When the heart contracts, and ejects blood into these arteries, the walls need to stretch to accommodate the blood surge, storing energy. The arterial hydrostatic pressure that results from ventricular contraction is the ‘systolic blood pressure’ (systole is greek for contract).

Tunica adventitia – has small ‘vasa vasorum’ as the large arteries need their own blood supply. Tunica media is broad and elastic with concentric fenestrated sheets of elastin, and collagen and only relatively few smooth muscle fibres.