The circulatory system consists of the heart and blood vessels. The heart acts as a pump to keep blood moving throughout the body. Arteries are blood vessels which carry blood away from the heart. This blood contains a lot of oxygen and nutrients for the body.
Veins are blood vessels which carry blood to the heart from various parts of the body.
This blood is low in oxygen and nutrients. Cellular Transport System Red blood cells function by carrying oxygen to every part of the body, and then carrying carbon dioxide back to the lungs. Red blood cells are very well designed to perform this important job. First, they are packed full of hemoglobin, which is an iron-bearing protein that transports oxygen to other cells. Interestingly, red blood cells have no nuclei, a feature which makes even more room for hemoglobin.