The Circulatory System

• Humans have a double circulatory system, with the heart pumping blood through the arteries and veins two times
• Blood flows into the two atria by the vena cava and the pulmonary vein
• The ventricles contract, forcing the blood into the pulmonary artery and aorta, and out of the heart
• Blood then flows to the organs through the arteries, and returns through the veins
• The heart is made of cardiac muscle, containing mitochondria o provide ATP for cells
• Pathway of oxygenated blood: Blood travels through the pulmonary vein, to the left atrium, down to the left ventricle, then to the aorta and round the systemic system.
• The Pulmonary vein supplies oxygen to the heart
• Blood in the arteries is at high pressure as it coms from the heart
• Blood in an artery is oxygenated because arteries take blood away the from the heart for respiration
• The atria receives blood from the pulmonary vein
• The septum separates the deoxygenated and oxygenated blood
• Muscle cells get the energy needed to work during exercise by cellular respiration, as it supplies ATP
• The structure of the heart which controls the direction of blood flow

  between the left atrium and left ventricle is the bicuspid valve