Human heart

• Surrounded by sac called the pericardium - pericardial fluid reduces friction on the heart wall
• Made of cardiac muscle - heart is two pumps separated by septum ( a wall of tissue )
• Double circulation separates oxyginated and deoxygenated blood
• Two upper chambers ( atria )

  two bottom chambers ( ventricles )
• Blood enters from atria and leaves from ventricles
• Ventricles have thicker muscles than atria as they are pumping blood further
• Deoxygenated blood enters right atrium from via vena cava ( main vein ) and leaves right ventricle via pulmonary artery to go to lungs to pick up oxygen
• Oxygenated blood enters left atrium from the lungs via pulmonary vein , leaves left ventricle via the aorta ( main artery ) to go to the body
• Walls on left side of heart thicker because higher forces needed to pump blood further , right ventricle walls thinner as blood pumps short distance to lungs
• Arteries carry blood away from heart
• Veins bring blood to the heart
• Arteries carry oxygenated blood ( apart from pulmonary artery )
• Veins carry deoxygenated blood ( apart from pulmonary vein )
• Coronary arteries supply glucose and oxygen for the heart for respiration
• Atrioventricular valves - valves between atria and ventricles
• Semi lunar valves - between ventricles and arteries which prevent back flow of blood
• right AV valve - tricuspid valve
• Left AV valve — bicuspid valve
• SL valve at entrance to pulmonary vein is called the pulmonary valve
• SL at entrance to aorta is called the aortic valve