The main components of the transport system in human beings are the heart, blood, and blood vessels and their function are as follows:

The heart helps in pumping the oxygenated blood throughout the body. From the various parts of the body the deoxygenated blood is accumulated in the heart and from there it goes to the lungs for oxygenation.
Blood is the main body fluid that helps in the transport of nutrients, oxygen, carbon dioxide, nitrogenous wastes, and hormones.
Blood also consists of white blood cells (WBCs) thus making it the main component of our immune system.
Blood also consists of platelets that cause the clotting of blood that helps in repairing
the damaged blood vessels. Also, the temperature of the body is also maintained by transportation.
Blood vessels (arteries, veins, and capillaries) are responsible for blood transportation either from the heart to various other body organs or from various body organs to the heart.
All arteries carry oxygenated except pulmonary arteries and they transport blood from the heart to various parts of the body while all veins carry deoxygenated blood except pulmonary veins.
The material that exchanges between the blood and tissues takes place inside the capillaries.