How Your Heart Works
Your heart is a pump, and it keeps blood moving around your
body. Your blood delivers oxygen and nutrients to all parts of your
body, and carries away unwanted carbon dioxide and waste
products.
Your heart has four chambers - two on the left side and two on
the right. The two upper chambers are called the
atria, and the two lower chambers are called the
ventricles. The two sides of the heart are divided
by a muscular wall called the septum. Each side of
the heart has a ‘one-way valve system’, which means that the blood
travels in one direction through the heart – a bit like a one-way
system.
The heart and circulatory system
Blood is pushed through the heart by the heart muscle
contracting. With each contraction, or heartbeat, the heart pumps
blood forward from the left side of the heart through the
aorta (the main artery leaving the heart) and into
the arteries. The arteries divide off into smaller and smaller
branches to supply a microscopic network of
capillaries, taking the blood to every part of
your body. The blood then travels back to the heart from the
capillaries into the veins, back to the heart. The
branches of the veins join to form larger veins, which deliver the
blood back to the right side of your heart.
As the heart relaxes in between each
heartbeat or contraction, blood from your veins fills the right
side of your heart and blood from the lungs fills the left side of
your heart. The two sides of the heart are separate, but they work
together. The right side of the heart receives dark, de-oxygenated
blood which has circulated around your body. It pumps this to your
lungs, where it picks up a fresh supply of oxygen and becomes
bright red again.
The heart wall is made up of special muscle
called myocardium. Like every other living tissue,
the myocardium itself needs a continuous supply of fresh blood.
This supply of blood comes from the coronary
arteries which start from the main artery (the aorta) as
it leaves the left ventricle. The coronary arteries spread across
the outside of the myocardium, feeding it with a supply of
blood.
More information
Visit our Publications
section to download or order:
Got any questions about this page?
