4 chambers of the heart

Your heart is roughly the size of a fist and sits in the middle of your chest, slightly to the left. It’s the muscle at the centre of your circulation system. It pumps blood around your body as your heart beats. This blood sends oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and waste products. Structure of your heart Your heart is made up of 3 layers of tissue: • epicardium • myocardium • endocardium These layers are surrounded by the pericardium, a thin outer lining protecting your heart. There are 4 chambers that make up the heart – 2 on the left side and 2 on the right. The 2 small upper chambers are the atria. The 2 larger lower chambers are the ventricles. These left and right sides of the heart are separated by a wall of muscle called the septum. Circulatory system Your heart pumps blood around the body all the time - about 5 litres (8 pints) of it. This is called circulation. Your heart, blood and blood vessels together make up your cardiovascular system (or heart and circulatory system). The right side of the heart receives blood that is low in oxygen because most has been used up by the brain and body. It pumps this to your lungs, where it picks up a fresh supply of oxygen. The blood then returns to the left side of the heart, ready to be pumped back out to the brain and the rest of your body. Blood vessels Your blood is pumped around your body through a network of blood vessels: • arteries – they carry oxygen-rich blood ...