Crystalline silica is a natural compound in the earth's crust and is a basic component of sand and granite. Silicosis is an incurable disease of the lungs caused by breathing crystalline silica dust. This dust can cause scar tissue to form in the lungs.
Vertebrates and invertebrates
Answer:
2.1 located between the left atrium and the left ventricle (left atrioventricular orifice).
2.2 it helps to prevent blood from flowing backward as it moves through the heart.
