Blood Circulation

Anatomy and Physiology of the Heart - Part 5


The circulation of blood can be divided into two cycles: the Systemic Cycle and the Pulmonary Cycle:

The Systemic Cycle:

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  1. The left atrium of the heart receives oxygen-rich blood from the lungs, through the 4 Pulmonary Veins.
  2. This blood is pumped into the left ventricle. During the contraction of the left ventricle, the blood is injected through the Aorta to the body.
  3. The blood flows through the Aorta and splits into Arteries to different organs, then the blood goes to Arterioles in the tissues, and then divides into very small branches of Capillaries where nutrients and gas exchange occurs.
  4. The oxygen-poor blood (Venousblood) together with the waste begins returning to the heart from the Capillaries through the Venules and Veins returning to the right atrium.


The Pulmonary Cycle:

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  1. The right Atrium of the heart receives blood poor in oxygen from the body via the Superior and Inferior Vena Cava and Coronary Sinus (from the heart muscle itself).
  2. This blood is pumped into the right Ventricle. During the contraction of the right Ventricle, the blood is injected through the Pulmonary trunk into the Pulmonary Arteries.
  3. The Pulmonary arteries carry this blood to Capillaries in the lungs for gas exchange (oxygenation).
  4. The oxygenated blood returns to the heart through the Pulmonary veins into the left Atriam.