question vv How thick are the walls of capillaries? One cell in thickness 2 layers thick 4 layers thick 3 layers thick Question 51 What is the definition of coronary artery disease? Heart attack Disease of the arteries surrounding the heart Abnormalities in the heart at birth Heart is unable to pump its required amount of blood

**Question vv:**<br /><br />How thick are the walls of capillaries?<br /><br />* **One cell in thickness** (This is the correct answer. Capillary walls are composed of a single layer of endothelial cells to facilitate efficient exchange of gases, nutrients, and waste products.)<br />* 2 layers thick<br />* 4 layers thick<br />* 3 layers thick<br /><br /><br />**Question 51:**<br /><br />What is the definition of coronary artery disease?<br /><br />* Heart attack (A heart attack is a *result* of coronary artery disease, not the definition itself.)<br />* **Disease of the arteries surrounding the heart** (This is the correct answer. Coronary artery disease involves the buildup of plaque in the coronary arteries, which supply blood to the heart muscle.)<br />* Abnormalities in the heart at birth (This describes congenital heart defects.)<br />* Heart is unable to pump its required amount of blood (This describes heart failure, which can be a *consequence* of coronary artery disease, but not the definition itself.)<br />