Structure of the heart

There are four chambers in the heart:

1. Right atrium
2. Right ventricle
3. Left atrium
4. Left ventricle

The atria are where blood flows into the heart from [lungs/ body] i.e. from veins.
The ventricles have thicker walls as they generate the pressure to pump blood away from the heart. The left ventricle generates more pressure to pump blood around the entire body.

The atrio-ventricular valves are valves situated between the atria and ventricles to prevent blood from flowing in the wrong direction.

Tendinous chords prevent the valves from turning inside out in the event of high blood pressure.

The main blood vessels are:

1. Aorta
2. Vena Cava
3. Pulmonery artery
4. Pulmonery vein
___________

1. Arteries
2. Veins
3. Capillaries

1. The Aorta is the main artery taking oxygenated blood away from the heart to the rest of the body. It has thick muscular walls and a narrow lumen to deliver blood under a high pressure.

2. The Vena Cava is the main vein taking deoxygenated blood to the heart from the rest of the body. It has thin walls and a wide lumen. It delivers blood under a low pressure but contains valves to prevent blood from flowing the wrong way.

3. The pulmonary artery is the blood vessel that takes deoxygenated blood away from the heart to the lungs. It has thick muscular walls and a narrow lumen to increase the blood pressure.

4. The pulmonary vein takes oxygenated blood away from the lungs to the heart under low pressure. This is a result of the blood passing through small capillaries where it loses its pressure.

5. Arteries in general transfer oxygenated blood to tissues and organs all over the body. They have thick muscular walls and a narrow lumen to increase the blood pressure. Therefore they have no valves - the blood already flows at a high pressure. They have elastic walls to allow the artery to expand and recoil.

6. Capillaries are have walls one cell thick to decrease the diffusion distance for gases during gas exchange. They allow the exchange of substances into and out of the blood.

7. Veins have thin walls and a large lumen. They contain blood under a low pressure therefore they have valves to prevent it from flowing in the wrong directions. They contain deoxygenated blood except the pulmonary vein which transfers oxygenated blood from the lungs to the heart.


Note that smoking can severely increase blood pressure resulting in blood vessels from bursting. The bad cholesterol levels are raised due to the chemicals in tobacco smoke and they block the lumen.