Unit 1: Structure and function of arteries, veins and capillaries

Veins have valves

to stop backflow of blood.

What are the very small branches of the arterial system, furthest from the heart called?

Arterioles.

How does a capillary having a small diameter help with diffusion?

Blood travels relatively slowly giving more opportunity for diffusion to occur.

Almost all arteries carry oxygenated blood. What are the exceptions?

The pulmonary artery and the umbilical artery during artery.

What do arteries do?

They carry blood away from the heart towards the cells of the body.

Veins have very little smooth muscle or elastic fibres

as there is no pulse of blood so no stretching and recoiling occurs

Veins have relatively thin walls

so the blood can flow under low pressures.

Arteries are lined with smooth layer of endothelial cells and have a narrow lumen

to provide a low friction surface to ease blood flow.

Arteries have a relatively thick wall

to withstand high blood pressure.

Arteries have elastic fibres

which allow the walls to stretch when blood is pumped into the artery and then recoil, smoothing blood flow.

Capillaries have very thin walls (just one cell thick)

which allows rapid exchange between blood and tissues.

Arteries have smooth muscle

which alters diameter of lumen to vary blood flow.

Veins have a wide lumen

which gives it a large volume which acts as a blood reservoir.

What is the function of the umbilical artery during pregnancy?

It carries deoxygenated blood from the fetus to the placenta.

What is the function of the pulmonary artery?

It carries deoxygenated blood from the heart to the lungs.