Suminder kaur, Academic Content Writer at Edumarz

  • Human body is a complex machine. Every organ of the body requires some vital nutrients to function properly. Therefore, the role of the human circulatory system comes into picture.

  • Human circulatory system is responsible for transportation of various essential substances such as oxygen, vitamins, waste materials and minerals across all the parts of the body.

  • It includes blood, blood vessels and a pumping organ – heart, blood capillaries and lymph.


  • Blood is red colored pigment that flows inside our body. It helps in transportation of oxygen, waste materials etc in the body. 

  • Blood consists of various elements : plasma, red blood cells (RBC), white blood cells (WBC), and platelets.

  • Plasma is white colored liquid which consists of 90% pf waster. It forms the matrix in which all other blood cells reside.

  • Red blood cells are red because of the presence of iron rich pigment hemoglobin. It helps in transportation of oxygen.

  • White blood cells lack hemoglobin. They are pale colored cells. They major in immunity.

  • Platelets play a major role in blood coagulation.


  • It is a clear liquid made up of white blood cells ( mainly lymphocytes).

  • It flows through the lymphatic system.

  • Has a role in providing immunity to the body.


  • Blood consists of cellular components – white blood cells, red blood cells and platelets.

  • Red blood cells are red colored cells due to the presence of iron rich pigment called hemoglobin. These cells have biconcave shape and they are responsible for transportation of oxygen to every part of the body.

  • White blood cells are amoeboid shaped white cells. They have a major role in providing immunity to the body. 

  • Platelets are responsible for blood coagulation which is a basic mechanism through which our body prevents excess loss of blood at the time of injury.


  • Pipes that carry blood across the body. These are of two types: arteries and veins.

  • Arteries are the blood vessels that carry oxygenated blood. These are thick walled blood vessels.

  • Veins carry deoxygenated blood. These are thin walled and have valves.

  • Oxygenation refers to the amount of oxygen that is present in the blood.


  • Capillaries are thin walled and narrow vessels. It helps in connecting arteries and veins. The exchange of substances such as carbon dioxide, water and oxygen between blood cells.


  • Heart is a natural pump. It’s a muscular organ that pumps blood to all parts.

  • It has 4 chambers, upper two chambers are called atria and lower chambers are called ventricles.

  • Musculature of chambers : ventricles are thicker as they have to pump blood to all parts of the body.

  • Left and right chambers are separated by a wall called a septum.

  • Septum prevents mixing of dO2 and O2 blood.

  • These chambers have valves that prevent backflow of blood.


  • The pulmonary vein allows oxygenated blood from the lungs to flow into the left atrium as it relaxes. The left ventricle expands when it contracts, allowing blood to flow into it. The left ventricle then contracts, allowing oxygenated blood to be pushed to all areas of the body via the aorta. 

  • Deoxygenated blood enters the right atrium through the vena cava after circulating throughout the body. The right ventricle swells when the right atrium contracts, allowing blood to flow into it. The right ventricle then contracts, pumping blood to the lungs via the pulmonary artery. Carbon dioxide is eliminated from the lungs, oxygen is absorbed, and oxygenated blood enters the left atrium again, repeating the process.

  • Since blood flows through the heart twice in one cycle, it is called double circulation.


  • The heart of mammals and birds has four chambers, with a septum separating the right and left sides of the heart. This keeps oxygenated and deoxygenated blood from mingling and ensures an adequate supply of oxygen. They require more energy to maintain their body temperature, so this is important.


  • They have three chambers and allow some mixing of oxygenated and deoxygenated blood.

  • These organisms do not maintain their body temperature.


  • These organisms have  two chambers and blood is purified in gills.

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