circulatory systems + vessels

• what are common features of circulatory systems?

  liquid transport medium, vessels that carry the transport medium, pumping mechanism to move fluid around the system
• what are all circulatory systems comprised of?

  heart, fluid in which substances are transported (link back to properties of water), and vessels through which the fluid can flow
• in a single circulatory system, how many times does blood pass through the heart per cycle?

  once
• what type of circulatory system do fish have?

  single closed
• what type of circulatory system do most mammals have?

  double closed
• structure of arteries?

  smooth muscle layer is thicker than veins they can constrict and dilate to control volume of blood, elastic layer thicker than veins to maintain blood pressure and so walls can stretch and recoil, collagen outer layer for support.
• structure of arterioles?

  Smooth muscle thicker than arteries to slow blood flow to capillaries, elastic layer thinner than arteries as pressure is lower, collagen layer thinner than artery
• capillaries structure?

  no smooth muscle, no elastic layer, no collagen, one cell thick (of squamous epithelial cells) providing a short diffusion distance for exchange between blood and cells
• venules structure?

  thin smooth muscle layer, no elastic layer, no collagen layer, contains valves
• vein structure?

  smooth muscle layer is thin so cannot control blood flow, elastic layer thin as pressure is low, contains lots of collagen, contains valves
• An open circulatory system consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel. In the haemocoel, the haemolymph directly bathes organs and tissues, enabling the diffusion of substances. When the heart relaxes, the haemolymph blood is sucked back in via pores called ostia. Haemolymph moves around the haemocoel due to the movement of the organism
• are closed or open circulatory systems less efficient?

  open
• why are open circulatory systems less efficient than closed?

  once the fluid leaves the heart it moves randomly
• why are closed systems not as sufficient for insects?

  requires energy to maintain
• is the left side of the heart bigger?

  yes
• why are transport systems needed?

  meet metabolic demands, low SA:V ratio
• in the haemocoel the transport medium is under low pressure
• in insects where does most gas exchange occur?

  Tracheal system
• what is insects blood called?

  haemolymph
• what does haemolymph transport?

  food, waste, cells involved in defence against disease
• in closed circulatory systems can the amount of blood flowing to a tissue be adjusted? can it in open?

  yes, no
• in closed circulatory systems how can the amount of blood flowing to a tissue be adjusted?

  widening or narrowing blood vessels
• why is the activity of animals with single closed circulatory systems low?

  blood pressure is low so blood returns to the heart slowly, lowering efficiency
• how are fish so active with a single closed circulatory system?

  countercurrent gas exchange, body weight is supported by water, do not maintain their own body temperature
• how many atria do double and single circulatory systems have?

  2, 1
• what do elastic fibres do?

  made of elastin, stretch and recoil
• what does smooth muscle do?

  contract and relax changing the size of the lumen
• what does collagen do?

  structural support to maintain shape and volume of vessel
• arteries carry blood away from the heart
• arteries carry oxygenated blood EXCEPT the pulmonary artery
• what does the umbilical artery carry and from where to where?

  Deoxygenated blood from fetus to placenta
• blood in arteries is under higher pressure than in the veins
• in arteries the elastic fibres enable it to withstand the force of blood pumped out of the heart
• the lining of the artery (endothelium) is smooth to reduce friction
• what links the arteries and capillaries?

  Arterioles
• when the smooth muscle in the arteriole contracts this is known as vasoconstriction
• when the smooth muscle in the wall of an arteriole relaxes, this is vasodilation
• how are capillaries adapted for their function?

  large surface area for diffusion, single endothelial cell thick, thin lumen gives slow movement of blood allowing more time for exchange
• what veins carry oxygenated blood?

  Pulmonary vein and umbilical vein
• what connect capillaries and veins?

  venules