Heart and circulatory system

• Where is the heart positioned within the chest?

  The heart is centrally positioned in the middle mediastinum, flanked and partially obscured by the lungs.
• How much of the heart lies to the left of the midsternal line?


  Approximately 2/3 of the heart lies to the left of the midsternal line.
• What is the approximate weight of the heart?


  The heart weighs approximately 250-350 grams.
• What is the role of the pericardium?


  • Protects the heart
  • Anchors the heart to surrounding structures
  • Prevents overfilling of the heart
• What are the two layers of the pericardium?


  The pericardium consists of a tough fibrous outer layer and an inner serous layer that is continuous with the epicardium of the heart.
• What is the function of the heart as a muscular pump?


  • Consists of 4 chambers: 2 atria and 2 ventricles
  • Allows synchronous contraction
  • Ensures unidirectional blood flow through valves
• What are the two phases of the cardiac cycle?

  The two phases are systole (contraction) and diastole (relaxation).
• How is blood flow analogous to a central heating system?


  The heart acts as a pump, arteries as conducting pipes, and capillary beds as radiators for heat exchange.
• What is the typical blood volume in the circulatory system?


  The typical blood volume is approximately 5 liters.
• What are the main internal features of the right atrium?

  • Inflow: Superior vena cava, inferior vena cava, coronary sinus
  • Outflow: Tricuspid valve to right ventricle
  • Contains fossa ovalis
• What is the function of the left atrium?


  The left atrium receives oxygenated blood from the lungs via four pulmonary veins.
• What are the internal features of the left ventricle?

  • Muscular ridges
  • Chordae tendineae
  • Aortic valve
  • Mitral valve
  • Papillary muscle
• How do the pulmonary and aortic valves function during the cardiac cycle?


  During systole, blood passes through the valves, and during diastole, elastic recoil forces blood between the cusps and the vessel wall.
• What is the relationship between the heart's weight and its blood supply?


  The heart is 1/200 of total body weight but requires 1/20 of the body's blood supply.
• How do coronary veins function in relation to the heart?

  • Anterior cardiac veins drain directly into the right atrium
  • Other veins converge on the coronary sinus, which enters the right atrium
• How does the heart ensure coordinated contraction?

  Both sides of the heart contract simultaneously due to electrical activity originating in the right atrium.
• What are the components of the electrical conduction pathways in the heart?

  • Sinoatrial node (pacemaker)
  • Atrioventricular node
  • Bundle of His
  • Purkinje fibres
• What role do the kidneys play in the cardiovascular system?


  The kidneys regulate blood volume within the cardiovascular system.
• How does the cardiovascular system integrate with other organ systems?


  • Oxygenation of blood in lungs
  • Regulation of blood volume by kidneys
  • Bulk flow of gases, nutrients, hormones, and waste
  • Temperature regulation and homeostasis
  • Host defense
• Where do the left ventricle and left atrium lie?

  The left atrium forms the base of the heart, lying posteriorly

  The left ventricle forms the inferior diaphragmatic surface
• What is the fossa ovalis and where can it be found?

  The fossa ovalis is an area within the heart, in the right atrium

  It was the sight of the foramen ovale in the foetus - it was an interatrial septum that allowed oxygenated blood from the heart to bypass the lungs, via placental absorption by the mother.
• Name the major veins and arteries

  A) B

  B) A

  C) C

  D) D

  E) E

  
• Name the main valves in the heart

  (4)

  A) A

  B) B

  C) C

  D) D

  
• Describe the function of coronary arteries


  The left and right coronary arteries arise from the aortic sinuses, just above the valve cusps

  The vessels lie in the epicardium and branch inwards
• What can affect the speed of the sinoarterial node?


  The autonomic nervous system

  
• Describe the conduction pathway of the heart

  1. Depolarisation spreads from the sinoarterial node then through the atria
  2. The depolarisation spreads to the atrioventricular node, this is immediately followed by the contraction of the atria
  3. This impulse is carried down the septum via the bundle of His, the left and right bundle branches to the purkinje fibres in the ventricle walls
  4. This causes the ventricles to contract
• What is the function of the papillary muscles and the chordae tendinae?


  prevent the atrioventricular valves from opening during systole
• What occurs in relation to the heart valves during systole?

  The atrioventricular valves close during systole - mitral and tricuspid valves
• What occurs in relation to the heart valves during diastole?


  Opening of the mitral and tricuspid valves - closing of the aortic
• What is tachycardia?


  A fast heart - over 100 bpm, for any reason