The human circulatory system, also known as the cardiovascular system, is a complex network of blood vessels, the heart, and blood that plays a vital role in sustaining life. The primary function of the circulatory system is to transport oxygen, nutrients, and hormones throughout the body. The system is also responsible for removing waste products from various parts of the body and excreting it. The heart acts as the central pump of the circulatory system, propelling oxygen-rich blood to organs and tissues through arteries, while veins return oxygen-depleted blood to the heart. Capillaries, the smallest blood vessels, facilitate the exchange of substances between blood and cells. This intricate system ensures the delivery of essential resources and the removal of metabolic waste, maintaining the body's health and functionality.

Organs in Circulatory System

The following are the parts of human anatomy directly involved in the circulatory system:

  • Heart: The heart is the central organ of the circulatory system which pumps blood throughout the body.
  • Blood Vessels: Arteries, veins and capillaries are the three types of blood vessels which play different roles in the flow of blood through the circulatory system.
  • Blood: Blood consists of red blood cells, white blood cells and platelets which play different roles in the flow of blood. The RBCs transport oxygen, WBCs defend against infections and platelets aid in blood clotting.

Pulmonary Circulation

The human circulatory system works in conjunction with the respiratory system to absorb oxygen and remove gaseous wastes through the lungs. The pulmonary circulation is a thus a subset of the circulatory system. The steps involved in the circulatory system are listed below:

  • Deoxygenated blood from the body is pumped by the right ventricle of the heart into the pulmonary arteries, which carry it to the lungs.
  • The blood enters a network of capillaries surrounding the lung's alveoli (tiny air sacs), where oxygen from the inhaled air diffuses into the bloodstream, while carbon dioxide, a waste product, moves from the blood into the air to be exhaled.
  • Oxygenated blood is then returned to the left atrium of the heart via the pulmonary veins.
  • An important point to be noted here is that pulmonay arteries carry deoxygenated blood to lungs and veins carry oxygenated blood to the heart.

Role of Kidneys in Circulatory System

Kidneys play an important role in the circulatory system, though they are not a part of the system. The role played by the kidneys is listed below:

  • The nephrons present in the kidneys filter waste products from the blood such as urea, creatinine, and excess salts.
  • The kidneys help regulate blood pressure by adjusting the volume of blood in the circulatory system.


Directions: In the questions given below, four options have been given. Click on the option which you think is the RIGHT ANSWER to the question.

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1. Which of the following are the possible blood groups of the offspring of the parents with blood group O and AB?

2. White blood cells act

3. In which one of the following is extra blood stored and is released when shortage occurs?

4. The average life span of red blood corpuscles is about

5. From which one of the following chambers of human heart is the oxygenated blood pumped into aorta?

6. If the radius of blood vessels of a person decreases his/her blood pressure will -

7. Insufficient blood supply in human body is referred as -

8. In the circulatory system, the mineral impurities in blood are removed by which organ?

9. Between which one of the following sets of blood groups, is the blood transfusion possible?

10. What is the pH of human blood?

11. In the human body, red blood cells are produced in -

12. Which is the anti-coagulant substance in blood?


13. In the circulatory system which vessel carries the venous blood to the lungs for oxygenation?

14. When a child is born, what happens to its blood circulation?

15. What is the approximate time required for a heart-beat?

16. Ventricles are related to -

17. Universal receivers can receive blood from -

18. Pulmonary artery carries -

19. Ions of which of the following minerals play an important role in blood clotting?

20. What is the condition in which heart is not pumping the blood effectively to meet the requirements of the body called?

21. At which part of the intestines is the digested food absorbed by the blood?

22. Fastest distribution of some injectible material/medicine and with no risk of any kind can be achieved by injecting it into the -

23. Where does the impulse of heart beat originate?

24. In the circulatory system, which of the following veins does not carry deoxygenated blood?

25. What is instrument for measuring blood pressure called?

26. What is the percentage of water in blood plasma?

27. Cheeks of the people in hilly areas are more red in colour due to

28. Mosquito borne disease dengue causes a reduction in which of the following blood components?

29. Transfusion of which of these blood components was resorted to during the initial surge of COVID-19?

30. Deficiency of which of these blood components may result in serious internal bleeding?