Characteristics of blood vessels

layer of artery

Thick smooth muscle

Thick elastic layer

Narrow lumen

Endothelial layer

Blood at high pressure

what does the artery do

take blood away from the heart .

elastic tissue

they can expand when pressure increases follow beat of the heart (systole)

then recoil while the heart relaxes (diastole).

This recoil helps to push the blood further along the vessel.

endothelial

helps reduce friction to ensure the blood flows smoothly

muscles are thicker

d help the vessel withstand the high pressures

. They can also contract (vasoconstriction) to restrict blood flow to a particular area

or relax (vasodilation) to allow more blood flow to the area

Vein structure

Thin smooth muscle

Thin elastic layer

Semilunar valve

Wide lumen

Blood at low pressure

what do veins do

Veins are blood vessels that transport blood from the body's tissues back to the heart.

semilunar valves do

To prevent backflow of blood, semilunar valves extend from the endothelial layer.

what does the lumen do

. Having a large lumen reduces the resistance on the blood allowing it to flow more easily.

capillaries structure

Wall one cell thick

Very narrow lumen

Squamous endothelium

Blood at very low pressure

function of capillaries

The function of capillaries is to allow exchange of substances between blood and tissues. To allow this exchange it must be easy for the substances to diffuse into or out of the blood.

1 cell thick and squamous

This reduces the diffusion pathway allowing rapid diffusion of substances. Furthermore, small gaps between endothelial cells also aid diffusion.