transport Flashcards
(15 cards)
capillaries
small (5-10um)
thin (1 cell thick)
composed of flattened endothelial cells
highly branched (SA:V)
continuous (muscle, skin, lung) / fenestrated (kidneys, small intestine, organs with high metabolic demands)
exchange
* w internal environment (supply of nutrients and O to respiring cells)
* w external environment (exchange of oxygen and CO2 w air in lungs)
* one-way exchange (capillaries absorb nutrients from small intestine to blood but nothing back)
arteries
small lumen
thick walls (elastin & smooth muscle)
elastin stretches to let the large volume of blood pass when heart contracts, and recoils when it relaxes > pushing blood forward)
* it also reduces fluctuations in blood pressure, protecting smaller blood vessels from damage
3 layers
* innermost (in contact with blood and contain endothelium layer = smooth, friction reduced lining)
* middle (thickest, contains smooth muscle cells and elastic fibres)
* outermost (collagen fibres and some elastin, protects artery and anchors it to surroundings)
veins
large lumen (blood flows back to heart at a much lower pressure)
thinner walls
same 3 layers as arteries
valves
flexible (compressed by skeletal muscle)
coronary arteries
branch from aorta to supply heart muscle with oxygen and nutrients
* occlusion leads to coronary heart disease CHD and possibly to myocardial infarction
CHD
caused by build up of plaque, fatty substances mostly of cholesterol that hardens over time and narrows down diameter reducing blood flow
ischaemia
lack of blood flow to a body part
sometimes the hardened tissue in the coronary artery (atherosclerotic plaque) ruptures and creates a blood clot that further restricts blood flow
atherosclerotic plaque
the hardened plaque in coronary artery
angina
pain in chest, fatigue and shortness of breath caused by reduced blood flow, oxygen and nutrients to heart
what do xylem and phloem do
xylem transports water and dissolved materials
phloem facilitates transport of carbon compounds including sugars and amino acids
xylem function
transport of water unidirectionally from roots to other plant parts
> often against gravity by capillary action
water evaporates from stomata
negative pressure potential is created
water pulled through xylem by capillary action
= due to transpiration or root pressure
characteristics of xylem
hollow tube made of dead specialized cells that have lost their contents
continuous columns from root to top
thin
lignin in walls
* strong
* walls are impermeable to water as lignin is hydrophobic
walls contain pits where cell wall is thin and there is no lignin, water can move between adjacent cells
lumen doesn’t contain a cytoplasm
lignin
a complex polymer that binds to cellulose creating rigidity and allowing plants to withstand tension and mechanical stress
waterproofs xylem making walls impermeable to water
vascular bundle
xylem inside, phloem outside
in between, cambium = cells can become xylem or phloem
epidermis in roots
a thin, outermost layer through which water, mineral ions are absorbed from soil
contains many finger-like projections called root hairs that increase surface area
rings in tree trunks indicating growth
light thick rings = fast growth in spring and summer
dark thin rings = slow growth during autumn and winter
