Blood vessels are tubular structures that carry blood throughout the body. There are three main types: arteries, capillaries, and veins. Each type has a distinct structure and function suited to its role in circulation.
Definition
Arteries — carry blood away from the heart
Capillaries — permit exchange of materials with tissues
Veins — return blood to the heart
Main Idea
Arteries carry blood away from the heart under high pressure. They have thick, elastic walls.
Capillaries are thin-walled vessels that allow exchange of gases, nutrients, and wastes between blood and tissues.
Veins return blood to the heart under low pressure. They have thinner walls and valves to prevent backflow.
Core Concept
Arteries = away from heart; thick walls; no valves; high pressure
Arterioles = small arteries; regulate blood flow
Capillaries = exchange vessels; one cell thick; low pressure
Venules = small veins; collect blood from capillaries
