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 main systems of the human body are the nervous, endocrine respiratory, circulatory, immune, digestive, excretory, skeletal, muscular, and the reproductive systems. They all work together in harmony and unison to keep us alive. The nervous and endocrine systems are what control most of the body. The nervous system includes the brain, spinal, cord and nerves. The endocrine system consists of various hormonal glands such as the pituitary. These two systems interact closely since they both have a part in controlling the body.