question_answer 115)

  Describe the flow of blood through the heart of human beings.

Answer:

                  Flow of blood through human heart Oxygen rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, to enter in the next chamber, the left ventricle, which expands, so that the blood is transferred to it. When the muscular left ventricle contracts reaches, the blood is pumped out to the body. De-oxygenated blood from the body to the upper chamber on the right, the right atrium, and it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood so the right ventricle, which in turn pumps it to the lungs for oxygenation. Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do.   The whole process is repeated continuously. The blood circulatory system in human is an example of double circulation since the blood travels twice through the heart in one complete cycle. (i) The pathway of blood from heart to the lungs and back to the heart is called pulmonary circulation. (ii) The pathway of blood from heart to rest of the body and back to the heart is called systemic circulation. These two together make double circulatory system.