click on areas of the diagram to reveal more
The heart is made to pump by a special electrical system which runs throughout the heart. Each normal heart beat begins in the natural pacemaker of the heart (the sinu-atrial or SA node) which lies in the right atrium. Electricity passes down the heart to a junction box (atrio-ventricular or AV node) which lies between the upper and lower chambers of the heart.
The AV node is the only way down into the bottom chambers normally. After passing through the AV node, electricity spreads through the left and right ventricles and causes the heart to pump.
In some people there are disturbances in the electrical system which may cause symptoms such as palpitations, light headedness, fainting, chest pain or shortness of breath. These disturbances may be caused by faults in the normal electrical system (often referred to as 'pathways').
We can test the way that the electricity works in the heart by doing a test known as an Electrophysiology study. This tells us if the electrical pathways in the heart are working normally or if there are extra pathways that are causing problems.
Each day the heart beats about 100,000 times and pumps about 5,000 gallons of blood. The normal heart at rest beats between 60 and 80 beats a minute.
Normal heart ECG trace
Right Atrium
Right upper chamber of the heart. The right atrium receives deoxygenated blood from the body through the vena cava and pumps it into the right ventricle through the tricuspid valve.
Left Ventricle
Section through the left ventricle.
(left picture looking from the bottom right, upwards)
Top is the Pulmonary Valve.
Middle is the the Aortic Valve and just below and right (the yellow coloured object) is the Mitral Valve.
Mitral Valve : Stops blood entering the left Atrium when the left Ventricle contracts.
Aortic Valve : Prevents blood, in the aorta, from returning to the left Ventricle
View of the left side of the heart showing left Atrium extending around the back of the heart under the Pulmonary Trunk. The Left Ventricle is on the lower left. The Aorta is the large vessel coloured red at the top of the picture.
Section through the Left Atrium as looking from the back of the heart. The object on the left is the Mitral Valve through which is the left ventricle.
The object on the right is the foramen ovale - which is a hole (the foramen ovale) in the wall (septum) between the right atrium and left atrium of the heart. The foramen ovale usually closes after birth but for 25% of people this doesn't happen. This, however, doesn't present any complications for people with this condition.
How the heart works
The heart is a specialised muscle pump which pumps blood around the body to supply vital organs with oxygen. It is divided into 4 parts known as chambers. There are two small chambers at the top of the heart (the right atrium and the left atrium) and two larger chambers at the bottom of the heart ( the right ventricle and the left ventricle). The left ventricle is the main pumping chamber.
The heart is made to pump by a special electrical system which runs throughout the heart.
Since the heart itself is living tissue, it needs to be supplied with fresh blood. The heart muscle is fed from the coronary arteries. When this supply of blood is interrupted or blocked the heart muscle can be damaged. This event is commonly know as a heart attack (mycardial infarction). When the coronary arteries are narrowed, due to build up of fatty deposits, the flow of oxygen to the heart muscle is decreased causing pain. This is known as angina. Each day the heart beats about 100,000 times and pumps about 5,000 gallons of blood. The normal heart at rest beats between 60 and 80 beats a minute. The heart is actually two pumps. The left side receives fresh blood from the lungs and pumps it around the body. The left side is therefore stronger as it has more work to do.
The right side of the heart receives de-oxygenated blood from the body and pumps it to the lungs. Since the lungs are closeby the heart has to do less work and consequently the right side is weaker.
Right Ventricle
The right side of the heart takes used or de-oxygenated blood that comes from the rest of the body, via large veins called the Inferior & Superior Vena Cava. Blood enters the right atrium then down into the right ventricle via the tricuspid valve.
When the right ventricle contracts the blood is pumped into the Pulmanory Artery ,through the Pulmonary Valve, away to the lungs to be re-oxygenated before returning to the heart via the Pulmonary Veins.
Right Ventricle showing the tricuspid valve and the pulmonary valve(top)
Coronary Arteries and Veins
These surround the heart muscle. The arteries (red) take blood to the heart muscle and the veins (blue) take the de-oxygenated blood back. Above shows the arteries and veins on the front-right side of the heart. The arteries and veins extend around and under the heart and attach to the aorta and the Vena Cava veins.
Since the heart itself is living tissue, it needs to be supplied with fresh blood. The heart muscle is fed from the coronary arteries. When this supply of blood is interrupted or blocked the heart muscle can be damaged. This event is commonly know as a heart attack (mycardial infarction or MI). When the coronary arteries are narrowed, due to build up of fatty deposits, the flow of oxygen to the heart muscle is decreased causing pain. This is known as angina.
Blocked or narrowed arteries are treated using angioplasty or by surgery(bypass).
