Cardiovascular SystemChapter 11

Blood Vessels: The Vascular System• Carry blood away from the heart• Arteries• Arterioles

Blood Vessels: The Vascular System• Exchanges between tissues and blood• Capillary beds

Blood Vessels: The Vascular System• Return blood toward the heart• Venules• Veins

Blood Vessels: The Vascular System

Blood Vessels: Microscopic Anatomy• Three layers (tunics)

Blood Vessels: Microscopic Anatomy• Tunic intima• Endothelium

• Tunic media• Smooth muscle

• Tunic externa• Mostly fibrous connective tissue

Differences Between Blood Vessels• Walls of arteries are the thickest• Lumens of veins are larger• Larger veins have valves to prevent backflow• Walls of capillaries are only one cell layer thick

Movement of Blood • Most arterial blood is pumped

by the heart

• Veins use the “milking” action of muscles to help move blood

Capillary Beds• Two types of vessels• Vascular shunt—vessel directly connecting an arteriole to

a venule• True capillaries—exchange vessels

Capillary Beds

Capillary Beds