The Flow of Bloodin the

Human Circulatory System

Blood re-enters heart from body

• Oxygen-poor blood

• Enters right atrium

• Upper body – Superior (Upper) Vena Cava

• Lower Body – Inferior (Lower) Vena Cava

RA

Right atrium contracts

• Tricuspid Valve opens

• Oxygen-poor blood

• Blood enters Right Ventricle

RA

RV

Right Ventricle Contracts

• Pulmonary valve opens

• Oxygen-poor blood

• Blood enters Pulmonary Artery

RV

Blood enters capillaries in lungs

• Pulmonary artery takes oxygen-poor blood to lungs

• Gas exchange occurs – Carbon dioxide leaves blood, oxygen enters blood

• Oxygen-rich blood returns to heart via Pulmonary Vein

Blood Enters Left Atrium

• Oxygen-rich blood returns to heart

• Pulmonary veins empty blood into left atrium

RV

LA

Left Atrium Contracts

• Bicuspid valve opens

• Oxygen-rich blood

• Blood exits left atrium, enters left ventricleRV

LA

LV

Left Ventricle Contracts

• Aortic valve opens• Oxygen-rich blood• Blood enters

Aorta, which branches into the Ascending (Upper) Aorta and Descending (Lower) Aorta

RV

LA

LV

Blood travels to all areas of the body

• Oxygen-rich blood

• Aorta branches into network of arteries and capillaries that supply each cell in the body with oxygen and nutrients

Oxygen-rich blood enters body capillaries

• Oxygen is dropped off at body cells and carbon dioxide is absorbed

• Nutrients are dropped off and wastes are absorbed

• Blood becomes oxygen-poor

Capillaries return blood to veins

• Oxygen-poor blood returns to veins

• Veins have series of valves to keep blood from flowing backwards

• Veins are often sandwiched between muscles that contract and squeeze the veins to keep blood moving

Blood re-enters heart from body

• Oxygen-poor blood

• Enters right atrium

• Upper body – Superior (Upper) Vena Cava

• Lower Body – Inferior (Lower) Vena Cava

RA