Arteries carry oxygen-rich blood away from the heart to all of the body's tissues. They branch several times, becoming smaller and smaller as they carry blood farther from the heart. These are small, thin blood vessels that connect the arteries and the veins. Their thin walls allow oxygen, nutrients, carbon dioxide and waste products to pass to and from the tissue cells. Veins These are blood vessels that take oxygen-poor blood back to the heart.
Veins become larger and larger as they get closer to the heart.
The superior vena cava is the large vein that brings blood from the head and arms to the heart, and the inferior vena cava brings blood from the abdomen and legs into the heart. Blood flows continuously through your body's blood vessels. Your heart is the pump that makes it all possible. Looking at the outside of the heart, you can see that the heart is made of muscle. On the inside, the heart is a four-chambered, hollow organ.