The Human Heart (AQA A Level Biology): Revision Note

Mammalian heart structure

• The human heart is divided into four chambers

  • The two top chambers are the left and right atria (singular atrium)

  • The bottom two chambers are the left and right ventricles

• The left and right sides of the heart are separated by a wall of muscular tissue called the septum that ensures that blood from the left and right sides of the heart doesn't mix

  • The left side of the heart contains oxygenated blood

  • The right side of the heart contains deoxygenated blood

• The heart contains valves to ensure that blood flows forwards in the right direction

  • The right atrium and ventricle are separated by the right atrioventricular valve, also known as the tricuspid valve

  • The left atrium and ventricle are separated by the left atrioventricular valve, also known as the bicuspid valve

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

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

• Two blood vessels bring blood to the heart

  • The vena cava brings blood from the body

  • The pulmonary vein brings blood from the lungs

• Two blood vessels take blood away from the hear

  • The pulmonary artery transports blood to the lungs

  • The aorta transports blood to the body

The thickness of the muscle walls in the heart differs depending on the amount of pressure that they need to generate

• The muscular walls of the atria are thinner than those of the ventricles because the atria pump blood over a much shorter distance

• The muscle of the left ventricle is thicker than that of the right ventricle because the blood leaving the right ventricle travels less distance than blood leaving the left ventricle