Heart

• Pericardium


  Fibre membrane found as an external covering around the heart
• Pericardium


  • Protects the heart by producing a serous fluid, which serves to lubricate the heart and prevent friction between the surrounding organs
  • Helps by holding the heart in its position and by maintaining a hollow space for the heart to expand itself when it is full
• Layers of the pericardium

  • Visceral Layer (directly covers the outside of the heart)
  • Parietal Layer (forms a sac around the outer region of the heart that contains the fluid in the pericardial cavity)
• Layers of the heart wall

  • Epicardium (outermost layer, thin-layered membrane that serves to lubricate and protect the outer section)
  • Myocardium (middle layer, muscle tissue responsible for the pumping action)
  • Endocardium (innermost layer, lines the inner heart chambers and covers the heart valves, prevents blood from sticking to the inner walls)
• Chambers of the heart

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle
• Atria


  Thin and have less muscular walls, smaller than ventricles, blood-receiving chambers fed by the large veins
• Ventricles


  Larger and more muscular chambers responsible for pumping and pushing blood out into circulation, connected to larger arteries that deliver blood for circulation
• The right ventricle and right atrium are comparatively smaller than the left chambers, with fewer muscles, due to their different functions
• Blood vessels


  • Veins (supply deoxygenated blood to the heart)
  • Capillaries (tiny, tube-like vessels which form a network between the arteries to veins)
  • Arteries (muscular-walled tubes mainly involved in supplying oxygenated blood away from the heart to all other parts of the body)
• Valves


  Flaps of fibrous tissues located in the cardiac chambers between the veins, ensure that the blood flows in a single direction (unidirectional) and prevent the blood from flowing backwards
• Types of valves


  • Atrioventricular valves (between ventricles and atria)
  • Semilunar valves (located between the left ventricle and the aorta, and between the pulmonary artery and the right ventricle)
• Heart


  Pumps around 6,000-7,500 litres of blood in a day throughout the body
• Heart


  • Situated at the centre of the chest
  • Points slightly towards the left
• The heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime
• Average male heart weight

  280 to 340 grams (10 to 12 ounces)
• Average female heart weight

  230 to 280 grams (8 to 10 ounces)
• Adult heart rate


  60 to 100 beats per minute
• Newborn baby heart rate

  90 to 190 beats per minute
• Heart chambers


  Your heart has four separate chambers. You have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of your heart.
• Right atrium


  • Two large veins deliver oxygen-poor blood to your right atrium. The superior vena cava carries blood from your upper body. The inferior vena cava brings blood from your lower body. Then the right atrium pumps the blood to your right ventricle.
• Right ventricle


  • The lower right chamber pumps the oxygen-poor blood to your lungs through the pulmonary artery. The lungs reload the blood with oxygen.
• Left atrium


  • After the lungs fill your blood with oxygen, the pulmonary veins carry the blood to the left atrium. This upper chamber pumps the blood to your left ventricle.
• Left ventricle


  • The left ventricle is slightly larger than the right. It pumps oxygen-rich blood to the rest of your body.
• Heart valves


  Your heart valves are like doors between your heart chambers. They open and close to allow blood to flow through. They also keep your blood from moving in the wrong direction.
• Atrioventricular (AV) valves


  • Tricuspid valve: Door between your right atrium and right ventricle.
  • Mitral valve: Door between your left atrium and left ventricle.
• Semilunar (SL) valves


  • Aortic valve: Opens when blood flows out of your left ventricle to your aorta (artery that carries oxygen-rich blood to your body).
  • Pulmonary valve: Opens when blood flows from your right ventricle to your pulmonary arteries (the only arteries that carry oxygen-poor blood to your lungs).
• Blood vessels


  • Arteries: Carry oxygen-rich blood from your heart to your body's tissues. The exception is your pulmonary arteries, which go to your lungs.
  • Veins: Carry oxygen-poor blood back to your heart.
  • Capillaries: Small blood vessels where your body exchanges oxygen-rich and oxygen-poor blood.
• Coronary arteries


  • Left coronary artery: Divides into two branches (the circumflex artery and the left anterior descending artery).
  • Circumflex artery: Supplies blood to the left atrium and the side and back of the left ventricle.
  • Left anterior descending artery (LAD): Supplies blood to the front and bottom of the left ventricle and the front of the septum.
  • Right coronary artery (RCA): Supplies blood to the right atrium, right ventricle, bottom portion of the left ventricle and back of the septum.