B2.2 Flashcards
why SA to V is important
small diffusion distances are more important
multicellular organisms have devolved different apdaptations to increase SA to V ratio
Alveoli in lungs
increase SA as
many alveolus have capillary networks surrounding them
circulatory system
made up of heart and blood vessels
double circulatory system
blood circulating through the heart twice in one cycle
order of blood pumped around the body
deoxygenated - pulmonary artery
lungs
oxygenated- pulmonary veins
through heart to the aorta
head and body
deoxygenated- vena cava
to the heart
properties of arteries
thick outer wall
thick layer of muscle and elastic fibres
small lumen
smooth lining
carrys blood away from the heart under high pressure
properties of veins
fairly thin outer wall
thin layer of muscle and elastic fibres
large lumen
smooth lining
has valves
returns blood back to the heart
capillary properties
very small lumen
wall made up of single layer of cells
links arteries and veins to tissues and organs
semipermeable so substance can move in and out
what is the heart
cardiac muscle (only type of muscle in heart)
contract together to produce a heart beat
four chambers
right atrium. left atrium
right ventricle left ventricle
what is in blood?
red blood cells- biconcave shapes, no nucleus, haemoglobin
white blood cells- large cells, contain nucleus, fight disease by making antibodies
plasma- straw coloured liquid, 90% water, transports materials such as amino acids and glucose, hormones and antibodies
platelets-help blood clot
structure of xylem
dead xylem cells
no cells walls at the end
water and dissolved mineral ions can flow
cellulose cell wall is thickened with lignin
one way only
water diffuses into roots via osmosis
mineral ions are taken in by active transport
structure of phloem
made of living cells
sieve plates which allows dissolved sugars to pass through
water and food
everywhere transported (two way flow)
permeable cells walls
how vascular bundles provide support
-in leaf form a network that’s supports softer leaf tissue
- in stem located around the other edge providing stem with strength
- in roots found in the centre, enables root to act as an anchor
what is transpiration
loss of water from leaves of plants so replaced by uptake of water from roots
transpiration stream
how water is lost from leaves
stomata on the surface of a leaf allows carbon dioxide to diffuse in for photosynthesis
guard cells allow stomata to open and close
while stomata are open water evaporates from cells indie the leaf into the leafs air spaces creating a concentration gradient
