3.1.2

• why do multicellular animas need transport systems?

  size - long diffusion distances, molecules are made in one place but need to be used in another

  metabolic rate - high, waste products from metabolism need to be removed to excretory organs

  SA:V - small, animal likely to be active so always needs glucose and oxygen for respiration
• a good transport system contains:

  transport fluid, pump, exchange surfaces, vessels for fluid, 2 circuits for pick up and delivery of oxygen
• single circulatory system

  the blood flows through the heart once for each circuit of the body

  
• double circulatory system

  the blood flows through the heart twice for each circuit around the body

  
• open circulatory


  blood is not held in vessel

  
• closed circulatory


  blood is held in vessel

  
• single circulatory system explained

  the heart pumps blood to the exchange surface and then to the rest of the body. it is at a low pressure as it is used in metabolically inactive animals such as fish
• double circulatory system explained

  the right side of the heart pumps blood to the lungs to get oxygen (pulmonary). the left side of the heart pumps blood to the body after recieving the oxygen (systemic). this is done at a high pressure for metabolically active animals
• single vs double circulatory systems

  single:

  • no need for complex organs
  • but... body activity levels must be low

  double:

  • fast flow of blood so nutrients received quickly
  • but... requires more energy
• closed circulatory system explained

  substances diffuse from the blood into the tissue and the blood is taken back to the heart. tissue fluid baths the tissue cells.

  + rapid removal and delivery due to high pressure

  + transport does not require body movement
• open circulatory system explained

  the heart is segmented and contracts in waves pumping haemolymph into single main artery

  the artery opens up into the body cavity

  haemolymph circulates the body cavity under low pressure, direct contact with tissue

  the haemolymph goes back into the artery through a series of valves

  found in insects

  x pressure is low

  x lack of movement affects circulation
• haemolymph


  transport fluid containing only food and nitrogenous waste
• an open body cavity is also known as

  a haemocoel
• artery function

  carry blood from heart to rest of body
• artery structure

  A) collagen

  B) thick smooth muscle

  C) elastic tissue

  D) folded smooth endothelium

  E) small lumen

  
• artery how structure aids function

  thick muscle wall and elastic fibres- stretch and recoil as heart pumps

  small lumen - retain high blood pressure

  smooth folded endothelium - allows for expansion
• lumen


  space within a blood vessel where the blood can flow
• arteriole function

  control blood flow to tissue from artery
• arteriole structure

  smaller artery

  A) smooth muscle

  B) less elastic tissue

  C) small lumen

  D) arteriole

  
• how arteriole structure aids function

  smooth muscles - can contract and expand to control blood flow
• arteries carry oxygenated blood apart from..


  pulmonary arteries that carry deoxygenated blood to the lungs
• capillary function


  exchange surface between vessel and tissue cells
• capillary structure

  smallest blood vessel in human body

  A) endothelium

  B) 1 cell thick

  C) small lumen

  
• how capillary structure aids function

  1 cell thick - efficient diffusion
• venule function

  join to form veins
• venule structure

  A) muscle cells

  B) thin wall

  
• vein function

  carry deoxygenated blood back to heart under low pressure
• veins carry deoxygenated blood apart from

  pulmonary veins that carry oxygenated blood from the lungs to the heart
• vein structure

  opposite of artery

  A) collagen

  B) little smooth muscle

  C) little elastic fibres

  D) smooth endothelium

  E) large lumen

  
• how vein structure aids function

  wide lumen - maintain low blood pressure

  valves - stop backflow

  in body muscles - contract for blood flow
• hydrostatic pressure

  the pressure exerted by a fluid (blood) on the walls of its container (blood vessels)
• oncotic pressure

  plasma proteins in the blood are hydrophilic and lower that water potential of the blood this causes the tendency for water to move back into blood via osmosis
• tissue fluid formation/excretion

  when blood enter the capillary bed it is at a high hydrostatic pressure as it has just been in an artery/arteriole. this pressure is greater than the hydrostatic pressure in the tissue causing fluid to be forced out of the capillary into the tissue. this is known as ultrafiltration and forms tissue fluid
• tissue fluid uses

  its contains dissolved solutes and nutrients that the cells take in and absorbs metabolic waste produced by the cells
• tissue fluid reabsorption

  when the tissue fluid was formed it created a low hydrostatic pressure in the capillaries due to the loss of fluid and also caused a high oncotic pressure as plasma proteins did not enter the tissue fluid. at the end of the capillary bed some tissue/water fluid re-enters the blood via osmosis due to the high oncotic pressure/ low water potential in the capillary bed and the high water potential in the tissue fluid
• when 90% of water re-enters the capillary bed what happens to the other 10%?


  it is absorbed into a lymph capillary and turned into lymph fluid
• how lymph vessel structure aids function

  valves - stops lymph from going backwards
• lymph capillaries lead to...

  lymph vessels that go to the thorax where the lymph fluid is returned to the blood
• how does lymph fluid move a long?

  the lymph vessels are squeezed by skeletal muscles
• differences between blood, tissue fluid and lymph

  blood creates tissue fluid that creates lymph

  A) yes

  B) no

  C) no

  D) yes

  E) yes

  F) yes

  G) no

  H) no

  I) yes

  J) few

  K) few

  L) only antibodies

  M) tissue fluid

  N) tissue fluid

  O) lymph

  P) tissue fluid

  Q) capillary walls

  R) higher