Lesson Progress
0% Complete
The mammalian heart has 4 chambers and 4 sets of valves:
  • 2 Atria (right and left)
  • 2 Ventricles (right and left)
  • 2 Atrioventricular (AV) valves
    • Right AV valve (also known as the tricuspid valve)
    • Left AV valve (also known as the mitral valve)
  • 2 Semilunar valves
    • Pulmonary valve
    • Aortic valve
Labeled diagram of the heart
Circulation through the heart

Venous return from the systemic organs and tissues via cranial and caudal vena cavae > Right atrium > Right ventricle > Pulmonary arteries > Lungs > Pulmonary veins > Left atrium > Left ventricle > Aorta > Systemic arteries > Systemic organs and tissues > Venous return (back to beginning)

The pulmonary and systemic circulatory systems

The pulmonary and systemic circulations exiting the right and left ventricles, respectively, are in series. Both circulatory systems are composed of the following in sequence:

  • arteries
  • arterioles
  • capillaries (within organs and tissues)
  • venules
  • veins (leading back to the heart)

The systemic circulation has many such systems arranged in parallel, each supplying different organs or tissues.