The circulatory system is the system that transports materials around the body to and from the cells.
Question? Why do humans need a circulatory system whereas bacteria and simple organisms do not?
Answer: Because the cells of a complex organism such as a human have many cells that are far from the outside environment where nutrients would come from. The system brings the materials to the cells that would not normally receive them.
Humans have a closed circulatory system: This means that the blood is always contained in tubes and vessel
Functions of Heart Structures
Inferior/Superior Vena Cava: Returns deoxygenated blood to the right atrium
from the body.Right Atrium: Thin walled chamber of the heart that receives deoxygenated blood from the body.
Tricuspid valve: Controls the flow of blood entering the right ventricle from
the right atrium.Right Ventricle: Muscular chamber that pumps blood TO the lungs.
Semilunar Valves: Valves that control the flow of blood out of the heart.
Pulmonary Arteries: Arteries that carry blood TO the lungs.
Pulmonary Veins: Veins that bring blood to the heart from the lungs.
Left Atrium: Thin walled chamber that receives oxygenated blood from
the lungs.Left Ventricle: Thick walled chamber that pumps blood out of the heart and
to the body.Aorta: Large artery that carries blood away from the heart and to all parts of the body.
Septum: A wall of muscle that separates the left side of the heart from
the right side. This prevents the mixing of oxygenated and deoxygenated blood.Bicuspid Valve: A valve that controls the flow of blood from the left atrium to
the left ventricle.