Breathing Muscle Below the Lungs and Heart
Puzzle 15 of Furniture Easy Pack
Question is: Breathing Muscle Below the Lungs and Heart
and the answer is: DIAPHRAGM
Word Meaning:
DIAPHRAGM — (anatomy) In mammals, a sheet of muscle separating the thorax from the abdomen, contracted and relaxed in respiration to draw air into and expel air from the lungs.
Definitions from Wiktionary.