ch5.2 blood vessels

• blood vessels carry blood to cells of the body or lungs and back to the heart again
• arteries:

  • carries oxygenated blood away from heart
  • except pulmonary artery which takes deoxygenated blood away from heart
  • walls contain smooth muscle + elastin fibres
  • vasoconstriction = muscles contract to restrict blood flow
  • vasodilation = muscles relax to increase blood flow
  • can redirect blood flow to areas in need
• capillaries: microscopic blood vessels that form a network to carry blood to almost every body cell

  • one cell thick
• veins:

  • carry deoxygenated blood towards the heart
  • except pulmonary veins which take oxygenated blood towards the heart
  • do not have muscular walls - cannot change their diameter
  • have valves
• blood flow - to cater for changes in requirements, blood flow must be able to change by:

  • changing output of blood from heart
  • changing diameter of blood vessels
• cardiac cycle = the sequence of events that occurs in one complete beat of the heart

  • systole = pumping phase (heart contracts)
  • diastole = filling phase (heart relaxes)
• cardiac output (mL/min) = stroke volume (mL) * heart rate (bpm)