Circulatory System + The Blood

• what does the blood consist of

  • plasma
  • red blood cells
  • white blood cells
  • platalets
• what is blood

  a tissue
• what's the blood responsible for

  transporting substances around body + fighting disease
• what do red blood cells do

  carry oxygen + CO2 from lungs to cells in the body
• what's another name for red blood cells

  erythrocytes
• how are red blood cells adapted to do their job

  • biconcave shape + no nucleus -> large surface area for absorbing oxygen
  • haemoglobin which contains iron (in the lungs haemoglobin binds to O2 -> oxyhemoglobin)
  • oxyhemoglobin splits into oxygen + haemoglobin to release oxygen in cells
• what's the function of white blood cells

  defend against infection
• what do phagocytes do

  change shape to engulf pathogens -> phagocytosis
• what do lymphocytes do

  produce antibodies + antitoxins to destroy pathogens
• what do platelets do

  help blood clot when there's a cut
• how do platelets do their job

  • travels to site of wound
  • causes it to clot -> stops bleeding
  • forms a scab -> prevents infections
• what happens if someone doesn't have enough platelets

  bleeds excessively or may bruise easily
• what's the function of plasma

  transports dissolved substances around body
• what are some of the things plasma transport

  • red + white blood cells + platelets
  • glucose + amino acids
  • CO2
  • urea
  • hormones
  • proteins
  • antibodies + antitoxins
• what are the 3 blood vessels

  • arteries
  • veins
  • capillaries
• what do arteries do

  carry blood under a high pressure AWAY from HEART
• describe the adaptations of arteries

  • strong walls + elastic to whithstand high pressure of blood
  • thick walls compared to lumen
  • walls contain thick layers of muscle -> makes them strong
  • elastic fibres stretch -> no bursting
• why is the lumen small in arteries

  allows blood to travel at a higher pressure if its smaller
• what do veins do

  carry blood back INTO heart
• describe the structure of veins

  • walls aren't as thick as arteries as blood is at much lower pressure
  • bigger lumen to help blood flow at low pressure
  • have valves -> helps blood move in right direction + prevents back flow
• what do capillaries do

  • connect arteries to veins
  • very small blood vessels -> too small to see
• describe the structure of capillaries

  • very narrow -> to go between cells so allows blood to be very close to cells + so short diffusion pathway
  • permeable walls for substances to diffuse
  • supply nutrients + food + oxygen
  • takes waste like CO2 away
  • one cell thick walls -> short diffusion pathway
  • red blood cells can only pass in single file -> max exchange of substances