscular structure separates the thoracic cavity from the abdominal cavity?

• A. Intercostal Muscles
• B. Pectoralis Major
• C. Latissimus Dorsi
• D. Diaphragm

Answer: (D)

The boundary that separates the thoracic cavity from the abdominal cavity is formed by the diaphragm. This large, dome-shaped muscle sits between the chest and abdomen, acting as the floor of the thorax and the roof of the abdomen. When it contracts, it moves downward, increasing the volume of the thoracic cavity and allowing air to flow into the lungs during inhalation. While the intercostal muscles assist with breathing by expanding and contracting the chest wall, they don’t divide the two cavities. Pectoralis major and latissimus dorsi are muscles involved in shoulder and trunk movements, not the anatomical divider between the thorax and abdomen.