Final answer:
The diaphragm is a large sheet of smooth muscle that separates the thorax from the abdomen. Its contraction and relaxation control breathing.
Step-by-step explanation:
The diaphragm is a large sheet of smooth muscle that separates the thorax from the abdomen.
It is dome-shaped, and its contraction and relaxation control breathing. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity and allowing for inhalation. When it relaxes, it moves upward, decreasing the volume of the thoracic cavity and causing exhalation.