Human Circulatory System - Transportation

Our body is a complex machine, requiring many processes to function efficiently. To keep these important processes running without any hitches, we need vital elements and components which are to be delivered to the various parts of our body.

This role of transportation is undertaken by the human circulatory system, moving essential nutrients and minerals throughout the body and metabolic waste products away from the body. Let us explore the intricates about the human circulatory system and its components in greater detail.

Human Circulatory System - Transportation

Circulatory system diagram highlighting the various pathways of blood (Blue=Dexoygenated blood & Red=Oxygented blood)

Human Circulatory System

The human circulatory system is a complex network consisting of arteries, veins, capillaries and the heart. Its primary role is to provide essential nutrients, minerals and other important components such as hormones to various parts of the body. Alternatively, the circulatory system is also responsible for collecting metabolic waste and toxins from the cells and tissues to be purified or expelled from the body.

Features of the Human Circulatory System

The important features of human circulatory are as follows:

  • Human Circulatory System consists of blood that transports, nutrients, gases, wastes and hormones.
  • The heart consists of two pumps-
    • one to pump deoxygenated blood to the lungs
    • the other to pump oxygenated blood to different organs and tissues.
  • Human Circulatory System consists of a system of blood vessels to circulate blood throughout the body.
  • It consists of organs like lungs and intestines that add materials to the blood and lungs and kidneys that remove wastes from the blood.

Also Read: Blood

Circulatory System Organs

The human circulatory system comprises of 4 main organs that have specific roles and functions. The important circulatory system organs include:

  • Heart

  • Blood

  • Blood Vessels

  • Lymph


The heart is a muscular organ located in the chest cavity, between the lungs, It is positioned slightly towards the left in the thoracic region and is enveloped by the pericardium. The human heart is divided into four chambers – two upper chambers called atria (singular: atrium) and two lower chambers called ventricles.

Heart - Human Circulatory System

Heart, a major part of the human circulatory system

Though there are other animals that possess a heart, however, the way their circulatory system functions are quite different from humans. And in some cases, the human circulatory system is more advanced than that of other animals like insects or molluscs, where the open circulatory system is observed.

Double Circulation

The way blood flows in the human body is unique, and it is quite efficient too. The blood circulates through the heart twice, hence, it is called double circulation. Other animals like fish have single circulation, where blood completes a circuit through the entire animal only once.

The main advantage of double circulation is that every tissue in the body has a steady supply of oxygenated blood and it does not get mixed with the deoxygenated blood.

Double Circulation

Circulation of blood in humans – Double circulation


Blood is the body’s fluid connective tissue and it plays an important role in circulating nutrients, hormones, minerals and other necessary products to different parts of the body. Blood flows through a specified set of pathways called blood vessels. The organ which is involved in pumping blood to different body parts is the heart.  Blood cells, blood plasma, proteins, and other mineral components (such as sodium, potassium, calcium etc) together constitute human blood. The composition of blood are:

  • Plasma is the fluid part of the blood and is composed of  90%  of water.

  • Red blood cells, white blood cells and platelets constitute the solid part of blood.

Types of Blood Cells

The human body consists of three types of blood cells, they are as follows:

Red blood cells (RBC) / Erythrocytes

Red blood cells are mainly involved in transporting oxygen, nutrients, and other substances to various parts of the body. These blood cells also remove waste from the body.

White blood cells (WBC) / Leukocytes

White blood cells are cells that specialize in defence. They provide immunity by fending off pathogens and harmful microorganisms.

Platelets / Thrombocytes

Platelets are cells that help to form clots and stop bleeding. They act on the site of an injury or a wound.

Blood Vessels

Blood vessels are a network of pathways through which blood travels throughout the body.  Arteries and veins are the two primary types of blood vessels in the circulatory system of the body.


Arteries are blood vessels that transport oxygenated blood from the heart to various parts of the body. They are thick, elastic and are divided into a small network of blood vessels called capillaries. The only exception to this is the pulmonary arteries, which carries deoxygenated blood to the lungs.


Veins are blood vessels that carry de-oxygenated blood towards the heart from various parts of the body.  They are thin, elastic and are present closer to the surface of the skin. However, pulmonary and umbilical veins are the only veins that carry oxygenated blood in the entire body.


The human circulatory system consists of another body fluid called lymph. It is also known as tissue fluid. It is a colourless fluid consisting of salts, proteins, water, etc. which transport and circulates digested food and absorbed fat to intercellular spaces in the tissues. Unlike the circulatory system, lymph is not pumped, instead, it passively flows through a network of vessels.

Circulatory System Function

The most important function of circulatory system is transporting oxygen throughout the body. The other important functions of the human circulatory system include:

  1. It helps in sustaining all the organ systems.
  2. It protects every cell from pathogens.
  3. It transports blood, nutrients, oxygen, carbon dioxide and hormones throughout the body.
  4. It helps in the cell to cell interaction.
  5. The substances present in the blood repair the damaged tissue.

Also Read: Circulatory System

Human Circulatory System Questions

1. How does the human circulatory system work?

The human circulatory system is a network of arteries, veins, capillaries designed to provide essential minerals, nutrients, and other important components to various parts of the body. It also collects metabolic waste to be filtered or expelled from the body.

2. What are the 3 types of circulation?

  • Pulmonary Circulation
  • Systemic Circulation
  • Coronary Circulation

3. Is the human circulatory system open or closed?

The human circulatory system is a closed system that pumps blood through a network of arteries and veins. This type of circulation is seen in all vertebrates and some invertebrates.

4. What is the advantage of a closed circulatory system?

In a closed circulatory system, more pressure is available in the system and the blood can reach body extremities much quicker. This translates to a much faster metabolism rate and quicker movements in organisms with closed circulatory systems.

5. What is double circulation?

Double circulation is a system of circulation where the blood flows through the heart twice. This type of circulation is very effective as the body has a constant supply of oxygenated blood.

Discover more about the circulatory system by registering at BYJU’S Biology. Find more concepts and important questions about human circulatory system class 11 by downloading BYJU’S – The Learning App.

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