Blood Vessels

Biology - Heart and Blood

What is an artery?

They are large vessels that carry blood at a high pressue away from the heart into the systemic circuit

What is a vein?

A vessel that carries deoxygenated blood from the systemic circuit to the heart at a relatively low pressure

Tunica Externa (artery)

Layer of collagen for structural support and prevents rupture due to high pressure

tunica media of artery

Layer of smooth muscle and elastic fibres

What does the smooth muscle do? (artery)

Can contract and relax, changing the size of the lumen

what do the elastic fibres do? (artery)

The stretch and recoil: stretching to accommodate an increase in volume and recoiling to push the blood forwards

Tunica interna (artery)

Smooth endothelium lining which decreases resistance/friction from blood flow

Narrow Lumen for? (artery)

Maintaining high blood pressure

tunica externa (vein)

Contains collagen for structural support and prevents collapse of vessel

Tunica media (vein)

thin layer of smooth muscle and elastic fibres

why the thin layer of muscle and elastic? (vein)

veins do not need to strecth and recoil as they transport blood at a relatively lower pressure than arteries

tunica interna (vein)

They have a smooth endothelium in order to decrease resistance/friction from blood flow

Why do veins have a large lumen?

It maintains the low blood pressure

why do veins have valves?

To prevent the backflow of blood (blood is at such low pressure that there is a danger of this)

what do capillaries NOT have

tunica media or externa

(no elastic/muscle tissue/collagen)

Why do capillaries have a narrow lumen?

The narrow lumen slows blood flow, giving more time for diffusion, therefore more diffusion can occur more efficiently

describe the capillaries outer layer:

the smooth endothelium is 1 cell thick meaning diffusion distance is extremey short increasing the rate

Why is the capillaries being porous an advntage?

As it allows for more nutrient exchange