The circulatory system consists of one heart, five liters of blood, and approximately 96,000 kilometers of blood vessels, responsible for transporting nutrients and waste throughout the body.

This short film offers a look at respiration and a tour around the circulatory system and digestive system in the human body, through blood vessels and into mitochondria. There is a detailed ...

For nine months, you were enveloped in the warm, comfortable world of your mother's womb. Your every need was taken care of. The placenta supplied you with oxygen from your mother's blood, so your ...

Day and night, the muscles of your heart contract and relax to pump blood throughout your body. When blood returns to the heart, it follows a complicated pathway. If you were in the bloodstream ...