(3) Relationship of wall thickness to required pressure levels. A
cross-section of the chambers shows that the atrial walls are relatively thin. The right
ventricular wall is much thicker. The left ventricular wall is three to five times thicker
than that of the right. These differences in wall thickness reflect the amount of muscle
tissue needed to produce the amount of pressure required of each chamber.
(4) Cardiac valves (figure 9-3).
Figure 9-3. Scheme of heart valves.