Blood Vessels

Artery:

Contains:

• Endothelium intima
• Thick Tunica Media (with smooth muscle and elastic fibres), to deal with the high pressure blood and allows the arteries to recoil
• Has a relatively thick tunica externa
• Relatively smaller lumen
• Has high pressure pulsitile blood

Function=To carry high pressure blood away from the heart 

Capillary:

Contains:

• Endothelium made up of 1 layer thick squamous epithelium (thin walls)
• 1 RBC thick lumen
• Average blood pressure

Function=Exchange vessel to the organs

Vein:

Contains:

• Endothelium intima
• Relatively thinner Tunica media
• Thinner tunica externa
• Valves, prevent the backflow of blood aiding its return (if valves fail to close then it can result in varicose veins or the build up of blood)
• Very large lumen
• Very low blood pressure

Function=Carry blood to the heart

Arterioles:

Function=Are able to contract forcing blood to go through a seperate tube straight into the venules. Also connect the arteries to the capillaries.

Venules:

Function=Connects veins to the capillaries

Blood Vessels

(A) Artery:

• Has a capsule/outer layer
• Has an endothelium
• Has a thick tunica media (smooth muscle and many elastic fibres, which allow the arteries to deal with high pressure blood)
• Has a proportionally thicker tunica externa
• Small lumen
• High pulsitile blood pressure 
• Function= carry blood away from the heart

(C) Capillary:

• Has an endothelium (squamous epithelium)
• 1 RBC thick lumen
• Average blood pressure
• Function= exchange surface to the organs

(B) Vein:

• Has a capsule/outer layer
• Has an endothelium
• Thin tunica media (smooth muscle and elastic fibres)
• Thin tunica externa
• Contains valves (stops the back flow of blood reducing the chance of varicose veins) 
• Large lumen
• Very low blood pressure
• Function= Carry blood to the heart