Blood Vessels

Lloyd Dean

NVQ Level 3 Personal Training

AimsBy the end of the lesson you should be able

to:

Describe the structure of the different blood vessels

Describe the function of each of the different blood vessels

Create a blood vessel comparison table

Structure of Blood Vessels

Structure of LayersTunica Externa / AdventitiaOuter layerLargely made up of collagen and elastin fibersSupports blood vessel by being shock absorber

Tunica MediaMiddle layerMainly smooth muscle with elastic layers and collagenUsed for vasoconstriction and vasodilation

Tunica IntimaComposed of smooth epithelial cells named

endotheliumMinimises friction between moving blood

Artery / ArteriolesArteriesPumps oxygenated blood to the bodyHave narrow lumensStrong as pumping blood at high pressure

ArteriolesBranches into smaller arteries (arterioles)

when nearer tissueMore smooth muscle to control blood flow

CapillariesThinnest blood vesselMade of single layer endothelial cellsBring blood as close as possible to all cellsExchange of oxygen, carbon dioxide, water,

salts, between the blood and the surrounding body tissues takes place

Large quantities cover the muscle, ensuring efficient exchange of gases

Veins / VenulesVenulesVessels formed from capillariesDrains blood from capillaries into veins

VeinsHave same walls as artery but less thinner,

elastic and muscularPressure and speed of blood is lowWider Lumen than arteryHave valves that prevent backflow of blood

Comparison of Blood VesselsFeature Artery Capillary Vein

Tunica Externa √ X √

Tunica Media Thick X Thinner

Tunica Interna √ √ √

Size of Lumen Small Microscopic Large

Valves X X √

AimsYou should now be able to:

Describe the structure of the different blood vessels

Describe the function of each of the different blood vessels

Create a blood vessel comparison table