Heart.

• Pulmonary system takes the blood from the heart to the lungs to receive oxygen.
• Systemic system takes blood from the heart to the rest of the body to release oxygen to respiring cells.
• The heart is Approximately the size of your fist​

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  •Structure​

  •Epithelial tissue- outer and inner layers​

  •Cardiac muscle- Middle layer​

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• Pulmonary System - Deoxygenated blood is pumped from the right ventricle to the lungs to be oxygenated, and the oxygenated blood returns to the left atrium. ​
• Systemic System - Oxygenated blood is pumped from the left ventricle around the body and the deoxygenated blood is returned to the right atrium. 
• The main function of the heart is to pump oxygenated blood around the body. ​

  As the blood flows through the heart it is known a double circulation. ​
• Deoxygenated blood returns to the heart from the body via the superior and inferior vena cava.​

  ...Right atrium contracts pushing all the blood through the tricuspid valve into the right ventricle.​

  ...Right ventricle contracts closing the tricuspid valve to prevent backflow. Closing of the valve results in the ‘lub’ sound.​

  ...Right ventricle continues to contract pushing the blood through the pulmonary valve.​

  The deoxygenated blood is carried by the pulmonary artery to the lungs to be oxygenated. Right ventricle relaxes and the pulmonary valve closes causing the ‘dub’ sound. 
• Oxygenated blood returns to the heart from the lungs via the pulmonary vein.​

  ...Left atrium contracts pushing the blood through the mitral valve into the left ventricle.​

  ...Left ventricle contracts closing the mitral valve to prevent backflow.  The closing of the valve results in the ‘lub’ sound.​

  ...Left ventricle continues to contract pushing the blood through the aortic valve.​

  The oxygenated blood is carried by the aorta around the body.Left Side:​

  Left ventricle relaxes and the aortic valve closes causing the ‘dub’ sound. 
• Blood pathway-

  Vena cava- right atrium- tricuspid valve- right ventricle- pulmonary valve- pulmonary artery - lungs- pulmonary vein- left atrium- mitral valve- left ventricle- atortic valve- aorta