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Introduction to Cardiovascular System


  • Pumps blood into the circulation.

  • Four

    • Two atria: A left atrium and a right atrium.

    • Two ventricles: A left ventricle and a right ventricle.

Dual Pump
  • Four chambers make two pumps in series.

Right Heart

  • = Right atrium + Right ventricle.

  • Receives deoxygenated blood from vena cava.

  • Pumps blood into the lungs for oxygenation.

Left Heart

  • = Left atrium + Left ventricle.

  • Receives oxygenated blood from lungs.

  • Pumps blood into the systemic circulation.

  • Maintains flow of blood in a specific direction.

Atrioventricular valves

  • Between atria and ventricles

  • Tricuspid valve: Between right atria and ventricle.

    • Made up of three cusps.

  • Bicuspid valve/Mitral valve: Between left atria and ventricle.

    • Made up of two cusps.

Semilunar Valves

  • Between ventricles and major arteries.

  • Made up of three flaps

  • Half moon-like shape (hence the name)

  • Pulmonary valve: between right ventricle and pulmonary artery.

  • Aortic valve: between left ventricle and aorta.

Blood Vessels

  • Circulate the blood throughout the body.

  • Arranged in series as well as parallelly.

Arterial System
  • Starting from heart, it includes the aorta, arteries, and arterioles in this order.

  • As we go from the aorta to arterioles:

    • Lumen gets smaller

    • Resistance increases. Arterioles have maximum resistance ⟶ Called resistance vessels.

  • Constriction and dilatation of arterioles and small arteries ⟶ :

    • Controls local blood flow.

    • Helps control arterial blood pressure.

  • Large in numbers ⟶ Total cross-section area is very large ⟶ blood flow is slow.

  • Wall is only one cell thin.

  • Slow blood flow and one cell thin wall provide a favorable situation for the exchange of diffusible substances.

Venous System
  • Includes venules, veins, and vena cava in this order.

  • As we go from capillaries to vena cava, the diameter increases.

  • Hold a large quantity of blood ⟶ called capacitance vessels.

Systemic vs Pulmonary Division

System Circulation
  • Also called greater circulation.

  • From left ventricle to right atrium.

  • Oxygenated blood is supplied to the tissues through arteries.

  • Deoxygenated blood returns to the heart through veins.

Pulmonary Circulation
  • Also called lesser circulation.

  • From right ventricle to left atrium.

  • Deoxygenated blood goes to lungs through arteries.

  • Blood gets oxygenated in the lungs.

  • Oxygenated blood returns to the heart through veins.


  • Supply nutrients and remove waste products from peripheral tissues.

  • Regulation of body temperature.

  • Fluid balance.

  • Adjustment of oxygen and nutrient supply.


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