B3.2 Transport Flashcards
Mass flow
the movement of fluids down a pressure gradient
living cells require
supply of water and nutrients
oxygen
waste products to be removed
types of vessels in circulation system
arteries
veins
capillaries
arteries
carry blood flow away from heart
veins
carry blood to heart
capillaries
fine networks of tiny tubes linking arteries and veins
adaptation of capillaries
tissues and cells
blood under low pressure to prevent walls from bursting
narrow tubes
diameter very small
blood flow reduced
increased rate of exchange of molecules
large surface area adaptation for exchange of material
branching
increases diffusion rate
narrow diameters adaptation for exchange of material
RBC close to wall to reduce diffusion distance
thin walls adaptation for exchange of material
fast diffusion
single layer of cells
gaps in walls adaptation for exchange of material
allow some components of blood to escape and contribute to tissue fluid
endothelium
innermost lining layer of arteries and veins, and the layer of cells that compromises the capillary
lines inside of the heart
structure of arteries
- walls are thicker and stronger
- collagen fibres present
- elastic and involuntary muscle fibres
- lumen is smaller
- maintains pressure
structure of veins
- walls are thinner because blood is at low pressure
- lumen is larger
- reduces friction between RBC & wall - free flow of blood
- valves to stop backflow
lumen
the hollow interior of a blood vessel through which the blood passes
aorta
main artery that carried blood away from the heart to the rest of the body
how do arteries withstand high blood pressure
Layers of muscle and elastic tissue in the walls
Adaptations of arteries
Wall thickness
elastic tissue
stretching walls
stretching fiber
increased distance
Adaptations of arteries - wall thickness
withstand blood pressure and prevent rupture
Adaptations of arteries - elastic tissue and collagen fibres
thick layer of elastic tissue to even out and maintain blood pressure
Adaptations of arteries - stretchy walls
To accommodate the huge surge of blood from heart
Adaptations of arteries - stretchy fibres
fibres stretch and recoil keeping the blood flowing forward
measurement of pulse rates
expansion of arteries are pulses
mostly where artery is near surface and passes over a bone
eg above wrist
radial artery where
wrist
carotid artery where
neck
functions of valves in veins
prevent back flow of blood under low pressure
what are valves made of
collagen protien
how does the valve prevent backflow
blood pushes against valves causing them to close
structure of viens
thin walls
external layer in thickest
few elastic fibres in the middle layers
walls are flexible to keep blood moving
venule
branch of vein
how are venules formed
a union of several capillaries - 15 mm Hg pressure
pressure of veins
5 mm Hg
lowest pressure
atherosclerosis
deposition of plaque in the inner wall of blood vessels
occlusion
blockage or closing of a blood vessel
how does disease of heart occur
atherosclerosis
- occlusion of arteries
- progressive degenration of artery walls
how does damage to artery walls occur
fatty tissue is deposited under endothelium
atheroma reduce lumen diameter
how does raise blood pressure occur
when fat deposits and fibrous tissues start to impede blood flow
- damage to arterial wall
- reduces elasticity
- lesion formation
- plaques ruptures
- blood clotting
consequences of atherosclerosis
embolous in small artery or arteriole
- blockage
- deprivation of oxygen causing tissues to die
- can cause heart to cease to be a pump
HEART ATTACK
heart bypass operation
- blood vessel taken from patients leg
- sometimes many bypasses needed
- common and high survival chances
what can cause atherosclerosis
- high cholestrol
high saturated fatty acids
increased blood clots
epidemiological studies
circumstantial evidence of health risks
suggests connection but doesnt establish a cause or biochemical connection
strengths of evidence for incidence of coronary heart disease
comparison of mean values and analysis of how different they are
analysis of variation within data
what do studies on coronary heart disease suggest
saturated fat intake
+ve correlation
strongest correlations dont provide a causal link
limitations of evidence for incidence of coronary heart disease
- whether measure of health was a valid one
- small sample less reliable
- data gathered from animals less reliable for humans
transpiration
evaporation of water from spongy mesophyll tissue
stems role in transpiration
supports leaves in sunlight and transports organic material, ions and water between roots and leaves
roots role in transpiration
anchors plant and its site of absorption of water and ions from soil
leaf role in transpiration
Specialized for photosynthesis
leaf blade connected to stem by a leaf stock
transpiration system
Evaporated water replaced comes from cytoplasm and mostly from water in spaces in walls of nearby cells and xylem
loss of water causes - transpiration
loss of water causes water to be drawn out of xylem vessels through walls by capillary action
what does tension do - transpiration
draws water up in xylem
Because of tension the water column doesn’t break or tear away from the sides of the xylem vessel
cohesion tension theory
Explanation of how water is drawn up the stem
transpiration stream
Flow of water through a plant from the roots to the leaves via xylem vessels
tension
Force that is transmitted through a substance when it is pulled tight by forces acting from opposite cells
experiment to find tension
Xylem vessel is pierced by a fine needle
bubble of air enters column and interrupts water
jet of water released from broken vessels under pressure
advantages of transpiration
- evaporation of water from cells of leaf causes strong cooling effect
- stream of water carries dissolved ions required by leaves
- allows living cells to be fully hydrated
- turgor pressure of cells provide support to leaf
xylem role in water movement
cells with cellulose walls and living contents
long hollow tubes during developement
living contents of xylem used up in deposition of cellulose thickening to inside of lateral walls
hardened by ligin - tough tissue
root role in water movement
huge surface area in contact with soil
plants have a system of branching roots that continually grow at each root tip pushing through the soil
root hairs
extensions of individual epidermal cells - short lived
apoplast pathway
the pathway through the non-living part of a cell
symplast pathway
the pathway through the cell membrane and plasodesmata
mass flow
interconnected free spaces between cellulose fibres of the plant cell walls
vascular pathway
water movement through the plasma membrane, cytoplasm and the vacuole
endodermis
single layer of cells that surrounds the vascular tissue in the roots of a plant
casparian strip
a band of cells containing suberin, a waxy substances impermeable to water found in ther endodermal cell walls of plant roots
adaptation of xylem vessels for transport of water
- thickened walls strengthened with lignin
- lignin - waterproof and stops water from escaping
- unimpeded flow of water and minerals
- withstand pressure and tension
- pits - areas for entry and exit of water
