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8.3 Blood vessels - Coggle Diagram
8.3 Blood vessels
Arteries
Tunica intima
Squamous epithelial cells
One cell thick
Tunica media
Lots of smooth muscle
Lots of elastic fibres
Thick
Tunica externa
Lots of elastic fibres
Collagen
Thick
Rather large circular lumen
Smooth muscle in muscular arteries/arterioles allows for vasoconstriction and vasodilation
Elasticity in elastic arteries keeps pressure even during systole and diastole
Veins
Very large irregular lumen
Tunica intima
Squamous epithelial cells
One cell thick
Tunica media
Some smooth muscle
Some elastic fibres
Thin
Tunica externa
Collagen
Some elastic fibres
Thinner than in arteries
Semilunar valves to prevent backflow
Capillaries
No tunica intima, media, or externa
Very small lumen, just large enough for one cell to pass
Made up of single layer of squamous epithelial cells