The heart

The heart

Structure
1. Atrium
  1. Thin-walled
    1. Pumps short distance - ventricle
  2. Elastic
  3. Stretches as blood is collected
2. Ventricle
  1. Thick-walled
  2. Pumps to lungs/whole body
3. Aorta
  1. Connected to LV
  2. Carries oxygenated blood to body
4. Vena Cava
  1. Connected to right atrium
  2. Brings deoxy blood back from body
5. Pulmonary artery
  1. Connected to right ventricle
  2. Deoxy blood from lungs
    1. Unusual for artery to carry deoxygenated
6. Pulmonary vein
  1. Connected to left atrium
  2. Brings oxygenated blood from lungs
    1. Unusual for vein to carry oxygenated
Cardiac cycle
1. 1) Electrical activity SAN -> across both atria -> atria contract
2. 2) Collagen stops wave crossing to ventricles
3. 3) Wave passes to AVN
4. 4) Electrical impulse -> bundle of His
5. 5) Wave -> down septum to base of ventricles, bundle branches into smaller fibres
6. 6) wave released from fibres -> ventricles contract apex up.
7. Diastole
  1. Blood returns to atria through pulmonary vein & vena cava
  2. As atria fill, pressure ^ -> AV valves open
  3. Walls of atria + Ventricles relaxed
    1. Relaxation of ventricles reduces pressure - lower than aorta/pulmonary artery
      1. SL valves close. "Dub"
8. Atrial systole
  1. Atria contracts, forcing remaining blood into ventricles
  2. thin walls as only to ventricles
  3. Ventricles relaxed
9. Ventricular systole
  1. Walls contract simultaneously once full
  2. Increases pressure - shuts AV valves "lub"
    1. SL open -> blood pushed into pulmonary artery & aorta
  3. Thick walls as pump to lungs/body
10. Myogenic
Supplying heart with O2
1. Coronary arteries branch off aorta shortly after leaving heart
  1. Blockage here leads to myocardial infarction
Valves
1. Atrioventricular
  1. between atrium&ventricle
  2. Prevent backflow when ventricles contract
2. Semi-lunar
  1. In aorta&pulmonary artery
  2. Prevent backflow when recoil in aorta/pulmonary artery causes pressure to exceed that in ventricles
Cardiac output
1. heart rate x stroke volume
2. Heart rate
  1. Rate of heart beat
3. Stroke volume
  1. Vol. blood pumped out at each beat

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	Created by Jody Lelean-Smith almost 12 years ago