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6.2.5 Explain the relationship
between the structure and function of
arteries, capillaries and veins
Mathilde Xiao and Liam Kennedy
• http://www.youtube.com/watch?v=3Q5x0znIFnI
Structure of the Artery
• Arteries
• • Fairly narrow lumen (blood at higher
pressure)
• No valves apart from the semi lunar valves.
• Thick tunica media, with muscle and elastin
fibres
• • Thick outer layer of collagen (withstand
high pressure)
Functions of the Arteries
• Withstand high blood pressures without the artery wall
bulging outwards (aneurysm) or bursting (haemorrhage)
• Accommodate large volumes of blood pumped out by the
ventricles of the heart and then pump it on to capillary
networks
Structure of the Vein
• Veins
• Larger lumen than the arteries (blood
travels at lower pressure)
• Thin outer layer (pressure low & allows
nearby muscles to push blood)
• Thin circular layer (blood not in pulses)
• Have valves (prevents blood pooling at
lower extremities as well as backflow)
Functions of the Veins
• Transport of blood, without leaks, from capillary networks to
the atria of the heart
• Prevention of backflow when blood pressure or flow rate is
low
• Flexibility to be squeezed by adjacent muscles to help pump
blood
Structure of the Capillary
• Capillaries
• Wall is fenestrated and one
cell thick (allows for diffusion)
• Very narrow lumen (single file
blood cells increase exchange of
materials)
Functions of the Capillaries
• Transport blood as close as possible to all living cells of the
body
• Allow the substances that blood is transporting to enter and
leave rapidly
• Allow part of the blood plasma to leak out into tissues but not
proteins or blood cells
Blood Vessel Disease
• Blood vessel diseases are caused by the narrowing down or
constriction of blood vessels
• This constriction is composed of plaque built from fat over long
periods of time
• Diet, gender, age and genetics can be factors that cause blood vessel
diseases
Different types of blood vessel
diseases:
-Coronary Artery Disease
-Aneurysm
-Peripheral Arterial Disease
-Hypertension
Symptoms
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Muscle cramps/ache
Cold hands and feet
Pale skin
Hair loss on the toes, feet and legs
Sores that take too long to heal
Sores when scabbed over appear black
Slight or no pulse in the feet or legs
Skin and nails appear reddish-blue in color