blood and the circulation

• name the 4 components of blood?

  • red blood cells
  • white blood cells
  • plasma
  • platelets
• red blood cells:

  • contain haemoglobin, binds to oxygen to transport it from the lungs to the tissues and cells that need it for respiration
  • don't have a nucleus so there's more space for haemoglobin
  • very small to fit through tiny capillaries
  • biconcave shape, large surface area for oxygen to quickly diffuse across
• white blood cells:

  • help to fight off infections
  • can change shape so they can squeeze out of the blood vessels into the tissues or surround and engulf pathogens
• platelets are fragments of cells which collect at wounds to trigger blood clotting and create scabs
• arteries:

  • take blood AWAY from the heart to the organs
  • thick walls made of elastic and muscle fibres to resist the high pressure of blood
• veins:

  • take blood from the organs back to the heart
  • thinner walls and valves to prevent back flow as pressure is lower
• capillaries:

  • joins arteries to veins
  • narrow vessels with walls 1 cell thick to allow substances to be exchanged with the tissues
• the heart pumps blood around the body in a double circulatory system
• vena cava (from body) -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary vein (from lungs)-> left atrium -> left ventricle -> aorta -> body
• the pulmonary artery carries deoxygenated blood from the heart to the lungs
• the pulmonary vein carries oxygenated blood from the lungs to the left atrium
• how are alveoli adapted for gaseous exchange?

  • large moist surface area
  • rich blood supply
  • very close to the blood capillaries so the distance for gases to diffuse is small