heart and blood vessels

• Heart

  An organ that pumps blood around the body in a double circulatory system
• Heart

  • Much of the wall of the heart is made from muscle tissue
• Main chambers of the heart

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle
• Blood flow through the heart

  1. Blood enters the atria

  2. Atria contract and force blood into the ventricles

  3. Ventricles contract and force blood out of the heart
• Right ventricle

  Pumps blood to the lungs where gas exchange takes place
• Left ventricle

  Pumps blood around the rest of the body
• Valves in the heart

  • Ensure that blood flows in the correct direction
• Blood flow through the body

  1. Blood flows from the heart to the organs through arteries

  2. Blood returns through veins
• Circulation systems

  • Lungs
  • All other organs of the body
• Natural resting heart rate

  Controlled by a group of cells located in the right atrium that act as a pacemaker
• Artificial pacemakers

  Electrical devices used to correct irregularities in the heart rate
• The body contains three different types of blood vessel:

  • arteries
  • veins
  • capillaries

  Arteries have thick walls containing muscle and elastic fibres. Veins have thinner walls and often have valves to prevent back-flow of blood.

  If arteries begin to narrow and restrict blood flow stents are used to keep them open.

  In the organs, blood flows through very narrow, thin-walled blood vessels called capillaries. Substances needed by the cells in body tissues pass out of the blood, and substances produced by the cells pass into the blood, through the walls of the capillaries.