heart

• The main layer of tissue forming the heart is the mycocardium, which is composed of cardiac muscle cells.
• cardiac muscle is myogenic and can sustain its own contactions
• Contraction of the heart muscle is known as systole and relaxation as

  diastole
• diastole means filling the heart with blood
• systole means emptying the heart with blood
• Atrio-ventricular valves are made of connective tissue and are present in the heart to ensure one way flow of blood from the atria to the ventricles.
• On the right hand side is the tricuspid valve and the left side the bicuspid valve
• Chordi tendinea stops AV valves blowing inside out ans stopping reflux of blood into atria. The chordae tendinae are attached to

  papillary muscle on the heart wall.
• semilunar valves are made from connective tissue but not chordi tendinea
• during the cardiac cycle, The left hand side of the heart pumps blood to the body while the right hand side pumps blood to the lungs. The

  lungs lie considerably closer to the heart, consequently the wall of the left ventricle is thicker than the right in order to allow a greater force of contraction to generate the greater pressure needed to pump the blood further.
• The 3 main stages of the cardiac cycle are?

  1. atrial systole
  2. ventricular systole
  3. Diastole
• atrial systole is the contraction of the atria
• Atrial Systole will force all remainder blood into the atria. The

  contraction of the chambers makes the pressure of blood within the chambers to increase. When this happens in atria, it causes the AV valves to open allowing the rest of the blood into the ventricles.
• Ventricular Systole is when the walls of the ventricles contract and the blood pressure in the ventricles rises. When the pressure of the blood in the ventricles exceeds that in the atria, the AV valves shut.

  Then, the pressure in the ventricles will also exceed that in the arteries leaving the heart. This will force open the semilunar valves allowing

  blood to leave the heart.
• 3. Diastole is Relaxation of the ventricles.

  As the ventricle walls relax, pressure of blood it has drops rapidly and falls below that in the arteries. Because of this, blood tries to move from where it is at higher pressure in the arteries to the ventricles. This causes the semi-lunar valves to shut – As the atria relax, blood will enter them from the veins.