Thoracic aorta (arch)	Abdominal aorta
Wall thickness	greater
Wall diameter	30-40% greater
Elastic fiber content	greater (decreases distal from root)
Derivation of SMCs*	ectoderm	Mesoderm
Vasa vasorum (media)**	numerous	few to absent
Functional differences	greater elasticity
Disease predilections	inflammatory cystic medial necrosis	more severe atherosclerosis
*SMC –smooth muscle cells **penetration of vasa vasora into medial layer
Table 1: Differences between the thoracic and abdominal aorta.