Overview
This lecture introduces the anatomy and functions of blood vessels, focusing on the basic structure, types, and roles of arteries, veins, and capillaries in the circulatory system.
Blood Vessel Classification
- The vascular system includes arteries, veins, and capillaries.
- Arteries carry blood away from the heart and typically transport oxygenated blood.
- Veins carry blood toward the heart, usually containing deoxygenated blood.
- Capillaries are small vessels where the exchange of gases, nutrients, and waste occurs between blood and tissues.
Structure of Blood Vessels
- All blood vessels (except capillaries) have three layers: tunica intima (inner), tunica media (middle), and tunica externa (outer).
- Tunica intima is made of endothelium and provides a smooth lining.
- Tunica media consists of smooth muscle and elastic fibers, allowing for vasoconstriction and vasodilation.
- Tunica externa is composed of connective tissue for vessel protection and support.
Types and Functions of Arteries
- Elastic arteries (like the aorta) have a lot of elastic tissue for high-pressure blood flow.
- Muscular arteries distribute blood to organs and tissues, controlling blood flow with muscle tissue.
- Arterioles are small arteries that regulate blood entering capillaries through vasoconstriction or vasodilation.
Types and Functions of Veins
- Veins have thinner walls than arteries and often contain valves to prevent backflow.
- Venules collect blood from capillaries and transport it to larger veins.
Capillary Structure and Function
- Capillaries consist of a single layer of endothelial cells to facilitate exchange.
- Three types of capillaries exist: continuous (least permeable), fenestrated (have pores), and sinusoidal (most permeable).
Key Terms & Definitions
- Artery — vessel carrying blood away from the heart.
- Vein — vessel carrying blood toward the heart.
- Capillary — smallest blood vessel for exchange of substances.
- Tunica intima — inner vessel layer of endothelium.
- Tunica media — middle vessel layer with smooth muscle and elastic fibers.
- Tunica externa — outer vessel layer of connective tissue.
- Vasoconstriction — narrowing of blood vessels.
- Vasodilation — widening of blood vessels.
Action Items / Next Steps
- Review vessel structure diagrams in the textbook.
- Memorize the three vessel layer names and functions.
- Read the next section on capillary exchange for further understanding.