The circulatory system
The circulatory system is the body's delivery service. It is made up of the heart and thousands of tubes called arteries and veins. The blood travels through them and delivers nutrients and oxygen to every cell.
A muscle that pumps blood around the body, day and night.
Tubes that carry blood away from the heart to the body.
Tubes that carry blood back to the heart.
The four parts of the heart
Your heart is about the size of your fist and it has four sections: two at the top called atria (one is an atrium) and two at the bottom called ventricles. There is a left side and a right side.
Left and right are the heart's own sides, as if you were looking at it from inside the body.
Put two fingers on the inside of your wrist, under your thumb. Can you feel a little beat? That is your pulse: your heart pushing the blood. Count the beats for one minute. Then jump 20 times and count again. Your heart beats faster when you exercise because your muscles need more oxygen.
because gives the reason: My heart beats faster because I am running. so gives the result: I am running, so my heart beats faster.
