Transportation in Animals and Plants

Circulatory System in Animals

This is one important chapter from the point of view of your exams. Therefore, we will try our best to explain the circulatory system in an elaborate way so that you get a clear understanding of the subject. In this specific chapter, we see blood circulatory system in animals.

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Circulatory System in Animals

While in smaller organisms, diffusion and osmosis help in the transportation of substances, it is not the case in larger animals and organisms. As the organism grows bigger, the processes become more and more complex and thus, there is a need for a more structured system for the transportation of various substances.

The human circulatory system is mainly composed of three main components. These are the heart, blood vessels, and blood. Let us now look at these components in further detail.

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Blood Circulatory System

Blood is the major tissue in the human body that is responsible for carrying substances and materials to different parts of the body. It is the main carrier of substances to other organs and parts of the body. Blood further has various components to it. Let us discuss them first. Blood is primarily composed of the following components:

  • Plasma: Plasma is what makes up the liquid part of the blood. It is the major component of blood and is basically pale in color.
  • Blood Cells: Two major types of blood cells in the human body include. Red Blood Cells and White Blood Cells.
  • Red Blood Cells or Red Blood Corpuscles (RBC): These are disc-shaped cells that contain a pigment that is called haemoglobin. This pigment is responsible for binding with oxygen and thus, is mainly responsible for transporting the oxygen throughout the human body. Haemoglobin also helps in some amount of carbon dioxide.
  • White Blood Cells or White Blood Corpuscles (WBC): These cells have various shapes and play a major role in engulfing foreign particles and harmful microbes. Thus, they help in fighting many diseases. These are what make up the immune system of the body.
  • Platelets: Platelets are the main components that are responsible for clotting or coagulation of blood. In cases of any injury or accidents, the blood clots after some time. This prevents excess loss of blood. Clotting of blood is a defense mechanism in the body.

Blood Vessels

The next important component of the circulatory system is the network of blood vessels. Blood vessels are of three main types. They are arteries, veins, and capillaries.

  • Arteries: Arteries have relatively thicker walls and are responsible for carrying oxygenated blood from the heart to different organs. An exception to this mechanism is the pulmonary artery as it is responsible for carrying deoxygenated blood from the heart to the lungs.
  • Veins: Veins are made of relatively thin walls compared to arteries. They carry out the function of transporting deoxygenated blood from different organs to the heart. Pulmonary vein is an exception because it carries oxygenated blood from the lungs to the heart.
  • Capillaries: These are nothing but very fine branches of arteries and veins.


Now, we come to the most important organ in the human body: The heart! The heart is a small muscular organ that carries out the primary function of pumping the blood to and from various organs of the body. The human heart has four chambers. They are called the right auricle, the right ventricle, the left auricle and the left ventricle.

The upper chambers are known an auricle or atrium. The lower chambers are known as ventricle. The blood is pumped in a fashion that is described below:

From the body → Right Auricle → Right Ventricle → Pulmonary Artery → Lungs → Pulmonary Vein → Left Auricle → Left Ventricle → To the body


Different chambers of the heart contract and relax when the heart is pumping the blood. This contraction and relaxation of the muscles produce a thumping sound that is known as the heartbeat. Each heartbeat indicates one cycle of pumping action of the heart.

blood circulatory system

A normal human being’s heart pumps for around 72 times in a single minute. In each beat, the heart is able to pump 70 ml of blood to the body. This indicates that the heart is able to pump around 5 litres of blood in a minute! That is simply amazing!


In certain locations of the body, like near the wrist, neck or ankle, you can hear or feel the heartbeat. The main reason behind this is the rushing of blood with every heartbeat. The pulse is a good way to check for your heartbeat. That is what doctors do with the help of stethoscopes. It is composed of a long tube made of rubber, a diaphragm, and two earpieces. This is all the basic knowledge about the human circulatory system.

Question For You

Q1. Which organ in the human body is responsible for pumping of blood?

Ans: Heart is responsible for pumping blood.

Q2. Which type of blood is carried by arteries?

Ans: Oxygenated Blood.

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