12.7 Overview of the Vascular System

Endothelium

Smooth, single-celled layer of endothelial cells in contact with the flowing blood in all blood vessels and the heart chambers

Arteriole

Main resistance vessels, controls distribution of blood flow

Venule

White blood cells released into tissues during inflammation and infection; capacitance vessels

Capillary

Exchange of gases, fluid, nutrients; uptake of waste and secretory products from cells; made of endothelium and associated extracellular basement membrane

Blood Pressure

Systemic arterial pressure higher than pulmonary arterial pressure; latter has lower vascular resistance