Heart

Heart

Two parts of the heart
1. Atrium
2. Ventircle
3. Separated by valves:
  1. Left atrioventricular (bicuspid)
  2. Right atrioventricular (tricuspid)
Vessels connecting to the four chambers of the heart
1. Aorta - left ventricle and carries O2 blood to the body apart from the lungs
2. Vena Cava
  1. Connected to right atrium, and brings de02 blood back from tissues of the body
3. Pulmonary artery
  1. connected to right ventricle and carries de02 blood to the lungs
4. Pulmonary vein
  1. connected to left atrium and brings 02 blood back from lungs
Coronary arteries supply the heart with its respiratory needs.
1. a blockage of these arteries, e.g by a blood clot, leads to myocardial infarction, or heart attack, as an are of the heart is deprived of 02 and thus dies.
Relaxation of the heart (diastole)
1. Blood returns to the atria of the heart from the pulmonary vein (from the lungs) and the vena Cava (from the body)
2. As the atria fill, the pressure in them rises, causing the AV valves to open, and so, blood passes into the ventricles
3. The walls of the atria and ventricles are relaxed at this stage.
Contraction of atria (atrial systole)
1. The thin muscle walls of the atria contract, and so, the remaining blood is pushed into the ventricles.
Contraction of ventricles
1. After they're filled, their walls contract simultaneously, increasing the pressure in them. The AV vavles close to prevent back flow.
2. As the pressure rises, the semi-lunar valves open, therefore blood is pushed into the pulmonary artery and aorta.

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