Reproduced with kind permission of the British Heart Foundation from their booklet The heart – technical terms explained 2007 www.bhf.org.uk. “This drawing is reproduced with the kind permission of the British Heart Foundation, the copyright owner.”
The heart and circulatory system
Your heart is a pump. It keeps the blood moving around your body. The blood delivers oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and other waste products.
The heart has four chambers – two on the left side and two on the right side. The upper chambers are called 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 only in one direction through the two chambers on each side.
The illustration below shows the direction of the blood flows in through your heart and the names of all the different parts of the heart
Your Heart and how it works
The right side of the heart receives blood back from the veins in the body and pumps it through the pulmonary artery to the lungs. There it picks up fresh oxygen and releases carbon dioxide and then passes through to the left side of the heart.
The left side of the heart receives oxygen- rich blood from the arteries in the lungs, and pumps it through the aorta into the body.
The illustration below shows the direction the blood flows in and we explain this in more detail next.
With each contraction of the heart muscle, or heart beat, the heart pumps blood forward from the left side of the heart through the aorta into the arteries. The arteries divide off into smaller and smaller branches to supply a microscopic network of capillaries, taking blood to every part of your body.
The blood then travels back to the heart. First it goes from the capillaries into the veins. The branches of veins join to form larger veins, which deliver the blood back to the right side of your heart.
As the heart relaxed 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 right red again.
Each side of the heart has a thin walled ‘collecting chamber’, (the atrium) which helps to fill the thick- walled main pump (the ventricle).
The heart wall is made of special muscles 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.
The circulatory system is called the cardiovascular system. It contains about 5 litres (8 pints) of blood which the heart is continuously recirculating. Every day your heart beats about 100,000 times and pumps about 23,000 litres (5,000 gallons) of blood.