1 adj Social means relating to society or to the way society is organized. ADJ n. ...the worst effects of unemployment, low pay and other social problems., ...long-term social change., ...changing social attitudes., ...the tightly woven social fabric of small towns., ...research into housing and social policy.
The human circulatory system (simplified). Red indicates oxygenated blood carried in arteries, blue indicates deoxygenated blood carried in veins. Capillaries, which join the arteries and veins, and the lymphatic vessels are not shown.
Artery Structure. arteries have three layers: a smooth inner layer; a strong, muscular layer; and a thin outer layer; connective fibers in artery walls allow for the elasticity needed for the artery to function; arteries are usually larger than veins.