blood vessels

• what are some features of arteries?

  folded endothelium

  elastic fibres

  thick layer of muscles
• Arteries

  • Arteries transport blood away from the heart to the organs.
  • Artery walls have thick layers of muscle.
  • The walls maintain a high pressure so blood can be pumped around the body.
  • Elastic fibres in the artery wall allow the arteries to stretch.
  • The endothelium is folded which also allows the arteries to stretch.
• Veins

  • Veins transport blood back to the heart.
  • The lumen of veins is wider than the arteries which allows the blood to flow at low pressure.
  • There is a thin muscle wall and elastic tissue in the vein walls.
  • Valves are located throughout the veins to ensure blood flows towards the heart.
• Arterioles

  • When arteries reach an organ, they split into many smaller vessels called arterioles.
  • The direction of blood flow can be controlled by contracting the arterioles to restrict blood flow and relaxing the arterioles to allow blood to flow.
• capillaries:

  arterioles branch into very small vessels, called capillaries. capillaries have thin walls and pass very close to the body cells to allows exchange between blood and the organs.
• capillaries:

  walls

  • capillary walls(endothelium) are only one cell thick.
  • this meanes that the diffusion distance of substances e.g. oxygen, from the bloodtream to the tissues is very short.
  • a short diffusion distance allows for efficient exchange.
• artery:

  thick muscle layer- contracts and relaxes to control blood flow

  thick elastic layer- stretches and recoils to maintain high blood pressure

  thick artery wall prevents bursting from high pressure.
• arteriole:

  thicker muscle layer- contracts to reduce blood flow into capillaries.

  thinner elastic layer.

  transports blood from arteries to capillaries.
• capillaries:

  lining layer is thin and lumen is narrow maintaining a short diffusion distance.

  numerous capillaries and highly branched creates a large surface area.
• vein:

  relatively thin elastic layer. overall thin vein wall. contains valves to stop backflow.
• the pulmonary vein carries oxygenated blood from the lungs to the heart.
• the aorta carries oxygenated blood from the heart to the renal arteries to the kidneys
• the pulmonary artery carries deoxygenated blood from the heart to the lungs.
• the renal vein carries deoxygenated blood from the kidneys to the vena cava.