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Biology 2nd Baccalaureate

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5.7. The blood circulation

Blood circulation

Blood circulation in humans is double, complete and closed:

  • It is double because there are two circuits, in such a way that the blood passes through the heart twice in each turn:
    • The minor or pulmonary circuit carries the blood of the heart, from the right ventricle and through the pulmonary arteries, to the lungs, it is oxygenated, it leaves the CO2, and it returns, through the pulmonary veins to the left atrium of the heart.
    • The major or general circuit carries blood from the left ventricle, through the aorta artery and reaches the cells of all organs, where from the capillaries, it gives up oxygen and collects waste. The capillaries meet in venules and then in veins that return blood, through the vena cava, to the right atrium of the heart.
  • It is complete because O2 rich blood never mixes with O2 poor blood.
  • It is closed, because the blood travels through the blood vessels without leaving them. The substances carried by the blood reach the tissues through diffusion.

The blood is loaded with nutrients in the liver, to which it has been carried by the blood itself from the digestive tract, and it is loaded with oxygen in the pulmonary alveoli.

Answer in your notebook

5.15.- Why do we say that the blood circulation is double and complete?

Answer in your notebook

5.16.- What happens when arterial blood passes through the intestinal villi? And when does it enter the kidney?

Answer in your notebook

5.17.- In the circulatory system, there are blood vessels that carry blood to the heart and others that draw blood from the heart. Similarly, some vessels carry oxygen-rich blood and others carry oxygen-poor blood. Based on these criteria, put the following names in the appropriate boxes in the table:

pulmonary vein - pulmonary artery - vena cava - aorta artery

  Vessel that carries blood to the heart Vessel that draws blood from the heart
Oxygen rich blood    
Blood poor in oxygen    

Answer in your notebook

5.18.- Order the following organs according to the position in which they are found in the blood path, starting from the left ventricle:
right ventricle - pulmonary vein - renal vein - pulmonary artery - right atrium - left atrium - vena cava - left ventricle - lung - kidney - aorta artery - renal artery.

Answer in your notebook

5.19.- What is the name of the blood vessel that carries blood from the heart to the pulmonary alveoli? And the one that carries the blood from the alveoli to the heart?

Answer in your notebook

5.20.- On which side of the heart does the oxygenated blood go?

Answer in your notebook

5.21.- A 4th year ESO student says that the arteries carry oxygen-rich blood and the veins carry oxygen-poor blood. What would you say to him, that you have more recent the subject?


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