Read the passage carefully and answer the following questions.

The heart is one of the most vital components of the human body. The heart of the human body has the continuous job to keep oxygen - rich blood flowing through the body. All the body's cells need a constant supply of oxygen, particularly in the brain. Heart disease can result from damage to the heart muscles, the valves or the pacemaker. If the muscle is damaged the heart is unable to pump properly. If the valves are damaged, blood cannot flow normally.