8.1 transport systems in multicellular animals Flashcards
Why is a specialised transport system needed?
metabolic demands of multicellular animals are high= diffusion of longer distances cannot provide enough nutrients
SA:V ratio gets smaller the larger an organism is= less surface area available to absorb/ remove substances
molecules like hormones/enzymes are made in one place but needed in another area
food digested in one organ system but needs to be transported to every cell for respiration and metabolism
waste products of metabolism need to be removed
Features of a typical circulatory system
liquid transport medium that circulates around system
vessels that carry transport medium
pumping mechanism to move fluid around system
what is a mass transport system
when substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
What is an open circulatory system
very few vessels as transport medium is pumped directly from heart into the body cavity of an animal
What is the open body cavity called in an open circulatory system?
haemocoel
–> where exchange takes place
What is the pressure in the haemocoel?
low pressure as it comes into direct contact with tissues and cells
How does the transport medium return to the heart in an open circulatory system?
through an open- ended vessel
What is the name for insect blood
haemolymph (carries no oxygen or CO2
–> transports food and nitrogenous waste products
How is the open circulatory system structured in insects?
body cavity (haemocoel) is split by a membrane
–> the heart extends along the length of the thorax & abdomen of insect
What is a closed circulatory system?
when the blood is enclosed with blood vessels and does not come into direct contact with cells of body
How is the amount of blood flowing to a particular tissue adjusted?
by widening or narrowing blood vessels
What is a single closed circulatory system
blood flows through the heart and is pumped out to travel all around body before returning to heart
–> blood only travels once through heart for each complete circulation of body
–> typically found in fish or annelid worms
Blood flow diagram in a single closed circulatory system
heart –> ventricle –> capillaries in gills –> capillaries in rest of body
–> atrium –> heart
in single closed circulation, how many sets of capillaries does it pass through?
2
1st set: exchanges O2 & CO2
2nd set: substances are exchanged between blood and cells
What happens due to the blood passing through two sets of very narrow blood vessels?
blood pressure drops so blood returns to heart slowly
–> limits efficiency of exchange process so activity levels of single closed circulation animals is low
