The West is blinking in disbelief â Vladimir Putin just invaded Ukraine. German diplomats, French Eurocrats and American pundits are all stunned.
The  circulatory system is the body's transport system. It is made up of a group of organs that transport blood throughout the body. The heart pumps the blood and the arteries and veins transport it. Oxygen-rich blood leaves the left side of the heart and enters the biggest artery, called the aorta.
The skin is the largest organ of the human body and of all mammals. In the average adult it weighs around six pounds, which is nearly twice the weight of the human brain or liver. The largest internal organ is the liver.