closed circulatory systems

closed circulatory systems

• blood is enclosed in vessels and does not come into direct contact with body cells

• blood is pumped at higher pressure, blood usually contains a pigment for oxygen transport

• is possible to adjust the flow of blood for different tissues

single cirulations

• fish have a closed, single circulatory system- blood is contained in vessels and the circulation forms a single loop around the body

why are closed systems more efficient

• require less transport fluid than open systems

what do capillary beds cause

• single closed systems to pump blood at fairly low speed and pressure

• this limits the activity levels of organisms with this system

slow blood flow of a fish

• there is a drop in pressure in the gills

• this results in slow blood flow and reduced oxygen to the cells

why do single closed systems work well for fish

• they have an efficient counter current exchange system to maximise oxygen uptake

• they are ectothermic (cold blooded so don’t need to maintain their own temp)

• their body weight is supported by water

human circulatory system

• double closed system

• blood flows through the heart twice on each journey round the body

capillary network per circuit

• 1 in humans

• relatively high pressure and fast flow can be maintained