blood vessels

• state the three main characteristics of blood vessels in mammals

  • elastic fibres- composed of elastin and can stretch and recoil, providing vessel walls with flexibility
  • smooth muscle- contracts/relaxes, changing the lumen size
  • collagen- provides structural support, to maintain the shape and volume of the vessel
• Arteries carry oxygenated blood away from the heart, apart from two exceptions, which carry deoxygenated blood away from the heart. Which two arteries carry deoxygenated blood?

  • pulmonary artery- from heart to lungs
  • umbilical artery- from heart to placenta during pregnancy
• state the types of tissue in artery walls and their functions

  • elastic fibres- withstand the force of blood being pumped out under high pressure, stretch to take larger blood volumes. Recoil- to even out surges of blood pumped out so it flows smoothly
  • collagen- to maintain structural support
  • smooth muscle- so blood flows smooth
• what two vessels do arterioles link together?

  arteries and capillaries
• describe the type of tissues found in arterioles

  • smooth muscle- constricts/dilates to control the flow of blood into organs. vasoconstriction= constricts vessel and prevents blood flowing into capillary bed. Vasodilation- blood flowing into capillary bed
  • not much elastin
  • not much collagen
• true or false? arteries and arterioles have smooth muscle, collagen and elastin in their walls

  TRUE- in varying proportions
• what two vessels do capillaries link together?

  Arterioles and venules
• true or false? The lumen of a capillary is small

  TRUE
• describe the state of blood as it enters and leaves capillaries

  • oxygenated- as it enters the capillaries from the arterioles
  • deoxygenated- as it leaves the capillaries from the venules because oxygen has been given to cells and carbon dioxide is removed from cells

  exceptions are lungs and placenta, as deoxygenated blood enters capillaries and oxygenated blood leaves them
• state the ways in which capillaries are adapted for their roles

  • large SA for the diffusion of substances in and out the blood
  • total cross sectional area is greater than arteriole supplying them so rate of blood flow decreases, slow rate gives time for substances to be exchanged between blood and cells
  • one endothelial cell thick- for short diffusion path
• veins carry deoxygenated blood to the heart, apart from two exceptions. What are these to exceptions?

  • pulmonary vein- carry oxygenated blood from lungs to heart
  • umbilical vein- carry oxygenated blood from placenta to fetus
• true or false? veins have a pulse

  FALSE
• state what tissues vein walls are made up of

  • lots of collagen
  • little elastic fibre
  • smooth muscle to ensure blood flows smoothly
• describe the structure of a vein

  • wide lumen- low blood pressure compared to the arteries
  • valves to ensure blood doesn't flow backward
• compare the structure of a venule to a vein

  VALVES:

  • Veins have valves and venules don't

  ELASTIN:

  • Veins have very little elastin and venules have no elastin

  SMOOTH MUSCLE:

  • Veins have smooth muscle and venules don't have any

  COLLAGEN-

  • veins have more collagen than venules

  
• compare arterioles and arteries

  COLLAGEN-

  • arteries have more collagen than arterioles

  SMOOTH FIBRES-

  • Arteries have less smooth fibres than arterioles

  ELASTIN-

  • arterioles have less elastin than arteries

  Aorta contains more collagen and elastic fibre than both, but less smooth muscle than both

  
• what three adaptations do the body have to pump blood under low pressure against gravity back to the heart?

  • one-way valves in veins- valves open to let blood flow towards the heart and close to prevent it flowing backward
  • bigger veins run between big active muscles like in arms and legs, when they contract they squeeze veins which force the blood to the heart, valves prevent backflow when muscles relax
  • breathing movements of the chest act as a pump- squeezing actions move blood toward heart
• describe the order of vessels that blood flows through from the heart to body cells and back to the heart again

  arteries -> arterioles -> capillaries -> venules -> veins