Question

Regarding arteries, veins, and capillaries: describe differences between their tunics, their internal pressures, and why they are constructed in the manner they are.

Answer 1

	Arteries	Veins	Capillaries
1.	They have tunica intima, tunica media and tunica externa.	They have tunica internal, tunica media and tunica externa	They have only tunica intima.
2.	The pressure inside the arteries is very high.	The pressure inside the vein is less than arteries.	Capillaries have lower pressure than arteries.
3.	Arteries carry blood away from the heart.	Veins carry blood towards the heart.	In the capillaries exchange of substances takes place.
4.	Tunica media is thicker in an artery	Tunica media is thinner in veins.	Tunica media is absent.
5	Tunica externa is thicker in arteries.	Tunica externa is thinner in veins.	Tunica externa is absent.