Anatomy and Physiology / Unit 8: The Cardiovascular and Lymphatic Systems
8.4 Heart Anatomy
Notes
The heart is about the size of a fist, lies in the mediastinum, and is surrounded by the pericardium. The heart wall has the epicardium, myocardium (cardiac muscle, thickest) and endocardium (lining).
- Four chambers: two upper atria (receive blood) and two lower ventricles (pump blood out). The right side pumps blood to the lungs (pulmonary circuit); the left side pumps blood to the body (systemic circuit). The left ventricle has the thickest wall because it pumps against greater resistance.
- Valves prevent backflow: tricuspid (right AV), mitral/bicuspid (left AV), pulmonary semilunar and aortic semilunar. The "lub" sound is AV valves closing; the "dub" is semilunar valves closing.
- Blood flow: vena cava, right atrium, tricuspid, right ventricle, pulmonary valve, pulmonary arteries, lungs, pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta, body.
- Coronary arteries supply the heart muscle; blockage causes a myocardial infarction (heart attack).
Practice
Which chamber pumps oxygenated blood to the body?
The left ventricle ejects blood into the aorta for the systemic circuit.
Which valve lies between the left atrium and left ventricle?
The mitral valve is the left AV valve.
Why is the wall of the left ventricle thicker than that of the right ventricle?
The systemic circuit has more resistance than the short pulmonary circuit.
Ready for more? Take the Unit 8 test.