B2.2 - transport and blood Flashcards
why are tapeworms able to survive with a single circulatory system?
- has a high surface area to volume ratio
- nutrients can dissolve quick enough to sustain the organism
why do multicellular organisms require adapted exchange surfaces?
- because their surface area to volume ratio is low
- so diffusion cannot occur fast enough to meet the organism’s demand
how have the lungs adapted to maximise the rate of diffusion into the bloodstream?
lungs contain lots of alveoli (increase surface area)
how have alveoli adapted to maximise diffusion? - 4
- steep concentration gradient (ventilation through air)
- thin alveoli walls (one cell thick - easy diffusion)
- high surface area to volume ratio
- capillaries close to the alveoli
how is the small intestine adapted to maximise diffusion rate?
finger like villi on walls
how do villi affect the rate of diffusion in the small intestine?
increase surface area
with microscopic villi on villi themselves
give examples of exchange surfaces and transport systems
- alveoli
- villi
- xylem
- phloem
what is the function of the circulatory system?
transport substances around the body and the cells that need them
what is the hollow cavity in the centre of blood vessels called?
lumen
state features of an artery
- thick outer wall (high pressure from heart)
- thick layer of muscle + elastic fibres (to contract)
- small lumen
state features of a vein (physical features)
- thin outer wall
- thin layer of muscle + elastic fibres
- large lumen
- valves (stop blood flowing wrong way)
state features of capillaries
- small lumen (allows small diffusion distance)
- single wall of cells
(maximise diffusion through semipermeable walls)
what is the function of arteries?
carry blood away from the heart
what is the function of veins?
return blood to heart
why do veins have valves?
- prevent back flow
- since blood is flowing at low pressure, it is more likely to flow backwards
function of capillaries?
link arteries and veins in tissues + organs
how do arteries work?
- muscle fibres contract to push blood forward
- then relax (and then the lumen expands)
what does the double circulatory system mean?
(how does that affect the pressure compared to a single circulatory ststem)
and what does it allow the body to do?
- for each journey around the body, blood is pumped twice
(so pressure is higher than single circulatory system) - materials are transported quickly around body
why are alveoli moist?
gases can only cross cell membrane when dissolved in water/aqueous solution
what is the use of haemoglobin?
binds to oxygen from the lungs
transports oxygen around body
what specifically travels in the phloem?
cell sap (sugars/salts/animo acids)
does transpiration or translocation happen in the phloem?
translocation (sugars moved around)
why are cardiac muscles special?
they contract without receiving a nerve impulse from the brain
what does the vena cava do?
brings deoxygenated blood to the heart from the body
what does the pulmonary artery do?
takes deoxygenated blood from the heart to the lungs
what does the pulmonary vein do?
brings oxygenated blood to the heart from the lungs
what does the aorta do?
carries oxygenated blood from the heart around the body