Cells are grouped into tissues and tissues are grouped into organs.
- Pulmonary artery – carries deoxygenated blood from heart to lungs
- Vena cava – brings deoxygenated blood from body to heart
- Aorta – carries oxygenated blood from heart to body
- Pulmonary vein – carries oxygenated blood from lungs to heart
The left ventricle is thicker than the right ventricle as it pushes blood all around the body.