Circulatory systems Flashcards
features of an open circulatory system
no blood vessels
blood held in cavities
organs are surrounded by blood
blood under low pressure
diffusion happens between blood and organs
features of a closed circulatory system
blood is held inside vessels
blood under high pressure
features of a single closed circulatory system
blood flows once through heart during a cycle
blood is at low pressure when reaching capillaries
fishes have the system
CO2 diffuses from blood into water
oxygen diffused from water into blood
deoxygenated blood pumped to gills where gas exchange takes place
features of a double closed circulatory system
blood flows through heart twice in a cycle
blood is at high pressure when reaching capillaries
deoxygenated blood pumped to lungs for gas exchange (in alveoli)
what are the advantages of a double closed circulatory system
blood does not mix
blood can be pumped at different pressures
repressurisation occurs- blood gets an extra boost around body meaning oxygen and glucose travels to cells quicker, gives mammals high metabolic rate.
what do unicellular organisms rely on and why
rely on diffusion
they have a large surface area: volume ratio
diffusion happens quick enough between the cells
what do multicellular organisms rely on and why
rely on a mass transport system
large volume so need blood vessels to carry substances round body
high pressure— low pressure
