Structure of the Heart (Cambridge (CIE) AS Biology): Revision Note

Mammalian heart structure

Heart structure

• The human heart has a mass of around 300g and is roughly the size of a closed fist

• The heart is a hollow, muscular organ located in the chest cavity

• The heart is divided into four chambers

  • The two top chambers are atria and the bottom two chambers are ventricles

• The left and right sides of the heart are separated by a wall of muscular tissue, called the septum

  • The septum is very important for ensuring blood doesn’t mix between the left and right sides of the heart

Valves in the heart

• Valves in the heart:

  • Open when the pressure of blood behind them is greater than the pressure in front of them

  • Close when the pressure of blood in front of them is greater than the pressure behind them

• Valves are important for keeping blood flowing forward in the right direction and stopping it flowing backwards

  • They are also important for maintaining the correct pressure in the chambers of the heart

• The right atrium and right ventricle are separated by the atrioventricular valve

  • This is also known as the tricuspid valve

• The right ventricle and the pulmonary artery are separated by the pulmonary valve

• The left atrium and left ventricle are separated by the mitral valve

  • This is also known as the bicuspid valve

• The left ventricle and aorta are separated by the aortic valve

• There are two blood vessels bringing blood to the heart:

  • Vena cava

  • Pulmonary vein

• There are two blood vessels taking blood away from the heart:

  • Pulmonary artery

  • Aorta

Coronary arteries

• The heart is a muscle and so requires its own blood supply for aerobic respiration

• The heart receives blood through arteries on its surface, called coronary arteries

• It’s important that these arteries remain clear of plaques, as this could lead to angina or a heart attack (myocardial infarction)