The Human Circulatory System (WJEC GCSE Biology)
Revision Note
The Flow of Blood around the Body
The circulatory system consists of a closed network of blood vessels connected to the heart
Oxygenated blood is carried away from the heart and towards organs in arteries
These narrow to capillaries as they pass through the organ
In the organs, respiring cells use oxygen from the blood
The capillaries widen into veins as they move away from the organs
Veins carry deoxygenated blood back towards the heart
Details of the four main arteries and veins that enter and leave the heart are as follows:
Main blood vessels of the circulatory system table
Name of blood vessel | Type of vessel | Organ blood moves from | Organ blood moves to |
|---|---|---|---|
Aorta | Artery | Heart | Body |
Pulmonary artery | Artery | Heart | Lungs |
Vena cava | Vein | Body | Heart |
Pulmonary vein | Vein | Lungs | Heart |
Double Circulatory Systems
The circulatory system is a double circulatory system
This means that the blood passes through the heart twice on each full circuit of the body
The circulatory system has two 'loops' or systems of blood vessels
One system carries deoxygenated blood from the heart to the lungs, where it becomes oxygenated and then carries the blood back to the heart
This system is called pulmonary circulation
The second system carries oxygenated blood from the heart to the respiring body tissues, where it delivers the oxygen to the cells for respiration, and then carries the deoxygenated blood back to the heart
This system is called systemic circulation
Circulatory system diagram
The circulatory system showing the pulmonary and systemic systems
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