Cardiovascular system

• Lymphatic circulatory system

  Lymph nodes and white blood cells work together to fight infection - systems work in tandem
• Veins

  • Have valves to prevent backflow
  • Far away from the heart so have a low pressure
• Arteries

  • Have no internal valve structure as they are under high pressure

  
• The heart

  • A muscular pump
  • Supplies O2 and nutrients to body cells - helps with energy cycles within cells
  • Maintains BP
  • Function is subject to continual physiological adjustment to maintain adequate blood supply
• Organs/structures associated with the heart (superiorly)

  • Aorta
  • Superior vena cava
  • Pulmonary artery
  • Pulmonary veins

  
• Organs/structures associated with the heart (posterior)

  • Oesophagus
  • Trachea
  • Descending aorta
  • Inferior vena cava
  • Thoracic vertebrae

  
• Aorta is the largest within the body and supplies the rest of the body
• Organs/structures associated with the heart (inferiorly, laterally, anteriorly)

  • Apex rests on central tendon of diaphragm
  • Lungs (left lung overlaps left side of heart)
  • Sternum, ribs, intercostal muscles

  
• Heart wall

  • Heart sits in a pericardial sac - infections here can compress the heart causing endocarditis
  • Pericardium (outer) - fibrous pericardium is for strength and structure
  • Myocardium (middle)
  • Endocardium (inner) - smooth to not disrupt flow of blood

  
• Pericardium

  • Two layers: Parietal and Visceral (epicardium)
  • Fluid in space allows smooth movement between the layers when heart beats
• Myocardium

  • Doesn't fatigue over time unlike skeletal muscle
• Endocardium

  • Lines the heart
  • Thin and smooth to allow for smooth flow of blood inside the heart

  
• Inside the heart

  • No mixing of oxygenated and deoxygenated blood due to the septum
  • Atrial septal defect = born with a whole in the heart = septum not full sealed - may naturally or surgically be fixed

  
• Heart valves

  • Atrioventricular: Between LA and LV = bicuspid/mitral, Between RA and RV = tricuspid
  • Semilunar: Between LV and aorta = aortic, Between RV and pulmonary artery = pulmonic

  
• How the heart valves work

  1. Open and close passively according to changes in the pressure within the chambers

  2. Tricuspid and mitral valve open when the pressure in atria is greater than that of the ventricles

  3. During ventricular systole (contraction) pressure in ventricles rises above that in atria and valves snap shut to prevent back flow of blood

  
• Heart sounds

  • Lub = closure of AV valves, start of ventricular systole
  • Dub = closure of pulmonary and aortic valves, ventricular diastole

  
• The heart

  • Cardiac muscle has auto-rhythmicity - generates its own electrical impulses and can beat independently of nervous system and hormonal control
  • ANS and hormones alter this intrinsic beat: Sympathetic NS via cardiac nerve - increased heart rate, Parasympathetic NS via vagus nerve - decreased heart rate

  
• Electrical conducting system

  • Sinoatrial node (1) - natural pacemaker
  • Atrioventricular node (2)
  • AV bundle/Bundle of His
  • Bundle branch fibres (L & R)
  • Purkinje Fibres
• Cardiac arrest

  When electrical activity suddenly stops
• Heart rate

  • Normal adult at rest = sinus rhythm 60-80 bpm
  • Autorhythmic element - set by sinoatrial node

  
• Left anterior descending (or interventricular) artery = most important as it supplies blood to the rest of the body
• Pulmonary circulation

  1. Blood passes from the right ventricle to the lungs via the pulmonary artery

  2. Through pulmonary capillaries

  3. Returns to the left atrium via the pulmonary veins

  
• Perfusion (in lungs)

  The volume of blood leaving the right ventricle of the heart each minute

  
• Cardiac output

  Stroke volume x heart rate

  
• 5.25 litres per minute = 70 millilitres x 75 bpm
• Distribution of pulmonary flow

  • As pulmonary BP is low, it is subject to the force of gravity: can be influenced
  • Blood is distributed preferentially to the dependent parts of the lung
  • This is therefore where perfusion (Q) is best
  • In an upright posture perfusion is greatest at the bases of the lungs