Blood Vessels & Circulation

Arteries

Carry blood away from the heart

Capillaries

Site of exchange with tissues

Veins

Carry blood toward the heart

Tunica Intima

4 Layers, most interior

Tunica media

middle

Tunica externa (adventitia)

most external

Metarterioles

Vessels with isolated smooth muscle cells along their walls

thoroughfare channel

vessels within the capillary network that extend in a direct fashion from metarteriole to venule

Medium veins

collect blood from small veins and deliver it to large veins

Large veins

Tunica intima is thin; Tunica media has circularly arranged smooth muscle cells

most important means of exchange

Diffusion

hydrostatic pressure

pressure against the walls of the capillary

osmotic pressure

Blood colloid pressure; interstitial pressure