Chapter 21, part 1

1. Chapter 21, part 1 Blood Vessels and Circulation

2. Learning Objectives • Distinguish among the types of blood vessels. • Describe fluid and dissolved material transport into and out of the cardiovascular system. • Describe the factors that influence blood pressure and blood pressure regulation. • Discuss the mechanisms involved in the movement of fluids between capillaries and interstitial spaces.

3. Learning Objectives • Describe how blood flow and pressure in tissues is regulated. • Identify the principle blood vessels of each circuit and the areas they serve. • Describe fetal circulation patterns and the changes that occur in these patterns at birth and during aging.

4. SECTION 21-1The Anatomy of Blood Vessels

5. Structure of vessel walls • Walls of arteries and veins contain three distinct layers • Tunic intima • Tunica media • Tunica externa

6. Figure 21.1 A Comparison of a Typical Artery and a Typical Vein Figure 21.1

7. Differences between arteries and veins • Compared to veins, arteries • Have thicker walls • Have more smooth muscle and elastic fibers • Are more resilient

8. Arteries • Undergo changes in diameter • Vasoconstriction – decreases the size of the lumen • Vasodilation – increases the size of the lumen • Classified as either elastic (conducting) or muscular (distribution) • Small arteries (internal diameter of 30 um or less) are called arterioles

9. Capillaries • An endothelial tube inside a basal lamina • These vessels • Form networks • Surround muscle fibers • Radiate through connective tissue • Weave throughout active tissues • Capillaries have two basic structures • Continuous • Fenestrated • Flattened fenestrated capillaries = sinusoids

10. Figure 21.2 Histological Structure of Blood Vessels Figure 21.2

11. Figure 21.4 Capillary Structure Figure 21.4

12. Capillary Beds • An interconnected network of vessels consisting of • Collateral arteries feeding an arteriole • Metarterioles • Arteriovenous anastomoses • Capillaries • Venules

13. Figure 21.5 The Organization of a Capillary Bed Figure 21.5a, b

14. Veins • Collect blood from all tissues and organs and return it to the heart • Are classified according to size • Venules • Medium-sized veins • Large veins

15. Venous Valves • Venules and medium-sized veins contain valves • Prevent backflow of blood

16. Figure 21.6 The Function of Valves in the Venous System Figure 21.6

17. Distribution of blood • Total blood volume is unevenly distributed • Venoconstriction maintains blood volume • Veins are capacitance vessels • Capacitance = relationship between blood volume and pressure PLAY Animation: Anatomy Review: Blood Vessel Structure and Function

18. Figure 21.7 The Distribution of Blood in the Cardiovascular System Figure 21.7

19. SECTION 21-2Cardiovascular Physiology

20. Circulatory Pressure • Circulatory pressure is divided into three components • Blood pressure (BP) • Capillary hydrostatic pressure (CHP) • Venous pressure

21. Figure 21.8 An Overview of Cardiovascular Physiology Figure 21.8

22. Resistance (R) • Resistance of the cardiovascular system opposes the movement of blood • For blood to flow, the pressure gradient must overcome total peripheral resistance • Peripheral resistance (PR) is the resistance of the arterial system

23. Overview of Cardiovascular Pressures • Factors involved in cardiovascular pressures include • Vessel diameter • Cross-sectional area of vessels • Blood pressure • Blood viscosity

24. Figure 21.9 Relationships among Vessel Diameter, Cross-sectional Area, Blood Pressure, and Blood Viscosity Figure 21.9