M3:S2 Transport in animals

• Multicellular organisms need transport systems
• Multicellular organisms


  • Have a low surface area to volume ratio
  • Have a higher metabolic rate
• Multicellular organisms need a transport system to supply cells with glucose and oxygen
• Circulatory system


  Uses blood to carry glucose and oxygen around the body
• What the circulatory system also carries

  • Hormones
  • Antibodies
  • Waste (like CO2)
• Fish circulatory system


  • Single circulatory system - blood passes through heart once per circuit
• Mammalian circulatory system


  • Double circulatory system - blood passes through heart twice per circuit
• Mammalian circulatory system

  1. Right side pumps blood to lungs

  2. Blood travels to left side of heart

  3. Blood returns to right side
• Pulmonary system


  Sends blood to the lungs
• Systemic system


  Sends blood to the rest of the body
• Advantage of mammalian double circulatory system is it can give blood an extra push between lungs and body
• Closed circulatory system

  • Blood is enclosed inside blood vessels
• Closed circulatory system

  1. Heart pumps blood into arteries

  2. Blood flows through capillaries

  3. Blood returns to heart via veins
• Open circulatory system

  • Blood flows freely through body cavity
• Open circulatory system

  1. Heart contracts in a wave to pump blood into main artery

  2. Blood flows around organs

  3. Blood flows back into heart segments
• Open circulatory systems don't supply oxygen - this is done by tracheal system
• Types of blood vessels

  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins
• Arteries

  • Carry blood from heart to body
  • Have thick, muscular walls with elastic tissue
  • Except pulmonary arteries which carry deoxygenated blood
• Arterioles

  • Smaller than arteries
  • Have smooth muscle to control blood flow
• Capillaries

  • Smallest blood vessels
  • Walls are one cell thick to allow efficient diffusion
• Blood flow through veins

  1. Veins have valves to stop backwards flow

  2. Helped by contraction of surrounding muscles

  3. Except pulmonary veins which carry oxygenated blood
• Tissue fluid

  Fluid that surrounds cells in tissues, formed from substances that leave blood plasma
• Formation of tissue fluid

  1. High hydrostatic pressure in capillaries forces fluid out

  2. Hydrostatic pressure reduces towards venules

  3. Oncotic pressure draws some fluid back in at venule end
• Lymph

  Excess tissue fluid that drains into lymph vessels
• Lymphatic system

  1. Lymph capillaries collect excess tissue fluid

  2. Lymph vessels with valves return lymph to blood near heart
• Differences between blood, tissue fluid and lymph

  • Blood contains red blood cells, white blood cells, platelets
  • Tissue fluid and lymph have higher water potential than blood
  • Tissue fluid and lymph have fewer dissolved solutes than blood
• Blood, tissue fluid and lymph

  Quite similar - tissue fluid is formed from blood, and lymph is formed from tissue fluid
• Main differences between blood, tissue fluid and lymph

  • Red blood cells (present in blood, absent in tissue fluid and lymph)
  • White blood cells (very few in tissue fluid, most in lymph)
  • Platelets (present in blood, absent in tissue fluid and lymph)
  • Proteins (most plasma proteins too big to get through capillary walls, so fewer in tissue fluid and lymph)
  • Water (tissue fluid and lymph have higher water potential than blood)
  • Dissolved solutes (can move freely between blood, tissue fluid and lymph)
• Tissue fluid and lymph have a higher water potential than blood
• Dissolved solutes can move freely between blood, tissue fluid and lymph
• Tissue fluid is the fluid drained out of a used tissue
• Red blood cells can't float around loose in tissues, otherwise you'd be bright red
• Platelets are only present in blood, as they cause blood clots
• Proteins and white blood cells are the only tricky bits in terms of differences between blood, tissue fluid and lymph
• Mammals have a double circulatory system, so their hearts are more complicated than just a pump
• Heart

  • Consists of two muscular pumps - the right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated blood to the rest of the body
• Parts of the heart

  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle
  • Aorta
  • Pulmonary artery
  • Superior vena cava
  • Pulmonary veins
• Atrioventricular valves

  Link the atria to the ventricles, prevent blood flowing the wrong way
• Semi-lunar valves

  Link the ventricles to the pulmonary artery and aorta, prevent blood flowing the wrong way
• How heart valves work

  1. Valves only open one way

  2. Higher pressure behind a valve forces it open

  3. Higher pressure in front of a valve forces it shut