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 human brain is the main organ of the human nervous system. It is located in the head, protected by the skull. It has the same general structure as the brains of other mammals, but with a more developed cerebral cortex.he human brain is the main organ of the human nervous system. It is located in the head, protected by the skull. It has the same general structure as the brains of other mammals, but with a more developed cerebral cortex.