Circulatory System 1 - Heart

• Circulatory system


  An example of an organ system whose role is to transport oxygen and nutrients to the body's tissues
• Circulatory system

  • Relies on 3 main things: blood, blood vessels, heart
• Blood flow through the circulatory system

  1. Blood flows from heart to lungs, gains oxygen, flows back to heart

  2. Oxygenated blood flows from heart to body, gives up oxygen, flows back to heart
• Heart


  Consists of 4 chambers with thick muscular walls, and veins/arteries
• When looking at a diagram of the heart, the left side is on the right and the right side is on the left
• Atria


  Top chambers of the heart
• Ventricles


  Bottom chambers of the heart
• Valves


  Prevent blood from flowing backwards, ensure blood flows in the right direction
• Blood flow through the heart

  1. Blood flows into right atrium and left atrium

  2. Atria contract, pushing blood into ventricles

  3. Ventricles contract, pushing blood out into pulmonary artery and aorta

  4. Atria refill with new blood, cycle repeats
• Pacemaker cells

  Group of cells in the right atrium that produce electrical impulses to regulate the heart rate
• Artificial pacemaker

  Small device implanted under the skin above the heart to regulate heart rate
• Artery


  Any vessel that carries blood away from the heart
• Vein


  Any vessel that carries blood to the heart
• Arteries don't always carry oxygenated blood, and veins don't always carry deoxygenated blood
• Coronary arteries

  Small arteries that branch off the aorta to supply the heart muscle with oxygenated blood
• Arteries


  Carry blood away from the heart
• Capillaries


  Exchange nutrients and oxygen with the tissues
• Veins


  Carry the blood back to the heart
• Arteries


  • Have a thick layer of muscle tissue to keep them strong
  • Have a thick layer of elastic tissue so they can stretch and recoil
• Capillaries


  • Have walls that are only a single cell thick
  • Are permeable, allowing substances to easily diffuse through them
  • Have a tiny lumen but a huge total cross-sectional area
• Veins


  • Have relatively large lumens
  • Have relatively thin walls with only small layers of elastic fibers and smooth muscle
  • Have valves to prevent blood from flowing backwards
• Calculating rate of blood flow

  Divide the amount of blood (2500 ml) by the time it took (8 minutes) to get the rate (320 ml/min)