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Have you ever wondered how all the nutrients that we obtain from food are transported to all the other parts of the body from the digestive system? How the air we respire reaches the various parts of the body from the lungs?

For survival, an organism requires food, water, and oxygen and a system to transport these substances to all the parts of the body for its proper functioning. This system is the circulatory system of the body.
Hence, the circulatory system plays a very important role in the functioning of the entire human body.
Human circulatory system
The circulatory system of humans is a transport system that comprises the network that circulates food, water, and oxygen to the various parts of the body.

It transports respiratory gases, nutrients, hormones and waste products within the body.
The circulatory system also protects the body from various harmful pathogens and plays a prominent role in regulating body temperature.
Circulatory system
The three main components that form the circulatory system are:
  1. Blood
  2. Heart
  3. Blood vessels
The red colour fluid which flows in the blood vessels of our body is known as blood.
Blood is a fluid connective tissue that contains plasma and blood cells.
Functions of blood
Blood serves as the medium of transportation for various substances like digested food from the small intestine to the other parts, oxygen from the lungs to the body's cells. It also transports the wastes to the excretory system for their removal from the body. It also plays a significant role in the regulation of body temperature.
Components of blood
The blood is capable of performing several functions due to its composition. The various components of blood are blood plasma,
  • Red blood corpuscles or cells (RBCs)
  • White blood corpuscles or cells (WBCs)
  • Platelets
Composition of blood
The red blood cells are produced in the bone marrow. They are red in colour as they contain a red-coloured pigment known as haemoglobin. The blood appears red due to the presence of this pigment.