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Chapter 6: Cardiovascular System
To head and arms
Pulmonary circulation
Pulmonary vein
Pulmonary artery
Aorta
Superior vena cava
Left atrium
Right atrium Right ventricle
Left ventricle
Oxygen-poor, CO 2 -rich blood
Oxygen-rich, CO 2 -poor blood
To organs
Venules
To trunk and legs Arterioles
Capillaries
Systemic circulation
FIGURE 6-2 The cardiovascular system.
blockage. This is known as atherosclerosis and contributes to the development of coronary artery disease (CAD). It is also sometimes called atherosclerotic heart disease (ASHD). Coronary arteries encircle the heart and keep it supplied with nutrients and oxygen. If an artery becomes completely occluded (blocked), then the heart muscle downstream dies from a lack of oxygen. This is known as a myocardial infarction (MI) or a heart attack. The Heart’s Electrical System Have you ever wondered what makes your heart beat? Your heart has its own special pacemaker that has been working since before you were born (Figure 6-3). A cluster of specialized cells in your right atrium called the sinoatrial (SA) node initiates an electrical impulse about 60 to 100 times per minute. These impulses are transmitted throughout all the muscle cells of your heart, resulting in an electrical charge called depolarization. When this occurs, the inside of the cardiac muscle cells becomes electrically positive in relation
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