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• 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