Basic AS SNAB Blood Vessels/ Cardiac Cycle

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To overcome limitations of diffusion, larger organisms use a mass transport system to transport nutrients and exchanged materials to specifically developed organs, such as the Lungs to deal with gaseous exchange.

Types of vessel=

ARTERY, VEIN, CAPILLARY

Artery- Blood AWAY from Heart (to lungs-pulmonary artery, after oxidised to body- aorta)

Vein- Towards Heart, (pulmonary vein takes oxidised blood back to heart, vena cava back from body)

Capillaries- directly takes blood to muscles, blood filters through capillaries between arterioles and venules.

STRUCTURE OF VESSELS-

Artery- thick wall, smooth muscle, elastic fibres, lined smooth endothelial cells, narrow lumen. Thick wall withstands high pressure, smooth muscle alters the size of the narrow lumen as response to varying blood flow, elastic fibres allow wall to stretch and recoil- smoothing blood flow, smooth lining= reduced friction, damage less likely.

Vein- thin walls, few elastic fibres/smooth muscle, large

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